Volume 12 Number 3 IJSPT

IJSPT

INTERNATIONAL JOURNAL OF SPORTS PHYSICAL THERAPY

VOLUME TWELVE issue THREE JUNE 2017

IJSPT

INTERNATIONAL JOURNAL OF SPORTS PHYSICAL THERAPY

Editor in Chief Michael L. Voight, PT, DHSc, OCS, SCS, ATC, CSCS Belmont University Nashville, Tennessee – USA

Associate Editors: John Dewitt PT, DPT, SCS, ATC The Ohio State University Sports Medicine Columbus, Ohio - USA

Senior Associate Editor Barbara Hoogenboom, PT, EdD, SCS, ATC Grand Valley State University Grand Rapids, Michigan - USA

Terry Grindstaff PhD, PT, ATC Creighton University Omaha, Nebraska - USA

Manuscript Coordinator Ashley Campbell, PT, DPT, SCS, ATC Associate Editor, Thematic Issues: Robert Manske, PT, DPT, Med, SCS, ATC, CSCS Wichita State University Wichita, Kansas – USA

International Associate Editors: Mario Bizzini, PT, MSc Schulthess Clinic Zürich – Switzerland Henning Langberg, PT, PhD, MSc Institute of Sports Medicine Copenhagen – Denmark

Editorial Board: Scott Anderson, PT, Dip Sport PT Northgate Physical Therapy Regina, Saskatchewan – Canada

Mark S. De Carlo, PT, DPT, MHA, SCS, ATC Accelerated Rehabilitation Indianapolis, Indiana – USA

Lindsay Becker, PT, DPT, SCS, CSCS The Ohio State University Sportsmedicine Center Columbus, Ohio – USA

Todd S. Ellenbecker, DPT, SCS, OCS Physiotherapy Associates Scottsdale Sports Clinic Scottsdale, Arizona – USA

Barton Bishop, PT, DPT, SCS, CSCS Sport and Spine Rehab of Rockville Rockville, Maryland – USA

John A. Guido, Jr., PT, MHS, SCS, ATC, CSCS Ochsner Health Systems New Orleans, Louisiana – USA

Turner A. “TAB” Blackburn, Jr., MEd, PT, ATC Clemson Sports Medicine and Rehabilitation Manchester, Georgia – USA

Elizabeth L. Harrison, PT, PhD, Dip Sport PT University of Saskatchewan Saskatoon, Saskatchewan – Canada

Lori A Bolgla, PT, PhD, MAcc, ATC Augusta University Augusta, Georgia – USA

Walter L. Jenkins, PT, DHS, ATC East Carolina University Greenville, North Carolina - USA

Robert J. Butler, PT, DPT, PhD Duke University Durham, NC – USA

Daniel S. Lorenz, PT, DPT, ATC, CSCS Providence Medical Center Kansas City, Kansas - USA

Duane Button, PhD, CSEP-CEP Memorial University St. John’s, Newfoundland and Labrador – Canada

Terry Malone, PT, EdD, ATC, FAPTA University of Kentucky Lexington, Kentucky – USA

Rick Clark, PT, DScPT, CCCE Air Force Academy Colorado Springs, CO – USA

Peter J. McNair, PT, PhD Auckland University of Technology Auckland – New Zealand

George J. Davies, PT, DPT, SCS, ATC, FAPTA Armstrong Atlantic State University Savannah, Georgia – USA

EDITORIAL STAFF & BOARD

Phil Page, PT, PhD, ATC, CSCS The Hygenic Corporation Akron, Ohio – USA

Timothy Uhl, PT, PhD, ATC University of Kentucky Lexington, Kentucky – USA

Mark Paterno, PT, PhD, MBA, SCS, ATC Cincinnati Children’s Hospital Medical Center Cincinnati, Ohio – USA

Mark D. Weber, PT, PhD, SCS, ATC University of Mississippi Medical Center Jackson, Mississippi – USA

Charles E. Rainey, PT, DSc, DPT, MS, OCS, SCS, CSCS, FAAOMPT United States Public Health Service Springfield, Missouri - USA

Kevin Wilk, PT, DPT Champion Sports Medicine Birmingham, Alabama – USA

Michael P. Reiman, PT, DPT, OCS, SCS, ATC, FAAOMPT, CSCS Duke University School of Medicine Durham, North Carolina – USA Mark F. Reinking, PT, PhD, SCS, ATC Saint Louis University St. Louis, Missouri – USA Jill Robertson, PT, MSc (PT), Dip Manip PT Beaverbank Orthopaedic and Sport Physiotherapy Halifax, Nova Scotia – Canada Kevin Robinson, PT, DSc, OCS Belmont University Nashville, Tennessee – USA Barbara Sanders, PT, PhD, SCS, FAPTA Texas State University-San Marcos San Marcos, Texas – USA Teresa L. Schuemann, PT, DPT, SCS, ATC, CSCS Colorado Physical Therapy Specialists Fort Collins, Colorado – USA Brandon Schmitt, PT, DPT, ATC PRO Sports Physical Therapy of Westchester Scarsdale, New York - USA Patrick Sells, DA, ES Belmont University Nashville, Tennessee – USA Laurie Stickler, MSPT, OCS Grand Valley State University Grand Rapids, Michigan – USA Steven R. Tippett, PT, PhD, SCS, ATC Bradley University Peoria, Illinois – USA Timothy F. Tyler, PT, ATC NISMAT Lenox Hill Hospital New York, New York – USA

Erik Witvrouw, PT, PhD Ghent University Ghent – Belgium

international JOURNAL OF

IJSPT

SPORTS PHYSICAL THERAPY

I N T E R N AT I O N A L J O U R N A L OF SPORTS PHYSICAL THERAPY

SPORTS PHYSICAL THERAPY SECTION

Editorial Staff

Executive Committee

Michael L. Voight, PT, DHSc, OCS, SCS, ATC Editor-in-Chief

Walter L. Jenkins, PT, DHS, LATC, ATC President

Barbara Hoogenboom, PT, EdD, SCS, ATC Grand Valley State University Grand Rapids, Michigan - USA Senior Associate Editor

Blaise Williams, PT, PhD Vice President Mitchell Rauh, PT, PhD, MPH, FACSM Secretary

Robert Manske, PT, DPT, Med, SCS, ATC, CSCS Wichita State University Wichita, Kansas – USA Associate Editor, Thematic Issues

Bryan Heiderscheit, PT, PhD Treasurer Stacey J. Pagorek, PT, DPT, SCS, ATC Representative-At-Large

Associate Editors John Dewitt PT, DPT, SCS, ATC The Ohio State University Sports Medicine Columbus, Ohio - USA

Administration Mark S. De Carlo, PT, DPT, MHA, SCS, ATC Executive Director

Terry Grindstaff PhD, PT, ATC Creighton University Omaha, Nebraska - USA

Mary Wilkinson Director of Marketing/Webmaster Managing Editor, Publications

International Associate Editors Mario Bizzini, PT, MSc Schulthess Clinic Zürich – Switzerland

Contact Information P.O. Box 431 Zionsville, Indiana 46077 877.732.5009 Toll Free 317.669.8276 Fax www.spts.org

Henning Langberg, PT, PhD, MSc Institute of Sports Medicine Copenhagen – Denmark Ashley Campbell Manuscript Coordinator Mary Wilkinson Managing Editor

Advertising Sales The International Journal of Sports Physical Therapy accepts advertising. Email Mary Wilkinson, Marketing Director, at mwilkinson@spts.org or contact by phone at 317.501.0805.

IJSPT is a bimonthly publication, with release dates in February, April, June, August, October and December.

I N T E R N AT I O N A L J O U R N A L OF SPORTS PHYSICAL THERAPY is a publication of the Sports Physical Therapy Section of the American Physical Therapy Association. IJSPT is also an official journal of the International Federation of Sports Physical Therapy (IFSPT).

ISSN 2159-2896

T

IFSPT

TABLE OF CONTENTS VOLUME 12, NUMBER 3 Page Number

Article Title

ORIGINAL RESEARCH 305 Dynamic Oscillatory Stretching Efficacy on Hamstring Extensibility and Stretch Tolerance: A Randomized Controlled Trial.

Authors: Michaeli A, Tee JC, Stewart A 314

Postural Stability and Kinetic Change in Subjects with Patellofemoral Pain after a Nine-Week Hip and Core Strengthening Intervention.

Authors: Carry PM, Gala R, Worster K, Kanai S, Miller NH, James D, Provance AJ, Carollo JJ

324

Kinematic and Kinetic Variables Differ Between Kettlebell Swing Styles.

Authors: Bullock GS, Schmitt AC, Shutt JM, Cook G, Butler RJ

333

A Dynamic Valgus Index That Combines Hip and Knee Angles: Assessment of Utility in Females With Patellofemoral Pain.

Authors: Scholtes SA, Salsich GB

341

The Associations Between Hip Strength and Hip Kinematics During a Single Leg Hop in Recreational Athletes Post ACL Reconstruction Compared to Healthy Controls.

Authors: Tate J, Suckut T, Wages J, Lyles H, Perrin B

352

Injury Incidence, Dance Exposure and the Use of the Movement Competency Screen (MCS) to Identify Variables Associated With Injury in Full-time Pre-professional Dancers.

Authors: Lee L, Reid D, Caldwell J, Palmar P

371

Dynamic Hip Adduction, Abduction and Abdominal Exercises From the Hölmich Groin-Injury Prevention Program Are Intense Enough To Be Considered Strengthening Exercises – A Cross-Sectional Study.

Authors: Krommes K, Bandholm T, Jakobsen MD, Anderson LL, Serner A, Hölmich P, Thorborg K

381

A Comprehensive Instrument for Evaluating Mild Traumatic Brain Injury (mTBI)/Concussion in Independent Adults: A Pilot Study.

Authors: Borges A, Raab S, Lininger M

390

Strength Profiles in Healthy Individuals With and Without Scapular Dyskinesis.

Authors: Hannah DC, Scibek JS, Carcia CR

402

Anodal Transcranial Direct Current Stimulation (tDCS) Increases Isometric Strength of Shoulder Rotator Muscles in Handball Players.

Authors: Hazime FA, Cunha R, Soliaman RR, Romancini A, Pochini A, Ejnisman B, Baptista AF

408

Load-Enhanced Movement Quality Screening and Tactical Athleticism: An Extension of Evidence.

Authors: Glass SM, Schmitz RJ, Rhea CK, Ross SE

417

EMG of Shoulder Muscles During Reactive Isometric Elastic Resistance Exercises.

Authors: Mullaney MJ, Perinson C, Kremenic I, Tyler TT, Orishimo K, Johnson C

425

The Effect of Electrical Stimulation Versus Sham Cueing on Scapular Position during Exercise in Patients with Scapular Dyskinesis Authors: Walker D, Hickey C, Mason T

437

Reliability and Validity of a Biomechanically Based Analysis Method for the Tennis Serve Authors: Myers NL, Kibler WB, Lamborn L, Smith BJ, English T, Jacobs C, Uhl TL

450

Do General Medical Practitioners Examine Injured Runners?

Authors: Videbaek S, Jensen AV, Rasmussen S, Nielsen RO

CASE STUDIES 458

Impairment Based Examination and Treatment of Osteochondritis: A Case Series.

Authors: Zaruba RA, Wilson E

468

Dry Needling Increases Muscle Thickness in a Subject with Persistent Muscle Dysfunction: A Case Report.

Authors: Cross KM, McMurray M

476

Aortic Injury due to Paragliding: A Case Report.

Authors: Omori K, Jitsuiki K, Majima T, Takeuchi I, Yoshizawa T, Ishikawa K, Ohsaka H, Tambara K, Yanagawa Y

CLINICAL COMMENTARY 481 Superior Capsule Reconstruction for Massive Rotator Cuff Tears – Key Considerations for Rehabilitation.

Authors: Pogorzelski J, DelVecchio BM, Hussain ZB, Fritz EM, Godin JA, Millett PJ 494

Rehabilitation following Medial Patellofemoral Ligament Reconstruction for Patellar Instability Authors: Manske R, Prohaska D

IJSPT

ORIGINAL RESEARCH

DYNAMIC OSCILLATORY STRETCHING EFFICACY ON HAMSTRING EXTENSIBILITY AND STRETCH TOLERANCE: A RANDOMIZED CONTROLLED TRIAL Arie Michaeli, MSc PT, MCMT1 Jason Cameron Tee, PhD2 Aimee Stewart, PhD3

ABSTRACT Background: While static stretch (SS), proprioceptive neuromuscular facilitation (PNF) and oscillatory physiological mobilization techniques are documented to have positive effects on a range of motion (ROM), there are no reports on the effect of dynamic oscillatory stretching (DOS), a technique that combines these three techniques, on hamstring extensibility.

Purpose: To determine whether DOS improves hamstring extensibility and stretch tolerance to a greater degree than SS in asymptomatic young participants.

Study Design: Randomized Controlled Trial.

Methods: Sixty participants (47 females, 13 males, mean age 22 ± 1 years, height 166 ± 6 centimeters, body mass 67.6 ± 9.7 kg) completed a passive straight leg (SLR) to establish hamstring extensibility and stretch tolerance as perceived by participants, using a visual analogue scale (VAS). Participants were randomly assigned to one of two treatment groups (SS or DOS) or a placebo control (20 per group). Tests were repeated immediately following and one hour after each intervention. Data were assessed using a two-way repeated measure analysis of variance (ANOVA) and Tukey’s post hoc test.

Results: Immediately post-intervention, there was a significant improvement in the hamstring extensibility as measured by the SLR in both the SS and DOS groups, with the DOS group exhibiting a significantly greater increase than the SS group (Control 73 ± 12°, SS 86 ± 8°, DOS 94 ± 11°, p < 0.001). One hour post-intervention, hamstring extensibility in the DOS group remained elevated, while the SS group no longer differed from the control group (Control 73 ± 12°, SS 80 ± 8°, DOS 89 ± 12°, p = 0.001). Furthermore, the stretch tolerance remained significantly elevated for the SS group, but there was no difference between the control and DOS groups, (Control 4.6 ± 1.3, SS 5.9 ± 0.8, DOS 4.3 ± 1.0 AU, p < 0.001).

Conclusion: DOS was more effective than SS at achieving an immediate increase in hamstring extensibility, and DOS demonstrated an increased stretch tolerance one-hour post-intervention.

Level of evidence: 2C Keywords: Dynamic oscillatory stretching, hamstring extensibility, stretch tolerance.

1

1.Private Practice, Johannesburg, South Africa Leeds Beckett University, UK 3 University of the Witwatersrand, Johannesburg, South Africa, Aimee.Stewart@wits.ac.za 2

CORRESPONDING AUTHOR Arie Michaeli, MSc PT, MCMT Clinical Solutions 32 Boundary Road, Rouxville, Johannesburg, 2192 South Africa Tel: (+27) 11 640 2097 Fax: (+27) 86 513 1891 E-mail: ari@clinisol.co.za

The International Journal of Sports Physical Therapy | Volume 12, Number 3 | June 2017 | Page 305

INTRODUCTION Reduction in the extensibility of the hamstring muscles has been reported to be associated with the occurrence of back pain,1 sacroiliac joint disorders,2 hamstring strain,3 patellofemoral pain syndrome,4 and patellar tendinopathy.5 Thus, extensibility of the hamstrings is important for optimal joint and muscle function. The extent to which muscles contract has been shown to be dependent on muscle length, and shortened or lengthened muscles may not develop maximum tension if their resting length has changed.6 The physiological mechanisms behind the changes in muscle extensibility are debatable.

Viscoelastic, reflex muscle relaxation, and stretch tolerance changes7 have been extensively studied and are widely regarded as contributing to short- and medium-term alterations in muscle extensibility.

More recently, there has been increasing attention being paid to Neurodynamics.8 Of these four mechanisms, the scientific literature mostly cites stretch tolerance for producing short- and medium-term alterations.7,9,10 Increased stretch tolerance means that stretching intervention enables individuals to tolerate higher levels of stretch discomfort rather than reflecting an actual change in the passive mechanical properties of tissue. In a well-designed study involving 60 healthy individuals, Ben and Harvey9 showed that static stretching did not induce any lasting changes in muscle extensibility. Rather, it merely improved participantsâ&#x20AC;&#x2122; tolerance for the discomfort associated with stretch, although it was not possible to ascertain the underlying physiological mechanism responsible for the improved stretch tolerance. The authors postulated that stretching has an influence on some characteristics of the sensory neural pathways stimulating muscle and joint mechanoreceptors, and this may reduce the sensation of pain.9

neuromuscular facilitation (PNF) technique. DOS is similar to agonist contract-relax (ACR),7 in that the agonist produces the stretching force on the opposite muscle (antagonist.) In this study the quadriceps femoris muscle, when attempting to stretch the hamstrings, is contracted to actively move the lower extremity into increased ROM utilizing the reciprocal inhibition mechanism.7,13 In addition, DOS incorporates as a modification a two-second oscillatory manual stretch at the end of the range, which is applied by the therapist to assist the agonist.15 DOS therefore consists of dynamic, oscillatory and passive stretching components. In several studies, dynamic stretches, including ACR, have been shown to be superior to SS in achieving greater ROM as well as improving the function of the antagonist muscles.7,14 The oscillatory component of DOS resembles oscillatory physiological mobilization as described by an Maitland,16 for the treatment of musculoskeletal disorders. Mobilization techniques have consistently been shown to be clinically effective in improving peripheral and spinal joint mobility.17,18 It is therefore postulated that DOS is a potentially superior technique to SS in improving ROM as it incorporates three evidence-based modalities (PNF, oscillatory passive physiological mobilization and SS), all of which have been clinically proven to increase ROM.11,13,14

Static stretch (SS) is commonly utilized to increase range of motion (ROM), to improve performance, to prevent or reduce injury risk, and to reduce delayed onset muscle soreness.11 However, research consistently shows that apart from improving extensibility, SS is largely ineffective in achieving the above-mentioned outcomes.11,12 The current study introduces a novel stretching technique â&#x20AC;&#x201C; dynamic oscillatory stretching (DOS). DOS is a modified proprioceptive

The research hypotheses were that hamstring extensibility would be affected more by DOS than SS, and that DOS would affect the self-reported perception of pain at the limit of the SLR.

To date, no reports have been found in the literature describing the effectiveness of DOS on hamstring extensibility and stretch tolerance. The purpose of this study was to compare the effects of static and dynamic oscillatory hamstring stretching on SLR, which is a measurement of hamstring extensibility. The study also used a visual analog scale to measure the most intense perception of pain as a proxy measurement at the point of greatest stretch tolerance, immediately and one hour after the performance of SS and DOS techniques in asymptomatic young adults.

METHOD Design The study was a randomized controlled trial with blinded outcome assessment. Treatment could not

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be blinded to the investigator or the subjects. Random number sequencing was generated using the Research Randomizer Computer Program by an independent investigator on the research team.

The numbers were placed into individually sealed opaque envelopes, which were handed to participants after they had each undergone their baseline assessment. Participants were then randomly assigned to one of three treatment groups: SS, DOS, or control. The dependent variables were the degree of SLR ROM, and the subjects’ perceived pain. The independent variables were time (pre-, immediately post, and one-hour post); and the three types of intervention: SS, DOS, and control. Sample size estimation was performed a priori, and determined that a sample size of nineteen participants per group would detect a clinically important difference of 5° in SLR ROM with the power of 90% and α = 0.05.

Participants Sixty-nine healthy young physiotherapy students recruited from a local university volunteered to participate in the study. Participants were excluded if they had a previous history of lower-extremity and/ or back pathology, and/or direct injury to the hamstring muscles in the previous six months; if they suffered from a neurological disorder; if they participated in a regular stretching regimen of the hamstring muscles group; or if they attended regular yoga classes. Volunteers were eligible for the study if their hamstring extensibility, as measured by SLR

ROM, was less than or equal to 90° of hip flexion. In accordance with other studies which excluded participants with flexibility greater than 90°,19,20 nine participants with hamstring extensibility greater than 90° were excluded from this study, leaving 60 participants (47 females and 13 male) (Figure 1).

Outcome measures Primary outcome: Measurements of hamstring extensibility performed with hip flexion and the knee in extension is referred to as the passive SLR test, which also reflects tension of the hip joint capsule21 and/or neural tissues.8 The SLR test demonstrates accepted inter-observer reliability (ICC 0.93 to 0.97).22 The measurements of SLR were performed by a research assistant, an experienced physical therapist, who was not present during the stretching treatment of each participant. Her within-session intra-rater reliability was previously determined as ICC = 0.89, with the Standard Error of Measurement < 1°.

The SLR measurement position was the same as the starting position of each stretching protocol. A hand-held inclinometer that measures in two degree increments (Isomed, US Neurologicals LLC, Washington, USA ) was used to measure SLR ROM. The proximal peg of the inclinometer was placed on the tibial tuberosity with the second peg parallel to the shaft of the tibia (Figure 2). The reliability of this measurement tool for SLR is ICC = 0.95 to 0.98.23 The authors adapted the Maitland-style movement

Assessed for eligibility, n - 69

Excluded n = 9 Not meeting inclusion criteria

Randomized, n = 60

Allocated to static stretch, n = 20 Received intervention, n = 20

Analyzed, n = 20

Allocated to dynamic oscillatory stretch, n = 20 Received intervention, n = 20

Analyzed, n = 20

Allocated to control, n = 20 Received intervention, n = 20

Analyzed, n = 20

Figure 1. Flow diagram for recruitment, follow-up and analysis The International Journal of Sports Physical Therapy | Volume 12, Number 3 | June 2017 | Page 307

Figure 2. Positioning of the Inclinometer for the measurement of straight leg raise test

diagram16 to quantify end-of-range stretch tolerance. Pain onset was defined as P1; maximal pain as P2; resistance onset as R1 and increased intensity of resistance that did not limit the SLR as R| (Figure 3). In their study, Hayes and Petersen24 rated the reliability of their end-feel and pain/resistance judgements as “generally good”. Intrarater kappa coefficients varied from 0.65 to 1.00 for end-feel, and intrarater weighted kappa coefficients varied from 0.59 to 0.87 for pain/resistance sequence.

The examiner passively raised the lower extremity to the point where the participant’s perception of the stretch discomfort could no longer be tolerated (P2); the ROM was read off of the inclinometer. This measurement was performed prior to, immediately after, and one hour following each intervention.

Secondary outcome: Maximal perception of pain intensity at greatest stretch tolerance (end of SLR ROM) was determined via the use of a horizontal 10 centimeter visual analogue scale (VAS) with anchor points of 0 (no pain) and 10 (worst perceived pain). Participants were requested to mark the intensity of their perceived pain on the VAS using a pencil (P2). The VAS was chosen for measurement of pain because of its ease of administration and responsiveness.25 The level of pain measurements was taken at baseline, immediately after, and one-hour post-intervention.

Figure 3. The lower extremity was passively raised from the point of onset of resistance (R1) to the point of highest stretch tolerance as subjectively reported by the participant (P2). P2 was the limiting factor of the SLR. While resistance had appeared earlier in the stretch range, this was not the limiting factor (R|).

AB represents normal range of motion of SLR. R| is defined as increased resistance but not the limiting factor of SLR. AC represents the intensity of perceived stretch tolerance.

BD is the end of SLR range (hamstring extensibility) and it is a broad, shaded area as the end of the range is not a distinct point.

Intervention The main investigator (first author) who performed the intervention on each participant and was not involved in the measurements has 30 years of experience in physical and manual therapy according to the Maitland concept.16 Stretching protocols Group 1: static stretching.

Participants were asked to state which leg they usually used when kicking a ball. This was then defined as their dominant leg.

Starting position: the stretch was performed on the dominant leg with participants in the supine position on a non-adjustable treatment plinth, with the knee remaining in extension and the femur in neutral rotation. A lumbar roll was used to maintain participants’ lumbopelvic lordosis in a neutral position throughout the test. The contralateral thigh remained completely in contact with the plinth, stabilized by a belt. The first author passively raised the

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Figure 4. Illustrates the straight leg raise technique for hamstring extensibility. The main investigator passively raised the leg to the point of the first sensation of stretch, waited 15 seconds until the participant could tolerate more stretching and then added a further stretch to achieve a new “tolerance point”.

leg to the point of the first sensation of a stretch, held it for 15 seconds until the participant could tolerate more stretching, and then added a further stretch to achieve a new “tolerance point”. This procedure was repeated four times for a total stretch duration of 60 seconds (Figure 4).

Group 2: dynamic oscillatory stretching Starting position: same as for SS. The first author passively raised the leg to the point of the first sensation of a stretch. Each participant assisted the stretch by contracting his/her hip flexor muscles, while the knee extensors maintained the position of knee extension. Hip flexor and knee extensor contractions were sustained throughout the stretch. A two-second, slow passive stretch at the end of the range was applied to assist in further extending the stretch (Figure 5). The main investigator counted 101, 102 to standardize the two second stretch. The agonist contraction was maintained throughout the stretch. This procedure was repeated 10 times over three sets. The lower extremity was stretched to a new point of tolerance with each set.

The total stretching time was again 60 seconds: 2 sec x 10 repetitions x 3 sets.

For both stretching groups at the completion of the stretch, the lower extremity was allowed to rest for

Figure 5. Illustrates the Dynamic Oscillatory Stretching technique for hamstring extensibility. The therapist raises the leg to the point of “first sensation of stretch” while the patient assists the stretch by contracting his/her hip flexor muscles, while the knee extensor maintains knee extension. The stretch is held for two seconds, and the therapist then lowers the leg to approximately 30 degrees. Thereafter the process is repeated.

10 seconds with a pillow under the knee; and thereafter measurement of SLR ROM and perceived pain intensity (stretch tolerance) at the new range was obtained.

Group 3: placebo-control Participants in the placebo-control group received a one-minute sham ultrasound to the dorsal aspect of the foot in side lying. This procedure was chosen as a placebo due to the known absence of an anatomical and physiological relationship between the dorsum of the foot and the hamstrings muscle.

Unfortunately, it is not possible to blind participants in studies of this kind. Although the control group might have realized they were not in the experimental group, the recruiting information stated that the study aimed to determine the effect of different interventions on hamstring extensibility.

Statistical Analysis Homogeneity of group characteristics (age, height, body mass) was determined by one-way analysis of variance (ANOVA) and Tukey’s post-hoc test. ShapiroWilk tests established the normal distribution of all data sets. Differences between interventions (DOS, SS, and control) for SLR and reported pain at three

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Table 1. Descriptive characteristics of 3 experimental groups (presented as group mean +/- standard deviation).

different time points (pre-test, post-test and posttest+1 hour) were determined by two-way repeated measures of ANOVA. Assumptions of sphericity were assessed using the Mauchly test of sphericity, with any violations adjusted by use of the Greenhouse-Geisser correction. Where significant interaction (intervention x time) effects were found, one-way repeated measures ANOVA and Tukey’s post hoc test were used to determine the simple main effect of the protocol. All data are reported as mean ± standard deviation level of significance, set at p < 0.05. Statistical analysis was performed using Statistical Package for the Social Sciences (version 22, IBM.com).

RESULTS The mean descriptive characteristics of the three experimental groups are presented in Table 1. There were no significant differences between groups.

Changes in ROM during SLR are presented in Figure 6. There was a significant interaction effect (intervention x time) for ROM. SLR was not different between groups pre-intervention (Control 73 ± 12°, SS 79 ± 8°, DOS 76 ± 10°, p = 0.322). Immediately post-intervention, both SS, and DOS groups increased their ROM above the control group (Control 73 ± 12°, SS 86 ± 8°, DOS 94 ± 11°, p < 0.001).

The increased ROM in DOS post-intervention was significantly greater than for SS (p < 0.001). One hour following intervention, there was no longer any difference in ROM between the control and SS groups, but ROM in the DOS group remained

elevated above both other groups (Control 73 ± 12°, SS 80 ± 8°, DOS 89 ± 12°, p = 0.001).

Changes in most intense perceived pain at the end of the range of SLR (stretch tolerance) are presented in Figure 7. A significant interaction effect (intervention x time) was present for the self-reported pain measure. Pain at the end of the range of SLR was not significantly different between groups preintervention (Control 4.8 ± 1.1, SS 5.4 ± 0.8, DOS 5.7 ± 1.5 AU). Immediately post-intervention, the DOS and SS groups reported a similar perception of pain, however, this was significantly greater reported pain than for the control group (Control 4.3 ± 1.3, SS 5.9 ± 0.8, DOS 5.3 ± 1.3 AU, p < 0.001). This similar pain response, however, was achieved in the statistically significantly increased ROM seen in

Figure 6. Range of motion during straight leg raise test following 3 different stretch protocols.

SS = static stretch, DOS = dynamic oscillatory stretch. * and # indicate significant difference from control and SS conditions respectively.

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Figure 7. Most intense perceived pain at the end range of straight leg raise test following two different stretch interventions and control.

SS = static stretch, DOS = dynamic oscillatory stretch. * and # indicate significant difference from control and DOS conditions respectively.

the DOS group as compared with the SS group (p < 0.001). One hour following intervention, there was no longer any difference in perceived pain between the control and DOS groups, but SS pain was significantly greater than both of these groups (Control 4.6 ± 1.3, SS 5.9 ± 0.8, DOS 4.3 ± 1.0 AU, p < 0.001) DISCUSSION The results of this study demonstrate that both SS and DOS protocols can improve hamstring extensibility. However, the increased extensibility achieved within the DOS group was greater than for the SS group, both immediately and one hour following the intervention. Beyond extensibility improvements one-hour post-intervention, the DOS group pain response appeared to be less than the SS but not different from the control group, suggesting that this approach also offers improvement in stretch tolerance. The improved hamstring extensibility and perceived tolerance to the stretch demonstrated by the DOS group may support the theories of muscle property changes and reflex muscle relaxation, but is most likely explained by the improved stretch tolerance theory.7,9,10 However, further discussion regarding the superiority of DOS is required. Hypoalgesic, biochemical, and fluid-dynamic hypoalgesic influences have been consistently documented following physiological oscillatory mobilization in both a patient population group and in asymptomatic volunteers.26 The exact mechanism of pain relief from manual therapy techniques is unclear, but it has been suggested that pain is modulated at either

the spinal cord or in higher levels within the central nervous system.27 Wright28 argued that passive physiological oscillatory movements preferentially activate the descending inhibitory noradrenergenic system and exert a hypoalgesic influence on the mechanical nociceptor. Given that musculoskeletal conditions appear to involve changes in mechanical nociceptors, it is possible that DOS, due to its similarity to the mechanism of passive physiological oscillatory techniques, could effectively promote pain tolerance and subsequently increase ROM. This study included only asymptomatic individuals, which raises the question of whether pain variables can be accurately measured via self-reporting in healthy individuals. The use of asymptomatic individuals is commonly reported in experimental pain studies utilizing quantitative sensory testing methodologies. These include mechanical pressure29,30,31 and experimentally induced pain32,33,34 with one study, like this study, measuring pain using VAS.21 Pain variables therefore, can be used accurately when measuring healthy individuals, but any conclusions drawn from the results of this study should be applied with caution.

Having dealt with the effect of DOS on stretch tolerance, attention can be turned to the effect of neural tissue mobilization on hamstring extensibility.

Decreased hamstring extensibility as evidenced by the limited range in the SLR test could also be due to altered neurodynamics of the sciatic and tibial nerves. Changes in mechanosensitivity of the sciatic nerve have been shown to reduce hamstring length in asymptomatic individuals.8,35 Neural mobilization techniques alone36 and in combination with static stretch37 have been demonstrated to be effective in increasing hamstring extensibility in healthy volunteers. Nee and Butler38 hypothesized that “oscillatory movements can have a positive impact on symptoms by improving intraneural circulation, axoplasmic flow, and neural connective tissue viscoelasticity”. Altering mechanosensitivity of the posterior thigh neural system could be a plausible mechanism for increasing hamstring extensibility utilizing DOS. It is therefore suggested that neural tissue mobilization could play a significant role in improving stretch tolerance.

Immediately post-intervention, the DOS, and SS groups reported similar pain scores as a measure of

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stretch tolerance, but the DOS group had increased ROM. This might indicate that DOS could be more comfortably tolerated than SS. This is important because static stretching in a clinical setting can be painful. However, clinicians believe that its longterm benefits outweigh the short-term disadvantage of patient discomfort. Stretching techniques like DOS that have the capacity to modify stretch tolerance could be effective as a therapeutic stretch.

This, however, requires further randomized studies on symptomatic individuals across a broader age group with longer follow-up, using stretching interventions that are effective at changing stretch tolerance. Therefore, the results of this study can be generalized only to a healthy, asymptomatic, young adult population. Enhanced understanding of the effect of stretching following the application of DOS, as a result of the findings of this study, will hopefully enable clinicians to provide more effective and scientifically-based treatment when incorporating stretching activities into rehabilitation programs.3 This is the first study to investigate stretching utilizing dynamic oscillatory movement, with PNF and static stretching incorporated. The results of only one study have indicated that stretching is effective in achieving pain relief.39 That study however, included a combination of manual therapy and static stretch.

CONCLUSION The results of the current study demonstrate that improvements in hamstring extensibility can be achieved with both DOS and SS techniques. Notably, DOS showed a superior increase in extensibility immediately and one-hour post-intervention while SS had lost the increased SLR one-hour post-intervention. DOS demonstrated an increase in stretch tolerance at the newly obtained range one-hour postintervention. The dynamic oscillatory stretching technique used in the current study could provide clinicians with an effective therapeutic stretching option for increasing extensibility with good tolerance of the technique.

REFERENCES 1. Van Wingerden JP, Vleeming A, Snijders CJ, et al. A functional-anatomical approach to the spine-pelvis mechanism: interaction between the biceps femoris

muscle and the sacrotuberous ligament. Eur Spine J 1993;2:140-144.

2. Radwan A, Bigney KA, Buonomo HN, et al.

Evaluation of intra-subject difference in hamstring flexibility in patients with low back pain: An exploratory study. J Back Musculoskelet Rehabil.

2015;28:61-66.

3. Heiderscheit BC, Sherry MA, Silder A, et al.

Hamstring strain injuries: recommendations for diagnosis, rehabilitation, and injury prevention. J Orthop Sports Phys Ther. 2010;40:67-81.

4. Lankhorst NE, Bierma-Zeinstra SM, van Middelkoop M. Factors associated with patellofemoral pain syndrome: a systematic review. Br J Sports Med. 2013;47:193-206.

5. Van der Worp H, Van Ark M, Roerink S, et al. Risk factors for patellar tendinopathy: a systematic review of the literature. Br J Sports Med. 2011:bjsports84079.

6. Herbert R. The passive mechanical properties of muscle and their adaptations to altered patterns of use. Aust J Physiother. 1988;34:141-149.

7. Fryer G. MET: efficacy and research in: Chaitow L. Muscle Energy Techniques. 2nd ed. Churchill Livingstone. Elsevier 2013; 95-132.

8. McHugh MP, Johnson CD, Morrison RH. The role of neural tension in hamstring flexibility. Scand J Med Sci Sports. 2012;22:164-169.

9. Ben M, Harvey LA. Regular stretch does not increase muscle flexibility: a randomized controlled trial.

Scand J Med Sci Sports. 2010;20:136-144.

10. Weppler CH, Magnusson SP. Increasing muscle flexibility: a matter of increasing the length or modifying sensation? Phys Ther. 2010;90:438-449.

11. McHugh MP, Cosgrave CH. To stretch or not to stretch: the role of stretching in injury prevention and performance. Scand J Med Sci Sports. 2010;20:169181.

12. Nishikawa Y, Aizawa J, Kanemura N, et al.

Immediate effect of passive and active stretching on hamstrings flexibility: a single-blinded randomized control trial. J Phys Ther Sci . 2015;27:3167.

13. Hindle K, Whitcomb T, Briggs W, et al.

Proprioceptive neuromuscular facilitation (PNF): Its mechanisms and effects on range of motion and muscular function. J Hum Kinet. 2012;31:105-113.

14. Meroni R, Cerri CG, Lanzarini C, et al. Comparison of active stretching technique and static stretching technique on hamstring flexibility. Clin J Sport Med. 2010;20(1):8-14.

15. Mattes AL. Active isolated stretching: The Mattes Method 2012, 2nd Edition; p 157.

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16. Maitland GD. Vertebral Manipulation Fifth edition.

Butterworths. 1986:Chapter 6,106;351-364, Appendix 1.

17. Vincent K, Maigne JY, Fischhoff C, et al. Systematic review of manual therapies for nonspecific neck pain. Joint Bone Spine. 2013;80:508-515.

18. Bronfort G, Haas M, Evans RL, et al. Efficacy of spinal manipulation and mobilization for low back pain and neck pain: a systematic review and best evidence synthesis. Spine J. 2004;4:335-356.

19. Medeiros DM, Cini A, Sbruzzi G, et al. Influence of static stretching on hamstring flexibility in healthy young adults: Systematic review of meta-analysis.

Physiother Theory Pract. 2016;32(6):438-445.

20. Fasen JM, O’Connor AM, Schwartz SL, et al. A randomized controlled trial of hamstring stretching: comparison of four techniques. J Strength Cond Res. 2009;23(2):660-667.

21. Davis DS, Quinn RO, Whiteman CT, et al.

Concurrent validity of four clinical tests used to measure hamstring flexibility. J Strength Cond Res. 2008;22:583-588.

22. Neto T, Jacobsohn L, Carita AI, et al. Reliability of the Active-Knee-Extension and Straight-Leg-Raise Tests in Subjects with Flexibility Deficits. J. Sport Rehabil . 2014.

23. Boyd BS. Measurement properties of a hand-held inclinometer during straight leg raise neurodynamic testing. Physio. 2012;98:174-179.

24. Hayes KW, Petersen CM. Reliability of assessing end-feel and pain and resistance sequence in subjects with painful shoulders and knees. J Orthop Sports Phys Ther. 2001;31(8):432-45.

25. Chapman JR, Norvell DC, Hermsmeyer JT, et al.

Evaluating common outcomes for measuring treatment success for chronic low back pain. Spine J. 2011;36:S54-S68.

26. Chaitow L. Manual therapies and hypoalgesia: What are the mechanisms? J Body w Mov Ther.

2015;19:389-390.

27. Bialosky JE, Bishop MD, Price DD, et al. The mechanisms of manual therapy in the treatment of musculoskeletal pain: a comprehensive model. Man Ther. 2009;14:531-538.

28. Wright A. Hypoalgesia post-manipulative therapy: a review of a potential neurophysiological mechanism.

Man Ther. 1995;1:11-16.

29. Fernández-de-las-Peñas C, Pérez-de-Heredia M, BreaRivero M, et al. Immediate effects on pressure pain threshold following a single cervical spine manipulation in healthy subjects. J Orthop Sports Phys Ther., 2007;37(6):325-9.

30. Fryer G, Carub J, McIver S. The effect of manipulation and mobilization on pressure pain thresholds in the thoracic spine. Int J Osteopath Med. 2004;7(1):8-14.

31. Vincenzino B, Cartwright T, Collins D, et al. An investigation of stress and pain perception during manual therapy in asymptomatic subjects. Eur J Pain. 1999;3(1):13-18.

32. Bennell K, Hodges P, Mellor R, et al. The nature of anterior knee pain following injection of hypertonic saline into the infrapatellar fat pad. J Orthop Res, 2004;22(1):116-121.

33. Wingenfeld K, Wolf S, Kunz M, et al. No effects of hydrocortisone and dexamethasone on pain sensitivity in healthy individuals. Eur J Pain, 2015;19(6):834-841.

34. Petrini L, Hennings K, Li X, et al. A human experimental model of episodic pain. Int J Psychophysiol, 2014;94(3):496-503.

35. Lew PC, Briggs CA. Relationship between the cervical component of the slump test and change in hamstring muscle tension. Man Ther. 1997;2:98-105.

36. Castellote-Caballero Y, Valenza MC, Puentedura EJ, et al. Immediate Effects of Neurodynamic Sliding versus Muscle Stretching on Hamstring Flexibility in Subjects with Short Hamstring Syndrome. J Sports Med (Hindawi Publ Corp). 2014;2014:127471.

37. Sharma S, Balthillaya G, Rao R, et al. Short-term effectiveness of neural sliders and neural tensioners as an adjunct to static stretching of hamstrings on knee extension angle in healthy individuals: A randomized controlled trial. Phys Ther Sport.

2016;17:30-37.

38. Nee RJ, Butler D. Management of peripheral neuropathic pain: integrating neurobiology, neurodynamics, and clinical evidence. Phys Ther Sport. 2006;7: 36-49.

39. Cunha ACV, Burke TN, França FJR, et al. Effect of global posture reeducation and static stretching on pain, range of motion, and quality of life in women with chronic neck pain: a randomized clinical trial.

Clinics - Hospital das Clinicas da Faculdade de Medicina da Universidade de Sao Paulo. 2008;63:763-770.

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IJSPT

ORIGINAL RESEARCH

POSTURAL STABILITY AND KINETIC CHANGE IN SUBJECTS WITH PATELLOFEMORAL PAIN AFTER A NINE-WEEK HIP AND CORE STRENGTHENING INTERVENTION Patrick M. Carry, MS1 Raj Gala, MD1 Kate Worster, PhD2 Susan Kanai, PT2 Nancy H. Miller, MD1 David James, PT, DPT, OCS, SCS, CSCS3 Aaron J. Provance, MD3 James J. Carollo, PhD, PE1,2

ABSTRACT Background: Idiopathic patellofemoral pain (PFP) has been linked to hip weakness and abnormal lower extremity mechanics.

The effect of a strengthening intervention on balance has not been well studied among individuals with PFP. Hypothesis/Purpose: The primary aim of this study was to evaluate changes in center of pressure displacement during the single limb squat following a nine-week physical therapy intervention among adolescent females with PFP. Study Design: Interventional and cross-sectional Methods: Seven adolescent females with PFP (10 extremities) were included in the study. Center of Pressure (CoP) excursions during a single limb squat task were measured before and after a nine week of physical therapy intervention focused on strengthening of the hip and core. Seven asymptomatic females were matched to the PFP group on the basis of age and activity level, and were tested as a reference group. CoP trajectories were reduced into four variables: mean distance (MDIST), root-mean-square distance (RDIST), range (RANGE), and 95% confidence interval circle area (AREA-CC). Maximum knee flexion angle, peak knee power generation and absorption were also recorded. Linear mixed models were used to test for within and between group differences in CoP metrics.

Results: Pre-intervention, CoP range, knee power absorption and generation were significantly decreased in the PFP group relative to the reference group. Post-intervention, the PFP group reported a significant decrease in symptom severity. There was also a significant (p<0.05) increase in MDIST, RDIST, RANGE, AREA-CC, peak knee flexion angle, peak power absorption and power generation. There was no difference (p>0.05) in knee flexion, knee power or CoP displacement between the two groups after the physical therapy intervention.

Conclusion: Hip and core-strengthening resulted in a significant decrease in symptom severity as well as significant reductions in CoP displacement.

Level of Evidence: 3 Key words: Balance, hip strength, patellofemoral pain syndrome, postural stability

1

The Musculoskeletal Research Center, Department of Orthopaedic Surgery, Children’s Hospital Colorado, Aurora, CO, USA 2 Center for Gait and Movement Analysis, Children’s Hospital Colorado, Aurora, CO, USA 3 Sports Medicine for Young Athletes, Children’s Hospital Colorado, Aurora, CO, USA

CORRESPONDING AUTHOR James J. Carollo, PhD, PE Children’s Hospital Colorado 13123 East 16th Avenue, B476 Aurora Co, 80045 (720) 777-5805 [office] (720) 777-7101 [fax] E-mail: James.Carollo@childrenscolorado.org

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INTRODUCTION Hip weakness and subsequent abnormal lower extremity mechanics may contribute to the development of Idiopathic Patellofemoral Pain (PFP).1,2 Poor control of the femur during weight bearing tasks is believed to alter the kinematics of the knee joint, leading to joint dysfunction and pain.3-5 Furthermore, hip muscles are integral in proper lower extremity mechanics and are especially important during single limb tasks.6 The single limb squat (SLS) has been used as an assessment of lower extremity mechanics and strength.7 Previous authors suggest adequate hip and core strength may help to minimize unnecessary femoral and pelvic motion during this task.6 Excessive motion of the trunk, pelvis and femur may make balance more challenging during any single limb support task, so measuring balance performance during the SLS may reveal proximal weakness and excessive compensatory movements during this maneuver.

Center of pressure (CoP) displacement during dynamic tasks has been used to assess balance and postural stability in many studies.8-11 For a task such as SLS, CoP measures may be used to evaluate how the subject prepares and responds to anticipated movements.12,13 The CoP represents the instantaneous point of application of the ground reaction force vector (GRF) in the plane of the supporting surface during weight bearing, and its time history or trajectory reflects a subjectâ&#x20AC;&#x2122;s ability to maintain balance.

People may use different strategies to control their posture that may reflect their available strength, balance, coordination, and/or body mechanics.

The primary aim of this study was to evaluate changes in center of pressure displacement during the single limb squat following a nine-week physical therapy intervention among adolescent females with PFP. The authors hypothesized that a hipstrengthening intervention would result in changes in center of pressure displacement during a single limb squat task.

METHODS Participant Selection Seven young females between the ages of 12 and 18 diagnosed with PFP were recruited from our institu-

tionâ&#x20AC;&#x2122;s Sports Medicine Clinics. The inclusion criteria were unilateral or bilateral PFP without history of any prior acute trauma to the lower extremity, and a history of an insidious onset of activity related pain for one to six months during two or more of the following activities: exercise/athletics, prolonged sitting for greater than one hour, ascending/descending stairs, squatting or kneeling. The diagnosis of idiopathic patellofemoral pain was confirmed by a fellowship trained, board certified, pediatric sports medicine physician. In subjects with bilateral pain, both legs were tested. A total of 10 symptomatic legs (three subjects were affected by bilateral PFP and four subjects were affected by unilateral PFP) were included in the symptomatic group.

Based on the demographics of each subject in the symptomatic group, seven young females without any history of knee pathology and/or knee pain were individually recruited to serve as the reference group. For analysis, the reference subjects were matched to the symptomatic subjects on the basis of age (difference <seven months). For matching purposes, a total of 10 limbs were included in the reference group. Table 1 lists the descriptive characteristics of all subjects. The study was approved by the Colorado Multi-Institutional Review Board.

All subjects and parents reviewed and signed an informed consent form before participating in any study related procedures.

Study Procedures Symptomatic subjects reported to one of two sports medicine trained physical therapists (Sport Certified Specialists) for a comprehensive physical examination. During this visit, the symptomatic subjects were given an individualized exercise prescription and formal instruction on how to properly complete the home physical therapy program (Appendix 1).

Completion of the physical therapy intervention consisted of progression from open kinetic chain exercises (3-4 times per week), to closed kinetic chain exercises (3-4 times per week), to functional exercises that emphasized dynamic hip and core movement patterns (3-4 times per week). All home based exercises were selected based on functional anatomy of muscle actions as well as their previous utilization in related research.14,15 The parameters of intensity and duration were derived from basic exercise physi-

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Table 1. Characteristics of the participants Symptomatic Group

Reference Group

P value

14.20 ± 0.75

14.12 ± 0.86

0.6543

Tegner Activity Level

6.43 ± 2.99

7.43 ± 1.51

0.2753

BMI (kg/m2)

17.40 ± 2.87

18.40 ± 3.21

0.8024

Age (yrs)

ology principles with parameters for strengthening and neuromuscular adaptation.16 The repetitions/ hold time, sets and frequency were individually prescribed for each patient by the PT. Progression was assessed and adjusted during a weekly physical therapy visit. The foundation of the intervention was adapted from a hip and core strengthening intervention initially described by Mascal and Powers.15 Symptom severity and knee function were assessed with the Anterior Knee Pain Symptom Scale (AKPS), Visual Analogue Scale for Worst (VAS-W) and Visual Analogue Scale for Usual pain over the past week (VAS-U)17-19 at the time of their pre-testing assessment. Within two weeks of this assessment, subjects reported to our laboratory and performed a SLS on two Bertec strain gage force platforms (Model 406010). Subjects started the squat maneuver in a closed chain position with one foot on each force platform.

Subjects were instructed to stand on one foot with arms in a self-selected position and at a self-selected tempo, squat down without losing balance to a comfortable degree of knee flexion, and then return to an upright position. During this task, the torso position was to remain vertical without forward trunk flexion, the foot was to remain flat on the force platform or as close to flat as possible, and subjects were not allowed to support themselves on any stationary fixture. All subjects were given a chance to practice this maneuver five times before data were collected during five complete repetitions. Due to concerns regarding pain intensity, subjects were only required to squat to tolerance. One complete repetition was defined as max knee extension to max knee extension. All trials in which a subject lost balance and subsequently put both feet down were excluded from the analysis.

The single limb squat task was selected because it simulates a common athletic position6 and because the increased knee flexion angles achieved during the task simulate movement patterns (stair ascent/descent) known to exacerbate knee pain symptoms. Proper

execution of the task requires adequate lower extremity strength and neuromuscular control. Each individual subject’s pattern of CoP displacement during the SLS represents their ability to maintain balance during a challenging, functional movement pattern.12,13 Prior to testing, 14 mm diameter retroreflective markers were placed on lower extremity bony landmarks, identified by palpation by one physical therapist with greater than five years of experience in a clinical movement analysis laboratory. The maker set was a modified version of the Helen Hayes marker set that includes the ten lower extremity markers described by Kadaba et al 20 in addition to markers (medial femoral condyle and medial malleolus) that were utilized during the static calibration trial only.

Marker trajectory data were recorded at 120 Hz using a thirteen camera Vicon MX motion capture system.

Analog data from the two Bertec force platforms were collected at a frequency of 1080Hz. Vicon Nexus™ was used to process all motion capture data and a conventional gait model (Vicon Plug-in-Gait™) was used to generate kinematics, kinetics and CoP, which were time normalized to the duration of the task. All kinetic measures were normalized to each subject’s body weight. Data were then imported into a custom Matlab (The MathWorks Inc., Natwick, MA, USA) program, which extracted peak knee flexion, peak power absorption, peak power generation, and Center of Pressure trajectory during the SLS. For all subjects, the same motion capture system, testing procedure and, software programs and processes were used during evaluation of symptomatic subjects, pre- and postintervention, and the reference group.

The CoP data were reduced according to the equations outlined by Prieto.21 In order to quantify the CoP movements during the task, the following four measures were used: Mean distance (MDIST): the average distance from the mean CoP; Root-meansquare distance (RDIST): the RMS distance from the mean CoP; Range (RANGE): the maximum distance

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between any two CoP locations; and 95% confidence interval circle area (AREA-CC): the area of a circle that contains approximately 95% of the distances from the mean CoP. All CoP measures were quantified using Matlab. For each of the CoP variables, the average value from the five trials was used for statistical analysis. Figure 1 shows a sample CoP trajectory from a single limb squat trial. The maximum knee flexion angle, maximum knee power absorption, and maximum knee power generation values achieved during each SLS trials were identified using a custom Matlab program. For each variable, the average value from the five trials was used for statistical analysis.

STATISTICAL METHODS Paired, two-tailed, t-tests were used to compare demographics in the two groups as well as changes in VAS-U, VAS-W, and AKPS scores following the physical therapy intervention. A generalized linear regression analysis was used to compare within group (symptomatic group pre- vs. post-intervention) and between group (symptomatic group pre-intervention vs. reference group and symptomatic group post-intervention vs. reference group) differences in CoP measures, knee flexion angles, and knee power.

When evaluating within group changes, the unstruc-

tured covariance structure was used to account for correlation due to repeated measures (pre- and postintervention time points). Random intercept models were used to account for the correlation due to the inclusion of multiple limbs from the same subject.

All statistical analyses were performed using SAS version 9.3 (SAS Institute Inc., Cary, NC, USA) RESULTS The clinical characteristics associated with the symptomatic and reference groups are listed in Table 1. There was no difference (p>0.05) in age, activity level or BMI between the two groups. After the nine week hip-strengthening intervention, there was a significant decrease in average Anterior Knee Pain Symptom Scale (AKPS), Visual Analogue Scale for Worst Pain (VAS-W) and Visual Analogue Scale for Usual Pain (VAS-U) over the past week (Table 2).

The clinical outcomes associated with the intervention (change in hip strength, hip kinematics and symptom severity) were not the focus of this study as they have been previously presented. 22 Although the reduction in symptom severity was not the focus of this manuscript, it has been reported to context for the CoP measurements.

Pre- vs. post-intervention changes in the symptomatic group Among subjects in the symptomatic group, there was a significant increase in the following CoP measures after the nine-week hip-strengthening intervention: AREA-CC (mean difference: 2012.88 mm2, 95% CI: 170.31 to 3855.45; p = 0.0347), MDIST (mean difference: 2.72 mm, 95% CI: 0.23 to 5.21; p = 0.0347), RDIST (mean difference: 3.31 mm, 95% CI: 0.67 to 5.96; p = 0.0182) and RANGE (mean difference: 12.62 mm, 95% CI: 5.37 to 19.87; p = 0.0026). There Table 2. Improvements in symptom severity following the intervention

Figure 1. Center of pressure tracing obtained from a symptomatic female subject pre and post intervention. The circles represent an estimate of the area that contains approximately 95% of the distances from the mean CoP.

Mean Difference

95% CI

P value

AKPS

13.86

8.82 to 21.89

0.0056

VAS-W

48.29

16.53 to 80.05

0.0098

VAS-U

52.14

42.12 to 62.17

<0.0001

AKPS = Anterior knee pain scale; VAS-W = visual analogue scale for worst pain over the past week; VAS-U = visual analogue scale for usual pain over the past week.

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was also a significant increase in peak knee flexion angle [mean difference: 8.04°, 95% CI: 4.25 to 11.84°, p = 0.0006], peak power generation [mean difference: 0.49 W/Kg), 95% CI: 0.21 to 0.78; p = 0.0025] and peak power absorption [mean difference: 0.49 W/Kg, 95% CI: 0.01to 0.96, p = 0.044].

Reference group vs. symptomatic group pre-intervention Prior to the intervention, peak power absorption, peak power generation and CoP range were significantly different between the symptomatic and reference groups. Peak power absorption during the single limb squat was an average of 0.92 W/Kg (95% CI: 0.45 to 1.38 W/Kg; p = 0.0029) higher in the reference group. Peak power generation was an average of 0.87 W/Kg (95% CI: 0.32 to 1.41 W/Kg, p = 0.0081) higher in the reference group. CoP range was higher in the reference group than the symptomatic group by an average of 7.73 mm (95% CI: 0.47 to 14.99, p = 0.0403). There was no significant difference in AREA-CC (p =0.4162), MDIST (p=0.1359), RDIST (p = 0.1066), or peak knee flexion angle (p = 0.8114).

Reference group vs. symptomatic group post-intervention After the physical therapy intervention, there was no significant difference in peak power absorption (p =0.1019]) peak power generation (p =0.3324) or CoP range (p = 0.3708) between groups. Similarly, there was no significant difference between groups with respect to AREA-CC (p =0.4057), MDIST (p = 0.4668), RDIST (p = 0.4967) or peak knee flexion angle (p = 0.2893). See Figures 2-3 for more information about the between and within group differences in peak knee flexion, peak knee power and the CoP measures.

DISCUSSION CoP displacement, represents the subject’s response to internal and external perturbations during a given task.13,23 Compared to CoP measures during static tasks, CoP measures during dynamic tasks are a better discriminator of injured versus un-injured populations.10,24 Therefore, the primary purpose of this study was to assess CoP displacement during a single limb squat (SLS) among subjects with idiopathic PFP before and after a hip and core strengthening inter-

vention Following the nine-week intervention, the symptomatic group self-reported a significant reduction in symptom severity. The subjects also demonstrated a significant increase in CoP area, range, mean distance and root mean square distance. Together, these results provide some evidence that increased postural stability may be representative of a positive clinical outcome following PFP interventions.

Prior to the physical therapy intervention, the symptomatic subjects demonstrated a lower COP range relative to the reference group. Following the intervention, there was no longer a significant difference in CoP range between groups (Figure 2). The trend towards decreased CoP displacement among symptomatic subjects prior to the intervention contradicts the CoP measures reported by Lee et al24 in a case control study of subjects with and without PFP. In their study, subjects with PFP demonstrated significantly increased peak and mean medial-lateral CoP displacements during a single limb step-down task compared to the reference group. However, Lee et al24 used a metronome to control the cadence of the single limb task used in their study. By imposing a temporal constraint, the task demands are likely to change and thus, CoP excursions reported in the present study may not be directly comparable to CoP measures observed by Lee et al.24 Paterno et al25 assessed the biomechanics of 56 athletes that underwent anterior cruciate ligament reconstruction. Within 12 months of the evaluation, 13 (23%) of the athletes suffered a repeat ACL tear. Postural stability (average degree of deflection on the overall stability score as measured by the Biodex stability system), transverse plane hip moment, coronal plane knee range of motion, and sagittal plane knee moment were all significantly related to re-injury risk in the multivariable model.

A deficit (increase) in unilateral postural sway during quiet standing was associated with increased likelihood of ACL re-injury (OR: 2.3, 95% CI: 1.1 to 4.7].

The results of the current study are consistent with a prospective study of a cohort of female soccer players.26 After controlling for other significant variables, Soderman et al26 demonstrated that a low postural sway was associated with a significantly greater risk for a lower extremity injury during the course of the soccer season. The design of the current study was unique in that CoP measures were evaluated before

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Figure 2. Comparison of Variables Derived from CoP Measures.*Significantly (p<0.05) different from post-intervention evaluation. **Significantly (P<0.05) different from post-intervention evaluation and reference group.

Figure 3. Comparison of Peak Knee Power and Peak Knee Flexion.*Significantly (p<0.05) different from post-intervention evaluation. **Significantly (P<0.05) different from post-intervention evaluation and reference group.

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and after a hip strengthening intervention. Following the nine-week intervention, dramatic improvements in the symptom severity were achieved according the VAS-W, VAS-U and AKPS. Symptomatic relief was accompanied by a significant increase in CoP area, range, mean distance and root mean square distance.

Increased CoP displacement following the intervention may be due to increased joint proprioception, due to an emphasis on hip and core strengthening during the intervention, and/or greater torque production at the hip joint. Along with improvements in stability, the subjects appeared to challenge themselves to a greater degree after the intervention. This was evidenced by an increase in peak knee flexion, peak knee power and peak knee absorption during the SLS. It is unclear, however, whether the changes in performance are due to improvements in neuromuscular control and strength or are due to the absence of pain during the task. Future research is needed to determine whether measures of CoP displacement such as area, range, MDIST, and RDIST are predictive of the onset of PFP in previously asymptomatic populations.

The peak (or maximum) knee flexion angle achieved during SLS is one of the measures used to subjectively evaluate symptomatic patients. Due to the fact that subjects with PFP routinely report the presence of pain during activities that involve increased knee flexion angles, such as stair ascent/descent,3 the authors of this study believe it is fair to assume that pain will limit the amount of knee flexion that is achieved during this task. Peak knee flexion angle was significantly higher in in the reference group compared to the symptomatic subjects prior to the intervention suggesting that pain may have limited the magnitude of knee flexion observed among the symptomatic subjects. Following the physical therapy intervention, there were no significant differences in the knee flexion angles between the reference and symptomatic groups. This suggests that the symptomatic subjects may have returned to a more normal peak knee flexion angle after the intervention. Peak power generation and peak power absorption, on the other hand, were significantly higher in the reference group prior to the intervention and were not significantly different after the intervention between the groups. As power is calculated from joint torque and angular velocity, this suggests that the PFP subjects after the intervention were completing the task

faster and/or with higher force. This supports the use of kinetic recordings to obtain metrics such as power and CoP displacement, rather than simply subjectively assessing knee joint angles.

There are several limitations to the study. Financial constraints limited the number of subjects the authors enrolled in this preliminary study. Comparisons of symptomatic and reference subjects were limited by the small sample size. Additionally, performance during single limb squat task was selfselected. Changes in postural stability following the intervention may have been related to the maximum knee flexion angle achieved during the task and/or changes in deceleration and acceleration during the downward and upward phases of the task, respectively. Future research should evaluate performance during a standardized version of the single limb squat test. Finally, individuals in the reference group were not re-tested and intervention was not randomized. It is not possible to assess causal relationship between hip therapy intervention, symptom severity, and increased postural stability. The possibility that changes in symptom severity and balance in the symptomatic group may have been due to greater familiarization with the task and/or the passing of time cannot be excluded based on this study alone.

CONCLUSION At the beginning of this study, subjects with PFP demonstrated significantly decreased CoP range, peak knee power absorption and peak knee power generation relative to an asymptomatic reference group.

Following a nine-week hip and core strengthening intervention, symptomatic improvements were accompanied by significant improvements in CoP excursions, peak knee power, and peak knee flexion angles. The results of the study suggest that changes in balance can be achieved in a population of subjects affected by PFP following a hip and core strengthening intervention. Furthermore, CoP measures may be an effective tool for assessing progression during a PT intervention designed to alleviate pain through improvements in lower extremity strength and neuromuscular control. Additional prospective cohort studies are needed to determine whether the CoP displacement measures used in this study during a single limb squat are also significantly predictive of the onset of PFP in previously asymptomatic populations.

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Patellofemoral kinematics during weight-bearing and non-weight-bearing knee extension in persons with lateral subluxation of the patella: a preliminary study. J Orthop Sports Phys Ther. 2003;33(11):677-685.

5. Souza RB, Powers CM. Differences in hip kinematics, muscle strength, and muscle activation between subjects with and without patellofemoral pain. J Orthop Sports Phys Ther. 2009;39(1):12-19.

6. Zeller BL, McCrory JL, Kibler WB, Uhl TL. Differences in kinematics and electromyographic activity between men and women during the single-legged squat. Am J Sports Med. 2003;31(3):449456.

7. Wallace DA, Salem GJ, Salinas R, Powers CM. Patellofemoral joint kinetics while squatting with and without an external load. J Orthop Sports Phys Ther. 2002;32(4):141-148.

8. Geldhof E, Cardon G, De Bourdeaudhuij I, et al.

Static and dynamic standing balance: test-retest reliability and reference values in 9 to 10 year old children. Eur J Pediatr. 2006;165(11):779-786.

9. Visser JE, Carpenter MG, van der Kooij H, Bloem BR. The clinical utility of posturography. Clin Neurophysiol. 2008;119(11):2424-2436.

10. Wikstrom EA, Tillman MD, Chmielewski TL, et al.

Dynamic postural stability deficits in subjects with self-reported ankle instability. Med Sci Sports Exerc.

2007;39(3):397-402.

11. Phillips N, van Deursen RW. Landing stability in anterior cruciate ligament deficient versus healthy individuals: a motor control approach. Phys Ther Sport. 2008;9(4):193-201.

12. Chaudhry H, Bukiet B, Ji Z, Findley T. Measurement of balance in computer posturography: Comparison of methods--A brief review. J Bodyw Mov Ther.

2011;15(1):82-91.

13. Pollock AS, Durward BR, Rowe PJ, Paul JP. What is balance? Clin Rehabil. 2000;14(4):402-406.

14. Kendall FP. Muscles: testing and function with posture and pain. Baltimore, MD [etc.]: Lippincott Williams & Wilkins; 2010.

15. Mascal CL, Landel R, Powers C. Management of patellofemoral pain targeting hip, pelvis, and trunk muscle function: 2 case reports. J Orthop Sports Phys Ther. 2003;33(11):647-660.

16. Brooks GA, Fahey TD, Baldwin KM. Exercise physiology : human bioenergetics and its applications.

Boston: McGraw-Hill; 2005.

17. Bennell K, Bartam S, Crossley K, Green S. Outcome measures in patellofemoral pain syndrome: test retest reliability and inter-relationships. Phys Ther Sport. 2000;1(2):32-41.

18. Crossley KM, Bennell KL, Cowan SM, Green S. Analysis of outcome measures for persons with patellofemoral pain: which are reliable and valid?

Arch Phys Med Rehabil. 2004;85(5):815-822.

19. Kujala UM, Jaakkola LH, Koskinen SK, et al. Scoring of patellofemoral disorders. Arthroscopy.

1993;9(2):159-163.

20. Kadaba MP, Ramakrishnan HK, Wootten ME. Measurement of lower extremity kinematics during level walking. J Orthop Res. 1990;8(3):383-392.

21. Prieto TE, Myklebust JB, Hoffmann RG, et al.

Measures of postural steadiness: differences between healthy young and elderly adults. IEEE Trans Biomed Eng. 1996;43(9):956-966.

22. Provance A, Carry PM, Kanai S, et al. Results of a Hip Strengthening Intervention Among Adolescent Females with Idiopathic Patellofemoral Pain.

American Medical Society for Sports Medicine; April 20-25, 2012, 2012; Atlanta, GA. 23. Karst GM, Venema DM, Roehrs TG, Tyler AE. Center of pressure measures during standing tasks in minimally impaired persons with multiple sclerosis.

J Neurol Phys Ther. 2005;29(4):170-180.

24. Lee SP, Souza RB, Powers CM. The influence of hip abductor muscle performance on dynamic postural stability in females with patellofemoral pain. Gait Posture. 2012;36(3):425-429.

25. Paterno MV, Schmitt LC, Ford KR, et al.

Biomechanical measures during landing and postural stability predict second anterior cruciate ligament injury after anterior cruciate ligament reconstruction and return to sport. Am J Sports Med. 2010;38(10):1968-1978.

26. Soderman K, Alfredson H, Pietila T, Werner S. Risk factors for leg injuries in female soccer players: a prospective investigation during one out-door season. Knee Surg Sports Traumatol Arthrosc.

2001;9(5):313-321.

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Appendix 1. Individualized exercise prescription and progression by phases

PHASE I: weeks 1 to 3

Exercise

Description

Side Lying Abduction Leg Raise

1. Lie on your side and straighten both hips and knees 2. Slowly raise your upper leg towards the ceiling (be sure to keep your leg in line with your body as you raise it towards the ceiling) 3. Return to the starting position

Side Lying Hip Abduction and External Rotation (Clamshell)

1. Lie on your side and bend your hips and knees 2. Slowly raise your upper leg towards the ceiling, rotating your knee outward (external rotation) as you raise your leg 3. Return to the starting position

Prone Hip Extension with Bent Knee

1. Lie on your stomach with one knee bent and one knee straight 2. Keeping your knee bent, lift your leg up and foot up towards the ceiling 3. Hold this position without lifting your pelvis or rotating your leg 4. Return to the starting position

Single Leg Stand Wall Isometric

1. Stand with your side next to a wall (parallel to the wall) 2. Lift the leg closest the wall so that your thigh is parallel with the ground and your knee is bent to 90 degrees 3. Keeping your body still, push against the wall with the outside of your bent knee 4. Continue to push your knee against the wall for 10 seconds

Phase II: Weeks 4-6

1. Kneel on your hands and knees Quadriped Hip 2. Keeping your knee bent, rotate your leg towards Abduction/External the ceiling Rotation into 3. Slowly straighten your knee and hip Abduction 4. Slowly return to the starting position

Band Resisted Lateral Walk

1. Stand with a resistive band around both ankles 2. Slightly bend both knees 3. Walk/shuffle sideways while you keep your hips, feet, and knees pointed forward.

Band Resisted Backward Diagonal Walk

1. Stand with a resistive band around both ankles 2. Slightly bend both knees 3. Keeping your knees pointed straight ahead, walk backward by taking turns moving each foot in a diagonal, backwards direction 1. Stand on one leg with your knee slightly bent 2. Maintaining your balance, bend forward at your hip 3. Reach your hand towards the floor in the directions outlined below 4. Repeat for each of the arrows below 5. Return to the starting position

Excursions

Bridge with Alternate Knee Extension

1

2

3

1. Lie on your back with your hips and knees bent 2. Tense your abdominal muscles and lift your trunk upward so that your trunk, torso and thighs are in line 3. Hold this position and straighten one knee until it is fully extended 4. Return your foot to the mat/floor and then lower your trunk to the mat/floor

Reps/Sets Repeat ___ times per limb Perform ___ sets per session

Repeat ___ times per limb Perform ___ sets per session

Repeat ___ times per limb Perform ___ sets per session

Repeat ___ times per limb Perform ___ sets per session

Repeat ___ times per limb Perform ___ sets per session

Repeat ___ times Perform ___ sets per session

Repeat ___ times Perform ___ sets per session

Repeat ___ times per limb Perform ___ sets per session

Repeat ___ times per limb

Perform ___ sets per session

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Appendix 1. Individualized exercise prescription and progression by phases (continued)

Phase III: weeks 7-9

Phase II: Weeks 4-6

Exercise

Description

1. Secure one end of a resistance band to table or railing Anterior 2. Loop the other end around one ankle and move forward until the band is taught.

Diagonal Hip Strengthening 3. Keeping knee straight, push your foot forward and inward towards your other foot 4. Pause and return to the starting position

Posterior Diagonal Hip Strengthening

1. Secure one end of a resistance band to a table or railing 2. Loop the other end around one ankle and move backwards until the band is taught.

3. Keeping knee straight, pull your foot backwards and away from your other leg 4. Pause and return to the starting position

Squat with Band Resisted Hip Rotation and Abduction

1. Stand with a resistance band around your thighs, above your knees 2. Squat down as if you are sitting back into a chair.

3. As you are squatting down, push your thighs outwards against the resistance band

Static Lunge with Band Resistance

1. Stand with one foot in front of the other in a lunge position 2. Secure a resistance band around the thigh of your front leg, just above your knee so that the band slightly pulls your thigh towards your midline 3. Bend both knees, dipping your body downwards towards the floor 4. Keep your front knee centered over the ball of your foot and do not allow your front knee to move towards your midline

Squat Jumps

1. Stand with your feet shoulder width apart 2. Squat down as if you are sitting in a chair 3. Jump straight up from the squat position 4. During landing, bend your knees and hips back into the squat position

Bridge with Alternate Knee Extension

1. Lie on your back with your hips and knees bent 2. Tense your abdominal muscles and lift your trunk upward so that trunk, torso, and thighs are in line 3. Hold this position and straighten one knee until it is fully extended.

4. Return your foot to the mat/floor and then lower your trunk to the mat/floor

Split Squats

1. Stand in a lunge position with one foot in front of the other 2. Place the toe of your back foot on a step/stool/chair that it is at least 18 inches tall 3. Bend both knees, dipping your body downwards towards the floor 4. Keep your front knee centered over the ball of your foot and try to minimize side-to-side movements of your knee

Reps/Sets Repeat ___ times per limb

Perform ___ sets per session

Repeat ___ times per limb Perform ___ sets per session

Repeat ___ times per limb

Perform ___ sets per session

Repeat ___ times per limb Perform ___ sets per session

Repeat ___ times per limb Perform ___ sets per session

Repeat ___ times per limb Perform ___ sets per session

Repeat ___ times per limb Perform ___ sets per session

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IJSPT

ORIGINAL RESEARCH

KINEMATIC AND KINETIC VARIABLES DIFFER BETWEEN KETTLEBELL SWING STYLES Garrett S. Bullock1 Abigail C. Schmitt, MS2 Jason M. Shutt, DPT3 Gray Cook, MSPT4 Robert J. Butler PhD, DPT3

ABSTRACT Background: Kettlebell (KB) and indian club swings (ICS) are used diversely for developing strength and power. It has been proposed that multiple swing techniques can be used interchangeably to elicit similar adaptations within performance training.

Hypothesis/Purpose: It was hypothesized that there will be not be a difference in peak joint angles between types of swings. Furthermore, given the nature of the overhead kettlebell swing (OKS), it was hypothesized that the OKS will be associated with a greater cycle time and a greater vertical impulse compared to shoulder height swing (SKS) and ICS. The purpose of this study was to analyze the kinematics and kinetics of the SKS, OKS, and ICS. Study Design: Cross-sectional cohort Methods: Fifteen healthy subjects underwent 3D biomechanical analysis for assessment of kinematic and kinetic data. Subjects performed two trials of ten repetitions at full effort for each swing in a randomized order using either a standard set of 0.45 kg indian clubs or sex specific KB loads (Female = 12kg, Male = 20kg). Lower extremity sagittal plane kinematics and kinetics were analyzed for peak values during the down and up portions of the swing patterns.

Statistical analyses were carried out utilizing one-way ANOVAs (p<.05) and effect size indices.

Results: Cycle time for the OKS was 34% longer than the SKS and ICS (p<.001; ESISKS= 2.09, ESIICS=1.92). In general, ankle (SKS: 0.82±0.16; OKS: 0.90±0.21; ICS: 0.60±0.15 BW*BH) and hip joint moments (SKS: 2.34±0.68; OKS: 2.32±0.53; ICS: 1.84±0.47 BW*BH) and joint powers, along with peak vertical ground reaction forces (vGRF) (SKS: 0.98±0.14; OKS: 0.96±0.10; ICS: 0.86±0.11 BW/s), were higher in the SKS and OKS than the ICS (p<.001; ankle: ESISKS/OKS=0.43, ESISKS/ICS=1.42; hip: ESISKS/OKS=0.03, ESISKS/ICS=0.87; vGRF: ESISKS/OKS=1.80, ESISKS/ICS=0.20). There were no observed differences found in peak joint angles between the movements.

Conclusion: Although these swings are kinematically similar, the differing kinetic demands of these exercises may be important in selecting the right training modality for specific strength and power training.

Level of Evidence: 2 Keywords: Kettlebell training, power, resistance training, strength

1

Duke University, Durham, NC, USA University of Florida, Gainesville, FL, USA 3 Saint Louis Cardinals Baseball Organization, Saint Louis, MO, USA 4 Mountain River Physical Therapy, Chatham, VA, USA. 2

CORRESPONDING AUTHOR Garrett Bullock SPT Duke University Doctor of Physical Therapy Program DUMC 104002 Durham, NC 27708 Phone: (919) 681-4380 Fax: (919) 684-1846 E-mail: garrett.bullock@duke.edu

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INTRODUCTION Strength and power are essential for athletic performance.1-6 Athletic tasks such as jumping require a high force production rate to enhance accomplishments.7 Allen et al.8 observed that that increasing strength improved triple jump performance. Marian et al.9 concluded that eight weeks of power squat jump training increased maximal strength, vertical jump and sprint performance in recreational athletes. As a result, implementing strength and power training to enhance athletic development is ideal to augment athletic capabilities.4 Traditional strength and power training involves a large amount of space and equipment, requiring budgets up to 60,000 dollars per year.6 Many training facilities, however, only have modest space and resources6,10 with the average high school strength and conditioning facility having an average of 9.1 square feet per athlete.10 Furthermore, lower school enrollment has a direct correlation to budgetary concerns.6 Alternative training approaches may optimize space and financial limitations for strength and conditioning training.5,10,11 In response, performance specialists have focused on strength and power training requiring minimal equipment.12 In recent years, alternative training approaches to strength and power development have gained popularity; particularly the use of kettlebells (KB) and indian clubs.12 The design of the KB and indian club permits the center of mass to extend beyond the hand.3 As a result, this implement design is conducive for whole body ballistic movements; that are similar to the clean, snatch and jerk in traditional weightlifting.3 KB swings have been shown to help facilitate gains in strength, power and endurance.2,3,5,11,13 Lake and Lauder2 examined the effects of six weeks of KB or jump squat training on strength and power development. Both KB training and squat jump training were found to provide an increase of 9.8% and 19.8% in strength and power respectively, with no statistically significant differences between cohorts.2 In another study by Manocchia and colleagues3 investigating the transferability of KB training to other weightlifting exercises, a 10-week KB training cycle was shown to improve bench press by 14.2 kg and clean and jerk performance by 4.2 kg. These studies suggest the utility and transferability of KB training

for the development of strength and power as compared to other more traditional methods.2,4,14 A common KB exercise is the shoulder height swing (SKS) (Figure 1: A, B).1,2,14-16 Previous authors 14,15,17 have investigated the kinematics and kinetics of the SKS. Kim et al.17 observed that beginners demonstrated greater range of motion in the shoulders and different angular joint velocities compared to KB experts. McGill et al.14 concluded that the SKS exhibited loads to the lumbar spine that are in the opposite direction compared to the traditional deadlift. From the basic foundational principles of the SKS technique, the exercise can transform into various progressions. Two swing progressions that, to the authorsâ&#x20AC;&#x2122; knowledge, have not been investigated within the literature are the overhead KB swing (OKS)18 and the indian club swing (ICS).19 The OKS is a KB swing with the KB momentum ceasing at full shoulder flexion, and elbow extension (Figure 1 C, D).18 The ICS consists of two lightweight clubs, one held in each hand, positioned with the upper extremities in 90 degrees of shoulder abduction and elbow flexion, followed by upper limb horizontal adduction while initiating a hip hinge pattern (Figure 1: E, F).19 Previous research has assessed the transferability of KBS and ICS for the development of strength and power;20 however, there is little information in the literature regarding the different mechanical demands between the SKS, OKS and ICS. In order to develop a better understanding of the different KB and IC training, this study examined the varying kinematic and kinetic demands of the different KB and IC swings. The purpose of this study was to analyze the kinematics and kinetics of the SKS, OKS, and ICS. Due to the parameters of the swings, it was hypothesized that no differences in peak joint kinematics would be found, (angles and velocities) which would suggest the swings are functionally similar. Furthermore, given the nature of the OKS, we hypothesize the OKS will be associated with a greater cycle time and a greater vertical impulse compared to SKS and ICS. METHODS To describe the mechanical demands of the SKS, OKS and ICS, 3D motion capture during a randomized exercise allocation was utilized.

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Figure 1. Visual representation of the shoulder height kettlebell swing, (SKS: A, B) overhead kettlebell swing, (OKS: C, D) and indian club swing (ICS: E, F) during the down and up phases, respectively.

Subjects Fifteen healthy recreational athletes, consisting of nine males and six females (n=15; age, 26.7 ± 4.3 years; height, 1.76 ± 0.09 m; mass, 77.6 ± 13.5 kg) volunteered for this study. A convenience sample was employed to recruit subjects from the local university community. Inclusion criteria included that subjects reported no pain during the exercises, were free from injury in the prior six months and had at least six months of past experience with KB or indian club training. Exclusion criteria consisted of participants reporting pain currently or in the prior three months, an injury in the prior six months that limited participation in athletic activities, any surgery in the last 12 months, and those who had not received past KB or indian club instruction. All subjects were informed of the risks and benefits of the testing and written consent was obtained. The Duke University Health System Institutional Review Board approved this study. All data were collected and analyzed at the Michael W. Krzyzewski Human Performance Laboratory.

Kettlebell swing analysis Participants were asked to wear spandex shorts and shirt and were given 10 minutes for instruction and

warm-up prior to data collection. Participants were fitted with a modified Helen-Hayes marker set with a total of 48 retro-reflective markers placed on various anatomic landmarks (Figure 2). Three-dimensional marker coordinate data were captured using an eight camera motion capture system sampling at 120 Hz (Motion Analysis Corporation; Santa Rosa, CA), while embedded force plates (AMTI, Watertown, MA) sampling at 1200 Hz were used to collect tri-axial ground reaction forces. The retro-reflective markers were placed by the same investigator for each participant to limit interrater variability between data collections.

Before each movement, a single test administrator demonstrated each swing exercise and gave standardized minimal verbal cues. For all exercises, universal instruction consisted of instructing the patient to give full effort. SKS directions entailed swinging the KB to shoulder height. OKS directions were swinging the KB to the full overhead position, and ICS coaching focused on pulling the clubs behind the body.18, 19 Full overhead position during the OKS was self determined by each subject due to each subjects past KB experience. The ICS consisted of the athlete forcefully adducting the shoulders and

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kinetics were analyzed during the down and up portion of the swing patterns.

Figure 2. Biomechanical Dynamic Marker Set

extending the elbows bilaterally, while concurrently initiating hip flexion and slight knee flexion. At this bottom position, the spine was held in neutral. The swing was reversed with the initiation of hip extension and bilateral shoulder abduction. The swing was completed when the indian clubs were back to the original 90 degrees of shoulder abduction and the hips were slightly flexed. After each exercise trial, a volitionally determined rest break was given to each patient to minimize fatigue and preserve external validity to further mimic a training or rehabilitation setting. The medial instep of each foot was aligned vertically to the axilla to standardize stance width.18 Subjects performed two trials of 10 repetitions, at full effort for each swing type. To account for variations in trial initiation and completion, only the middle eight swings were used for analysis. Each subject used a standard set of 0.45 kg indian clubs and sex specific KBâ&#x20AC;&#x2122;s (Female = 12 kg, Male = 20 kg). The sex specific KB masses were originally described by Pavel Tsatsouline in the Kettlebell Strong First Certification. Data were collected while subjects performed swing patterns with each foot on a separate force plate. Lower extremity sagittal plane kinematics and

Data Analysis Coordinate data were filtered using a fourth-order low-pass Butterworth filter at 7Hz, and the ground reaction force data were filtered at 100Hz. Kinematic and kinetic data were calculated using Visual 3D (C-Motion, Bethesda, Maryland, USA). Joint angles were calculated as Cardan angles between segments with an order of sagittal plane, followed by frontal plane, and then transverse plane. Inverse dynamics were used to calculate joint moments, expressed as internal moments and normalized to mass and height. Ground reaction forces were normalized to and expressed as a percentage of body mass. The total cycle time for each swing was calculated from the peak of the vertical displacement of the motion to the subsequent vertical peak and averaged across swing type. To account for individual differences in timing of the swing cycle, each swing was normalized to the cycle time for analysis. Each variable of interest was extracted from these individual swings and averaged across swings and trials. Data were averaged between right and left limbs to account for slight variations in technique across participants.

The six kinematic variables of interest included peak hip flexion, peak knee flexion, peak dorsiflexion, as well as the peak joint angular velocities at the hip, knee, and ankle (Table 1). The kinetic variables of interest included peak hip extension moment, peak knee extension moment, peak plantarflexion moment, peak hip extension power, peak knee extension power, peak ankle plantarflexion power, the peak vertical ground reaction force (vGRF), and vertical impulse before and after peak vGRF (Table 2). These dependent variables were calculated and extracted using custom software developed in Matlab R2010a (MathWorks Inc., Natick, MA).

Statistical Analysis Statistical analyses were carried out using a series of one-way repeated-measures ANOVAs to assess differences between the SKS, OKS, and ICS. To account for increased Type I error from multiple comparisons, a conservative alpha was used (Îą= .01). A Bonferroni adjustment considering the 15 total comparisons would result in a p< .003, which would

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Table 1. Mean ± standard deviation, ANOVA and effect size index results for cycle time and kinematic variables of interest for each condition.

Variable Peak ankle dorsiflexion (deg) Peak knee flexion (deg) Peak hip flexion (deg) Peak ankle plantarflexion velocity (deg/s) Peak knee extension velocity (deg/s) Peak hip extension velocity (deg/s) Cycle Time (s)

Shoulder height kettlebell swing (SKS)

Overhead kettlebell swing (OKS)

Indian club swing (ICS)

p-value

ESISKS/OKS

ESISKS/ICS

ESIOKS/ICS

11.3 ± 6.4

10.5 ± 6.5

9.7 ± 6.3

.385

0.12

0.25

0.13

60.8 ± 16.4

61.8 ± 16.2

62.2 ± 19.8

.787

0.06

0.08

0.02

69.8 ± 9.3

69.7 ± 10.4

73.7 ± 12.8

.081

0.01

0.35

0.34

89.4 ± 32.8 *

72.2 ± 29.7 *

64.3 ± 33.9 *

.005

0.55

0.75

0.25

257.3 ± 41.4 †

207.1 ± 49.0

252.1 ± 53.2 †

.003

1.11

0.11

0.88

303.4 ± 66.2

270.5 ± 60.3

315.7 ± 70.1

.068

0.52

0.18

0.69

1.45 ± 0.16 †

1.92 ± 0.29

1.44 ± 0.21†

< .001

2.09

0.05

1.92

Notes. p < .05 considered significant. † significantly different than OKS * all swings significantly different

increase the probability of a Type II error. Tukey’s HSD post-hoc analysis was used to identify significant pairwise comparisons. Effect size indices (ESIs) were calculated in order to understand the clinical relevance that was not due to sample size. Statistical analyses were completed using SPSS 21 (SPSS Inc, IBM, Chicago, Illinois).

RESULTS No significant differences were observed for peak ankle or knee angles across swing types. While no significant difference was observed in peak hip flexion angles, there was a small effect between SKS and ICS (ESI=0.35) and OKS and ICS (ESI=0.35). A small effect was exhibited in peak ankle plantarflexion velocity during the SKS compared to the OKS (ESI=0.55), although this was not statistically significant. However, peak plantarflexion SKS velocity was greater than the ICS (p= .005; ESI=0.75). Knee extension velocity was greater for the SKS compared to OKS (p=.003; ESI=1.11) and OKS related to ICS (p=.003; ESI=0.88). No differences were found between swing types for hip extension velocity; nevertheless there was a moderate effect between SKS and OKS (ESI=0.52) and OKS and ICS (ESI=0.69).

Cycle time for the SKS was significantly shorter than the OKS (p<.001: ESI=2.09), while equal to the ICS

(ESI=0.05). The OKS cycle time was also greater than the ICS (p<.001; ESI=1.92) (Table 1).

The vertical impulse before the peak vGRF, during the down portion of the swing, was smaller in the SKS compared to the OKS (p<.001; ESI=1.80), which was greater than the ICS (p<.001; ESI=1.23). The SKS and ICS vertical impulse prior to the peak vGRF were comparable (ESI=0.20). The vertical impulse after peak vGRF was less in the SKS in relation to the OKS (p<.001; ESI=1.14). The ICS displayed the least impulse after peak vGRF (p< .001; ESISKS=2.00; ESIOKS=3.00). Unsurprisingly, the peak vGRF was greater in both the SKS and OKS (ESI=.17) when compared to the ICS (p< .001; ESISKS=0.96; ESIOKS=0.95).

Peak ankle plantarflexion moments were similar between the SKS and OKS; but displayed a moderate effect (ESI=0.43). The SKS and OKS were both significantly greater than the ICS (p< .001; ESISKS=1.42; ESIOKS=1.67). No significant differences were displayed in knee extension moment. Peak hip extension moment was similar between the SKS and OKS (ESI=0.03), which were both larger than the ICS (p< .001; ESISKS=0.87; ESIOKS=0.96). Similarly, peak ankle plantarflexion power was greater in the SKS and OKS (ESI=0.15) compared to the ICS (p= .001; ESISKS=2.82; ESIOKS=2.32). No significant difference

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Table 2. Mean ± standard deviation, ANOVA and effect size index results for kinetic variables of interest for each condition.

Variable

Vertical Impulse prior to peak vGRF (BW*s) Vertical Impulse after peak vGRF (BW*s) Peak vertical ground reaction force (BW) Peak ankle plantarflexion moment (BW*BH) Peak knee extension moment (BW*BH) Peak hip extension moment (BW*BH) Peak ankle plantarflexion power (BW*BH) Peak knee extension power (BW*BH) Peak hip extension power (BW*BH)

Shoulder height kettlebell swing (SKS)

Overhead kettlebell swing (OKS)

Indian club swing (ICS)

p-value

ESISKS/OKS

ESISKS/ICS

ESIOKS/ICS

0.43 ± 0.07 ¥

0.61 ± 0.13 ¥

0.45 ± 0.13

< .001

1.80

0.2

1.23

0.45 ± 0.09 *

0.57 ± 0.12 *

0.30 ± 0.06 *

< .001

1.14

2.00

3.00

0.98 ± 0.14 ¥

0.96 ± 0.10 ¥

0.86 ± 0.11

< .001

0.17

0.96

0.95

0.82 ± 0.16 ¥

0.90 ± 0.21 ¥

0.60 ± 0.15

< .001

0.43

1.42

1.67

0.50 ± 0.36

0.47 ± 0.31

0.50 ± 0.37

.812

0.09

0.00

0.09

2.34 ± 0.68 ¥

2.32 ± 0.53 ¥

1.84 ± 0.47

< .001

0.03

0.87

0.96

0.71 ± 0.24 ¥

0.67 ± 0.28 ¥

0.23 ± 0.10

< .001

0.15

2.82

2.32

1.36 ± 0.83

0.98 ± 0.44

1.09 ± 0.70

.052

0.60

0.35

0.19

5.22 ± 2.18 ¥

5.40 ± 1.92 ¥

3.55 ± 1.39

< .001

0.09

0.94

1.12

Notes. p < .05 considered significant. BW = Body Weight, BH = Body Height ¥ significantly different than ICS; * all swings significantly different

was evident in peak knee extension power across the three swing types; however there was a moderate effect between the SKS and OKS (ESI=0.60) and SKS and ICS (ESI=0.35). Lastly, peak hip extension power was greater in the SKS and OKS (ESI=0.09) when compared to the ICS (p< .001; ESISKS=0.94; ESIOKS=1.12)(Table 2).

DISCUSSION Strength and power is essential for athletic performance.1,3-5,12 Developing strength and power through training methods that use minimal equipment is beneficial for space and budgetary demands.5,10,11 KB and indian club training are alternative methods in which to develop strength and power.12,19 As a result,

understanding the different mechanical demands of varying KB and indian club exercises is necessary to select the proper training modality for desired adaptations.14, 20 The purpose of this study was to analyze the mechanical demands imposed by SKS, OKS, and ICS. In support of the hypothesis, there were no differences in peak ankle or knee joint angles or hip extension velocity for the SKS, OKS or ICS. However, peak plantarflexion velocity was greater in the SKS compared to the OKS, which was greater than the ICS. The SKS had a superior knee extension velocity compared to the OKS, while the ICS had a similar knee extension velocity in relation to the SKS. The SKS displayed a decreased cycle time than the OKS, which was larger than the ICS. Contrary to the

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hypothesis, the SKS and ICS displayed a bigger vertical impulse prior to peak vGRF in contrast to the OKS. However, in support of the hypothesis, the SKS and ICS had a decreased vertical impulse after peak vGRF in relation to OKS. Consistent with the hypothesis, there were no significant differences in peak joint angles between any of the various swing types. This suggests the swings are mechanically similar and, given the similarities in the lowest positions, move through a comparable lower extremity range of motion. While not statistically significant, when variance was normalized, a moderate difference was observed in peak hip flexion between the KB swings (SKS and OKS) and ICS. While there are no studies to the authorsâ&#x20AC;&#x2122; knowledge investigating ICS, the greater peak hip flexion may be due the specific techniques employed for the SKS, OKS and ICS.16,18,19 As previously described, the KB used in the SKS and OKS must pass between the knees to the bottom position.16 This is in contrast to the ICS, in which the indian clubs project in a lateral downward path.19 From this trajectory, the hips may require increased range of motion, in order to allow the indian clubs to effectively pass the without striking the body, compared to the KB swings. The SKS displayed similar peak plantarflexion velocity compared to the OKS, which were both greater than the ICS. The SKS was associated with greater peak knee extension velocity than the OKS, which had a lesser peak knee extension velocity in comparison to the ICS. The SKS and ICS had similar peak knee extension velocities. All three-swing variations displayed similar peak hip extension velocity. Future research is necessary in order to understand how different techniques employed by the KB and indian clubs can affect kinematics at both the trunk and upper extremity.

Supporting the hypothesis, the SKS presented with a 34% lesser cycle time compared to the OKS, which was greater than the ICS. While no studies to the authorsâ&#x20AC;&#x2122; knowledge have examined the OKS, two previous studies14,20 have investigated the mechanical workload of a similar exercise, the KB snatch.

The KB snatch is a unilateral KB swing, terminating in full shoulder flexion and elbow extension.13,20 While both the OKS and KB snatch end in an overhead position, the KB snatch utilizes a single hand

swing in comparison to the OKS two handed swing.

Furthermore, the KB snatch integrates a more vertical trajectory to reach overhead, compared to the more curvilinear arc of the OKS.18,19 Lake and colleagues20 discerned that the KB snatch had greater vertical center of mass displacement (22 cm vs. 18 cm) compared to SKS. The bilateral OKS terminal position is similar to the unilateral KB snatch end point.18 With each swing beginning with a similar starting point, the OKS ending overhead caused a greater cycle time compared to the SKS and ICS.13-15,18 While this study did not investigate upper extremity and spine kinematics and kinetics during the OKS swing, future studies are needed to understand the role these body parts play due to the overhead requirements elicited during this KB swing pattern.

Unsurprisingly, the SKS exhibited less vertical impulse during the propulsion (up) phase when compared to the OKS, which was larger than and ICS, while the SKS and ICS displayed similar vertical impulse during the propulsion phase. Furthermore, the vertical impulse during the braking (down) phase of the SKS was less in relation to the OKS, while larger in contrast to the ICS. This is consistent with previous work14, 20 and may be attributed to the larger amount of additional mass associated with the kettlebells as compared to the indian clubs.

In order to progress back to the standard KB swing bottom position; a decreased downward vertical displacement, and thus time, is required for the SKS and ICS when compared to the OKS.14, 20 Previous authors21-23 have discussed the importance of impulse in regards to power production. Knudson22 has proposed that impulse establishes the degree and velocity of motion, and thus power is a nonoptimal factor. Schilling et al.21 demonstrated that an increase in impulse resulted in greater velocities and force within squatting. As a result, for a fixed mass, a larger force or a longer time period for a given force will result in greater velocity.21 As a result, the vGRF is being absorbed over a shorter cycle time during the SKS or ICS in order to bring the KB or indian clubs back to bottom position.14,18,20,24,25 This data suggests that while the SKS and OKS generate similar peak loads, the decreased SKS impulse created may be due to the shorter cycle time. The decreased cycle time observed in the SKS is associated with a

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smaller amount of time under tension, which may elicit lower internal joint and tissue loads than OKS during the swing-braking (down) phase, while simultaneously generating similar peak loads as the OKS.26 The peak vGRF was similar between the SKS and OKS; which were both greater than ICS (Table 1). These findings support previous work of Lake and colleagues,20 in which the KB snatch and the SKS displayed similar vertical propulsion mean force values of 271.89 N and 291.37 N respectively. The OKS requires greater overhead mobility in order to proceed to terminal position,18 while the SKS and ICS proceed only to shoulder height.2,19 The similar peak vGRF observed between the SKS and OKS, suggests these swings require similar lower extremity force outputs to reach overhead and shoulder heights.20 The SKS and OKS exhibited greater peak ankle plantarflexion moments and peak hip extension moments compared to the ICS. Similarly, the two KB swings (SKS and OKS) were associated with greater peak ankle plantarflexion and peak hip extension power production compared to the ICS. These findings are similar to those from Lake and Laudner’s study,20 in which different KB swing types had comparable power outputs. Since all three swings displayed similar lower extremity joint excursion and hip extension velocities, the main component discrepancy between the KB swings and ICS is due to the force needed to propel the dissimilar weighted instruments, as displayed with the SKS and OKS demonstrating greater peak vertical vGRF compared to the ICS. The indian clubs utilized within this study had a mass of 0.45 kg. This is in contrast to the 12 and 20 kg sex specific KB’s employed for the SKS and OKS respectively. Unsurprisingly, these mass differentials required subjects to utilize more force during the SKS and OKS, and thus more power from the hip and plantarflexors compared to the ICS. Future research is necessary in order to understand how different techniques employed by the KB and indian clubs can affect power and force production.

Limitations As with any investigation, there are limitations.

The primary flaws within this study are due to the pre-determined sex specific KB’s. Different subjects had varying strength and force production capacity,

beyond sex specificity. As a result, having standardized KB’s could create different mechanical outputs, depending on the strength and power abilities of each individual. Furthermore, the subjects in the study had dissimilar KB and indian club swinging experience. Additional investigation is necessary in order to understand the effect past KB and indian club training experience has on the proficiency of mechanical outputs.

CONCLUSION In conclusion, while the SKS, OKS and ICS had overall similar mechanical characteristics; there were specific differences within each exercise. Specifically, the SKS exhibited a shorter cycle time and less downward and upwards-vertical impulse compared to the OKS. Furthermore, the SKS and OKS displayed greater peak moments and power from ankle plantarflexion and hip extension and greater vGRF compared to the ICS. This is the first study to compare kinematics and kinetics of the standard shoulder height kettlebell swing to the overhead kettlebell swing and the indian club swing. Understanding the different mechanical demands of the SKS, OKS, and ICS can facilitate selecting an appropriate exercise for the desired strength and power training adaptation.

REFERENCES 1. Hulsey CR, Soto DT, Koch AJ, et al. Comparison of kettlebell swings and treadmill running at equivalent rating of perceived exertion values. J Strength Cond Res. 2012;26(5):1203-7.

2. Lake JP, Lauder MA. Kettlebell swing training improves maximal and explosive strength. J Strength Cond Res 2012; 26(8):2228-33.

3. Manocchia P, Spierer DK, Lufkin AK, et al.

Transference of kettlebell training to strength, power, and endurance. J Strength Cond Res. 2013;27(2):477-84.

4. McKewon I, Chapman DW, Taylor K, et al. Time course of improvements in power characteristics in elite development netball players entering a full time training program. J Strength Cond Res. 2016;30(5):1308-15.

5. Otto WH 3rd, Coburn JW, Brown LE, et al. Effects of weightlifting vs. kettlebell training on vertical jump, strength, and body composition. J Strength Cond Res 2012;26(5):1199-202.

6. Judge LW1, Petersen JC, Bellar DM, et al. The current state of NCAA Division I collegiate strength facilities:

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size, equipment, budget, staffing, and football status.

J Strength Cond Res. 2014;28(8):2253-61.

7. Hay JG. Citius, altius, longius (faster, higher longer): the biomechanics of jumping for distance. J Biomech.

1993:26;7-21.

8. Allen SJ, Yeadon MR, King MA. The effect of increasing strength and approach velocity on triple jump performance. J Biomech. 2016; Oct 19.

9. Marian V, Katarina L, David O, Matus K, Simon W. Improved maximum strength, vertical jump and sprint performance after 8 weeks of jump squat training with individualized loads. J Sports Sci Med. 2016;15(3):492-500.

10. Duehring MD, Ebben WP. Profile of high school strength and conditioning coaches. J Strength Cond Res. 2010;24(2):538-47.

11. Jay K, Jakobsen MD, Sundstrup E, et al. Effects of kettlebell training on postural coordination and jump performance: a randomized controlled trial. J Strength Cond Res. 2013; 27(5):1202-9.

12. Brumitt J, En Gilpin H, Brunette M, et al.

Incorporating kettlebells into a lower extremity sports rehabilitation program. N Am J Sports Phys Ther. 2010;5(4):257-65.

13. Falatic JA, Plato PA, Holder C, et al. Effects of Kettlebell Training on Aerobic Capacity. J Strength Cond Res. 2015;29(7):1943-7.

14. McGill SM, Marshall LW. Kettlebell swing, snatch, and bottoms-up carry: back and hip muscle activation, motion, and low back loads. J Strength Cond Res. 2012;26(1):16-27.

15. Lake JP, Lauder MA. Mechanical demands of kettlebell swing exercise. J Strength Cond Res. 2012; 26(12):3209-16, 2012 16. Luke E, James F, James S. A comparison of the effect of kettlebell swings and isolated lumbar extension

training upon acute torque production of the lumbar extensors. J Strength Cond Res. 2016; 30(5):1189-95.

17. Kim YK, Back CY, Joo JY, Park CH, Moon CW. Kinematic comparisons of kettlebell two arm swings between experts and beginners. ISBS-Conference Proceedings Archive. 2016. 34. 2.

18. Tsatsouline P. Enter the Kettlebell. St. Paul, MN: Dragon Door Publications, Inc., 2006.

19. Cook, G. Jones B, Thomas E. Club Swinging Essentials. Chatham, VA: Functional Movement Systems Inc., 2010.

20. Lake JP, Hetzler BS, Lauder MA. Magnitude and relative distribution of kettlebell snatch force-time characteristics. J Strength Cond Res 2014;28(11):3063-72.

21. Schilling BK, Falvo MJ, Chiu LZ. Force-velocity, impulse-momentum relationships: implications for efficacy of purposefully slow resistance traininig. J Sports Sci Med. 2008: &(2); 299-304.

22. Knudson DV. Correcting the use of the term “power” in the strength and conditioning literature. J Strength Cond Res. 2009:23;1902–1908.

23. Lake JP, Mundy PD, Comfort P. Power and impulse applied during the push press exercise. J Strength Cond Res. 2014:28(9):2552-9.

24. Bobbert, MF, Huijing, P, and van Ingen Schenau, GJ. Drop jump II. The influence of dropping height on the biomechanics of jumping. Med Sci Sports Exerc.. 1987;19: 339-346.

25. McNitt-Gray, JL. Kinematics and impulse characteristics of drop landings from three heights. Int J Sport Biomech. 1991;7: 201-224.

26. Mohamad NI, Cronin JB, Nosaka KK. Difference in kinematics and kinetics between high- and lowvelocity resistance loading equated by volume: implications for hypertrophy training. J Strength Cond Res. 2012;26(1):269-75.

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IJSPT

ORIGINAL RESEARCH

A DYNAMIC VALGUS INDEX THAT COMBINES HIP AND KNEE ANGLES: ASSESSMENT OF UTILITY IN FEMALES WITH PATELLOFEMORAL PAIN Sara A. Scholtes, PT, DPT, PhD1 Gretchen B. Salsich, PT, PhD1

ABSTRACT Background: Two-dimensional motion analysis of lower-extremity movement typically focuses on the knee frontal plane projection angle, which considers the position of the femur and the tibia. A measure that includes the pelvis may provide a more comprehensive and accurate indicator of lower-extremity movement.

Hypothesis/Purpose: The purpose of the study was to describe the utility of a two-dimensional dynamic valgus index (DVI) in females with patellofemoral pain. The hypothesis was that the DVI would be more reliable and valid than the knee frontal plane projection angle, be greater in females with patellofemoral pain during a single-limb squat than in females without patellofemoral pain, and decrease in females with patellofemoral pain following instruction.

Study Design: Controlled Laboratory Study Methods: Data were captured while participants performed single limb squats under two conditions: usual and corrected. Two-dimensional hip and knee angles and a DVI that combined the hip and knee angles were calculated.

Three-dimensional sagittal, frontal, and transverse plane angles of the hip and knee and a DVI combining the frontal and transverse plane angles were calculated.

Results: The two-dimensional DVI demonstrated moderate reliability (ICC=0.74). The correlation between the twodimensional and three-dimensional DVI’s was 0.635 (p<0001). Females with patellofemoral pain demonstrated a greater two-dimensional DVI (31.14°±13.36°) than females without patellofemoral pain (18.30°±14.97°; p=0.010).

Females with patellofemoral pain demonstrated a decreased DVI in the corrected (19.04°±13.70°) versus usual (31.14°±13.36°) condition (p=0.001).

Conclusion: The DVI is a reliable and valid measure that may provide a more comprehensive assessment of lowerextremity movement patterns than the knee frontal plane projection angle in individuals with lower-extremity musculoskeletal pain problems.

Level of Evidence: 2b Key Words: Frontal plane projection angle, movement, rehabilitation

1

Saint Louis University, St. Louis, MO, USA

This work was funded by the Eunice Kennedy Shriver National Institute of Child Health and Human Development, Award #R15HD059080. The content is solely the responsibility of the authors and does not necessarily represent the official views of the Eunice Kennedy Shriver National Institute of Child Health and Human Development or the National Institutes of Health.

ACKNOWLEDGMENT The authors acknowledge Leah Fischer, DPT, who assisted with 2D video processing and data analysis.

CORRESPONDING AUTHOR Gretchen B. Salsich, Program in Physical Therapy, Saint Louis University 3437 Caroline St. St. Louis, MO 63104 E-mail: salsichg@slu.edu

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INTRODUCTION Lower-extremity musculoskeletal pain problems, including anterior cruciate ligament injuries, iliotibial band friction syndrome, and patellofemoral pain (PFP) may be associated with faulty movement patterns of the hip and knee.1 For this reason, movement patterns and the effect of movement retraining have been investigated, most often with three-dimensional (3D) motion analysis. Two-dimensional (2D) motion analysis, however, has become a more commonly utilized tool for answering clinical questions as it is cost-effective, available to clinicians, and less time intensive than 3D motion analysis. The reliability of 2D measures also has been reported to be acceptable with reliability values ranging from 0.59 to 0.98 depending on the 2D method, task analyzed, and type of reliability reported.2-6 Three-dimensional and 2D motion analysis both have been utilized to assess an abnormal movement pattern often called dynamic knee valgus (Figure 1). Three-dimensional kinematic compo-

Figure 1. Dynamic knee valgus two-dimensional angular measures. 1a. Hip frontal plane projection angle, calculated as 90° minus the angle (α) between the pelvis segment and the thigh segment. Knee frontal plane projection angle, calculated as 180° minus the angle (β) between the thigh segment and the shank segment. 1b. Example of individual demonstrating an observable dynamic knee valgus, resulting in increased hip and knee frontal plane projection angles and a larger dynamic valgus index.

nents of dynamic knee valgus have been quantified during single limb squat,7 providing insight into the contribution of hip adduction, hip medial rotation, knee adduction, and knee lateral rotation to the dynamic knee valgus movement pattern.

Two-dimensional motion analysis, however, typically focuses solely on the knee using a knee frontal plane projection angle (FPPA; Figure 1).4, 5, 8-13 The knee FPPA visually appears to be knee abduction, although it is likely created by a combination of hip adduction, hip medial rotation, knee abduction, and knee lateral rotation that occurs during weight bearing knee flexion.13, 14 The knee FPPA, while capturing the 2D orientation of the femur and tibia, may not accurately reflect the entire lower-extremity movement pattern, as 3D motion analysis does, because the pelvis’ contribution to the lower extremity movement pattern is not taken into account. Pelvic drop may contribute to a hip adducted position. Noehren et al15 reported a greater hip adduction position in individuals with iliotibial band friction syndrome, suggesting the adducted position led to increased tension on the lateral structures of the knee, resulting in pain. Takacs and Hunt16 and Dunphy et al17 reported increased knee adduction moments in individuals who demonstrated contralateral hip drop without concomitant ipsilateral trunk lean. A more adducted position of the hip or increased knee adduction moment may alter or increase the stress to the patellofemoral joint, thus contributing to PFP. Knowledge of the pelvis’ contribution to hip motion during a particular task may provide important information about different movement strategies used by individuals to accomplish a task. Furthermore, because people may present with varying degrees of hip and knee angles that contribute to the pain problem, a 2D variable that combines the hip and knee angles may be a more comprehensive representation of the entire lower-extremity movement pattern than the knee FPPA alone.

To the authors’ knowledge, a hip and knee combined variable has not previously been reported.

Therefore, the purpose of the current study was to describe the utility of a dynamic valgus index (DVI) in females with PFP. The authors hypothesized that the 2D DVI (1) would be more reliable and valid than the knee FPPA in the current study,

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(2) would be greater in females with PFP during a single-limb squat compared to females without PFP, and (3) would decrease in females with PFP following within-session verbal instruction. Identifying a 2D variable that is potentially more comprehensive, reliable, and valid than the knee FPPA may result in a measure that more accurately reflects the entire lower-extremity movement pattern and lead to better identification and treatment of lower-extremity movement impairments. Furthermore, demonstrating successful utility of a comprehensive 2D variable provides additional support for the use of 2D measures during clinical assessment and to answer clinical questions related to lower-extremity movement impairments in individuals with musculoskeletal pain problems, particularly active individuals.

METHODS Participants Twenty women with chronic PFP and 16 women without PFP participated. Chronic PFP was defined as pain located at the patellofemoral articulation (behind or around the patella) of at least two months duration.18 To be included in the study, average pain reported for the prior week had to be a minimum of 3/10 using a verbal pain rating scale (0 representing no pain, 10 representing severe pain). Pain also had to be reproduced by at least two of the following tests: resisted isometric quadriceps contraction performed with the knee in approximately 10° of flexion, squatting, prolonged sitting, and stair ascent or descent.19 Females with PFP also had to demonstrate observable dynamic knee valgus during single limb squat. Observable dynamic knee valgus was defined as a visual frontal plane knee angle increase of 10° or more during the decent phase of the single limb squat test.7, 8 Females without PFP qualified for the study if they had no history or current report of PFP and did not demonstrate an observable dynamic knee valgus during a single-limb squat. Exclusion criteria for both groups included (1) body mass index greater than 30 kg/m2, (2) history of knee ligament, tendon, or cartilage injury; traumatic patellar dislocation; patellar instability; or prior knee surgery, (3) known pregnancy, and (4) neurological involvement that would influence balance and coordination during kinematic testing. Saint Louis University’s Institutional Review Board approved the study protocol

and informed consent. All federal and state regulations for the protection of human participants were followed, as were the guidelines of the Declaration of Helsinki. Prior to participation in the study, all participants read and signed the informed consent.

Kinematic Assessment Two-dimensional and 3D data were captured simultaneously while participants completed single limb squats under two conditions: usual and corrected.

Single limb squat was performed because it is often pain provoking and likely to induce dynamic knee valgus.13, 20, 21 Participants with PFP performed the squats on their involved limb. Participants without PFP were randomly assigned to perform the squat on their right or left leg. All participants completed trials using their usual method first. For the usual trials, participants were instructed to keep their trunk straight and arms at their side while bending their knee to at least 60° (visually confirmed by investigator). No additional instructions were given about the position of the knee relative to the hip or foot.

During the corrected trials, participants repeated the single limb squat with additional instructions. Participants were instructed to “keep your knee over the middle of your foot (don’t let your knee fall in”) during the descent phase of the squat. The corrected squat was demonstrated to the participants before they were allowed to practice the task. For both conditions, participants were allowed several practice trials prior to data collection to become comfortable with the task. Three trials were collected for the usual and corrected conditions; the average of three trials was used for data analysis.

Two-dimensional data were captured with a Sony DCR-HC96 Handycam camcorder (Sony Corporation of America, Park Ridge, NJ, USA). The camera was positioned at a height of 45 cm, 3 meters anterior to the participant. Data were processed with Dartfish ProSuite 7 (Dartfish, Switzerland). All 2D angles (Figure 1) were measured from a frontal plane view by one investigator blinded to condition. A line drawn between markers placed on the anterior superior iliac spines defined the pelvic segment. A line drawn from the midpoint of the knee, bisecting the thigh, defined the thigh segment. A line drawn from the midpoint of the knee to the midpoint of the

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ankle defined the shank segment. For each trial, hip and knee angles were obtained at peak knee flexion determined visually by the investigator. The knee FPPA angle was calculated as 180° minus the angle between the thigh segment and the shank segment (Figure 1a). A positive knee FPPA angle indicated apparent knee abduction. The hip FPPA was calculated as 90° minus the angle between the pelvis segment and the thigh segment (Figure 1a). A positive hip FPPA indicated apparent hip adduction. The 2D DVI was calculated as the sum of the hip and the knee FPPAs. Three-dimensional data were captured with an 8-camera motional analysis system (Vicon, Oxford Metrics LTD. Oxford, England) sampled at 120 Hz. Data were captured and processed using previously described methods.7 Prior to data collection, reflective markers were placed over the second sacral vertebrae, bilateral iliac crests, anterior superior iliac spines, medial and lateral femoral epicondyles, medial and lateral malleoli, calcaneus, lateral midfoot, anterior midfoot, and 1st and 5th metatarsal heads. Thermoplastic shells with four reflective markers were placed on the lateral mid-thigh and lateral mid shanks. Data captured from these markers were processed using Visual3DTM software (C-Motion, Inc., Rockville, MD, USA). Marker trajectories were low-pass filtered using a 4th-order Butterworth filter with a 6 Hz cutoff frequency. A six degrees of freedom model incorporating the pelvis (CODA model, Charnwood Dynamics Ldt., UK), thigh, shank, and foot was used for data processing. Hip and knee angles in the sagittal, frontal, and transverse planes were calculated and expressed in the reference frame of the proximal segment. For each trial, hip and knee angles were obtained at peak knee flexion determined by the Visual3DTM software.

The 3D DVI was the sum of hip and knee frontal and transverse plane angles, where hip adduction, hip medial rotation, knee abduction, and knee lateral rotation were considered positive values. The ICC3,1 (0.81-0.98) and SEM (1.0-3.5°) values for the trial-totrial variability of 3D hip and knee angles have been reported previously.7 STATISTICAL METHODS Data were analyzed with IBM SPSS Statistics version 20 (SPSS, Chicago, IL, USA).

Intra-rater reliability of Dartfish measurements for repeated measures of hip and knee FPPAs completed a minimum of five days apart was assessed with intraclass correlation coefficients (ICC2,1).

Inter-rater reliability of Dartfish measurements for hip and knee FPPAs, completed on a smaller sample by two individuals was assessed with intraclass correlation coefficients (ICC2,1).

Trial-to-trial within-session error for the 2D hip and knee FPPAs across the three trials was assessed by calculating ICC3,1 and standard error of the measure (standard deviation*√(1-ICC3,1)). Pearson product-moment correlation coefficients were calculated to examine concurrent validity between 2D and 3D variables captured during the usual condition. Independent samples t-tests were used to compare group differences in participant characteristics, peak knee flexion, knee FPPA, hip FPPA, and dynamic valgus indices in the usual condition. Paired t-tests were used to analyze differences between the usual condition and the corrected condition in participants with PFP. The alpha level was set at 0.05 for all statistical tests.

RESULTS There were no group differences in age (mean ± SD; PFP: 22.4 ± 4.3 years, no PFP: 21.6 ± 3.0 years; P=0.544), BMI (mean ± SD; PFP: 22.4 ± 3.2 kg/ m2, no PFP: 22.7 ± 2.8 kg/m2; P=0.678), or angle of peak knee flexion during the usual condition (mean ± SD; PFP: 70.0° ± 7.49°, no PFP: 68.3° ± 6.6°; P=0.484). There also was no difference in peak knee flexion between conditions in females with PFP (mean ± SD; usual: 70.0° ± 7.49°, corrected: 66.9° ± 8.5°; P=0.86).

Reliability The intra-rater reliability ICC2,1 of Dartfish measurements for repeated measures of hip and knee FPPAs completed a minimum of five days apart was 0.99.

The inter-rater reliability ICC2,1 of Dartfish measurements for hip and knee FPPAs, completed on a smaller sample by two individuals was 0.97 for the hip FPPA and 0.99 for the knee FPPA. Trial-to-trial within-session variability ICC3,1 values ranged from 0.68-0.83 (Knee FPPA: 0.68, DVI: 0.74, Hip FPPA: 0.83) for 2D measures in the usual condition with standard error of the measures ranging from 3.29° to 8.63° (Table 1).

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Table 1. Intraclass correlation coefficients for trial-to-trial variability, and standard error of the measure for two-dimensional hip and knee variables.

Table 2. Correlations between two-dimensional and three-dimesional variables in the usual condition.

Concurrent validity The 2D measures of hip and knee kinematics demonstrated fair to excellent concurrent validity22 when compared to 3D kinematic measures (Table 2). The 2D DVI was positively correlated with 3D hip adduction, hip medial rotation, knee lateral rotation, and the 3D DVI. The hip and knee FPPAs were positively correlated with 3D hip adduction, 3D knee lateral rotation, and the 3D DVI. The correlations between the 2D DVI and all of the 3D variables were greater than the correlations between the knee FPPA and the 3D variables.

Comparison between groups Females with PFP demonstrated a greater 2D DVI (mean ± SD; 31.14° ± 13.36°) than females without PFP (mean ± SD;18.30° ± 14.97°; P=0.010; Table 3). Females with PFP also demonstrated a greater 3D DVI (mean ± SD; 12.41° ± 9.77°) than females

without PFP (mean ± SD; 1.81° ± 13.44°; P=0.010; Table 3). The components of the 2D DVI also were different between groups. Females with PFP demonstrated a greater hip FPPA (mean ± SD; 19.66° ± 7.70°) than females without PFP (mean ± SD; 14.15° ± 6.53°; P=0.030; Table3). Females with PFP also demonstrated a greater knee FPPA (mean ± SD; 11.48° ± 7.45°) than females without PFP (mean ± SD; 4.14° ± 9.62°; P=0.014; Table 3).

Comparison between conditions Females with PFP demonstrated decreased dynamic valgus indices (mean ± SD; 2D DVI Usual Condition: 31.14° ± 13.36°, Corrected Condition: 19.04° ± 13.70°; P=0.001), as well as hip (mean ± SD; Usual Condition: 19.66° ± 7.70°, Corrected Condition: 14.48° ± 7.48°; P<0.001) and knee FPPAs (mean ± SD; Usual Condition: 11.48° ± 7.45°, Corrected Condition: 4.56° ± 7.48°; P=0.003) following

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Table 3. Between groups and between conditions comparisons of variables.

verbal instruction (Table 3). Females without PFP did complete the corrected trials. However, because they did not demonstrate observable dynamic knee valgus during single-leg squat, it was not expected the movement would change with cuing. Consistent with this hypothesis, there was no statistically significant change in any of the variables in females without PFP (p>0.05 for all comparisons).

DISCUSSION The purpose of the current study was to describe the utility of a DVI in females with PFP. The authors hypothesized that the 2D DVI (1) would be more reliable and valid than the knee FPPA, (2) would be greater in females with PFP during a singlelimb squat compared to females without PFP, and (3) would decrease in females with PFP following within-session verbal instruction. The results of the current study suggest the DVI may be an important variable to consider when examining lower-extremity movement patterns.

The DVI is a reliable and valid measure. The DVI demonstrated moderate trial-to-trial reliability, consistent with, or better than reliability of the knee FPPA reported previously in the literature and in the current study.4-6 Willson et al6 reported withinday reliability of the knee FPPA to be 0.88 during a single limb squat. Munro et al5 reported ICC values between 0.59 and 0.88 for the knee FPPA during different lower extremity tasks; the ICC value for single limb squat in females was reported to be 0.59. Using similar methods for measuring the knee FPPA, Herrington4 reported a reliability of 0.72 for the knee FPPA during a single limb squat.

The concurrent validity of the DVI during single limb squat also was consistent with or better than the concurrent validity of the knee FPPA reported in the current study and previously in the literature, when using similar methods.13 Willson et al13 reported correlations between the 2D knee FPPA and 3D segmental rotations of the pelvis, femur, and

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tibia to range between 0.01 and 0.61. The highest correlation reported by Willson et al13 was between the knee FPPA and the femoral adduction. This is consistent with the current study where the highest correlation between the 2D DVI and a 3D variable also was hip adduction.

Females with PFP demonstrated a greater 2D DVI than females without PFP. Females with PFP also demonstrated a greater knee FPPA than females without PFP, consistent with the findings of Willson et al,13 who reported a 4.1° difference in the knee FPPA between females with and females without PFP. The knee FPPA, however, does not capture the position of the pelvis, thus does not capture all movement that potentially contributes to stress at the knee. Pelvic position, however, could contribute to additional stress at the knee through different mechanisms. First, contralateral pelvic drop may increase lateral tension on the structures of the knee via the stretch of the tensor fascia latae/iliotibial band across the hip and knee.15 Noehren et al15 reported individuals with iliotibial band friction syndrome demonstrated greater hip adduction during the stance phase of running, suggesting the adducted hip position led to increased tension on lateral structures of the knee, resulting in pain. Similarly, an adducted position of the hip could result in tension on the lateral structures of the knee, affecting patellar alignment, leading to PFP. Second, contralateral pelvic drop without concomitant ipsilateral trunk lean results in a medial shift of the line of gravity, which increases the knee adductor moment.1, 16, 17 Takacs and Hunt16 and Dunphy et al17 reported increased knee adduction moments in individuals who demonstrate contralateral hip drop without concomitant ipsilateral trunk lean when compared to individuals who do not demonstrate contralateral hip drop. The increase in knee adduction moment may alter the stress distribution on the patellofemoral joint, potentially contributing to PFP. Assessment of the DVI, which captures positioning of the tibia, femur, and pelvis, may provide important, comprehensive information about different movement strategies used to accomplish a task and contribute to the pain problem.

Females with PFP also demonstrated a decrease in the DVI following verbal instruction targeting the knee position. Prior to the current study, the ability of 2D measures to detect change in multi-joint move-

ment patterns in females with PFP was unclear.

Olson et al.10 reported that 2D methods were sensitive enough to detect changes in the knee FPPA following a 4-week neuromuscular retraining program.

However, only healthy females were examined and only the knee FPPA was quantified. The current study, which detected changes in hip and knee FPPAs, as well as the 2D DVI in females with PFP following verbal instruction confirms the potential for 2D methods to be used as a research and clinical tool to examine changes in both hip and knee movement patterns in clinical populations. Both the hip and knee FPPAs decreased following instruction, but, consistent with the instruction provided, there was a greater decrease in the knee FPPA than the hip FPPA. Additional instruction targeting pelvic position may result in a greater decrease in the DVI. Further research is necessary to explore cuing of the pelvis and knee when the faulty movement pattern includes poor pelvic position.

The current study has limitations. The 2D data was captured as part of a larger 3D study; the methods for 2D motion capture may have been less precise resulting in increased error. Better positioning of the camera for 2D data collection would likely decrease some error. In the current study, however any error created by camera placement was systematic across all participants. A second limitation is that the current data is from a small sample of females performing the single-limb squat. The information may not be generalizable to a larger sample of a different population or task. Further research is necessary to explore the importance of examining the DVI with other tasks and populations.

CONCLUSION The DVI combines 2D motion analysis of the hip and the knee, creating a more comprehensive 2D assessment of lower-extremity movement than the 2D knee FPPA alone. The DVI is reliable, valid, can discriminate between groups, and is sensitive to change.

The successful utility of the DVI in the current study provides additional support for the use of 2D measures during clinical assessment and to answer clinical questions related to lower-extremity movement impairments in individuals with musculoskeletal pain problems, particularly active individuals.

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REFERENCES 1. Powers CM. The influence of abnormal hip mechanics on knee injury: a biomechanical perspective. J Orthop Sports Phys Ther. 2010;40:42-51.

2. Mizner RL, Chmielewski TL, Toepke JJ, et al.

Comparison of 2-dimensional measurement techniques for predicting knee angle and moment during a drop vertical jump. Clin J Sport Med. 2012;22:221-227.

3. Miller A, Callister R. Reliable lower limb musculoskeletal profiling using easily operated, portable equipment. Phys Ther Sport. 2009;10:30-37.

4. Herrington L. Knee valgus angle during single leg squat and landing in patellofemoral pain patients and controls. Knee. 2014;21:514-517.

5. Munro A, Herrington L, Carolan M. Reliability of 2-dimensional video assessment of frontal-plane dynamic knee valgus during common athletic screening tasks. J Sport Rehabil. 2012;21:7-11.

6. Willson JD, Ireland ML, Davis I. Core strength and lower extremity alignment during single leg squats.

Med Sci Sports Exerc. 2006;38:945-952.

7. Salsich GB, Graci V, Maxam DE. The effects of movement pattern modification on lower extremity kinematics and pain in women with patellofemoral pain. J Orthop Sports Phys Ther. 2012;42:1017-1024.

8. Harris-Hayes M, Steger-May K, Koh C, et al.

Classification of lower extremity movement patterns based on visual assessment: reliability and correlation with 2-dimensional video analysis. J Athl Train. 2014;49:304-310.

9. Hollman JH, Ginos BE, Kozuchowski J, et al.

Relationships between knee valgus, hip-muscle strength, and hip-muscle recruitment during a singlelimb step-down. J Sport Rehabil. 2009;18:104-117.

10. Olson TJ, Chebny C, Willson JD, et al. Comparison of 2D and 3D kinematic changes during a single leg step down following neuromuscular training. Phys Ther Sport. 2011;12:93-99.

11. Stensrud S, Myklebust G, Kristianslund E, et al.

Correlation between two-dimensional video analysis and subjective assessment in evaluating knee control among elite female team handball players.

Br J Sports Med. 2011;45:589-595.

12. Whatman C, Hume P, Hing W. The reliability and validity of physiotherapist visual rating of dynamic pelvis and knee alignment in young athletes. Phys Ther Sport. 2013;14:168-174.

13. Willson JD, Davis IS. Utility of the frontal plane projection angle in females with patellofemoral pain.

J Orthop Sports Phys Ther. 2008;38:606-615.

14. McLean SG, Walker K, Ford KR, et al. Evaluation of a two dimensional analysis method as a screening and evaluation tool for anterior cruciate ligament injury.

Br J Sports Med. 2005;39:355-362.

15. Noehren B, Davis I, Hamill J. ASB clinical biomechanics award winner 2006 prospective study of the biomechanical factors associated with iliotibial band syndrome. Clinical biomechanics (Bristol, Avon).

2007;22:951-956.

16. Takacs J, Hunt MA. The effect of contralateral pelvic drop and trunk lean on frontal plane knee biomechanics during single limb standing. J Biomech.

2012;45:2791-2796.

17. Dunphy C, Casey S, Lomond A, et al. Contralateral pelvic drop during gait increases knee adduction moments of asymptomatic individuals. Hum Mov Sci. 2016;49:27-35.

18. Kannus P, Natri A, Paakkala T, et al. An outcome study of chronic patellofemoral pain syndrome.

Seven-year follow-up of patients in a randomized, controlled trial. J Bone Joint Surg Am. 1999;81:355363.

19. McConnell J. The management of chondromalacia patellae: a long term solution. Aust J Physiother.

1986;32:215-223.

20. Souza RB, Draper CE, Fredericson M, et al. Femur rotation and patellofemoral joint kinematics: a weight-bearing magnetic resonance imaging analysis. J Orthop Sports Phys Ther. 2010;40:277-285.

21. Willson JD, Davis IS. Lower extremity mechanics of females with and without patellofemoral pain across activities with progressively greater task demands.

Clin Biomech. 2008;23:203-211.

22. Portney LG, Watkins MP. Foundations of Clinical Research: Applications to Practice. Vol 2nd. Upper Saddle River, NJ: Prentice Hall Health; 2010.

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IJSPT

ORIGINAL RESEARCH

THE ASSOCIATIONS BETWEEN HIP STRENGTH AND HIP KINEMATICS DURING A SINGLE LEG HOP IN RECREATIONAL ATHLETES POST ACL RECONSTRUCTION COMPARED TO HEALTHY CONTROLS Jeremiah Tate, PT, PhD1 Tell Suckut, DPT1 Jensen Wages, DPT1 Heather Lyles, DPT1 Benjamin Perrin, DPT1

ABSTRACT Background: Only a small amount of evidence exists linking hip abductor weakness to dynamic knee valgus during static and dynamic activities.

The associations of hip extensor strength and hip kinematics during the landing of a single leg hop are not known.

Purpose: To determine if relationships exist between hip extensor and abductor strength and hip kinematics in both involved and uninvolved limb during the landing phase of a single leg hop in recreational athletes post anterior cruciate ligament (ACL) reconstruction. The presence of similar associations was also evaluated in healthy recreational athletes.

Study Design: Controlled Laboratory Study; Cross-sectional Methods: Twenty-four recreational college-aged athletes participated in the study (12 post ACL reconstruction; 12 healthy controls). Sagittal and frontal plane hip kinematic data were collected for five trials during the landing of a single leg hop. Hip extensor and abductor isometric force production was measured using a hand-held dynamometer and normalized to participants’ height and weight. Dependent and independent t-tests were used to analyze for any potential differences in hip strength or kinematics within and between groups, respectively. Pearson’s r was used to demonstrate potential associations between hip strength and hip kinematics for both limbs in the ACL group and the right limb in the healthy control group.

Results: Independent t-tests revealed that participants post ACL reconstruction exhibited less hip extensor strength (0.18 N/Ht*BW vs. 0.25 N/ Ht*BW, p=<.01) and landed with greater hip adduction (9.0 º vs. 0.8º, p=<.01) compared with their healthy counterparts. In the ACL group, Pearson’s r demonstrated a moderate and indirect relationship (r=-.62, p=.03) between hip extensor strength and maximum hip abduction/adduction angle in the involved limb. A moderate and direct relationship between hip abductor strength and maximum hip flexion angle was demonstrated in the both the involved (r=.62) and uninvolved limb (r=.65, p=.02). No significant associations were demonstrated between hip extensor or abductor strength and hip flexion and/or abduction/adduction angles in the healthy group.

Conclusion: The results suggest that hip extensors may play a role in minimizing hip adduction in the involved limb while the hip abductors seem to play a role in facilitating hip flexion during the landing phase of a single leg hop for both limbs following ACL reconstruction. Researchers and clinicians alike should consider the importance of the hip extensors in playing a more prominent role in contributing to frontal plane motion.

Levels of Evidence: Level 2a Keywords: ACL reconstruction, hip strength, kinematics, single leg hop

1

Physical Therapy Department, University of Tennessee at Chattanooga, Chattanooga, TN

This study was approved by the Institutional Review Board at the University of Tennessee at Chattanooga on 09/18/2014 (#14-112).

Financial Disclosure and Conflict of Interest: The authors of this manuscript affirm that we have no financial affiliation (including research funding) or involvement with any commercial organization that has a direct financial interest in any matter included in this manuscript, except as disclosed in an attachment and cited in the manuscript. Any other conflict of interest (ie, personal associations or involvement as a director, officer, or expert witness) is also disclosed in an attachment.

CORRESPONDING AUTHOR Jeremiah J. Tate, PT, PhD UC Foundation Assistant Professor Physical Therapy Department University of Tennessee at Chattanooga 311 MLK Blvd.

Room 203 Mapp Building Chattanooga, TN 37403 Phone: 423-425-5710 Fax: 423-425-2380 E-mail: Jeremiah-Tate@utc.edu

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INTRODUCTION An estimated 200,000 people suffer an anterior cruciate ligament (ACL) injury each year.1 Further evidence suggests that only 70% will return back to their previous level of function.2 For those that do return to sport, approximately 30% will be at risk of suffering a subsequent ACL injury to either the contralateral limb or ipsilateral limb.3 The majority of ACL injuries have been attributed to noncontact mechanisms during sudden decelerations and jumplandings.4,5 Risk factors associated with noncontact ACL injuries have been classified as environmental, anatomical, hormonal, or biomechanical.6,7 Of these four risk factors, biomechanical factors have received the most attention since they are likely the easiest to change through neuromuscular training.8 In particular, excessive knee valgus during dynamic activities involving jump-landings and cutting has received the most attention due to its link to ACL (re)injury.9-11 A recent evidence-based review has highlighted the value of hip-specific neuromuscular exercise interventions that are capable of modifying dynamic knee valgus in efforts to prevent anterior cruciate ligament (ACL) injuries.12 Separate studies by Leetun13 and Nadler14 demonstrated that female athletes who experienced lower extremity injury were more likely to demonstrate decreased hip strength.

Howard et al15 demonstrated that weakness of the hip abductors and external rotators was associated with increased knee valgus during single-leg landing tasks. This line of research has shown a possible association between weak hip abductors and excessive valgus motion at the knee.16 However, a recent systematic review demonstrated only a small amount of evidence linking hip abductor weakness to dynamic knee valgus.17 Previous studies tended to only analyze either hip abductor and/or external rotator strength.18-25 Therefore, researchers and clinicians alike may have focused primarily on hip abductor and external rotator strength and overlooked the capability of the hip extensors to provide dynamic stability within the frontal plane. For this reason, it would be of interest to know if potential associations between hip extensor strength and hip kinematics exist during dynamic movements in individuals who have undergone ACL reconstruction as well as healthy athletes.

The single leg hop test is frequently used by clinicians to assess functional performance after ACL reconstruction to determine readiness to return to athletics.26,27 In particular, Engelen-van Melick et al27 demonstrated that the single leg hop is the most frequent measurement used to assess patientsâ&#x20AC;&#x2122; function more than two years after ACL reconstruction.

Trigsted et al28 demonstrated less maximal knee flexion in the involved limb during the landing phase of a single leg hop in individuals who had returned to sport following ACL reconstruction compared to healthy controls. Xergia et al29 further demonstrated that individuals after ACL reconstruction landed with greater hip flexion on the involved limb compared to healthy controls. These studies highlight the continued asymmetries that exist in athletes after ACL reconstruction despite these individuals having returned to sport.

A recent systematic review demonstrated that knee extensor and flexor weakness along with hip extensor weakness is typical following ACL reconstruction and may persist for two years or more.30 Knee extensor and flexor strength deficits were associated with graft choice, indicating that extensor weakness is more common with patellar tendon grafts, while knee flexor weakness is associated with hamstring grafts. These altered biomechanics in landing when compared to the uninvolved limb can be directly attributed to these weaknesses.22,31,32 For example, Oberlander et al32 revealed that 78% of the extensor knee joint moment variability during the landing phase of a single leg hop at 12 months following ACL reconstruction was explained by the strength of the knee extensors. It remains unknown if hip extensor weakness would result in similar compensatory patterns in individuals post ACL reconstruction when performing dynamic landing activities, such as a single leg hop.

Therefore, the primary purpose of this study was to determine if relationships exist between hip extensors (primarily gluteus maximus) and maximum hip flexion and/or abduction/adduction during the landing phase of a single leg hop in both the involved and uninvolved limb of recreational athletes post ACL reconstruction and also in healthy controls.

A secondary purpose was to determine if relationships exist between hip abductors and maximum hip

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flexion and/or abduction/adduction as well. It was hypothesized that both groups would both exhibit significant associations between hip strength and hip kinematics during the landing phase of a single leg hop.

METHODS Participants and Screening Recreational athletes from 18 to 30 years old who had undergone unilateral ACL reconstruction, completed formal rehabilitation, and released by their physician to return to sport or activity were recruited via university email. A secondary group of healthy, recreational athletes was recruited from a population of convenience from the physical therapy program and matched to participants in the ACL group based on gender and activity level. Additional inclusion criteria required that participants in both groups were currently active in a sport or recreational activity a minimum of 2x/week for at least 30 minutes and participated in a jumping or cutting activity at least 1x/month. Participants in the ACL reconstruction group were excluded if they had any other knee ligament injury requiring surgical repair.

Participants were excluded from the healthy, recreational athlete group if they had a history of lower extremity surgery. Participants in both groups were excluded if they had scoliosis, limb length inequality, or history of low back pain or lower extremity injury in the prior six months that limited activity for more than two weeks.

All procedures were approved by the Institutional Review Board at the University of Tennessee at Chattanooga and all participants provided written informed consent to participate. All participants who met the inclusion criteria were screened for the presence of a limb length inequality or scoliosis.

Participants were instructed to wear athletic shoes, shorts, and a t-shirt for the screening. Limb length inequality was assessed using an indirect method33, while scoliosis was assessed using the forward bend test34 by a licensed physical therapist with 16 years of experience in outpatient orthopaedics. Any participant with a limb length inequality > 6.4 mm or having a positive forward bend test was excluded as both limb length inequality and scoliosis have the potential to affect hip posture and hip kinematics.

Participantsâ&#x20AC;&#x2122; height and weight were measured using a standard scale. The single leg hop for distance35 was also assessed for each limb, averaging three successful attempts. Participants were allowed free movement of their upper extremities during this single leg hop. Any participant who was unable to jump a distance of at least 75% of their height was excluded. This standardized distance requirement was adopted because participants were required to place their hands on their hips when performing the single leg hop during motion analysis. This requirement was based on the methods of Oberlander et al32 and helps control for the possibility of asymmetrical arm movement patterns that might occur due to hip weakness, particularly in the frontal plane. Controlling upper extremity movement was necessary because the upper extremities were not included in the biomechanical model used during motion analysis. Participants were then scheduled for their motion lab visit for a motion analysis of the landing phase of a single leg hop.

Motion Analysis An 8-camera motion capture system (Vicon Motion Systems, Centennial, CO) sampling at 240 Hz was synchronized with two force platforms (Bertec Corporation, Columbus, OH) sampling at 960 Hz, to collect three-dimensional kinematics and ground reaction force data, respectively. Retroreflective markers were attached to both lower extremities and the pelvis and trunk prior to data collection. Markers placed over anatomical landmarks were used to define joint centers and segment coordinate systems (iliac crests, greater trochanters, lateral and medial femoral epicondyles, lateral and medial malleolli, first and fifth metatarsal heads). Molded thermoplastic shells with four non-collinear markers36 were attached to pelvis, thigh and shank segments using neoprene wraps and Velcro.37 Three non-collinear markers were attached to the heel to assess rear-foot motion. A standing trial was collected and anatomical markers were removed.

Participants warmed up for five minutes by walking on a treadmill at a self-selected pace. Participants then stretched their quadriceps, hamstrings, and triceps surae for three repetitions of 30 seconds each. The single leg hop required each participant

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to hop a distance equal to 75% of their height and stick the landing for two seconds, while maintaining their hands on their waist. Participants were allowed to practice until they felt comfortable with the task, which usually resulted in three to five practice trials per limb prior to data collection. Five successful trials were collected and the process was repeated on the contralateral limb.

Hip Strength Measurements Hip extensor and abductor maximum isometric force production was measured using a hand-held dynamometer (JTech Medical Industries, Herber City, UT) approximately one week after collecting singleleg hop data. Non-elastic straps were used to stabilize the participant and to provide resistance to the hip motion through the dynamometer.18 Two different testers participated in strength assessment, one for each group. Both testers were trained by the lead author (JT) prior to data collection. The test positions used in this study have demonstrated acceptable interrater reliability.38 The order of muscle testing was randomized with the participant completing the strength measurement on both limbs before moving to the next measurement. Hip extensor strength was measured with the participant in prone with a nonelastic strap securing them to the plinth just superior to their iliac crest. The dynamometer was placed on a contoured plate (approximately 15cm X 9 cm) constructed from thermoplastic material in efforts to decrease the amount of pressure and thus minimize any discomfort related to the interface between the dynamometer and the thigh.39 The inferior edge of the plate was placed 5 cm superior to the popliteal crease, and the dynamometer was secured with a non-elastic strap. The participantâ&#x20AC;&#x2122;s knee was flexed to 90° to emphasize the gluteus maximus.40 Hip abductor strength was measured with the participant in sidelying41 with a non-elastic strap securing them to the plinth just superior to their iliac crest. The dynamometer was placed on the contoured plate of which the inferior edge was placed 5 cm superior to the lateral femoral epicondyle and secured with a non-elastic strap. The participant was instructed to perform a sub-maximal practice trial at the beginning of each new test position for each limb to become familiarized with the procedure. Three initial trials were performed for each participant. Participants

were instructed to give maximal effort, and verbal encouragement was given to elicit optimal contraction during each trial. Each contraction was held for five seconds, with a 30 second rest given between each trial. If a participant achieved a significantly higher score on the third trial, then two to three additional trials were performed to allow the participant to demonstrate maximal strength. The highest three trials were averaged for use in data analysis.

Data Reduction Marker trajectories data were low-pass filtered using a fourth-order recursive Butterworth filter with cutoff frequencies of 8 Hz. Kinematic data were calculated using standard rigid body analysis techniques with Visual 3D software (C-Motion, Rockville, MD).

Joint angles were determined using the joint coordinate system.42 Joint angles were defined using the right-hand rule with flexion-extension, abductionadduction, and internal-external rotation as the first, second, and third rotation, respectively. The landing phase, defined as the period from initial foot contact (ie, > 10N) to peak knee flexion angle, was of interest. Peak values for hip flexion and abduction/ adduction angles that occurred during the landing phase were determined for each trial and averaged.

Strength measures for each participant were normalized to the participantâ&#x20AC;&#x2122;s height and weight.

Statistical Analysis Descriptive statistics were calculated for demographic variables and single leg hop test data. Independent t-tests were used to analyze any potential differences between groups related to demographic measures and the single leg hop test. Absolute limb symmetry indexes were also calculated for both groups for the single leg hop test during the screening process. The absolute limb symmetry index (LSI) was calculated by dividing the smaller average hop distance of either limb by the larger average hop distance of the other limb and multiplying by 100%.

The absolute LSI allows for between group comparisons since limbs may differ based on surgical status or limb dominance. All dependent variables were assessed for normality using the Shapiro-Wilk test.

Dependent and independent t-tests were used to analyze any potential differences in maximum hip flexion and hip abduction/adduction angles and hip

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extensor and abductor strength within and between groups, respectively. The limb that underwent ACL reconstruction was the limb of interest in the ACL group for between group comparisons. The limb used for statistical comparison in the healthy group was the right limb based on the fact that there were no limb differences in hop distance or hip kinematics for the healthy participants. Furthermore, all healthy participants reported their right limb as being dominant (ie, the leg used to kick a ball for maximum distance). A LSI for hip extensor and abductor strength values was also calculated for the ACL group by dividing the average strength value of the involved limb by the average strength value of the uninvolved limb and multiplying by 100%.

Scatterplots were assessed prior to calculation of the Pearson correlation coefficient (r) to assess for the presence of a linear relationship and possible outliers. Pearson’s r was used to assess for any potential relationships between hip strength and hip kinematics in the limbs of interest in both groups. Pearson’s r was interpreted as follows: >0.75-1.0 = good to excellent; .50-.75 = moderate; .25-.50 = fair; and 0.00-.25 = little or no relationship.43 A P < .05 was utilized for all statistical analyses.

RESULTS A total of 24 participants (12 ACL/12 healthy) met the inclusion criteria and completed the study protocol. Each group consisted of seven females and five males. Only one potential ACL participant was unable to achieve the required hop distance of 75% of their height and was not allowed to continue in the study. The healthy control group was slightly older than the ACL reconstruction group, while other demographic data and single leg hop values were similar (Table 1). The participants in the ACL group had undergone surgery an average of 32 months (range 9-58) prior to study participation. Seventy-five percent of participants in the ACL group suffered non-contact injuries, with the remaining injuries occurring via contact. Seven of the injuries occurred to the right knee and five to the left knee. The majority of participants had their ACL reconstructed using an autograft (11/12) with the vast majority of these grafts being patella tendon (10/11) and the other being hamstring tendon (1/11).

The remaining participant’s ACL was repaired with

an allograft tendon. Half of the ACL participants reported a known meniscal injury as well.

Strength and Kinematic Variables Within ACL Group All dependent variables of interest met the assumption of normality. No significant differences were noted between limbs for peak hip flexion and abduction/adduction angles during the landing phase of a single leg hop (Table 2). Likewise, no significant differences were noted between limbs for hip extensor or abductor strength (Table 2). The limb symmetry index for the hip extensors was 93% + 15 and 105% + 08 for the hip abductors.

Strength and Kinematic Variables Between Groups An independent t-test revealed that the hip extensor strength of the ACL group was statistically

Table 1. Mean (SD) of demographic variables for participants in both groups.

Table 2. Mean (SD) of kinematic and strength variables for involved and uninvolved limbs in the ACL group.

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Table 3. Mean (SD) of kinematic and strength variables for participants in both groups.

significantly less than the healthy group (Table 3).

No statistically significant difference in hip abductor strength was noted between groups. Significant differences were noted between groups for peak hip abduction/adduction angles during the landing phase of a single leg hop (Table 3). Specifically, participants in the ACL group landed with greater hip adduction. No statistically significant difference in peak hip flexion angle was noted between groups.

Hip Strength and Kinematic Associations in the Involved Limb of ACL Group Moderate and statistically significant relationships were demonstrated for hip extensor strength and abduction/adduction angle (r=-.62; p=.03) and hip abductor strength and flexion angle (r=.62; P=.03).

A fair relationship was demonstrated for hip extensor strength and hip flexion angle (r=.40), however; it was not statistically significant (p=.19). No association was demonstrated between hip abductor strength and hip abduction/adduction angle (r=-.18; p=.57).

Hip Strength and Kinematic Associations in the Uninvolved Limb of ACL Group A moderate and statistically significant relationship was demonstrated for hip abductor strength and hip flexion angle (r=.65; p=.02). Fair and statistically non-significant relationships were demonstrated for hip extensor strength and hip flexion angle (r=-.27, p=.40) and hip extensor strength and hip abduction/ adduction angle (r=-.34, P=.28). No association was demonstrated between hip abductor strength and hip abduction/adduction angle (r=-.13; p=.69).

Hip Strength and Kinematic Associations in the Healthy Group A fair and non-significant relationship was demonstrated for hip abductor strength and hip flexion angle (r=.39, p=.21). Little to no associations were demonstrated between hip extension strength and hip flexion angle (r=-.09; p=.79), hip extension strength and hip abduction/adduction angle (r=.15; p=.65), or hip abductor strength and hip abduction/ adduction angle (r=-.17; p=.60).

DISCUSSION The purpose of this study was to analyze potential relationships between hip strength and hip kinematics during the landing phase of a single leg hop in individuals post ACL reconstruction and a healthy group of recreational athletes. It was hypothesized that both groups would exhibit significant associations between maximal isometric hip strength and peak hip kinematics during the landing phase of a single leg hop. This hypothesis was only partially supported by the fact that moderate associations were demonstrated in the ACL group, but not in the healthy recreational athletes. Specifically, a moderate and indirect relationship was present between the hip extensors and maximum hip abduction/ adduction angle, while a moderate and direct relationship existed for the hip abductors and maximum hip flexion angle.

The most interesting finding was the indirect relationship between the hip extensors and maximum hip abduction/adduction angle during the single leg hop. This relationship suggests that individuals after ACL reconstruction who have relatively strong hip extensors land with less dynamic knee valgus compared to those with weak hip extensors (see Figure 1). Powers44 has recently suggested that the gluteus maximus is capable of producing hip abduction. Fujisawa et al45 demonstrated that the gluteus maximus was active during isometric hip abduction and the activity increased as the hip flexion angle increased.

A recent study by Cronin et al46 supports the notion that the hip extensors play a key role in minimizing hip adduction. In their study, Cronin et al similarly hypothesized that hip abductors primarily act to minimize frontal plane hip motion during the landing phase of a single leg hop followed by a cutting

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Figure 1. (a) representative landing of a participant with “strong” hip extensors and (b) representative landing of a participant with “weak” hip extensors. Note: Images sampled at maximum knee flexion.

task. Their results, however, indicated that no difference in frontal plane kinematics existed for participants who had a lower rate of hip abductor strength development compared to those with a high rate of development. They were surprised, however, to see that group differences in the rates of hip extensor strength development yielded statistically significant differences in frontal plane landing kinematics.

Hollman et al47 also demonstrated a significant relationship between hip extensor activity and frontal plane knee motion during a single leg squat. These findings combined with this study support the idea that the gluteus maximus plays a significant role in contributing to frontal plane motion at the hip and may limit excessive dynamic knee valgus.

The results also demonstrated that hip abductors were primarily associated with hip motion within the sagittal plane. A recent systematic review demonstrated only a small amount of evidence linking hip abductor weakness to dynamic knee valgus.17 The results suggest that the hip abductors may act to stabilize the pelvis in space during the landing

phase of a single leg hop as opposed to controlling hip adduction. This suggestion is based on the direct relationship seen between hip abductor strength and the maximum hip flexion angle. It might be the case that a person with strong hip abductors is able to maintain a more level pelvis thus enabling greater hip flexion to occur during the landing. Pollard et al48 demonstrated that adolescent female soccer players that exhibited high amounts of hip and knee flexion during a drop landing task also exhibited decreased internal knee adductor moments. Therefore, increased hip flexion may also lead to less frontal plane loading at the knee joint.

Landing kinematics demonstrated that individuals post ACL reconstruction land with greater peak hip adduction angles compared to those individuals in the healthy group. The increased knee adduction differs from Trigsted et al 28 who saw similar peak hip adduction patterns during a single leg hop landing between participants who had undergone ACL reconstruction compared to healthy controls.

A difference in methodology may explain these

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differences as Trigsted et al28 had their participants hop for maximum distance. Increased hip adduction is an undesired movement pattern during a jump landing due to the decreased ability to avoid dynamic valgus collapse. Furthermore, the results demonstrated that peak hip flexion and adduction were similar between limbs in the ACL group.

These results differ from those of Trigsted et al28 who reported less peak hip flexion in the involved limb while peak hip adduction angles were similar.

Again, this lack of agreement could be explained by differences in methodology. Typically, symmetry between limbs is a desired outcome. However, the fact that the ACL group landed with greater hip adduction compared to the healthy control group is of concern for the overall limb alignment as it relates to a potential increase in dynamic knee valgus.

The ACL group exhibited significant weakness in their hip extensors, which may partially explain the increased hip adduction seen during the jump landing. It should be noted that quadriceps weakness commonly seen after ACL reconstruction30 is also another potential cause linked to the kinematic asymmetries. Recent studies have demonstrated the significant effects of weak quadriceps on landing mechanics49 and bilateral hip extensor strength50 for individuals who had a previous ACL reconstruction.

Future studies, therefore, should attempt to perform strength measurements of all major lower extremity muscle groups in addition to measurements of trunk/core stability. In addition, body marker sets that include not only the pelvis and lower extremities, but also the trunk and upper extremities should be included in the methods to help researchers determine the influence of strength deficits on whole body movement patterns.

The other important finding is that significant associations between hip strength and hip kinematics exist in the ACL group, but not in the healthy comparison group. We are unaware of any other study that has demonstrated an association between strength and kinematics in a group of individuals post ACL reconstruction, but not present in the healthy comparison group. It could be speculated that movement strategies related to single leg jump landings likely differ in the presence of weakness. ACL reconstruction rehabilitation guidelines frequently suggest introducing

single leg landing activities as early as three to four months post-surgery.51,52 Therefore, individuals three to four months post ACL reconstruction likely exhibit limited variability in movement patterns during a jump landing due to lower extremity strength deficits, especially in the sagittal plane. Limited variability in movement has been suggested as a cause of injury and is therefore an undesired trait.53 Limited hip strength may result in a reduced number of movement patterns and might explain why participants in the ACL group demonstrated significant associations with hip strength compared to healthy individuals.

Individuals with hip weakness may rely more on ligament dominance.54 Limited variability may also be linked to the risk of subsequent ACL injury. The results suggest that the ACL group on average had an acceptable LSI of 90% for their hip extensors. However, both limbs in the ACL group could be considered weaker when compared to the healthy control group. This finding alone highlights the importance of an increased focus on development of hip extensor strength in individuals after ACL reconstruction.

Overall, the results of this study suggest that researchers and clinicians should focus more on the function of the hip extensors, in particular the gluteus maximus, in efforts to improve lower extremity kinematics observed during sporting activities.

A recent evidence-based review has highlighted the value of hip-specific neuromuscular exercise interventions that are capable of modifying dynamic knee valgus in efforts to prevent anterior cruciate ligament (ACL) injuries.12 Recent work by Stearns and Powers55 demonstrated that following a fourweek training program which increased hip extensor and abductor strength, healthy female recreational athletes demonstrated improved landing mechanics during a drop-jump task. It remains unknown whether a similar training program would also produce improvements in landing mechanics during dynamic tasks, such as a single leg hop in individuals after ACL reconstruction.

Limitations This study contains some limitations. First, even though the sample is representative of the general population who typically incur ACL injuries, the sample size remains relatively small. Secondly, the

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sample was selected based on convenience and further limited to college-age, recreational athletes whose ACL reconstruction occurred approximately 32 months prior. Specific information related to selfreported function was not collected, but we feel that the ACL group was comparable to participants in other cross-sectional studies. Nyland et al56 demonstrated that individuals who thought they were capable of participating in their current sport activities had an IKDC score of 87.2 on average. Trigsted et al28 reported a similar average IKDC score of 88.6 for females following ACL reconstruction that were of similar age and activity level compared to participants in the ACL group. Furthermore, single leg hop distance of the females in their study was similar to the hop distance of the females who participated in this study. Therefore, we feel that the ACL group who participated in this study would have similar IKDC scores when compared to participants in both of these studies. The majority of participants in this study had also undergone ACL reconstruction utilizing a bone-tendon-bone graft. Thus, these results cannot be applied to individuals who had their ACL reconstructed with other graft sources (ie, hamstring tendon or allograft). The study design also did not allow for a uniform postoperative rehabilitation process. However, all participants did report having undergone formal physical therapy after surgery.

Additionally, the influence of trunk position on lower extremity biomechanics was not assessed during a landing from a single leg hop and should not be discounted. Oberlander et al32 demonstrated that individuals who have undergone ACL reconstruction tend to demonstrate greater forward and ipsilateral trunk lean during single leg hop landings. The results of this study apply specifically to the performance of a single leg hop test, as other movements were not investigated. Finally, this study does not explain all of the variation in hip kinematics during the landing of a single leg hop. Other factors that affect landing kinematics should be studied.

CONCLUSIONS College-aged recreational athletes who were on average 32 months removed from ACL reconstruction had decreased hip extensor strength and landed with greater hip adduction compared to healthy controls.

Significant associations were demonstrated between

hip strength and hip kinematics, but only for participants in the ACL group. The results suggest that hip extensors, particularly the gluteus maximus, may serve to contribute to hip adduction, while the hip abductors may play more of a role in stabilizing the pelvis in space and may contribute to the amount of hip flexion that occurs during a single leg hop landing. Researchers and clinicians alike should consider the importance of the hip extensors in playing an important role in controlling frontal plane motion of the hip following ACL reconstruction.

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21. Nilstad A, Krosshaug T, Mok KM, et al. Association Between Anatomical Characteristics, Knee Laxity and Muscle Strength, and Peak Knee Valgus During Vertical Drop Jump Landings. J Orthop Sports Phys Ther. 2015;1-26.

22. Noehren B, Abraham A, Curry M, et al. Evaluation of proximal joint kinematics and muscle strength following ACL reconstruction surgery in female athletes. J Orthop Res. 2014;32:1305-1310.

23. Khayambashi K, Ghoddosi N, Straub RK, et al. Hip Muscle Strength Predicts Noncontact Anterior Cruciate Ligament Injury in Male and Female Athletes: A Prospective Study. Am J Sports Med. 2016;44:355-361.

24. Homan KJ, Norcross MF, Goerger BM, et al. The inďŹ&#x201A;uence of hip strength on gluteal activity and lower extremity kinematics. J Electromyogr Kinesiol.

2013;23:411-415.

25. Imwalle LE, Myer GD, Ford KR, et al. Relationship between hip and knee kinematics in athletic women during cutting maneuvers: a possible link to noncontact anterior cruciate ligament injury and prevention. J Strength Cond Res. 2009;23:2223-2230.

26. Barber-Westin SD, Noyes FR. Objective criteria for return to athletics after anterior cruciate ligament reconstruction and subsequent reinjury rates: a systematic review. Phys Sportsmed. 2011;39:100-110.

27. Engelen-van Melick N, van Cingel RE, Tijssen MP, et al. Assessment of functional performance after anterior cruciate ligament reconstruction: a systematic review of measurement procedures. Knee Surg Sports Traumatol Arthrosc. 2013;21:869-879.

28. Trigsted SM, Post EG, Bell DR. Landing mechanics during single hop for distance in females following anterior cruciate ligament reconstruction compared to healthy controls. Knee Surg Sports Traumatol Arthrosc. 2015; 29. Xergia SA, Pappas E, Zampeli F, et al. Asymmetries in functional hop tests, lower extremity kinematics, and isokinetic strength persist 6 to 9 months following anterior cruciate ligament reconstruction.

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30. Petersen W, Taheri P, Forkel P, et al. Return to play following ACL reconstruction: a systematic review about strength deďŹ cits. Arch Orthop Trauma Surg.

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31. Thomas AC, Villwock M, Wojtys EM, et al. Lower extremity muscle strength after anterior cruciate ligament injury and reconstruction. J Athl Train.

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32. Oberlander KD, Bruggemann GP, Hoher J, et al.

Altered landing mechanics in ACL-reconstructed patients. Med Sci Sports Exerc. 2013;45:506-513.

33. Brady RJ, Dean JB, Skinner TM, et al. Limb length inequality: clinical implications for assessment and intervention. J Orthop Sports Phys Ther. 2003;33:221-234.

34. Horne JP, Flannery R, Usman S. Adolescent idiopathic scoliosis: diagnosis and management. Am Fam Physician. 2014;89:193-198.

35. Reiman M, Manske R. Functional Testing in Human Performance. 1st Edition. Champaign, IL: Human Kinetics; 2009.

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36. Cappozzo A, Cappello A, Della Croce U, et al.

Surface-marker cluster design criteria for 3-D bone movement reconstruction. IEEE Trans Biomed Eng. 1997;44:1165-1174.

37. Manal K, McClay I, Stanhope S, et al. Comparison of surface mounted markers and attachment methods in estimating tibial rotations during walking: an in vivo study. Gait Posture. 2000;11:38-45.

38. Scott DA, Bond EQ, Sisto SA, et al. The intra- and interrater reliability of hip muscle strength assessments using a handheld versus a portable dynamometer anchoring station. Arch Phys Med Rehabil. 2004;85:598-603.

39. Hansen EM, McCartney CN, Sweeney RS, et al.

Hand-held Dynamometer Positioning Impacts Discomfort During Quadriceps Strength Testing: A Validity and Reliability Study. Int J Sports Phys Ther.

2015;10:62-68.

40. Rowe J, Shafer L, Kelley K, et al. Hip strength and knee pain in females. N Am J Sports Phys Ther.

2007;2:164-169.

41. Widler KS, Glatthorn JF, Bizzini M, et al. Assessment of hip abductor muscle strength. A validity and reliability study. J Bone Joint Surg Am. 2009;91:26662672.

42. Grood ES, Suntay WJ. A joint coordinate system for the clinical description of three-dimensional motions: application to the knee. J Biomech Eng. 1983;105:136-144.

43. Portney L, Watkins M. Foundations of Clinical Research: Applications to Practice. 2nd. Prentice Hall; 2000.

44. Powers CM. The influence of abnormal hip mechanics on knee injury: a biomechanical perspective. J Orthop Sports Phys Ther. 2010;40:42-51.

45. Fujisawa H, Suzuki H, Yamaguchi E, et al. Hip Muscle Activity during Isometric Contraction of Hip Abduction. J Phys Ther Sci. 2014;26:187-190.

46. Cronin B, Johnson ST, Chang E, et al. Greater Hip Extension but Not Hip Abduction Explosive Strength Is Associated With Lesser Hip Adduction and Knee Valgus Motion During a Single-Leg Jump-Cut. Orthop J Sports Med. 2016;4:2325967116639578.

47. Hollman JH, Galardi CM, Lin IH, et al. Frontal and transverse plane hip kinematics and gluteus maximus recruitment correlate with frontal plane knee kinematics during single-leg squat tests in women. Clin Biomech (Bristol, Avon). 2014;29:468-474.

48. Pollard CD, Sigward SM, Powers CM. Limited hip and knee flexion during landing is associated with increased frontal plane knee motion and moments.

Clin Biomech (Bristol, Avon). 2010;25:142-146.

49. Ithurburn MP, Paterno MV, Ford KR, et al. Young Athletes With Quadriceps Femoris Strength Asymmetry at Return to Sport After Anterior Cruciate Ligament Reconstruction Demonstrate Asymmetric Single-Leg Drop-Landing Mechanics.

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50. Bell DR, Trigsted SM, Post EG, et al. Hip Strength in Patients with Quadriceps Strength Deficits after ACL Reconstruction. Med Sci Sports Exerc. 2016;48: 1886-1892.

51. Wilk KE, Macrina LC, Cain EL, et al. Recent advances in the rehabilitation of anterior cruciate ligament injuries. J Orthop Sports Phys Ther.

2012;42:153-171.

52. Adams D, Logerstedt DS, Hunter-Giordano A, et al.

Current concepts for anterior cruciate ligament reconstruction: a criterion-based rehabilitation progression. J Orthop Sports Phys Ther. 2012;42: 601-614.

53. Hamill J, Palmer C, Van Emmerik RE. Coordinative variability and overuse injury. Sports Med Arthrosc Rehabil Ther Technol. 2012;4:45.

54. Hewett TE, Paterno MV, Myer GD. Strategies for enhancing proprioception and neuromuscular control of the knee. Clin Orthop Relat Res. 2002;76-94.

55. Stearns KM, Powers CM. Improvements in hip muscle performance result in increased use of the hip extensors and abductors during a landing task.

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56. Nyland J, Wera J, Klein S, et al. Lower extremity neuromuscular compensations during instrumented single leg hop testing 2-10 years following ACL reconstruction. Knee. 2014;21:1191-1197.

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IJSPT

ORIGINAL RESEARCH

INJURY INCIDENCE, DANCE EXPOSURE AND THE USE OF THE MOVEMENT COMPETENCY SCREEN (MCS) TO IDENTIFY VARIABLES ASSOCIATED WITH INJURY IN FULL-TIME PRE-PROFESSIONAL DANCERS Linda Lee, BPhty, MHSci (hons), PGDip Sp & Ex Medicine, PGCert Physio (Msk)1 Duncan Reid, DHSc, FNZCP, MHsc, PGDip (Manip Physio), Dip PT, BSc2 Jill Cadwell, MHSci(Hons), PGDHSci(Manip Ther.), PGDSportsMed, BPhty, DipPhys2 Priya Palmer, BSc, MSc, PhD2

ABSTRACT Background/Purposes: Prospective studies utilizing standardized injury and exposure measures are needed to consolidate our knowledge of injury incidence and associated risk factors for musculoskeletal injury amongst pre-professional dancers. The purpose of this study was to investigate the injury incidence amongst pre-professional dancers attending a fulltime training school in New Zealand. The secondary purposes of this study were to investigate the relationship between dance exposure and injury risk, and the relationship between risk factors (specifically the MCS outcome scores) and injury risk.

Methods: A prospective cohort study of 66 full-time pre-professional dancers was undertaken over one full academic year (38 weeks), included 40 females (mean age 17.78 yrs, SD 1.18) and 26 males (mean age 18.57yrs, SD 1.72). Injury surveillance included both reported and self reported injury data. Dancers were screened using the MCS in the first week of term one.

Results: Eighty-six per cent of dancers sustained one or more injuries. Fifty-nine per cent of all injuries were time-loss. The injury incidence rate was 2.27 per 1000 hours of dance exposure (DEhr) and 3.35 per 1000 dance exposures (DE). There was a significant association between the total number of injuries and total DE per month (B=0.003, 95% CI 0.001 - 0.006, p=0.016). Dancers who had a MCS score < 23 were more likely to be injured than those who scored ≥23 (B= -0.702, 95% CI = -1.354 – -0.050, p=0.035).

Conclusion: Injury prevalence and incidence was comparable with other international cohorts. The number of dance exposures was more highly associated with injury risk than the hours of dance exposure. The MCS may be a useful tool to help identify dancers at risk of injury.

Level of Evidence: Level 3b, Prospective Longitudinal Cohort Study Keywords: Dance, exposure, functional movement screening, injury, pre-professional

1 2

Sandringham, Auckland, New Zealand Auckland University of Technology, Auckland, New Zealand

CORRESPONDING AUTHOR Linda Lee Physiotherapist The Sandringham Physio Room Auckland 1025, New Zealand Phone: +6496295544, +6421324574 E-mail: linda@physioroom.nz

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INTRODUCTION Pre-professional dance training is demanding, and requires significant physical and artistic ability.1,2 Long training hours coupled with highly repetitive movement patterns during a time of maturation and development places the pre-professional dancer in a vulnerable position with regard to injury risk.3,4 Several authors have highlighted musculoskeletal injuries as a significant ongoing health issue for pre-professional dancers.1-3,5-20 However, consistent reporting of injury incidence is still necessary to enable the development and monitoring of injury prevention strategies.1,21-23 Risk factors for dance related injury are still not well understood.1,5,6,24 The negative effects of changes in training load and/or training loads beyond an athlete’s capacity have been cited as potential risk factors for injury.25-31 To date there is a paucity of prospective studies examining the relationship between dance exposure and injury risk amongst pre-professional dancers. 1,12,16,32,33 Pre-participation or pre-season screening within dance schools and professional companies has become more widely adopted as the need to optimize dancers’ health is recognized as a critical factor in both developing and maintaining talent. 34-42 Functional movement screening tools designed to identify deficits in neuromuscular control, have gained popularity within the sporting arena as an effective and efficient screening strategy.

43-50 The utility of functional movement screening tools, and more specifically the MCS, to detect dancers at risk of injury requires further investigation. 45,47,51,52 The purpose of this study was to investigate the injury incidence amongst pre-professional dancers attending a fulltime training school in New Zealand. The secondary purposes of this study were to investigate the relationship between dance exposure and injury risk, and the relationship between risk factors (specifically the MCS outcome scores) and injury risk.

METHODS Study design A prospective cohort study was conducted over one full academic year (38 weeks). Approval for was gained from the Auckland University of Technology (AUT) Ethics Committee. All participants received both verbal and written study information and gave written informed consent.

Participants Students attending an elite full-time pre-professional dance school in New Zealand were invited to participate (n=86). A total of 66 dancers completed the necessary documentation and movement screening session at the beginning of the study.

Injury Surveillance Participating dancers completed an initial questionnaire that collected information on potential risk factors including: age, height, weight, BMI, gender, previous and current injury history, year of pre-professional dance training, dance major, and age started dancing. Prospective injury surveillance was undertaken over one full academic year.

The dance school physiotherapist completed a standardized Injury Summary Sheet (Appendix 1) and International Performing Arts Injury Reporting Survey (IPAIRS©) for all reported injuries. Selfreported injury data was collected via an online survey tool (http://surveymonkey.com) and sent to participating students every three weeks. Injury was defined as, “any physical complaint sustained by a dancer resulting from performance, rehearsal or class, and resulting in a dancer injury report or triage, irrespective of the need for medical attention or timeloss from dance activities”.53 Injury was then also sub-classified based on current recommendations; including time-loss or non time-loss, nature of injury i.e. acute or overuse, and if an injury was new or recurrent.54-56 Recurrent injuries were further classified as exacerbations or re-injuries.55 (Appendix 2) Injury severity was coded, S0 (no days off or modified), S1 (activity modification), S2 (≤ 7 days off), S3 (> 7 days off) or S4 (year ending).3,57 Dance Exposure Dance exposure (DE) was defined as, “one dancer participating in one class, rehearsal or performance in which he or she is exposed to the possibility of dance injury regardless of the time associated with that participation”.58 Total dance exposure (hours and events), was calculated from the weekly timetables for each year of study (major and gender).

MCS screening and scoring All participants were screened using the Movement Competency Screen (MCS©) in the first week of term

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one. The MCS is comprised of five fundamental movement patterns (body weight squat, lunge twist, single leg squat, bend and pull, push up) and three dynamic jump patterns (counter movement jump, counter movement jump with unilateral land, broad jump with unilateral land) (Appendix 3, Appendix 4).47,59 The subjects were filmed using Casio EX-ZR100 digital cameras (Shibuya-ku, Tokyo). Video analysis of each movement pattern was performed by the primary researcher, and scored using standardized criteria directly adapted from the original MCS 100 criteria described by Kritz,45 and that were used by Vanweerd47 for the Netball Movement Competency Screen.45,47,59 (Appendix 5) Whole body movement is assessed for each movement pattern and scored from 0 â&#x20AC;&#x201C; 3, based on identification of primary or secondary areas of concern as described by Kritz.45 Primary areas of concern are those that are most likely to impact on the athleteâ&#x20AC;&#x2122;s movement competency during the selected movement task.45 A score of one indicates poor movement competency, while a score of three indicates good movement competency. All unilateral movements were assessed and scored bilaterally. The scores of all individual movements were totalled to provide a composite outcome score (out of a possible 36). The reliability of the MCS has been shown to be good to excellent in adolescent female netballers52 and in military populations.60 Prior to the current study a pilot study assessed the intra-rater reliability of the primary researcher using the MCS. Intra-rater reliability was established using average measures intra-class correlation coefficient (ICC). The ICC (2,1) for the overall MCS scores in ten subjects was excellent (ICC (2,1) 0.99, CI 0.98 - 0.99).

Statistical Analysis Descriptive analysis of the data established the injury prevalence and incidence of reported injuries. Injury prevalence was defined as the total number of reported injuries in one full academic year. Injury incidence over the academic year (Jan-Dec) was expressed as the number of reported injuries per 1000 hours of dance exposure (DEhr). Injury rates were also calculated using the number of reported injuries per 1000 dance exposures (DE), as it is considered to achieve a higher level of reliability as well as comparability betweeen cohorts, and is also consistent with reporting methods utilized by other international sporting bodies.58,61

Pearsonâ&#x20AC;&#x2122;s correlations were used to determine the relationship between dance exposure and injury.

A univariate linear regression model was used to investigate the relationship between injury status and individual potential risk factors. A multivariate linear regression model was used to examine the influence of a combination of risk factors for becoming injured.

Covariates were fitted into the model using a forward selection procedure and were retained in the final linear regression model if they reached a statistical threshold of p<0.10 or were of clinical significance.

A logistic regression was used to investigate the relationship between injury severity and possible risk factors. All analyses were performed using Statistical Programme for Social Science (SPSS) software (SPSS V.22, IBM Corporation, New York, USA). Alpha levels were set at 0.05 (95% confidence level).

RESULTS Participants Sixty-six dancers (females = 40, males = 26) aged between 16-24 years old (mean 18.15yrs, SD 1.45) gave consent to participate. There were 28 dancers in year one, 25 in year two and 13 in year three.

Thirty-two were ballet majors and 34 were modern majors. Seventy-seven per cent of dancers attending the dance school participated in the study. During the course of the study one dancer opted out of reported injury data collection and four dancers left the school. Demographic characteristics of participants are presented in Table 1.

Injury Prevalence Fifty-seven (86.4%) dancers reported a history of previous dance related injury at the start of the study.

A total of 125 reported injuries, involving 56 dancers (86.2%), were recorded over the academic year.

Injury prevalence across the year ranged from 1.5% to 36.9% per month. No significant demographic differences were found between dancers who reported any injury or time-loss injuries and those who did not (Table 2).

Injury Characteristics Reported injury characteristics are shown in Table 3. The ankle was the most common site of lower limb injury, followed by the knee, foot, and hip/ thigh respectively. The thoracic spine was the most

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Table 1. Demographic data, reported as mean (SD) Full Sample

Females

Males

Subjects (n)

66

40

26

Age (years)

18.15 (1.45)

17.78

(range: 16 - 24)

(1.18)

(range: 16 - 20)

18.57

p-value

(1.72)

0.054

(range: 16 - 24)

Weight (kg)

59.79

(9.67)

53.93

(6.04)

68.81

(6.29)

<0.001*

Height (cm)

171.17

(9.35)

165.63

(6.52)

179.75

(5.88)

<0.001*

BMI

20.25

(1.88)

19.54

(1.74)

21.33

(1.52)

<0.001*

Age started dancing (yrs)

11.83

(3.39)

11.56

(3.16)

12.24

(3.76)

0.442

BMI= Body mass index *Statistically significant at p<0.05

Table 2. Descriptive characteristics of injured and non-injured groups

N

Injury reported Mean (SD) 56

Age (years)

18.23

(1.47) 17.77

(1.30)

0.388

Height (cm)

170.66

(9.36) 173.33

(9.50)

0.432

Weight (kg)

59.23

(9.43) 62.88

(11.58)

0.299

BMI

20.25

(1.87) 20.31

(2.00)

Major

p-value

0.935

Injury reported N (%) 49 (87.5%)

No injury reported N (%) 8 (88%)

p-value

10

(17.9%)

1

(12%)

1.000†

Male

22

(39.3%)

3

(33.3%)

1.000†

Female

34

(60.7%)

6

(66.6%)

Ballet

27

(48.2%)

5

(55.6%)

Modern 29

(51.8%)

4

(44.4%)

Previous history injury Current injury Gender

No injury reported Mean (SD) 9

Year of training 1st

23

(41.1%)

4

(44.4%)

2nd

21

(37.5%)

4

(44.4%)

3rd

12

(21.4%)

1

(11.1%)

0.600†

1.000† 0.902†

N= number of dancers; SD = standard deviation; BMI= Body mass index † p-value calculated using fishers exact test

common site of trunk injury, followed by the lumbar spine. The shoulder was the most common upper limb injury.

Injury Severity Of all reported injuries, 59.2% (n=74) were timeloss resulting in a total of 433 full days off dance.

Eighty-six per cent (n=64) of all time-loss injuries required the dancer to take ≤ 7 days off dance (S2), with 13.5% (n=10) taking >7 days off dance

(S3). Injuries requiring the greatest time off dance included: lower limb stress fractures, posterior cruciate and meniscal injury, and tendon injuries of the foot and ankle. The distribution of injury severity via injury location is presented in Figure 1.

Injury Incidence The total injury incidence rate over the academic year was 2.27 (95% CI 2.25-2.28) per 1000 dance exposure hours (DEhr) and 3.35 (95% CI 3.33-3.37)

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Table 3. Characteristics and severity of reported and self-reported injuries Characteristics Total injuries % dancers injured New Recurrent - Re injury - Exacerbation Acute Overuse Head/Neck Trunk Lower Limb Upper Limb

Reported Injuries n 125

%

104 21 8 13 51 74

86.2 83 16.8 38.1 61.9 40.8 59.2

4 25 85 11

3.2 20 68 8.8

Injury Severity Reported as mean (SD) or n Mean numerical pain score

5.29 (1.91)

Time-loss injuries:

n=74

Full days off dance

5.85 (6.37) (range: 1 - 42 days)

Non time-loss injuries:

n= 51

Days of modified activity

7.14 (5.49) (range: 0 - 28 days)

Activity modification: none mild moderate severe

n=1 n=7 n=43 n=0

%

59.2

40.8

2 14 84 0

SD = standard deviation n = number

per 1000 dance exposures (DE). The total injury incidence for time-loss injuries was 1.34/1000DEhr and 1.98/1000DEâ&#x20AC;&#x2122;s. The injury incidence rates, for reported injuries were similar for males and females (2.39 and 2.19/1000DEhr), and ballet and modern dancers (2.11 and 2.17/1000DEhr). First year students had the highest injury incidence rate for reported injuries (2.95/1000DEhr). Injury incidence also decreased term-by-term, with the highest incidence in term one (3.60/1000DEhr). Injury incidence (DEhr and DE) for reported injuries is presented in Tables 4 and 5.

Relationship between dance exposure and injury The total number of dance exposures (DE) per month was significantly associated with the total number of reported injuries reported per month

(p=0.016) (Figure 2). A significant association was also found between the average number of dance exposures (DE) per dancer per month and the total number of injuries per month (p=0.027). The total hours of dance exposure (DEhr) was found not to be a significant predictor of injury (p=0.964).

Relationship between reported injuries and risk factors The association between potential risk factors and injury is presented in Table 6. A MCS score <23 was significantly associated with increased risk of injury (p=0.035). Furthermore, the higher number of injuries in those with a MCS score <23 was more likely to be explained by a greater number of trunk injuries (p=0.036). No significant difference in total MCS scores was found for age, gender, major, or year group (p>0.05).

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injuries were more common amongst first year students, decreasing for every year of study (B=-0.152, p=0.025).

DISCUSSION Participants The key strengths of this prospective study included: (1) seventy-seven per cent of eligible dancers participated in the study, (2) the use of reported injury and exposure data collected over a full academic year and, (3) this is the first prospective longitudinal study of elite pre-professional dancers in New Zealand.

Prevalence, incidence and severity Injury severity was coded based on definitions from previous research

by Dick, Agel, Marshall 57 and Bowerman 64 S0= No days off or modified S1= Activity modification only S2= ≤ 7 days off dance S3= > 7 days off dance S4= Year ending - if a dancer was unable to return to training due to injury

Figure 1. Location severity of reported injuries.

A history of previous injury was found not to be associated with increased injury risk. However, a significant association between previous history of injury and gender was noted, whereby more females had sustained previous injuries compared to males (p=0.022). A significant association was found between injury location and major, whereby modern majors were more likely than ballet majors to sustain trunk injuries (B=-0.304, p=0.042) and upper limb injuries (B=0.324, p=0.001). Upper limb

Prevalence At the start of the study 86% (n=57) of dancers reported a previous history of dance-related injury. This was comparable with previous studies (82-95%).17,18,62,63 The injury prevalence over the academic year was (86.2%), which was within the upper range reported in current literature (3094%).2,7,8,10-12,16,18,63 Further to this, 21% of injuries sustained were considered ‘recurrent’, 8% of which were re-injuries. This was fewer than that reported

by Ekegren, Quested, Brodrick7 where 14% of time-loss injuries were considered a re-injury.

Future research utilizing the Subsequent Injury Categorization (SIC) model as proposed by Finch and Marshall64 may enable a better understanding between injury and each subsequent injury; which can have a considerable impact on a dancer’s training and career.19,65

Table 4. Injury incidence rates for reported injuries per dance exposure hours (DEhr) Variable Subjects Total Total Mean SD 95% CI Injuries DEhr DEhr N % RI 27 41.5 59 20021 741:30 180:00 670:16 – 812:43 Year 1 25 38.5 44 22733 909:19 148:22 848:04 – 970:33 Year 2 13 20.0 22 12408 954:26 86:58 901:52 – 1006:59 Year 3 25 38.5 50 20930 837:11 206:31 751:56 – 922:26 Male 40 61.5 75 34232 855:46 158:34 805:46 – 906:29 Female 31 47.7 58 27434 784:40 217:03 705:03 – 846:17 Ballet 34 52.3 67 30836 906:57 103:32 870:44 – 943:04 Modern 43 66.1 74 55162 848:33 177:12 804:43 – 892:32 Time-Loss 35 53.8 51 55162 848:33 177:12 804:43 – 892:32 Non Time-Loss 65 100.0 125 55162 848:33 177:12 804:43 – 892:32 Total Cohort N = number of subjects RI= reported injuries DEhr = dance exposure hours CI = confidence interval

Reported Injuries per 1000 DEhr 95%CI 2.95 1.94 1.77 2.39 2.19 2.11 2.17 1.34 0.92 2.27

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2.92 – 2.97 1.92 – 1.95 1.75 – 1.79 2.37 – 2.41 2.18 – 2.21 2.10 – 2.13 2.16 – 2.19 1.33 – 1.35 0.91 – 0.93 2.25 – 2.28

Table 5. Injury incidence rates for reported injuries per number of dance exposures (DE) Variable Total Total Mean SD 95% CI Subjects Injuries DE DE N % RI 27 41.5 59 13771 510.04 Year 1 25 38.5 44 15258 610.32 Year 2 13 20.0 22 8285 637.31 Year 3 25 38.5 50 14113 564.52 Male 40 61.5 75 23201 580.03 Female 31 47.7 58 17138 552.83 Ballet 34 52.3 67 20176 593.41 Modern 43 66.1 74 37314 574.06 Time-Loss 35 53.8 51 37314 574.06 Non Time-Loss 65 100.0 125 37314 574.06 Total Cohort N = number of subjects RI= reported injuries DE = dance exposures

142.79 453.55 – 566.52 100.75 568.73 – 651.91 25.62 621.82 – 652.00 140.50 506.52 – 622.52 113.19 543.82 – 616.22 167.86 491.26 – 614.41 56.43 573.72 – 613.10 123.57 543.44 – 604.68 123.57 543.44 – 604.68 123.57 543.44 – 604.68 CI = confidence interval

Reported Injuries per 1000 DE 95%CI 4.28 2.88 2.66 3.54 3.23 3.38 3.32 1.98 1.37 3.35

4.25 – 4.32 2.86 – 2.91 2.62 – 2.69 3.51 – 3.57 3.21 – 3.26 3.36 – 3.41 3.29 – 3.35 1.97 – 1.99 1.35 – 1.38 3.33 – 3.37

Figure 2. Dance exposure and injury.

Incidence Prospective studies utilizing reported injury data and a mixed cohort with which to compare the overall results of this study are lacking. The incidence of reported injuries for ballet majors alone was 2.11/1000DEhr, which although comparable with previous studies, is at the upper end of the range (range: 0.9-2.9/1000hrs).11,16,18 Fewer studies have

reported the injury incidence for modern dance students. In this study the injury incidence (2.17/1000) was somewhat lower than the 4/1000hours of dance reported amongst modern dancers at the Escuela Nacional de Danza in Mexico.13 Comparisons between dance schools should, however, be made with caution as differences in demands, nature of exposures, and age of dancers may also impact on injury rates.

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Table 6. Association between the total number of reported injuries and risk factors Independent B 95% CI p-value Adjusted R Variables Square -0.001 -0.235 – 0.233 0.992 Age -0.016 0.039 -0.141 – 0.220 0.667 BMI -0.013 -0.125 -0.817 – 0.567 0.720 Gender -0.014 -0.100 -0.774 – 0.575 0.769 Major -0.014 -0.272 -0.714 – 0.169 0.222 Year of training 0.008 -0.081 -0.186 – 0.023 0.125 Total MCS score 0.022 -0.702 -1.354 – -0.050 0.035* Mean MCS score 0.054 -0.685 -1.646 – 0.277 0.160 Previous Injury 0.016 *Statistically significant at p ≤ 0.050

The findings of this study support current evidence that overuse injuries are a significant issue for dancers.2,7,11,16,17,66,67 The incidence of overuse injuries was found to be lower than that reported in a recent study of pre-professional ballet dancers (2.4/10000DEhr and 3.52/1000DE).3 The shorter inception period of the compared study (6 months) and single genre cohort may contribute to these differences. Comparatively, Ekegren, Quested, Brodrick7 reported a higher prevalence of overuse injuries (72%) compared to this current study (59.2%). The higher average dance exposure per year (1030hr) may be a contributing factor, whereby longer training hours, with less relative time for recovery is considered a significant extrinsic risk factor for sustaining overuse injuries.25,68 Severity Severity of injuries amongst pre-professional dancers has, thus far, been infrequently reported and the different measures utilized to define injury severity have also limited comparisons. The injury incidence for time-loss injuries in this study was comparable with findings from a recent prospective study of 266 pre-professional ballet dancers in London that utilised the same time-loss injury definition (1.38/1000DEhr, 1.87/1000DE).7 The current study found the majority of injuries to be classified as S2 (≤7 days off dance). Although a recent study of preprofessional ballet dancers classified the majority of injuries as S1 (activity modification), this only included overuse injuries of the lumbar spine and lower limb which is likely to contribute to this difference.3

Relationship between dance exposure and injury risk A significant finding in this study was that the total number of dance exposures was found to be more highly associated with injury risk than the total hours of dance exposure. There is considerable potential for variation in volume, intensity, technical demand and nature of exposures during a dancers day/week/ term and year.69 It may be hypothesized that this can result in significant fluctuations in demand, over training or indeed under training the dancer and, hence, contribute to injury risk. Optimizing dance schedules using periodization have been reported to be an effective strategy in reducing injury risk and drop out rates in a pre-professional dance school,70 and to improve mood states prior to performance in professional dancers.31 The findings of this research support further investigation into strategies to optimize training outcomes and minimizing injury risk for pre-professional dancers.30,34,69 Current evidence indicates that rapid changes in training load precede the onset of injury.29,71 This is consistent with findings in this study, whereby a greater number of reported injuries were sustained in term one (after the holiday period), peaking again after returning from each semester break.

Current literature suggests that high acute:chronic workload ratios may contribute to increased risk of injury.71,72 Although further research is necessary, this may be a factor contributing to the findings in this study. This study found the number of reported injuries decreased as the year progressed despite a relatively consistent volume of exposure each term.

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Unlike previous research, assessments periods and increased exposure to rehearsal and performance (at the end of the year) did not result in a higher number of reported injuries.16,30 It may be that as the year progressed dancers were better conditioned to meet their demands and therefore more resilient and accustomed to the workload, or simply reported fewer injuries to avoid missing vital assessment and performance opportunities.73 In contrast to previous research, the year of pre-professional training was not associated with increased injury risk, despite increasing dance exposure.7 It is possible that emerging adolescent dancers have a lower threshold for injury, as has been reported for other sports.74 The small cohort and, specifically, the limited number of third year dancers in this study may have contributed to this finding. Further research investigating the dose-response relationship between training and injury and workload ratios across differing age groups and genres is needed.

Relationship between injury and risk factors A primary aim of this study was to establish the relationship between the Movement Competency Screen (MCS), and injury risk. MCS scores were analyzed both as a continuous (total MCS score) and categorical (mean MCS score) variables. The mean (and median) MCS score for this cohort was 23, and this was used to define the categorical variables group assignment (1= < 23, 2= â&#x2030;Ľ23). Those dancers who scored below the mean (<23) were considered to demonstrate reduced or altered movement control during functional movement patterns, beyond that which was typically seen within the cohort. Utilizing the mean MCS score as a cut off score enabled comparisons with previous research of movement screening tools, which have also utilized dichotomized pass/fail scores. In this study dancers who scored less than 23 were more likely to sustain an injury than those who scored at or above 23 (p=0.035). This suggests that those dancers who demonstrated reduced or altered movement control during functional movement patterns, beyond what was typically seen within the cohort, may be more susceptible to future injury. This provides some support for the inclusion of the MCS as part of an overall injury screening strategy, whereby those dancers who may benefit from further assessment,

conditioning or load modification can be identified in a timely manner. No other studies utilizing the MCS, inclusive of dynamic jump tasks, were identified in the literature, although a recent prospective study of elite rowers in New Zealand did investigate the relationship between the total MCS score (five fundamental movements only) and risk of lower back injury.51,75 The authors of that study found rowers who scored at or higher than the mean MCS score were more likely to develop low back pain compared to those who scored lower, however, this finding was not statistically significant (OR=2.57, p=0.07). Studies evaluating the efficacy of other functional movement screening tools to identify those at risk of injury have also reported positive associations. The most reported tool to do so is the Functional Movement Screen (FMSTM).76-80 In spite of this, the efficacy of the FMSTM to predict injury risk should be considered in the context of those studies where no association and bimodal associations have been found.81-83 The variability presented within the research highlights the difficulty of utilizing cut-off scores for predicting injury risk, where the sensitivity of the cut-off score is inversely related to the specificity.84 While a single screening tool alone is unlikely to identify all those at risk of injury, identifying the most effective and efficient tools which detect factors that contribute to the injury risk profile of dancers is essential. The MCS has the potential to be utilized more widely by dance teachers, strength and conditioning coaches, and healthcare providers, and to educate dancers as part of an injury prevention strategy.

The findings of this study support the development of injury prevention programs targeting neuromuscular control in those with identified deficits. A recent three-year prospective study utilized the functional movement screen (FMSTM) to guide the development of individualized conditioning programmes for a group of professional ballet dancers. 85 This resulted in a significant reduction in all injuries as well as recurrent injury over the three years.

As injury prevalence has been shown to be high amongst adolescent dancers, specifically lower limb injuries, injury prevention programes involving neuromuscular control aimed at the broader adolescent dance population may have the biggest impact in reducing injury risk.

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Limitations of the study Interpretation of these results should be considered alongside the following methodological limitations.

The sample size in this study was small due to the limited number of dancers attending the dance school, and as a result the relationship between some risk factors and injury is unclear.86 The loss of five dancers during the course of the study may have also affected observed associations. Furthermore, although statistical analysis demonstrated an association between the mean MCS score and injury, there are still a lot of unknown factors that contribute to these injuries. This was highlighted by the very low adjusted R-squared value (R2 =0.054) (see Table 6). Further research is therefore still required to identify other possible risk factors for these injuries. The number of days of modified activity for time-loss injuries was not included and should be taken into consideration when interpreting the impact and severity of time-loss injuries on dance participation. The intensity and nature of dance exposures, and workload ratios was not included in exposure analysis. These factors may impact on the potential injury risk of individual dancers.

Dance exposure was calculated each week from the timetables, for each year group (major and gender), but not individually, hence may not truly reflect the actual hours of training or engagement by each individual dancer. Non-scheduled dance practice or additional workouts such as attending the gym, were also not included in the total hours of dance.

As the dancers progressed through the year their movement competency may have changed, and also their injury risk in relation to MCS scores. Research undertaking screening at more regular intervals over the year may better establish the relationship between outcomes scores and injury risk.

Functional movement screening has the capacity to identify dancers at risk of injury. As such, future intervention studies targeting those at risk individuals/groups with focused prevention/conditioning programmes are indicated. Multicentre studies examining training loads (acute and chronic) and nature of exposures in relation to injury risk are necessary to optimise training and performance outcomes across differing age groups and genres. Future research is needed to examine if MCS scores taken at

regular intervals during the year may be more useful in establishing injury risk. Research establishing the inter-rater reliability of the MCS is necessary for this tool to be useful between providers and across the broader population.

CONCLUSION This is the first prospective longitudinal study of pre-professional dancers in New Zealand. Injury prevalence and incidence rates were high, although comparable to those reported internationally. The results of this study indicate, that the number of dance exposures was more highly associated with injury risk than the hours of dance exposure. Furthermore, dancers had a greater risk of sustaining injury in term one, reducing with each term of the year. There is a need for further prospective longitudinal studies examining dance exposure and the relationship to injury. An MCS score < 23 was associated with an increased risk of future injury. Therefore, including the MCS as part of an overall injury screening strategy may be an efficient and effective strategy to help identify those dancers who could benefit from focused injury prevention strategies.

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78. O’Connor FG, Deuster PA, Davis J, et al. Functional movement screening: predicting injuries in officer candidates. Med Sci Sports Exerc. 2011;43(12):22242230.

79. Kiesel KB, Butler RJ, Plisky PJ. Prediction of injury by limited and asymmetrical fundamental movement patterns in American football. Journal of Sport Rehabil. 2014;23:88-94.

80. Kiesel KB, Pilsky PJ, Voight MK. Can serious injury in professional football be predicted by a preseason functional movement screen. N Am J Sports Phys Ther. 2007;2(3):147-158.

81. Warren M, Smith CA, Chimera NJ. Association of Functional Movement Screen™ with injuries in Division I Athletes Journal of Sport Rehabil.

2015;24(2):163-170.

82. Hall TR. Prediction of Athletic Injury with a Functional Movement Screen(TM) [Masters Thesis]. North Carolina, United States, East Carolina University; 2014.

83. Wiese BW, Boone JK, Mattacola CG, et al.

Determination of the Functional Movement Screen to predict musculoskeletal injury in intercollegiate athletics. Athletic Training & Sports Health Care.

2014;6(4):161-169.

84. Bahr R. Why screening tests to predict injury do not work-and probably never will...: a critical review. Br J Sports Med. 2016;50(13):776-780.

85. Allen N, Nevill A, Brooks J, et al. Ballet injuries: injury incidence and severity over 1 year. J Orthop Sports Phys Ther. 2012;42(9):781-790.

86. Portney L, Watkin M. Foundations of clinical research 3rd Edition ed. New Jersey: Pearson Prentice Hall; 2009.

87. Fuller CW, Ekstrand J, Junge A, et al. Consensus statement on injury definitions and data collection procedures in studies of football (soccer) injuries. Br J Sports Med. 2006;40(3):193-201.

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APPENDIX 1

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APPENDIX 2 Injury and severity definitions Definitions utilised for injury recording and associated variables include: Injury: Any physical complaint sustained by a dancer resulting from performance, rehearsal or class, and resulting in a dancer injury report or triage, irrespective of the need for medical attention or time-loss from dance activities53.

Time-Loss Injury: “an anatomic tissue-level impairment as diagnosed by a registered health care practitioner that results in full time loss from activity for one or more days beyond the day of onset”58.

Non Time-Loss Injury: An injury that does not rise to the level of a reported time-loss injury58.

Reported Injury: Any injury (time-loss or non timeloss) meeting the injury definition which was triaged, assessed or managed by the NZSD physiotherapist.

Self-Reported Injury: Any injury meeting the injury definition (time-loss or non time-loss), reported via online questionnaire directly from the dance student.

Traumatic/Acute Injury: “An injury that results from a specific identifiable event”84.

Overuse Injury: “An injury caused by repeated micro-trauma without a single identifiable event responsible for the injury”84.

Injury severity was measured by time-loss (days) or degree of activity modification and were defined as: Time-loss: is the total number of full days off dance, from the date of injury to the date of the dancer returning to participation57.

Activity Modification: is the extent to which a dancer had to modify or reduce their training load due injury. This was rated using a descriptive scale, describing the degree of activity modification the dancer had to undertake as a result of the injury as listed below.

1. Not at all: dancer is able to attend all classes/ rehearsals/performance, without any limitations 2. Minor: dancer is able to attend all classes/rehearsals/performance with only minor limitations 3. Moderate: dancer is able to attend all classes/ rehearsals/performance but with moderate limitations such as; participating in petite allegro but not grand allegro, keeping legs below 45 degrees 4. Major: dancer is unable to participate in significant components of classes/rehearsals/performance, including having to sit out some but not all timetabled classes over a normal school day or avoiding significant components such as jumping or pointe work

Recurrent Injury: An injury with the same diagnosis as a previously recorded injury and that occurs within two months after the dancer’s return to full participation55,82. Recurrent injuries were further categorised according to Fuller et al (2007) as either:

Injury severity was also coded based on definitions adapted from previous research by Dick, Agel, Marshall57 and Bowerman64

1. Exacerbations: “worsening state of a non-recovered injury such that the dancer is unable to take a full part in dance related activities that would normally be required”82.

S1 Activity modification only

2. Re-Injury: “an injury of the same type and at the same site as the first episode, occurring after a dancers return to full participation from the initial injury within two months”82.

S4 Year ending - if a dancer was unable to return to training due to injury

S0 No days off or modified

S2 ≤ 7 days off dance S3 > 7 days off dance

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APPENDIX 3 Movement Competency Screen Testing Sequence

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APPENDIX 4

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APPENDIX 5 Movement Competency Screen Scoring Criteria Body Region/Capacity

MCS Task 1 Body Weight Squat

Head Shoulders

Held stable in a neutral position and centrally aligned Held down Held down away Held down Held down away and away from ears. and away from ears. from ears.

Elbows in line from ears.

Elbows with ears.

Rotation appear in appears to line with occur through ears. thoracic spine.

Thoracic Elbows is at extension is least inline evident with the lead knee at end range of rotation Neutral Maintains Held stable, Maintains curve lumbar curve, no neutral spine lumbar curve, no hyperextension, is maintained hyperextension, rotation or through out rotation or rotation. flexion flexion Rotation and/or lateral flexion does not occur about the lumbar region during trunk rotation Horizontally Movement is initiated with hip Horizontally aligned and flexion. Remain horizontally aligned, stable to aligned during flexion and mobile and minimize extension. Obviously moving stable to elevation and back and down during flexion prohibit depression elevation and during landing depression during rotation Aligned with hips and feet during Aligned with Aligned with flexion hips and feet hips and feet during flexion and do not move laterally with rotation Mobility allow adequate dorsiflexion during knee and hip flexion Stable Stable with heels grounded Heel of lead during lower limb flexion leg in contact with the floor, trail foot flexed and balanced on forefoot Evenly distributed Maintained on Able to control each leg and stick landing 90 degrees 70 degrees or Lead thigh 70 degrees of hip or greater of greater of hip parallel to the flexion hip flexion flexion floor

Lumbar

Hips

Knees

Ankles Feet

Balance Depth

MSC Task 2 Counter Movement Jump

MSC Task 3 Lunge and Twist

MCS Task 4 Bilateral broad jump with unilateral land

MCS Task 5 Body weight single leg squat

MCS Task 6 Counter movement jump off two landing on one

Held down away from ears. Elbows in line with ears.

Thoracic extension is clear

Shoulders held down away from ears. Elbows in line with ears.

Held stable in a neutral spine position throughout lower limb flexion and extension

Maintains lumbar curve, no hyperextension, rotation or flexion

Movement is initiated with hip flexion. Remain horizontally aligned during flexion and extension. Clearly moving back and down during flexion, minimal weight shift over stand leg.

Aligned with the hip and foot during flexion and extension

Aligned with hips and feet

Stable with heels grounded during lower limb flexion

Maintained on each leg 70 degrees of hip flexion

Able to control stick landing 70 degrees of hip flexion

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APPENDIX 5 (continued) Movement Competency Screen Scoring Criteria Body Region/Capacity

MCS Task 7 Bend and Pull

Head

Held stable in a neutral position

Shoulders

Held down and away from ears during arm flexion and extension. Scapulae move balanced and rhythmic and are not excessively abducted at arm extension Held in stable neutral spine position

Knees

Held down away from ears during arm flexion and extension. Scapulae move balanced and rhythmic and are not excessively abducted at arm extension Held stable in neutral spine position throughout trunk flexion and extension Movement is initiated with hip flexion.

Extension is obvious and controlled Neutral position and held stable

Ankles

NA

NA

Feet

Pointing straight

Feet straight, heels not falling in or out

Balance

Maintained

NA

Depth

75 - 90 degrees or greater of trunk flexion

Chest touches floor

Lumbar Hips

MSC Task 8 Press up

Held in line with the body during arm flexion and extension Extended and held stable

Adapted from Kritz (34), Kritz 45,59 and Vanweerd 47

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IJSPT

ORIGINAL RESEARCH

DYNAMIC HIP ADDUCTION, ABDUCTION AND ABDOMINAL EXERCISES FROM THE HOLMICH GROIN-INJURY PREVENTION PROGRAM ARE INTENSE ENOUGH TO BE CONSIDERED STRENGTHENING EXERCISES – A CROSS-SECTIONAL STUDY Kasper Krommes1 Thomas Bandholm2 Markus D. Jakobsen3 Lars L. Andersen3,4 Andreas Serner1,5 Per Hölmich1 Kristian Thorborg1

ABSTRACT Background: Training intensity is an important variable in strength training and above 80% of one repetition maximum is recommended for promoting strength for athletes. Four dynamic and two isometric on-field exercises are included in the Hölmich groin-injury prevention study that initially failed to show a reduction in groin injuries in soccer players. It has been speculated that exercise-intensity in this groin-injury prevention program was too low to induce the strength gains necessary to protect against groin-related injuries.

Purpose: To estimate the intensity of the six exercises from the Hölmich program using electromyography (EMG) and possibly categorize them as strength-training exercises.

Study Design: Cross-sectional study.

Methods: 21 adult male soccer players training >5 hours weekly were included. Surface-EMG was recorded from adductor longus, gluteus medius, rectus abdominis and external obliques during isometric adduction against a football placed between the ankles (IBA), isometric adduction against a football placed between the knees (IBK), folding knife (FK), cross-country skiing on one leg (CCS), adduction partner (ADP) and abduction partner (ABP). The EMG-signals were normalized (nEMG) to an isometric maximal voluntary contraction for each tested muscle.

Results: Adductor longus activity during IBA was 84% nEMG (95% CI: 70-98) and during IBK it was 118% nEMG (95% CI 106-130). For the dynamic exercises, ADP evoked 87% nEMG (95% CI 69-105) in adductor longus, ABP evoked 88% nEMG (95% CI 76-100) in gluteus medius, FK evoked 82% nEMG (95% CI 68-96) rectus abdominis, and 101% nEMG (95% CI 85-118) in external obliques. During CSS <37% nEMG was evoked from all muscles.

Conclusion: These data suggest that exercise-intensity of all the six investigated exercises in the Hölmich groin injury prevention program, except cross-county skiing, is sufficient to be considered strength-training for specific muscle groups in and around the groin region.

Level of Evidence: 3 Key words: Abdominals, adductor longus, electromyography, gluteus medius, soccer

1

Sports Orthopedic Research Centre—Copenhagen (SORC-C), Department of Orthopaedic Surgery, Copenhagen University Hospital, Amager-Hvidovre, Denmark 2 Physical Medicine & Rehabilitation Research - Copenhagen (PMR-C), Department of Physical and Occupational Therapy, Department of Orthopaedic Surgery, Clinical Research Center, Amager-Hvidovre Hospital, University of Copenhagen, Copenhagen, Denmark 3 National Research Centre for the Working Environment, Copenhagen, Denmark 4 Physical Activity and Human Performance group, SMI, Department of Health Science and Technology, Aalborg University, Denmark 5 Sports Groin Pain Centre, Aspetar Orthopaedic and Sports Medicine Hospital, Doha, Qatar

Acknowledgements The authors would like to thank all the players who took the time to participate in the study, as well as the team of physiotherapy students Jonas Nesse-Karlsen, Kaare Mejding and Kaare Frandsen for help with the practical work during the tests.

CORRESPONDING AUTHOR Kasper Krommes Sports Orthopedic Research Centre Copenhagen (SORC-C), Department of Orthopaedic Surgery, Copenhagen University Hospital, Amager-Hvidovre, Denmark.

Kettegaard Alle 30, 2650 Hvidovre, Denmark Tel: +45 42 55 55 50 E-mail: krommes@gmail.com

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INTRODUCTION Groin injuries are one of the most common types of injuries in soccer, accounting for 8-18% of all injuries.1–3 Groin injuries in soccer are primarily related to the hip adductors, accounting for approximately 60% of all acute and long-standing groin injuries, but can also be related to varied anatomical locations/ tissues, such as the hip flexors, the abdominal muscles, and the inguinal canal.3–5 The latest systematic reviews on risk factors for groin injuries concluded that there is relatively consistent Level 1 and 2 evidence to suggest that hip adductor and abductor strength is associated with increased risk of groin injuy.6-7 A randomized controlled trial

by Hölmich et. al.8 concerning injury prevention of groin injuries in soccer included exercises targeting these risk factors by performing a comprehensive exercise program focusing on strength and stability. The trial included nearly 1000 players and was aimed at reducing groin injury rates by 50%, however, only a 30% non-significant difference in injury rates was found.8 One of the possible reasons for the lack of an intended effect (≥50% reduction) on the prevention of groin injuries in soccer has been suggested to be related to a lack of adequate intensity of the included exercise.8 To promote strength gains in athletes, it is recommended to recruit the entire pool of motor units, based on the size principle.9–11 The threshold for high-threshold motor units varies for different muscles, with small muscles, such as muscles of the fingers, requiring as little as 30% of maximum effort to reach total recruitment,12 and larger muscles, such as the tibialis anterior and biceps brachialis, having thresholds at 80% and 90%, respectively.12,13 In that respect, intensity is recommended to be at least 80% of one repetition maximum (RM) for a stimulus that can induce strength gains in athletes.9 As opposed to joint-torque or external load of a given exercise, EMG (electromyography) is often used to quantify exercise intensity of specific muscles by measuring the recruitment and firing characteristics during exercise.14–19 In that respect, longitudinal strength gains have been repeatedly found when utilizing exercises at above 80% EMG intensity,19–24 as a quasilinear relationship between EMG and force output has been described.14–16,25–29 Thus, EMG normalized

(nEMG) to a maximal voluntary isometric contraction30 (MVC) with correct electrode placement14,15 and in a non-fatigued state15,16,29 is suggested as a valid option when estimating exercise intensity of specific muscles,14–19 with 80% of maximum as the rough cut-off required to promote strength gains in athletes.9 Six exercises were included in the Hölmich prevention program of which the two isometric exercises were shown in a previous investigation to produce high levels of muscle activity (nEMG values > 80%) in the adductor longus.19 However, resistance training is recommended to include dynamic muscle contractions9,31,32 and no information exists on the specific intensity of the dynamic exercises in the prevention program introduced by Hölmich et al.8 Considering that the dynamic exercises in the program require no use of additional equipment for resistance, compared to weight training machines, free weights, elastic bands or other forms of exercise equipment that help quantify intensity, it may be that these exercises do not induce sufficient intensity to promote strength gains in soccer players.

The purpose of this study was therefore to estimate the intensity of the six exercises from the Hölmich program using electromyography (EMG) and possibly categorize them as strength-training exercises.

METHODS Study design The present study used a cross-sectional design in which participants were investigated once having been familiarized with the trial procedures on a previous occasion. During the first session, they performed a 10-min. standardized warm-up of running drills and mobility exercises and were subsequently familiarized with all the exercises. The second session was conducted at least four days after to avoid delayed onset of muscle soreness. After the same standardized warm-up, the subjects performed MVCs to be used as reference contractions followed by two trials of the six exercises in a random order with minimum 60 s between, while muscle activity was recorded using surface EMG. Participants rated the level of perceived exertion during all exercises on the BorgCR10-scale, a categorical numeric rating scale with verbal anchors ranging from 0 ~

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‘Nothing at all’ to 10 ~ ‘Extremely strong’33 to provide additional data on subjective intensity. No exercise or training was allowed the day before testing and both sessions took place at Hvidovre Hospital, Copenhagen, Denmark. The reporting of the study follows the STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) guidelines, using the checklist for cross-sectional studies34 and was approved by the Danish National Committee on Health Research Ethics (H-3-2011-145.). All participants gave written consent according to the Helsinki Declaration before testing was initiated. The study is not pre-registered.

Participants Through convenience sampling, participants were recruited on a voluntary basis through contacts from local rugby and soccer clubs in Copenhagen, Denmark, from March to June 2012. Players were eligible for inclusion if they did not have injuries which could be presumed to influence the execution of the exercises, and had no or only minimal self-reported hip or groin pain, indicated by a score of above 80 out of 100 on the Hip and Groin Outcome Score (Sports subscale).35 The six exercises from the Hölmich groininjury prevention program The present study included two isometric and four dynamic exercises introduced by Hölmich et al.8 Three repetitions of each dynamic exercise were used for analysis of the EMG signal in order to reduce the accumulation of fatigue. The isometric exercises were performed for 10 s, as described by Hölmich et al.8 1: Isometric adduction against a soccer ball placed between the ankles (IBA): when lying supine, the thigh in neutral position, applying pressure against the ball as hard as possible (Figure 1a).8 2: Isometric adduction against a soccer ball placed between the knees (IBK): when lying supine with flexed hips and knees and feet flat on the surface, the thigh in neutral position, applying pressure against the ball as hard as possible (Figure 1b).8 3: ‘Folding knife” (FK): a combined abdominal sit-up and hip flexion. Starting from the supine position, with a football between flexed knees, repetitions are performed in a slow pace by flexing the hip and the

lower back, bringing knees and chest together (Figure 1c).8 4: Standing one-leg coordination exercise called “cross-country skiing on one leg” (CSS): flexing and extending the knee and swinging the arms in the same rhythm, repetitions are performed on the dominant leg (defined as the preferred kicking leg) as the standing leg (Figure 1d).8 Exercises 5 and 6 are partner exercises where two players perform both exercises together simultaneously: 5: Hip adduction against a partner’s hip abduction called “adduction partner” (ADP): in the sitting position, supported by the hands placed on the ground behind the trunk, the tested player places his legs straight and wide apart with the feet and lower shin on the outside of the partners feet and lower shin.

He adducts while the partner abducts eccentrically and slowly presses his feet together (Figure 1e).8 6: Hip abduction against a partner’s hip adduction called “abduction partner” (ABP): from the reversed starting position as “adduction partner” with feet and lower shins now placed medially on his partner’s feet and lower shin, the player abducts concentrically (“abduction partner”) while the partner adducts eccentrically, and is slowly brought into abduction (Figure 1f).8 Both partner-exercises were performed for 6 seconds per repetition with a 3 s concentric and a 3 s eccentric contraction, with as much effort as possible, still allowing the partner to follow the tempo for the duration of the exercise.8 ELECTROMYOGRAPHY (EMG) Rectangular (20 x 30 mm) non-disposable differential surface-electrodes with 1 cm inter-electrode distance (DE-2.1, Delsys, Boston, MA, USA) were placed unilaterally to collect data from adductor longus, gluteus medius, rectus abdominis and the external oblique muscles after standard skin preparation. Using electrode gel and medical grade adhesive (Delsys electrode interface, Delsys, Boston, MA, USA), the electrodes were aligned parallel with the direction of the muscle fibres. Verification of EMG signal quality was conducted by visual inspection of

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Figure 1. The six included exercises: a = ”isometric adduction against a football placed between the ankles”; b = ”isometric adduction against a football placed between the knees”; c = “folding knife”; d = “crosscountry skiing on one leg”; e = “adduction partner” performed by the player to the left; f = “abduction partner” performed by the player to the left.

the raw EMG signal while the subjects performed movements similar to the six evaluated exercises and isometric contractions specific to each muscle of interest after initial electrode placement and again after the warm-up routine. The electrodes were attached to 150 cm shielded wires, connected directly to small built-in preamplifiers and further to a main amplifier unit (Bagnoli-16, Delsys, Boston, MA, USA) with a band-pass of 15–450 Hz and a

common-mode rejection ratio of 92 dB. Sampling was done at 1 kHz using a 16-bit A/D converter (6036E, National Instruments, Austin, TX, USA). Data analysis was performed on a personal computer (EMGworks acquisition 3.1, Delsys, Boston, MA, USA).

Electrode placements Adductor longus; medially on the thigh equivalent to the proximal third of the distance from the

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ball placed between the knees. Gluteus medius MVC; side-lying with hip and knees straight, the tested leg is held in approximately 25 degrees of hip abduction by the therapist.37,41An isometric hip abduction was performed against a belt fixed around the lateral femoral epicondyle, as the use of belts has been shown to be less demanding on the therapist, preferred by participants and increases the reliability of maximal hip abduction torque measurements.42 Rectus abdominis and external obliques; a lumbar spine flexion with isometric abdominal contraction in a supine position against a fixed training belt strapped around the chest.

Figure 1. Mean peak of median nEMG with standard error for adductor longus, gluteus medius, external obliques and rectus abdominis during the exercises. nEMG = Normalized electromyography.

pubic tubercle to the insertion on femur.17,36,37 Gluteus medius; half the distance between the iliac crest and the greater trochanter antero-superiorly from the gluteus maximus.36, 37 Rectus abdominis; half the distance between the umbilicus and the pubic symphysis38 and centered on the muscle belly, i.e. 2-4 cm laterally from the umbilicus, depending on the size of the participant. External obliques; directly below the most inferior point of the ribs in direction towards the opposite pubic tubercle.39 Reference electrode; on the contralateral patella. A previous study of dynamic exercises for adductor longus has shown a high intra session reliability of EMG-activity in both legs.19 It was therefore decided only to measure unilaterally on the dominant side, defined as the side of the preferred kicking leg.

Reference contractions The participants performed two MVCs in three different test positions in a randomized order to estimate the maximal muscle activity. The highest value from any of the contractions was used as the reference contraction, i.e. 100%, to normalize the EMG recordings from the exercises. MVCs lasted 5 s each and participants were given at least 30 s rest between each contraction.40 A standard verbal encouragement of “three, two, one, start, push, push, push, push, stop” was used. Adductor longus MVC; supine with straight hips and knees, bilateral isometric hip adduction was performed against a

Data reduction The raw EMG signals were visually inspected and contractions with signal artifacts were discarded.

All raw EMG signals were digitally filtered using a Butterworth 4th order high-pass filter (10 Hz cutoff frequency), and subsequently smoothed and filtered using a moving root-mean-square (RMS) filter of 500 ms.43 Peak EMG of each muscle within each contraction was identified as the maximum value of the smoothed RMS EMG signal and normalized to the maximal RMS EMG obtained during the MVC. Statistical methods Based on a mean of 108% nEMG and a 35.5% standard deviation from a previous investigation of the IBK exercise,19 a significance level of 0.05 and statistical power of 80% to detect differences of 20% between muscles and exercises, a sample of 21 participants was needed based on the paired t-test (G*Power 3.1.9.2). All Borg CR10 values are presented as medians with interquartiles ranges and their corresponding verbal anchors. All nEMG values are reported as least square means with 95% confidence intervals (CI). A repeated measures oneway analysis of variance (ANOVA) with a significance level of p ≤ 0.05 was used to compare the peak nEMG for each muscle in the different exercises, in order to compare all exercises to each other. The mean of peak from all three repetitions was used for the dynamic exercises. A Bonferroni correction was made to account for the multiple comparisons in the post hoc analysis. All analyses were performed for participants with complete data sets (per protocol) and no imputations were made.

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Table 1. Peak normalized EMG measurements for all exercises and muscles Isometric IBA Adductor longus

84 (7)

Dynamic

IBK *

118 (6)

FK *†

CSS

ADP

ABP *

33 (5)

13 (2)

86 (9)

8 (1)

*

Gluteus medius

11 (2)

11 (2)

19 (4)

38 (5)

12 (2)

88 (6)†*

Rectus abdominis

8 (2)

4 (1)

83 (7)†

4 (1)

12 (2)

10 (2)

14 (3)

31 (5)

25 (5)

External obliques

19 (4)

14 (4)

†*

100 (8)

Values reported as mean normalized electromyography (standard error). IBA = “isometric adduction against a football placed between the ankles”; IBK = “isometric adduction against a football placed between the knees”; FK = “folding knife”; CSS = “crosscountry skiing on one leg”; ADP = “adduction partner”; ABP = “abduction partner”. * = significantly higher peak nEMG for this muscle than for other muscles during the exercise (p < 0.002). † = significantly higher peak nEMG during this exercise for this muscle than during any other exercise (p < 0.0001).

RESULTS Twenty-four healthy male soccer and rugby players were enrolled in the study. Data from three participants were missing due to broken reference electrodes, excessive artifacts or erroneous data extraction. The decision to exclude these data was made prior to the data analyses. Thus, the comparative analysis included 21 participants, mean age 21.4 ± 3.3 y, height 182.1 ± 7.7 cm, weight 83.1 ± 13.4 kg and scoring 96.7 ± 5.2 points on the HAGOS (Sports subscale). The participants had a training frequency of 5.2 (± 1.1) hrs per week with 1-2 weekly matches.

EMG activation levels are presented in Table 1. Five exercises reached specific muscle activation levels above 80% nEMG. In the isometric exercises, IBA muscle activity of the adductor longus was 84% nEMG (95% CI 70-98) and during IBK it was 118% nEMG (95% CI 106-130). With respect to the dynamic exercises, ADP evoked 87% nEMG (95% CI 69-105) in adductor longus, in the ABP exercise gluteus medius was reached 88% nEMG (955CI 76-100), for the FK rectus abdominis was 82% nEMG (95% CI 68-96), and external obliques was 101% nEMG (95% CI 85-118). During CSS all muscles were <37% nEMG. In the two isometric exercises, the adductor longus muscle activity was greater than in all other muscles, with greatest activity in the IBK (p<0.0001).

For the dynamic exercises, the adductor longus activation was higher in the ADP exercise than in all other dynamic exercises (p<000.1). Gluteus medius activation was greater in the ABP exercise, than in

all other exercises (p<0.001), and rectus abdominis and external obliques activation in the FK was higher than in all other exercises (p<0.001). The levels of perceived exertion rated on the BorgCR10 scale during exercises ranged from ‘Weak’ to ‘Strong’, with CSS being perceived as ‘Weak’ (median 2.5, IQR 1.1-3.75), ABP as ‘Moderate’ (median 4, IQR 3-6) and the remaining exercises as ‘Strong’ (ADP median 5, IQR 4-6.75; FK median 5, IQR 3-6.75; IBA median 5, IQR 3-7; IBK: median 5, IQR 4.25-6.75).

DISCUSSION The main purpose of this study was to examine the level of muscle activity during two isometric and four dynamic strengthening exercises from a previously published groin-injury prevention program.8 The two isometric exercises have previously been investigated for muscle activity and showed similar levels as in the current study with both ≥80% nEMG.19 The results of the current study indicate that three of the dynamic exercises in the groin injury prevention program can be categorized as exercises with sufficient intensity for strength improvements in athletes, targeting important muscle groups relevant in the prevention of groin injuries; adduction partner for adductor longus, abduction partner for gluteus medius, and folding knife for rectus abdominis and external obliques. These muscles are important as most groin injuries are related to the adductor longus but may also be related to the abdominal muscles and the inguinal canal.3–5 Authors of several studies6,7

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have identified decreased strength in the adductors preceding and following the onset of groin injuries, which makes adductor strength training a top priority in prevention and rehabilitation of groin injuries. In addition, targeted strengthening around the hip may contribute to pelvic alignment (frontal plane pelvic angle),44 which has been mentioned as an important factor in both prevention and management of groin injuries.45–47 Decreased strength in the hip abductors (gluteus medius) has also been found in athletes who since sustained a groin injury, making hip abductor strength training another key muscle for groin injury prevention.6,7 The exercise “cross-country skiing on one leg” did not reach sufficient intensity for strength training but it might promote dynamic stability in single leg stance and pelvic alignment through improved endurance capacity of gluteus medius, especially during minor to moderate and repetitive loading situations, such as in sub-maximal running and change of direction, an intensity also often utilized during a soccer game or practice. Based upon the current data it seems unlikely that inadequate exercise intensity should be the explanation for the lack of a substantial effect (50% groin injury reduction) of such a program in soccer players, as five of the six included exercises have been demonstrated in the current study to be sufficiently intense to promote strength gains in muscles relevant in groin injury prevention. Previous investigations of muscle activity of adductor longus during exercise have shown that muscle activity during the Barbell squat increases if the stance width and external hip rotation is increased. However, the highest nEMG found was only 23.1%.48 Commonly used unilateral frontal plane exercises for rehabilitation of lower extremity injuries; lunges, step-up and step up-and-over were in another study found to only evoke nEMG of the adductors in the range of 16-22%.49 Delmore et al. examined several specific hip adductor exercises that showed intensities of 14-36% nEMG.50 However, one exercise in the study by Delmore et al., resisted sidelying hip adduction showed adductor longus nEMG of 60%,50 in concordance with previous findings of 64% nEMG from Serner et al.19, although un-resisted in their study. The relatively low nEMG results found in these studies indicate that exercises in which the adductors are working as stabilizers or hip-extensors such as in during squat variations are not able

to induce the same muscle activity as the exercises included in the present study. In comparison the “adduction partner”, although limited by the partner determining and providing the level of resistance, has no need for extra external resistance devices and demonstrated muscle activity similar to exercises previously implemented using strength training equipment such as strength training machines and elastic bands.51 The dynamic Copenhagen Adduction exercise also relies on partner-assistance, performed sidelying and as the partner holds the upper leg at the height of the hip, the athlete lifts his entire body with using primarily his hip adductors until it reaches a straight line.20 The Copenhagen Adduction has been shown to induce high muscle activity of 108% of MVC,19 and longitudinal strength gains.20 However, isometric exercises induce angle-specific strength gains52 and are predominantly recommended in the course of muscle injury rehabilitation when pain and range of motion limits the ability to perform dynamic muscle contractions recommended for strength training.9,31,32,53 Thus, the three dynamic exercises included in the current study in combination with the Copenhagen Adduction exercise seem to be some of the most relevant exercises to include when considering the initiation of a groin injury prevention program, because they evoke muscle activity above 80% opposed to other dynamic equipment-free exercises investigated in the literature.

This allows for speculation regarding other possible factors influencing the lack of statistical injury reduction in the previous Hölmich trial. Besides intensity, other important exercise variables could also be part of the explanation, such as frequency, total volume and adherence, which were largely unknown in the trial.7 Another factor that has recently be shown to have a substantial impact on the risk of injury is the ratio between acute workload (1 week total distance) and chronic workload (4-week average acute workload) during both training and competitive matches in soccer. These two factors should be either controlled for or observed as a potential confounding factor in future trials aimed at preventing injuries in soccer. 54,55 A substantiating argument for the use of dynamic high intensity exercises for soccer players is that exercises targeting the at-risk muscle with high muscle activity have been able to significantly reduce

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other muscle-tendinous injuries, as well as increase strength.22,24,56 For example, one study implemented the Nordic Hamstring exercise,24,56 which has shown biceps femoris long head nEMG of 91%23 and is performed eccentrically to match the deceleration phase of the leg during running/sprinting, where hamstring injuries often occur.56 As such, the exercises from the current study seem highly relevant to implement in future trials aiming at reducing groin injuries.

The BorgCR10 scale was used in the current study which is closely related to exercise intensity.51,57 Other measures of perceived exertion could also be used in clinical practice, such as the Repetitions in Reserve (RIR) which used for strength training at intensities near repetition-failure, by having the athlete subjectively estimate how many additional repetitions were possible.58 As players in the present study only performed three repetitions in order to minimize the presence of fatigue and thereby allowing meaningful interpretations of the EMG data, using RIR would however not be relevant METHODOLOGICAL LIMITATIONS There are several limitations of using EMG to estimate exercise intensity. For example when using dynamic exercises, the EMG amplitude can be relatively higher than the expected force based on assumptions of a linear force-EMG relationship.

The association between EMG and force are also not always linear as the force-velocity and forcelength relationship is not accounted for, neither is the electromechanical delay. Nevertheless, using appropriate methods, e.g. using slowly controlled contractions and appropriate analytical methods, there seems to be a good and linear relationship between normalized EMG and percentage of load utilized during 1RM in certain exercises.27 The application of surface electrodes carries the risk of crosstalk from adjacent muscles.14,15 Accordingly, the muscle activity of adductor longus could possibly reflect the muscle activity of the adductor group as a whole. As muscle activity of more than 100% nEMG was found during the isometric exercise IBK, which is consistent with previous findings,20 thus, it could be assumed that this exercise and position might be more appropriate to perform the MVC in if performed according to MVC guidelines with standardized order, instruction and duration.30

CONCLUSION These data suggest that the exercise intensity of all but one of the six investigated exercises from the previous published Hölmich groin injury prevention program is sufficient to be categorized as strengthening exercises for specific relevant muscle groups in and around the groin region.

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39. Anders C, Wagner H, Puta C, et al. Trunk muscle activation patterns during walking at different speeds. J Electromyogr Kinesiol Off J Int Soc Electrophysiol Kinesiol. 2007;17(2):245-252.

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47. Kinchington M. Groin Pain: A view from below; The impact of lower extremity function and podiatric interventions. Aspetar Sports Med. 2013;2(3):360-368.

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50. Delmore RJ, Laudner KG, Torry MR. Adductor longus activation during common hip exercises. J Sport Rehabil. 2014;23(2):79-87.

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54. Nassis GP, Gabbett TJ. Is workload associated with injuries and performance in elite football? A call for action. Br J Sports Med. 2016;doi:10.1136/ bjsports-2016-095988 55. Murray NB, Gabbett TJ, Townshend AD, et al.

Individual and combined effects of acute and chronic running loads on injury risk in elite Australian footballers. Scand J Med Sci Sports. 2016; doi:10.1111/sms.12719 56. Petersen J, Thorborg K, Nielsen MB, et al.

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IJSPT

ORIGINAL RESEARCH

A COMPREHENSIVE INSTRUMENT FOR EVALUATING MILD TRAUMATIC BRAIN INJURY (MTBI)/CONCUSSION IN INDEPENDENT ADULTS: A PILOT STUDY Amanda Borges, PT, DPT, ATC, CSCS1 Scot Raab, PhD, ATC, LAT1 Monica Lininger, PhD, ATC, LAT1

ABSTRACT Background: One common component of concussion rehabilitation is a computerized cognitive test free of concomitant physical demands. Healthcare professionals may be able to provide more patient-centered care after a diagnosed concussion if specific areas of impairment are identified and treated, such as the physical aspect of neurocognitive function.

Hypothesis/Purpose: To evaluate the test-retest reliability of a unique combination of neurocognitive assessment tools currently utilized in concussion assessments into one single, inclusive instrument that measures both neurocognitive function and physical capability.

Study Design: Original research â&#x20AC;&#x201C; diagnostic tests.

Methods: Fourteen individuals (nine males, age: 29 + 17.9, five females, age: 46.0 Âą 21.5 years) either with normal cognitive function (NBI) without history of a health event (e.g. cerebral vascular accident/stroke, mTBI) that resulted in brain injury within one year of the study, or who had suffered a health event that has resulted in a medically documented brain injury (BI) participated in the study. Participants completed the full hybrid assessment instrument for a baseline test, then completed a follow-up test using the same instrument within 72-96 hours of baseline. Test-retest reliability was measured using Pearson product-moment correlations of the first and second testing sessions, and a two-way ANOVA (group between factor: NBI and BI and time within factor: session 1 and session 2) was performed on the summative scores to determine differences between each group.

Results: Test-retest reliability was strong and statistical significant for both the NBI (r = .858, p = .014) and the BI (r = .967, p =.033) groups. There was a significant difference between summative scores for the NBI and BI groups (F1,20 = 42.325, p < .0001).

Conclusion: The newly created Comprehensive Instrument for Evaluating Mild Traumatic Brain Injury (CIEMTBI) demonstrates good test-retest reliability and was able to discriminate the results between individuals in the NBI and BI groups. Further research, specifically with different samples, is needed to better determine the reliability and diagnostic accuracy of the instrument.

Level of Evidence: 2c Key words: Balance, C3 Logix, Computerized, ImPACT, King Devick

1

Northern Arizona University, Flagstaff, AZ, USA

CORRESPONDING AUTHOR Monica Lininger, PhD, ATC, LAT Assistant Professor Athletic Training Education Program Northern Arizona University PO Box 15094 Flagstaff, AZ 86011 928.523.7442 (phone) 928.523.4315 (fax) E-mail: monica.lininger@nau.edu

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INTRODUCTION The diagnosis and treatment of an athlete who sustains a concussion, also known as a mild traumatic brain injury (mTBI), is presently one of the most controversial and poorly understood topics in sports medicine.1-4 Baseline testing is presently regarded as a key component in the standard for neurocognitive assessment following a suspected concussion.5 Current standard baseline testing is commonly performed using a computerized neurocognitive tool that assesses cognitive speed, processing, visual motor speed, and memory before and after distraction (both short and long term memory).6 A computerized assessment (i.e. ImPACT (ImPACT Applications, Inc. © 2016) or CCAT (Cogstate, LLC. 2011) is used at baseline and after injury as a tool for return to play evaluations.6,7 Progressive concussion treatment protocols for athletes include re-testing the concussed athlete with a computerized neurocognitive assessment after symptoms have resolved, comparing the results of the post-injury test to baseline test results, and progressing that athlete back into sport by gradually increasing physically demanding sport-specific activities.8-10 The neurocognitive assessment is typically performed on a computer and may not identify physical impairments (common sequelae of concussion) and may lack meaningful test-retest reliability.6,7 Neurocognitive testing, such as the ImPACT, may miss individuals attempting to manipulate test scores, supporting the inclusion of additional assessments in order to limit invalid outcomes.11 New tests and methods are being developed and utilized to measure common physical deficits associated with concussions, and some tools have been shown to be reliable for identifying visual, vestibular, and balance dysfunction.12-16 These new assessment methods combined with aspects of computerized tools already utilized to assess cognitive function could assist athletic trainers and physicians in making return to play decisions, and help target treatments to areas of impairment. However, with so many methods for evaluating different aspects of concussion available, there may be confusion among health care providers regarding areas and severity of impairment. A unified tool that utilizes aspects of several different concussion-testing methods, and combining those methods into a single instrument,

could help create a standard evaluation and guide patient care universally among health care providers.

The purpose of this study was to evaluate the testretest reliability of a novel and comprehensive instrument for evaluating mild traumatic brain injury (referred to as “CIEMTBI”) that combines several currently utilized concussion assessment methods9,13,17-27 into one single, inclusive instrument that measures both neurocognitive function and physical capability. This newly developed instrument was evaluated for test-retest reliability within participants, and the results were compared between participants in two groups: one non-brain injured group in which participants have not sustained a brain injury and therefore should have normal neurocognitive function (NBI), and another brain injured group in which participants have sustained brain injury and should demonstrate impaired neurocognitive function (BI). The hypothesis is that the hybrid instrument will reliably identify both neurocognitive and physical impairments following a concussion, making it a reliable tool for assessing individuals who may have sustained a concussion.

METHODS This research was designed as a pilot study to determine the test-retest reliability of a hybrid instrument created to detect impairments related to concussion/ mTBI. The study was conducted on the campus of Northern Arizona University from September 2014 to March 2015. The protocol and design were submitted to the university institutional review board (IRB) and approved. During the course of the study, all procedures were in accordance with the ethic standard of the IRB. Participants were assigned a pseudo code identification number to maintain anonymity of study data and provided full disclosure prior to consent being attained.

Participants Fourteen individuals (nine males, age: 29 + 17.9, five females, age: 46.0 ± 21.5 years) participated in the study. Participants were recruited to volunteer for the study via referral from local healthcare providers. Furthermore, these participants met the inclusionary criteria of being capable of living independently, and either 1) having normal cognitive function without history of a negative health event

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(e.g. cerebral vascular accident/stroke, mTBI) that resulted in brain injury or cognitive impairment within one year of the study, or 2) having suffered a health event that has resulted in a medically documented impairment of cognitive function. Furthermore, those participants with impaired cognitive function were 14 days or more post-injury with persistent symptoms. Seven participants were assigned to the normal neurocognitive function, or non-braininjured (NBI) group, and seven participants were assigned to the brain-injured (BI) group. Exclusionary criteria included history of concussion within one year of testing (for NBI participants only) and no symptoms of central vestibular pathology.

Measures The CIEMTBI included the Dizziness Handicap Inventory (DHI),17,18 a symptom checklist22 incorporated with the C3 Logix system (developed by iComet Technologies in Cleveland, OH), a cognitive assessment battery20,21 that included challenges to immediate memory, concentration, language abilities, abstraction ability, coordination, delayed recall, balance (via C3 Logix),23-25 Vestibular/Ocular Motor Screening (VOMS),9,13 King-Devick test (manufactured by King-Devick Test in Oakbrook Terrace, IL),19 and the remainder of the C3 Logix system battery of tests,25-27 including Trails ‘A’ and ‘B’ along with processing speed assessments. All assessments will be described in detail later in this manuscript.

Cognitive Assessment The cognitive assessment measured immediate memory by having the researcher read a list of five simple words to the participant. The participant was then given two trials to repeat the list of five words.

The participant received one point for each word correctly remembered, and did not need to repeat words in the correct order. If the participant failed the first trial and could not repeat any words, a list of alternate words was used for the second trial.

Concentration Concentration was assessed through challenges incorporating digit recall, attention, serial 7’s, and listing the months of the year in reverse order. Digit recall was similar to the immediate memory test, but it required the participant to repeat back a list

of single digits read aloud by the researcher. First, the participant was asked to repeat a series of five digits in the same order as the researcher read, then the next four series of digits were repeated in the reverse order of what the researcher read. Each reverse order series increased the number of digits by one, from three to six digits. The attention assessment required the participant to tap their hand on a firm surface, which in this study was a desk, every time the researcher reads the letter “A” aloud in a series of other random letters. The participant was assigned zero points if they had no errors, or five points per error up to 10 points (two errors maximum). Serial 7’s required the participant to start at 99 and subtract by seven to countdown aloud to the number one. On repeated assessments participants were instructed to start at 98 or 99 to minimize learning effects. Participants received points for each number stated correctly. Finally, participants were asked to list aloud the months of the year in reverse order. No points were given if the participant did not make any errors, and 10 points were assigned if the participant made any errors. This was also timed.

Language Language abilities were assessed by having the participant repeat sentences that were read aloud to them one time. One point was assigned for each correctly repeated sentence, with a maximum of six points possible. Abstraction was tested by requiring the participant to state the similarity between two words. Two points were assigned if the participant was able to correctly state a similarity, while the participant was given zero points if they could not correctly state a similarity. Examples might include listing an ‘orange’ and ‘apple’; the expected reply would have been ‘fruit’.

Coordination was assessed only for the upper limbs, and was evaluated by having the participant move their finger (participant selected which arm to use) from their nose to as far in front of their nose as possible and back as quickly as they are able five times while fully extending the elbow and not missing the nose. After the coordination exam was complete, the participants were asked to repeat the five words that were read to them in the immediate memory section of the hybrid test. This was the delayed recall portion of the hybrid test. The participant received one point for each correctly recalled word.

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C3 Logix Tests The C3 Logix system is an iPad based application that has modules which assess for neurocognitive ability in several domains: symptomatology, reaction time, working memory and information processing, neuromotor function, balance, visual acuity, and vestibular function.22-27 The symptomatology was assessed at the beginning of the CIEMTBI with a graded symptom checklist that is comparable to the SCAT3.

The symptom checklist on the iPad-based C3 Logix system was used instead of the SCAT3 form (which is filled in by the participant on paper) because it was more user friendly, particularly for some of the participants in the BI group with motor deficits and difficulty writing, and because it integrated well with the rest of the C3 Logix system. Balance was assessed approximately midway through the CIEMTBI via use of a belt that attached the iPad to the participant’s waist in order to measure sway using the Balance Error Scoring System (BESS). The balance assessment utilized the gyroscope and accelerometers in the iPad to detect quantifiable movement or sway (Figure 1). BESS procedures were followed according to standard protocol,23 with the participant only being tested on a firm surface (foam surface testing was not performed for safety of the BI group).

Footwear was noted, with participants preferably only wearing socks, but not allowed to wear shoes, tape, or braces. The surface for balance testing was always hard congoleum tile, and the foot tested was always the participant’s non-dominant foot.

The remainder of the C3 Logix system test battery included assessments for processing speed, simple reaction time, choice reaction, and “Trails A and B”.

Processing speed was assessed via a memory test that required association of symbols with numbers.

Simple reaction time was measured by having the participant place their dominant hand index finger on a button that said “touch and hold” on the iPad screen below another yellow button on the iPad screen. The participant then had to move their finger from the touch and hold button to the yellow button as quickly as possible after the yellow button turned green. The choice reaction time test was similar to simple reaction, but it required both hands to be used, two yellow buttons were placed above two touch and hold buttons, and the participant had to move only the ipsilateral hand to the single yellow

Figure 1. Balance Error Scoring System using iPad attached to subject’s waist by a belt to detect quantifiable movement or sway.

button that turned green. Trails A and B assessed neuromotor function by requiring the participant to draw a line between points that were either letters, numbers, or a mix of both, while also locating the numbers and/or letters in ascending sequence.

Vestibular/Ocular Motor Screening (VOMS) The Vestibular/Ocular Motor Screening (VOMS) asked the participant to complete seven different head and eye movements, and rate their symptoms in four categories after each movement. These movements were: horizontal and vertical smooth pursuits, horizontal and vertical saccades, horizontal and vertical vestibuloocular reflex (VOR), and visual motion sensitivity. The researcher was positioned 10 feet away from the participant for all movements, and began all tests at the participant’s eye level directly in front of the participant’s eyes. Smooth pursuits

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required the participant to move their eyes while keeping the head still as the researcher moved a finger between points three feet apart in horizontal and vertical planes. This sequence was completed twice in each plane. Saccades were performed by having the researcher hold up one finger on each hand three feet apart. The participant was then instructed to keep their head still and quickly move their eyes between the two fingers ten times in each vertical and horizontal plane. Vestibuloocular reflex was tested similarly to saccades, except the participant kept their eyes focused on a single point directly in front of their face 10 feet away and were instructed to move their head 45° in each direction (up and down for vertical plane, left and right for horizontal plane) 10 times at a 180 bpm pace. Visual motion sensitivity was tested by instructing the participant to hold a hand (self-selected) out with arm fully extended and thumb pointing up. The participant then kept their head still with eyes focused on the thumb, and rotated their body in the transverse plane 180° back and forth at a pace of 50 bpm five times.

King-Devick test The King-Devick test was used as an assessment that tests for impairments in the following areas: saccades, attention, concentration, reading ability, and speech/language.19 This test requires the participant to read aloud a series of single digit numbers in order according to an established direction. The digits were printed on a card, and each series/card became increasingly more difficult via removal of the lines connecting the numbers, and then spacing the numbers closer together.

each test used for the CIEMTBI can be seen in Table 1. No participants became ill during testing, and all follow-up testing was performed within 72-96 hours of baseline testing, as planned. However, some participants in the BI group were unable to complete certain sections of the CIEMTBI instrument due to inability (physical and/or cognitive) and/or refusal to attempt to complete the section. In that case, testing in that section of the instrument was stopped, a maximum score (most errors, or lowest performance rating) was assigned for that section, and the assessment continued until completion of the instrument.

In a post-concussion setting, this practice would allow the score to demonstrate improvement during recovery; and it is expected that some patients immediately post mTBI might have difficulty completing all of the involved tasks.

Statistical Analyses Creation of a Summative Score All variables were recoded to be on a 10-point scale to prevent one item from being more influential over others. These subscales were then added together to Table 1. Individual Tests of Comprehensive Instrument for Evaluating Mild Traumatic Brain Injury (CIEMTBI) Dizziness Handicap Inventory Symptom Checklist38 Cogni ve Assessment Ba ery of Tests: Immediate memory39,40 Concentra on39,40 Language39 Abstrac on39

Procedures Baseline evaluation data were collected for demographics, exclusionary criteria, and the hybrid instrument (which includes assessments designed to measure symptoms related to mTBI, cognitive skills related to memory, concentration, language abilities, abstraction ability, coordination, balance, visual acuity, and processing/reaction time). Participants were each assessed using the CIEMTBI instrument a total of two times: once at baseline, and once at a follow-up test within 72-96 hours of baseline testing to establish test re-test values. Each testing session took approximately 60 minutes. A table identifying

Coordina on40 Delayed recall39,40 Balance38 Ves bular/Ocular Motor Screening King-Devick test C3Logix Ba ery of Tests: 38 Processing speed Trails A and B Simple reac on me Choice reac on me

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create 11 different variables that were then summed together, creating one summative value for each testing session. These 11 variables included: DHI, Symptoms, Cognition, Language, Abstract, Coordination, Delayed Recall, Balance, VOMS, King-Devick and Processing Speed. Placing each of the 11 subscales on a 10-point scale allowed for the summative score to range from 0-110. The lower the summative score the less cogitatively impaired the individual. If necessary, subscale values were reversed to assign lower scores to indicate fewer errors the participant made per variable.

age summative score for the NBI participants (12.65 + 4.75) was nearly 23 points lower than that of the participants in the BI group (35.71 + 11.66). Furthermore, there was no interaction between group membership and testing session (F1,20 = .602, p = .447).

For all of the comparisons on the time variables the NBI participants were significantly faster (Serial 7s/ Months in Reverse Order: F1,20 = 5.990, p = .024; Trails A/B: F1,17 = 7.917, p = .012; Simple/Choice Reaction Times: F1,20 = 20.946, p < .0001; and King Devick average time: F1,19 = 37.667, p < .0001).

Test-retest reliability Test-retest reliability was measured using Pearson product-moment correlations of the first and second administration of the test, specifically the summative score of each testing session. Also, one paired t-test was performed on the summative scores within each group (NBI and BI) to ensure that the within group variance was stable between the first and second testing sessions. A two-way ANOVA was conducted using testing session as the within participants variable (session 1 and session 2) and group membership as the between participants variable (NBI and BI). The following averages of time were created for comparisons (Serial 7s/Months in Reverse Order, Trails A/B, Simple/Choice Reaction Times, and King-Devick average time). A two-way ANOVA was performed on the four continuous time dependent variables with the within participants variable (session 1 and session 2) and the between participants variable (NBI and BI). All analyses were performed using Statistical Package for the Social Sciences (SPSS, version 21) with alpha set to p<0.05.

DISCUSSION The researchers evaluated the test-retest reliability of a newly created instrument, the CIEMTBI, that measures both neurocognitive function and physical capability. Reliability was assessed by comparing testing results within participants and between participants in two different groups. These two groups - one with normal neurocognitive function and one with impaired neurocognitive function - were compared in order to demonstrate that the testing scores remained consistent within participants, but varied between groups. This suggests that the CIEMTBI instrument was reliable with repeated testing sessions, and it was also able to detect differences between neurocognitive impairment or functional limitations and normal neurocognitive function. Thus, with further replications, this instrument may be able to detect a change in an athleteâ&#x20AC;&#x2122;s mental and physical status before and after sustaining a concussion.

RESULTS The test-retest reliability was strong for both the NBI (r = .858, p = .014) and the BI (r = .967, p = .033) groups showing that the outcomes were repeatable and stable between testing sessions. There were also no differences seen between the means, as an entire sample, from testing session 1 to session 2 (t10 = .001, p = 1.000). There was a significant difference between the NBI and BI groups on the summative scores (F1,20 = 42.325, p < .0001), suggesting that the instrument is able to detect differences between neurocognitive impairment or functional limitations and normal neurocognitive function. The aver-

The CIEMTBI instrument combines several currently utilized concussion assessment methods into a single tool, and the reliability of the instrument as a whole (r = .858 in the NBI group, r = .967 in the BI group) was similar to or higher than the reliability of each individual component. The Dizziness Handicap Inventory has been reported to have testretest reliability of r = .97.28 The hybrid instrument also utilizes several components of the Standardized Assessment of Concussion (SAC) and the Montreal Cognitive Assessment (MoCA). Barr and McCrea29 reported moderate test-retest reliability for the SAC (r = .55), and Nasreddine et al.30 reported strong test-retest reliability for the MoCA (r = .92).

Kontos et al31 reported high internal consistency for the VOMS (Cronbach Îą = .97). The Kontos et al

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study was not able to report test-retest reliability data because only time points from a single evaluation were available for statistical analysis. Although the instrument test-retest reliability findings of this study cannot be directly compared to the internal consistency findings of Kontos et al, the high internal consistency of the VOMS supports its inclusion in the hybrid instrument, and it is not likely that the VOMS as a subscale of the instrument reduced the reliability of the CIEMTBI instrument. Further research is warranted to determine the test-retest reliability of the newly developed VOMS.

that the mean age of the NBI group (25.0 + 2.3) was much lower than that of the BI group (47.8 + 25.6).

This could potentially lead to a greater difference between groups on the summative scores due to typical decreases in neurocognitive function due, in part, to normal aging.36,37 Furthermore, this study had a low sample size. Although this was a pilot study and was designed considering a low sample size, not having a large enough sample could potentially affect the results. A final limitation of this work could be the cost of the C3 Logix system (~$1,800.00), which requires the use of an iPad as well.

Furthermore, Galetta et al32 found strong test-retest reliability for the King-Devick test (ICC = .97). Bell et al.23 reported adequate reliability for the BESS test (ICC = .70). Serial 7s has also been shown to have reliability similar to that of our CIEMTBI instrument, which also utilizes serial 7s (serial 7s r = .7-.81, hybrid instrument r = .858 in the NBI group, r = .967 in the BI group).33,34 Moreover, the reliability of the CIEMTBI instrument (r = .858 - .967) was found to be higher than previous studies found using intraclass correlation coefficients (ICC) for the ImPACT test (ICC < .75)6 or for the Axon Sports Computerized Cognitive Assessment Tool (ICC = .401 - .672).7 Although the reported findings of this study cannot be definitively compared to the ICC values previously found for other tests, the present findings support the need for further research to perform ICC analysis of the CIEMTBI instrument. Additionally, our study supports previous work that indicates comprehensive concussion assessment should be multifaceted4-6,9,13,35 because the CIEMTBI was able to detect differences between neurocognitive impairment or functional limitations and normal neurocognitive function, and it showed significant differences in time and balance variables between the BI and NBI groups.

Clinical Relevance The results from this study suggest that the CIEMTBI may be a viable option for sports medicine teams to use in the evaluation of athletes who may have sustained a concussion, although its use does not need to be limited to athletics. This could also apply to other individuals at risk of mTBI/concussion, such as military personnel.5 Furthermore, because the effects of concussion vary between individuals, this instrument may be a valuable tool that can be used as a standard measure of concussion impairment. Since there are many other tools available to assess different aspects of impairment that may be due to concussion, health care providers may not be using the same evaluation methods, which could potentially cause confusion. A unified, single tool, such as the CIEMTBI, could help create a standard evaluation of concussion, and can help guide plan of care on a universal level.

Limitations One limitation of this study is that the researchers did not have detailed medical records or medical histories for our participants. Only the participantsâ&#x20AC;&#x2122; medical history that was relevant to the study (i.e. history of brain injury or head trauma, having been diagnosed with ADD/ADHD, etc.) was collected, and all medical history was self-reported by the participants without documentation to verify participant reports. Another potential limitation of the study is

Further research is needed to examine the reliability of this instrument with a larger sample size of both brain-injured and healthy participants. The CIEMTBI should also be studied to evaluate its diagnostic accuracy for detecting impairments related to concussion. Although the results from this study provide data that suggests the hybrid instrument is able to detect differences between neurocognitive impairment or functional limitations and normal neurocognitive function, a validation study would allow for determination of the exact impairments the hybrid instrument can detect, and with what accuracy.

CONCLUSION Baseline and post-injury testing is currently part of the standard of care in concussion management.

It was found that the CIEMTBI, which combines sev-

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eral aspects of concussion assessment and challenges both neurocognitive and physical abilities, has good test-retest reliability, and also may be able to detect differences between neurocognitive impairment and normal neurocognitive function. This may be a valuable tool for clinicians involved in concussion assessment and return to play decisions. Further research is needed to better determine the reliability and diagnostic accuracy of the instrument.

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3. Sullivan KA, Edmed SL, Allan AC, Karlsson LJ, Smith SS. Characterizing self-reported sleep disturbance after mild traumatic brain injury. J Neurotrauma.

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5. Roebuck-Spencer TM, Vincent AS, Schlegel RE, Gilliland K. Evidence for added value of baseline testing in computer-based cognitive assessment.

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7. MacDonald J, Duerson D. Reliability of a computerized neurocognitive test in baseline concussion testing of high school athletes. Clin J Sport Med. 2015;25(4):367-372.

8. Covassin T, Elbin RJ, Crutcher B, Burkhart S. The management of sport-related concussion: Considerations for male and female athletes. Transl Stroke Res. 2013;4(4):420-424.

9. Collins MW, Kontos AP, Reynolds E, Murawski CD, Fu FH. A comprehensive, targeted approach to the clinical care of athletes following sport-related concussion. Knee Surg Sports Traumatol Arthrosc.

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11. Gaudet CE, Weyandt LL. Immediate post-concussion and cognitive testing (ImPACT): A systematic review of the prevalence and assessment of invalid performance. Clin Neuropsychol. 2016:1-16.

12. Erickson GB, Citek K, Cove M, et al. Reliability of a computer-based system for measuring visual performance skills. Optometry. 2011;82(9):528-542.

13. Mucha A, Collins MW, Elbin RJ, et al. A brief Vestibular/Ocular motor screening (VOMS) assessment to evaluate concussions: Preliminary findings. Am J Sports Med. 2014;42(10):2479-2486.

14. Kao CL, Hsieh WL, Wang SJ, Chen SJ, Wei SH, Chan RC. Efficacy of a computerized sensor system for evaluation and training of dizzy patients. Sensors (Basel). 2010;10(8):7602-7620.

15. Alberts JL, Hirsch JR, Koop MM, et al. Using accelerometer and gyroscopic measures to quantify postural stability. J Athl Train. 2015;50(6):578-588.

16. Vital D, Hegemann SC, Straumann D, et al. A new dynamic visual acuity test to assess peripheral vestibular function. Arch Otolaryngol Head Neck Surg.

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17. Vereeck L, Truijen S, Wuyts FL, Van dH. The dizziness handicap inventory and its relationship with functional balance performance. Otology & Neurotology. 2007;28(1).

18. Treleaven J. Dizziness handicap inventory (DHI).

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19. Galetta KM, Brandes LE, Maki K, et al. The King– Devick test and sports-related concussion: Study of a rapid visual screening tool in a collegiate cohort. J Neurol Sci. 2011;309(1–2):34-39.

20. Guskiewicz KM, Register-Mihalik J, McCrory P, et al.

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21. Schweizer TA, Al-Khindi T, Macdonald RL. Minimental state examination versus montreal cognitive assessment: Rapid assessment tools for cognitive and functional outcome after aneurysmal subarachnoid hemorrhage. J Neurol Sci. 2012;316(1–2):137-140.

22. Piland SG, Motl RW, Guskiewicz KM, McCrea M, Ferrara MS. Structural validity of a self-report concussion-related symptom scale. Med Sci Sports Exerc. 2006;38(1):27.

23. Bell DR, Guskiewicz KM, Clark MA, Padua DA. Systematic review of the balance error scoring system. Sports Health. 2011;3(3):287-295.

24. Iverson GL, Kaarto ML, Koehle MS. Normative data for the balance error scoring system: Implications for brain injury evaluations. Brain Inj. 2008;22(2):147-152.

25. Antonucci MM, Sass BJ, Sass CM. Utilization of C3 Logix in a multimodal neurological treatment approach in a patient with dysautonomia and cognitive impairments. Frontiers in Neurology. (76).

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26. Broglio SP, Macciocchi SN, Ferrara MS. Sensitivity of the concussion assessment battery. Neurosurgery.

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27. Schatz P, Ybarra V, Leitner D. Validating the accuracy of reaction time assessment on computer-based tablet devices. Assessment. 2015;22(4):405-410.

28. Jacobson GP, Newman CW. The development of the dizziness handicap inventory. Arch Otolaryngol Head Neck Surg. 1990;116(4):424-427.

29. Barr WB, McCrea M. Sensitivity and specificity of standardized neurocognitive testing immediately following sports concussion. J Int Neuropsychol Soc. 2001;7(6):693-702.

30. Nasreddine ZS, Phillips NA, Bedirian V, et al. The montreal cognitive assessment, MoCA: A brief screening tool for mild cognitive impairment. J Am Geriatr Soc. 2005;53(4):695-699.

31. Kontos AP, Sufrinko A, Elbin RJ, Puskar A, Collins MW. Reliability and associated risk factors for performance on the Vestibular/Ocular motor screening (VOMS) tool in healthy collegiate athletes.

Am J Sports Med. 2016.

32. Galetta KM, Barrett J, Allen M, et al. The king-devick test as a determinant of head trauma and concussion in boxers and MMA fighters. Neurology.

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33. de Leon J, Ellis G, Rosen P, Simpson GM. The test-retest reliability of the mini-mental state

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IJSPT

ORIGINAL RESEARCH

A COMPREHENSIVE INSTRUMENT FOR EVALUATING MILD TRAUMATIC BRAIN INJURY (MTBI)/CONCUSSION IN INDEPENDENT ADULTS: A PILOT STUDY Amanda Borges, PT, DPT, ATC, CSCS1 Scot Raab, PhD, ATC, LAT1 Monica Lininger, PhD, ATC, LAT1

ABSTRACT Background: One common component of concussion rehabilitation is a computerized cognitive test free of concomitant physical demands. Healthcare professionals may be able to provide more patient-centered care after a diagnosed concussion if specific areas of impairment are identified and treated, such as the physical aspect of neurocognitive function.

Hypothesis/Purpose: To evaluate the test-retest reliability of a unique combination of neurocognitive assessment tools currently utilized in concussion assessments into one single, inclusive instrument that measures both neurocognitive function and physical capability.

Study Design: Original research â&#x20AC;&#x201C; diagnostic tests.

Methods: Fourteen individuals (nine males, age: 29 + 17.9, five females, age: 46.0 Âą 21.5 years) either with normal cognitive function (NBI) without history of a health event (e.g. cerebral vascular accident/stroke, mTBI) that resulted in brain injury within one year of the study, or who had suffered a health event that has resulted in a medically documented brain injury (BI) participated in the study. Participants completed the full hybrid assessment instrument for a baseline test, then completed a follow-up test using the same instrument within 72-96 hours of baseline. Test-retest reliability was measured using Pearson product-moment correlations of the first and second testing sessions, and a two-way ANOVA (group between factor: NBI and BI and time within factor: session 1 and session 2) was performed on the summative scores to determine differences between each group.

Results: Test-retest reliability was strong and statistical significant for both the NBI (r = .858, p = .014) and the BI (r = .967, p =.033) groups. There was a significant difference between summative scores for the NBI and BI groups (F1,20 = 42.325, p < .0001).

Conclusion: The newly created Comprehensive Instrument for Evaluating Mild Traumatic Brain Injury (CIEMTBI) demonstrates good test-retest reliability and was able to discriminate the results between individuals in the NBI and BI groups. Further research, specifically with different samples, is needed to better determine the reliability and diagnostic accuracy of the instrument.

Level of Evidence: 2c Key words: Balance, C3 Logix, Computerized, ImPACT, King Devick

1

Northern Arizona University, Flagstaff, AZ, USA

CORRESPONDING AUTHOR Monica Lininger, PhD, ATC, LAT Assistant Professor Athletic Training Education Program Northern Arizona University PO Box 15094 Flagstaff, AZ 86011 928.523.7442 (phone) 928.523.4315 (fax) E-mail: monica.lininger@nau.edu

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INTRODUCTION The diagnosis and treatment of an athlete who sustains a concussion, also known as a mild traumatic brain injury (mTBI), is presently one of the most controversial and poorly understood topics in sports medicine.1-4 Baseline testing is presently regarded as a key component in the standard for neurocognitive assessment following a suspected concussion.5 Current standard baseline testing is commonly performed using a computerized neurocognitive tool that assesses cognitive speed, processing, visual motor speed, and memory before and after distraction (both short and long term memory).6 A computerized assessment (i.e. ImPACT (ImPACT Applications, Inc. © 2016) or CCAT (Cogstate, LLC. 2011) is used at baseline and after injury as a tool for return to play evaluations.6,7 Progressive concussion treatment protocols for athletes include re-testing the concussed athlete with a computerized neurocognitive assessment after symptoms have resolved, comparing the results of the post-injury test to baseline test results, and progressing that athlete back into sport by gradually increasing physically demanding sport-specific activities.8-10 The neurocognitive assessment is typically performed on a computer and may not identify physical impairments (common sequelae of concussion) and may lack meaningful test-retest reliability.6,7 Neurocognitive testing, such as the ImPACT, may miss individuals attempting to manipulate test scores, supporting the inclusion of additional assessments in order to limit invalid outcomes.11 New tests and methods are being developed and utilized to measure common physical deficits associated with concussions, and some tools have been shown to be reliable for identifying visual, vestibular, and balance dysfunction.12-16 These new assessment methods combined with aspects of computerized tools already utilized to assess cognitive function could assist athletic trainers and physicians in making return to play decisions, and help target treatments to areas of impairment. However, with so many methods for evaluating different aspects of concussion available, there may be confusion among health care providers regarding areas and severity of impairment. A unified tool that utilizes aspects of several different concussion-testing methods, and combining those methods into a single instrument,

could help create a standard evaluation and guide patient care universally among health care providers.

The purpose of this study was to evaluate the testretest reliability of a novel and comprehensive instrument for evaluating mild traumatic brain injury (referred to as “CIEMTBI”) that combines several currently utilized concussion assessment methods9,13,17-27 into one single, inclusive instrument that measures both neurocognitive function and physical capability. This newly developed instrument was evaluated for test-retest reliability within participants, and the results were compared between participants in two groups: one non-brain injured group in which participants have not sustained a brain injury and therefore should have normal neurocognitive function (NBI), and another brain injured group in which participants have sustained brain injury and should demonstrate impaired neurocognitive function (BI). The hypothesis is that the hybrid instrument will reliably identify both neurocognitive and physical impairments following a concussion, making it a reliable tool for assessing individuals who may have sustained a concussion.

METHODS This research was designed as a pilot study to determine the test-retest reliability of a hybrid instrument created to detect impairments related to concussion/ mTBI. The study was conducted on the campus of Northern Arizona University from September 2014 to March 2015. The protocol and design were submitted to the university institutional review board (IRB) and approved. During the course of the study, all procedures were in accordance with the ethic standard of the IRB. Participants were assigned a pseudo code identification number to maintain anonymity of study data and provided full disclosure prior to consent being attained.

Participants Fourteen individuals (nine males, age: 29 + 17.9, five females, age: 46.0 ± 21.5 years) participated in the study. Participants were recruited to volunteer for the study via referral from local healthcare providers. Furthermore, these participants met the inclusionary criteria of being capable of living independently, and either 1) having normal cognitive function without history of a negative health event

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(e.g. cerebral vascular accident/stroke, mTBI) that resulted in brain injury or cognitive impairment within one year of the study, or 2) having suffered a health event that has resulted in a medically documented impairment of cognitive function. Furthermore, those participants with impaired cognitive function were 14 days or more post-injury with persistent symptoms. Seven participants were assigned to the normal neurocognitive function, or non-braininjured (NBI) group, and seven participants were assigned to the brain-injured (BI) group. Exclusionary criteria included history of concussion within one year of testing (for NBI participants only) and no symptoms of central vestibular pathology.

Measures The CIEMTBI included the Dizziness Handicap Inventory (DHI),17,18 a symptom checklist22 incorporated with the C3 Logix system (developed by iComet Technologies in Cleveland, OH), a cognitive assessment battery20,21 that included challenges to immediate memory, concentration, language abilities, abstraction ability, coordination, delayed recall, balance (via C3 Logix),23-25 Vestibular/Ocular Motor Screening (VOMS),9,13 King-Devick test (manufactured by King-Devick Test in Oakbrook Terrace, IL),19 and the remainder of the C3 Logix system battery of tests,25-27 including Trails ‘A’ and ‘B’ along with processing speed assessments. All assessments will be described in detail later in this manuscript.

Cognitive Assessment The cognitive assessment measured immediate memory by having the researcher read a list of five simple words to the participant. The participant was then given two trials to repeat the list of five words.

The participant received one point for each word correctly remembered, and did not need to repeat words in the correct order. If the participant failed the first trial and could not repeat any words, a list of alternate words was used for the second trial.

Concentration Concentration was assessed through challenges incorporating digit recall, attention, serial 7’s, and listing the months of the year in reverse order. Digit recall was similar to the immediate memory test, but it required the participant to repeat back a list

of single digits read aloud by the researcher. First, the participant was asked to repeat a series of five digits in the same order as the researcher read, then the next four series of digits were repeated in the reverse order of what the researcher read. Each reverse order series increased the number of digits by one, from three to six digits. The attention assessment required the participant to tap their hand on a firm surface, which in this study was a desk, every time the researcher reads the letter “A” aloud in a series of other random letters. The participant was assigned zero points if they had no errors, or five points per error up to 10 points (two errors maximum). Serial 7’s required the participant to start at 99 and subtract by seven to countdown aloud to the number one. On repeated assessments participants were instructed to start at 98 or 99 to minimize learning effects. Participants received points for each number stated correctly. Finally, participants were asked to list aloud the months of the year in reverse order. No points were given if the participant did not make any errors, and 10 points were assigned if the participant made any errors. This was also timed.

Language Language abilities were assessed by having the participant repeat sentences that were read aloud to them one time. One point was assigned for each correctly repeated sentence, with a maximum of six points possible. Abstraction was tested by requiring the participant to state the similarity between two words. Two points were assigned if the participant was able to correctly state a similarity, while the participant was given zero points if they could not correctly state a similarity. Examples might include listing an ‘orange’ and ‘apple’; the expected reply would have been ‘fruit’.

Coordination was assessed only for the upper limbs, and was evaluated by having the participant move their finger (participant selected which arm to use) from their nose to as far in front of their nose as possible and back as quickly as they are able five times while fully extending the elbow and not missing the nose. After the coordination exam was complete, the participants were asked to repeat the five words that were read to them in the immediate memory section of the hybrid test. This was the delayed recall portion of the hybrid test. The participant received one point for each correctly recalled word.

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C3 Logix Tests The C3 Logix system is an iPad based application that has modules which assess for neurocognitive ability in several domains: symptomatology, reaction time, working memory and information processing, neuromotor function, balance, visual acuity, and vestibular function.22-27 The symptomatology was assessed at the beginning of the CIEMTBI with a graded symptom checklist that is comparable to the SCAT3.

The symptom checklist on the iPad-based C3 Logix system was used instead of the SCAT3 form (which is filled in by the participant on paper) because it was more user friendly, particularly for some of the participants in the BI group with motor deficits and difficulty writing, and because it integrated well with the rest of the C3 Logix system. Balance was assessed approximately midway through the CIEMTBI via use of a belt that attached the iPad to the participant’s waist in order to measure sway using the Balance Error Scoring System (BESS). The balance assessment utilized the gyroscope and accelerometers in the iPad to detect quantifiable movement or sway (Figure 1). BESS procedures were followed according to standard protocol,23 with the participant only being tested on a firm surface (foam surface testing was not performed for safety of the BI group).

Footwear was noted, with participants preferably only wearing socks, but not allowed to wear shoes, tape, or braces. The surface for balance testing was always hard congoleum tile, and the foot tested was always the participant’s non-dominant foot.

The remainder of the C3 Logix system test battery included assessments for processing speed, simple reaction time, choice reaction, and “Trails A and B”.

Processing speed was assessed via a memory test that required association of symbols with numbers.

Simple reaction time was measured by having the participant place their dominant hand index finger on a button that said “touch and hold” on the iPad screen below another yellow button on the iPad screen. The participant then had to move their finger from the touch and hold button to the yellow button as quickly as possible after the yellow button turned green. The choice reaction time test was similar to simple reaction, but it required both hands to be used, two yellow buttons were placed above two touch and hold buttons, and the participant had to move only the ipsilateral hand to the single yellow

Figure 1. Balance Error Scoring System using iPad attached to subject’s waist by a belt to detect quantifiable movement or sway.

button that turned green. Trails A and B assessed neuromotor function by requiring the participant to draw a line between points that were either letters, numbers, or a mix of both, while also locating the numbers and/or letters in ascending sequence.

Vestibular/Ocular Motor Screening (VOMS) The Vestibular/Ocular Motor Screening (VOMS) asked the participant to complete seven different head and eye movements, and rate their symptoms in four categories after each movement. These movements were: horizontal and vertical smooth pursuits, horizontal and vertical saccades, horizontal and vertical vestibuloocular reflex (VOR), and visual motion sensitivity. The researcher was positioned 10 feet away from the participant for all movements, and began all tests at the participant’s eye level directly in front of the participant’s eyes. Smooth pursuits

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required the participant to move their eyes while keeping the head still as the researcher moved a finger between points three feet apart in horizontal and vertical planes. This sequence was completed twice in each plane. Saccades were performed by having the researcher hold up one finger on each hand three feet apart. The participant was then instructed to keep their head still and quickly move their eyes between the two fingers ten times in each vertical and horizontal plane. Vestibuloocular reflex was tested similarly to saccades, except the participant kept their eyes focused on a single point directly in front of their face 10 feet away and were instructed to move their head 45° in each direction (up and down for vertical plane, left and right for horizontal plane) 10 times at a 180 bpm pace. Visual motion sensitivity was tested by instructing the participant to hold a hand (self-selected) out with arm fully extended and thumb pointing up. The participant then kept their head still with eyes focused on the thumb, and rotated their body in the transverse plane 180° back and forth at a pace of 50 bpm five times.

King-Devick test The King-Devick test was used as an assessment that tests for impairments in the following areas: saccades, attention, concentration, reading ability, and speech/language.19 This test requires the participant to read aloud a series of single digit numbers in order according to an established direction. The digits were printed on a card, and each series/card became increasingly more difficult via removal of the lines connecting the numbers, and then spacing the numbers closer together.

each test used for the CIEMTBI can be seen in Table 1. No participants became ill during testing, and all follow-up testing was performed within 72-96 hours of baseline testing, as planned. However, some participants in the BI group were unable to complete certain sections of the CIEMTBI instrument due to inability (physical and/or cognitive) and/or refusal to attempt to complete the section. In that case, testing in that section of the instrument was stopped, a maximum score (most errors, or lowest performance rating) was assigned for that section, and the assessment continued until completion of the instrument.

In a post-concussion setting, this practice would allow the score to demonstrate improvement during recovery; and it is expected that some patients immediately post mTBI might have difficulty completing all of the involved tasks.

Statistical Analyses Creation of a Summative Score All variables were recoded to be on a 10-point scale to prevent one item from being more influential over others. These subscales were then added together to Table 1. Individual Tests of Comprehensive Instrument for Evaluating Mild Traumatic Brain Injury (CIEMTBI) Dizziness Handicap Inventory Symptom Checklist38 Cogni ve Assessment Ba ery of Tests: Immediate memory39,40 Concentra on39,40 Language39 Abstrac on39

Procedures Baseline evaluation data were collected for demographics, exclusionary criteria, and the hybrid instrument (which includes assessments designed to measure symptoms related to mTBI, cognitive skills related to memory, concentration, language abilities, abstraction ability, coordination, balance, visual acuity, and processing/reaction time). Participants were each assessed using the CIEMTBI instrument a total of two times: once at baseline, and once at a follow-up test within 72-96 hours of baseline testing to establish test re-test values. Each testing session took approximately 60 minutes. A table identifying

Coordina on40 Delayed recall39,40 Balance38 Ves bular/Ocular Motor Screening King-Devick test C3Logix Ba ery of Tests: 38 Processing speed Trails A and B Simple reac on me Choice reac on me

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create 11 different variables that were then summed together, creating one summative value for each testing session. These 11 variables included: DHI, Symptoms, Cognition, Language, Abstract, Coordination, Delayed Recall, Balance, VOMS, King-Devick and Processing Speed. Placing each of the 11 subscales on a 10-point scale allowed for the summative score to range from 0-110. The lower the summative score the less cogitatively impaired the individual. If necessary, subscale values were reversed to assign lower scores to indicate fewer errors the participant made per variable.

age summative score for the NBI participants (12.65 + 4.75) was nearly 23 points lower than that of the participants in the BI group (35.71 + 11.66). Furthermore, there was no interaction between group membership and testing session (F1,20 = .602, p = .447).

For all of the comparisons on the time variables the NBI participants were significantly faster (Serial 7s/ Months in Reverse Order: F1,20 = 5.990, p = .024; Trails A/B: F1,17 = 7.917, p = .012; Simple/Choice Reaction Times: F1,20 = 20.946, p < .0001; and King Devick average time: F1,19 = 37.667, p < .0001).

Test-retest reliability Test-retest reliability was measured using Pearson product-moment correlations of the first and second administration of the test, specifically the summative score of each testing session. Also, one paired t-test was performed on the summative scores within each group (NBI and BI) to ensure that the within group variance was stable between the first and second testing sessions. A two-way ANOVA was conducted using testing session as the within participants variable (session 1 and session 2) and group membership as the between participants variable (NBI and BI). The following averages of time were created for comparisons (Serial 7s/Months in Reverse Order, Trails A/B, Simple/Choice Reaction Times, and King-Devick average time). A two-way ANOVA was performed on the four continuous time dependent variables with the within participants variable (session 1 and session 2) and the between participants variable (NBI and BI). All analyses were performed using Statistical Package for the Social Sciences (SPSS, version 21) with alpha set to p<0.05.

DISCUSSION The researchers evaluated the test-retest reliability of a newly created instrument, the CIEMTBI, that measures both neurocognitive function and physical capability. Reliability was assessed by comparing testing results within participants and between participants in two different groups. These two groups - one with normal neurocognitive function and one with impaired neurocognitive function - were compared in order to demonstrate that the testing scores remained consistent within participants, but varied between groups. This suggests that the CIEMTBI instrument was reliable with repeated testing sessions, and it was also able to detect differences between neurocognitive impairment or functional limitations and normal neurocognitive function. Thus, with further replications, this instrument may be able to detect a change in an athleteâ&#x20AC;&#x2122;s mental and physical status before and after sustaining a concussion.

RESULTS The test-retest reliability was strong for both the NBI (r = .858, p = .014) and the BI (r = .967, p = .033) groups showing that the outcomes were repeatable and stable between testing sessions. There were also no differences seen between the means, as an entire sample, from testing session 1 to session 2 (t10 = .001, p = 1.000). There was a significant difference between the NBI and BI groups on the summative scores (F1,20 = 42.325, p < .0001), suggesting that the instrument is able to detect differences between neurocognitive impairment or functional limitations and normal neurocognitive function. The aver-

The CIEMTBI instrument combines several currently utilized concussion assessment methods into a single tool, and the reliability of the instrument as a whole (r = .858 in the NBI group, r = .967 in the BI group) was similar to or higher than the reliability of each individual component. The Dizziness Handicap Inventory has been reported to have testretest reliability of r = .97.28 The hybrid instrument also utilizes several components of the Standardized Assessment of Concussion (SAC) and the Montreal Cognitive Assessment (MoCA). Barr and McCrea29 reported moderate test-retest reliability for the SAC (r = .55), and Nasreddine et al.30 reported strong test-retest reliability for the MoCA (r = .92).

Kontos et al31 reported high internal consistency for the VOMS (Cronbach Îą = .97). The Kontos et al

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study was not able to report test-retest reliability data because only time points from a single evaluation were available for statistical analysis. Although the instrument test-retest reliability findings of this study cannot be directly compared to the internal consistency findings of Kontos et al, the high internal consistency of the VOMS supports its inclusion in the hybrid instrument, and it is not likely that the VOMS as a subscale of the instrument reduced the reliability of the CIEMTBI instrument. Further research is warranted to determine the test-retest reliability of the newly developed VOMS.

that the mean age of the NBI group (25.0 + 2.3) was much lower than that of the BI group (47.8 + 25.6).

This could potentially lead to a greater difference between groups on the summative scores due to typical decreases in neurocognitive function due, in part, to normal aging.36,37 Furthermore, this study had a low sample size. Although this was a pilot study and was designed considering a low sample size, not having a large enough sample could potentially affect the results. A final limitation of this work could be the cost of the C3 Logix system (~$1,800.00), which requires the use of an iPad as well.

Furthermore, Galetta et al32 found strong test-retest reliability for the King-Devick test (ICC = .97). Bell et al.23 reported adequate reliability for the BESS test (ICC = .70). Serial 7s has also been shown to have reliability similar to that of our CIEMTBI instrument, which also utilizes serial 7s (serial 7s r = .7-.81, hybrid instrument r = .858 in the NBI group, r = .967 in the BI group).33,34 Moreover, the reliability of the CIEMTBI instrument (r = .858 - .967) was found to be higher than previous studies found using intraclass correlation coefficients (ICC) for the ImPACT test (ICC < .75)6 or for the Axon Sports Computerized Cognitive Assessment Tool (ICC = .401 - .672).7 Although the reported findings of this study cannot be definitively compared to the ICC values previously found for other tests, the present findings support the need for further research to perform ICC analysis of the CIEMTBI instrument. Additionally, our study supports previous work that indicates comprehensive concussion assessment should be multifaceted4-6,9,13,35 because the CIEMTBI was able to detect differences between neurocognitive impairment or functional limitations and normal neurocognitive function, and it showed significant differences in time and balance variables between the BI and NBI groups.

Clinical Relevance The results from this study suggest that the CIEMTBI may be a viable option for sports medicine teams to use in the evaluation of athletes who may have sustained a concussion, although its use does not need to be limited to athletics. This could also apply to other individuals at risk of mTBI/concussion, such as military personnel.5 Furthermore, because the effects of concussion vary between individuals, this instrument may be a valuable tool that can be used as a standard measure of concussion impairment. Since there are many other tools available to assess different aspects of impairment that may be due to concussion, health care providers may not be using the same evaluation methods, which could potentially cause confusion. A unified, single tool, such as the CIEMTBI, could help create a standard evaluation of concussion, and can help guide plan of care on a universal level.

Limitations One limitation of this study is that the researchers did not have detailed medical records or medical histories for our participants. Only the participantsâ&#x20AC;&#x2122; medical history that was relevant to the study (i.e. history of brain injury or head trauma, having been diagnosed with ADD/ADHD, etc.) was collected, and all medical history was self-reported by the participants without documentation to verify participant reports. Another potential limitation of the study is

Further research is needed to examine the reliability of this instrument with a larger sample size of both brain-injured and healthy participants. The CIEMTBI should also be studied to evaluate its diagnostic accuracy for detecting impairments related to concussion. Although the results from this study provide data that suggests the hybrid instrument is able to detect differences between neurocognitive impairment or functional limitations and normal neurocognitive function, a validation study would allow for determination of the exact impairments the hybrid instrument can detect, and with what accuracy.

CONCLUSION Baseline and post-injury testing is currently part of the standard of care in concussion management.

It was found that the CIEMTBI, which combines sev-

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eral aspects of concussion assessment and challenges both neurocognitive and physical abilities, has good test-retest reliability, and also may be able to detect differences between neurocognitive impairment and normal neurocognitive function. This may be a valuable tool for clinicians involved in concussion assessment and return to play decisions. Further research is needed to better determine the reliability and diagnostic accuracy of the instrument.

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3. Sullivan KA, Edmed SL, Allan AC, Karlsson LJ, Smith SS. Characterizing self-reported sleep disturbance after mild traumatic brain injury. J Neurotrauma.

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4. Zasler ND. Sports concussion headache. Brain Inj. 2015;29(2):207-220.

5. Roebuck-Spencer TM, Vincent AS, Schlegel RE, Gilliland K. Evidence for added value of baseline testing in computer-based cognitive assessment.

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6. Resch J, Driscoll A, McCaffrey N, et al. ImPact test-retest reliability: Reliably unreliable? J Athl Train. 2013;48(4):506-511.

7. MacDonald J, Duerson D. Reliability of a computerized neurocognitive test in baseline concussion testing of high school athletes. Clin J Sport Med. 2015;25(4):367-372.

8. Covassin T, Elbin RJ, Crutcher B, Burkhart S. The management of sport-related concussion: Considerations for male and female athletes. Transl Stroke Res. 2013;4(4):420-424.

9. Collins MW, Kontos AP, Reynolds E, Murawski CD, Fu FH. A comprehensive, targeted approach to the clinical care of athletes following sport-related concussion. Knee Surg Sports Traumatol Arthrosc.

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10. Meehan WP,3rd, d’Hemecourt P, Collins CL, Comstock RD. Assessment and management of sport-related concussions in united states high schools. Am J Sports Med. 2011;39(11):2304-2310.

11. Gaudet CE, Weyandt LL. Immediate post-concussion and cognitive testing (ImPACT): A systematic review of the prevalence and assessment of invalid performance. Clin Neuropsychol. 2016:1-16.

12. Erickson GB, Citek K, Cove M, et al. Reliability of a computer-based system for measuring visual performance skills. Optometry. 2011;82(9):528-542.

13. Mucha A, Collins MW, Elbin RJ, et al. A brief Vestibular/Ocular motor screening (VOMS) assessment to evaluate concussions: Preliminary findings. Am J Sports Med. 2014;42(10):2479-2486.

14. Kao CL, Hsieh WL, Wang SJ, Chen SJ, Wei SH, Chan RC. Efficacy of a computerized sensor system for evaluation and training of dizzy patients. Sensors (Basel). 2010;10(8):7602-7620.

15. Alberts JL, Hirsch JR, Koop MM, et al. Using accelerometer and gyroscopic measures to quantify postural stability. J Athl Train. 2015;50(6):578-588.

16. Vital D, Hegemann SC, Straumann D, et al. A new dynamic visual acuity test to assess peripheral vestibular function. Arch Otolaryngol Head Neck Surg.

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17. Vereeck L, Truijen S, Wuyts FL, Van dH. The dizziness handicap inventory and its relationship with functional balance performance. Otology & Neurotology. 2007;28(1).

18. Treleaven J. Dizziness handicap inventory (DHI).

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19. Galetta KM, Brandes LE, Maki K, et al. The King– Devick test and sports-related concussion: Study of a rapid visual screening tool in a collegiate cohort. J Neurol Sci. 2011;309(1–2):34-39.

20. Guskiewicz KM, Register-Mihalik J, McCrory P, et al.

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21. Schweizer TA, Al-Khindi T, Macdonald RL. Minimental state examination versus montreal cognitive assessment: Rapid assessment tools for cognitive and functional outcome after aneurysmal subarachnoid hemorrhage. J Neurol Sci. 2012;316(1–2):137-140.

22. Piland SG, Motl RW, Guskiewicz KM, McCrea M, Ferrara MS. Structural validity of a self-report concussion-related symptom scale. Med Sci Sports Exerc. 2006;38(1):27.

23. Bell DR, Guskiewicz KM, Clark MA, Padua DA. Systematic review of the balance error scoring system. Sports Health. 2011;3(3):287-295.

24. Iverson GL, Kaarto ML, Koehle MS. Normative data for the balance error scoring system: Implications for brain injury evaluations. Brain Inj. 2008;22(2):147-152.

25. Antonucci MM, Sass BJ, Sass CM. Utilization of C3 Logix in a multimodal neurological treatment approach in a patient with dysautonomia and cognitive impairments. Frontiers in Neurology. (76).

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26. Broglio SP, Macciocchi SN, Ferrara MS. Sensitivity of the concussion assessment battery. Neurosurgery.

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27. Schatz P, Ybarra V, Leitner D. Validating the accuracy of reaction time assessment on computer-based tablet devices. Assessment. 2015;22(4):405-410.

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29. Barr WB, McCrea M. Sensitivity and specificity of standardized neurocognitive testing immediately following sports concussion. J Int Neuropsychol Soc. 2001;7(6):693-702.

30. Nasreddine ZS, Phillips NA, Bedirian V, et al. The montreal cognitive assessment, MoCA: A brief screening tool for mild cognitive impairment. J Am Geriatr Soc. 2005;53(4):695-699.

31. Kontos AP, Sufrinko A, Elbin RJ, Puskar A, Collins MW. Reliability and associated risk factors for performance on the Vestibular/Ocular motor screening (VOMS) tool in healthy collegiate athletes.

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32. Galetta KM, Barrett J, Allen M, et al. The king-devick test as a determinant of head trauma and concussion in boxers and MMA fighters. Neurology.

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33. de Leon J, Ellis G, Rosen P, Simpson GM. The test-retest reliability of the mini-mental state

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IJSPT

ORIGINAL RESEARCH

STRENGTH PROFILES IN HEALTHY INDIVIDUALS WITH AND WITHOUT SCAPULAR DYSKINESIS Daniel C. Hannah, MA, ATC1 Jason S. Scibek, PhD, ATC1,2 Christopher R. Carcia, PhD, PT, OCS, SCS1,3

ABSTRACT Background: Muscular weakness of the shoulder complex is commonly found in patients presenting with scapular dyskinesis; however, little is known regarding muscular performance in healthy individuals with scapular dyskinesis.

Purpose: To compare isometric strength measures of the shoulder complex between healthy individuals with and without scapular dyskinesis. It was hypothesized that healthy individuals with scapular dyskinesis would demonstrate decreased isometric strength of the scapular stabilizers and rotator cuff when compared to healthy individuals without scapular dyskinesis.

Study Design: Cross-sectional study.

Methods: Forty healthy, college-aged participants were recruited. Sixty-eight percent of subjects (27 of 40) presented with scapular dyskinesis. Thus, a matched-pairs analysis was conducted with 26 subjects (age: 22.00 ± 2.06 y; height: 168.77 ± 8.07 cm; mass: 70.98 ± 13.14 kg; BMI: 24.75 ± 3.04 kg/m2; 6 males; 20 females). The presence of scapular dyskinesis was determined visually using the scapular dyskinesis test with a dichotomous outcome (yes/no). Strength of the scapular stabilizers and rotator cuff was assessed via manual muscle testing using a handheld dynamometer. Force measures obtained with the handheld dynamometer were used to quantify strength. For each muscle tested, the mean peak force of three trials were normalized to body weight and used for data analysis. Additionally, strength ratios were calculated and analyzed. Differences in strength and strength ratios between those with and without scapular dyskinesis were compared using separate two-way mixed ANOVAs with repeated measures.

Results: No significant differences for either strength (F1.83,43.92 = 1.10, p = .34) or strength ratios (F1.83,44.02 = 1.93, p = .16) were observed between those with and without scapular dyskinesis. A significant main effect (F1.83,43.92 = 239.32, p < .01) for muscles tested was observed, and post-hoc analysis revealed significant trends resulting in a generalized order: the upper trapezius generated the greatest amount of force, followed by serratus anterior and middle trapezius, lower trapezius, supraspinatus, medial rotators, and lateral rotators.

Conclusion: The results of this study indicate that differences in shoulder muscle strength do not exist between healthy subjects with and without scapular dyskinesis. Additionally, scapular dyskinesis appears to be prevalent in healthy populations.

Level of Evidence: Level 3 Key words: Muscular performance, rotator cuff, scapular dysfunction, scapular stabilizers, shoulder

1

Rehabilitation Science, John G. Rangos, Sr., School of Health Sciences, Duquesne University, Pittsburgh, PA, USA 2 Department of Athletic Training, John G. Rangos, Sr., School of Health Sciences, Duquesne University, Pittsburgh, PA, USA 3 Department of Physical Therapy, John G. Rangos, Sr., School of Health Sciences, Duquesne University, Pittsburgh, PA, USA

CORRESPONDING AUTHOR Daniel C. Hannah, MA, ATC Rehabilitation Science, John G. Rangos, Sr., School of Health Sciences Duquesne University Pittsburgh, PA 15282 Phone: 412.396.4738 Fax: 412.396.4160 E-mail: hannahd@duq.edu

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INTRODUCTION Musculoskeletal disorders of the shoulder complex are common among the general population and those who participate in overhead sports. Incidence rates for shoulder pain in the general population are between 0.9 – 2.5% with a lifetime prevalence between 6.7-66.7%.1 The frequency of shoulder pain is much higher in those individuals participating in overhead sports.2-4 As such, the socioeconomic impact can be quite substantial. In fact, direct health care expenditures associated with treatment of shoulder dysfunction in the year 2000 totaled $7 billion.5 The occurrence of shoulder pain has been linked to scapular dysfunction.6-8 Scapular dyskinesis is used to describe aberrant movement patterns of the scapula, which may serve as a potential source of impairment to normal shoulder function.8 It is common to find scapular dyskinesis associated with a variety of shoulder pathologies including, but not limited to, impingement, rotator cuff tears, labral pathology, acromioclavicular separations, and multidirectional instability of the glenohumeral joint.8 However, it is increasingly apparent that scapular dyskinesis exists in healthy populations as well.9-11 Therefore, the question remains as to whether scapular dyskinesis predisposes an individual to injury. Unfortunately, conflicting evidence exists among prospective studies regarding whether scapular dyskinesis is a causative factor for upper extremity injury.9,12-14 While the amount of research on the role of the scapula continues to increase, the exact cause for the development of scapular dyskinesis is not fully understood. There are several probable causes including, bony pathology (e.g., clavicular fracture), joint pathology (e.g., acromioclavicular separation), neurological pathology (e.g., long thoracic nerve palsy), soft tissue inflexibility (e.g., pectoralis minor tightness), and decreased muscle performance (e.g., altered activation patterns or strength deficits).7,8 Decreased muscle performance of the scapulothoracic musculature has been linked to altered shoulder kinematics,15,16 which may predispose an individual to injury.17,18 Thus, rehabilitation programs have been suggested to focus on improving the performance of the rotator cuff and scapular stabilizers.7,8,19-23 Clinicians may benefit from collecting shoulder strength data to better identify those with scapular

dyskinesis who would benefit from a rehabilitation program focused on improving muscle performance.

These data can easily be collected with a handheld dynamometer given that it is cost-effective, reliable, and valid.24,25 Normative strength data, including antagonist ratios, exists for the rotator cuff26 and scapular stabilizers27 in healthy populations. Others have reported strength profiles of the shoulder in healthy overhead athletes.28,29 While these studies included only healthy participants, none of these studies controlled for the presence of scapular dyskinesis. Those studies that have controlled for scapular dyskinesis have revealed rotator cuff weakness.22,23,30-32 However, it is important to note that these studies delimited the scapular dyskinesis groups with only symptomatic participants.22,23,30-32 In addition, authors have speculated that weakness of the scapular stabilizers exists in those with scapular dyskinesis based on studies examining electromyographic activity, or comparing strength data in those with and without shoulder impingement.6-8 Currently, only one study has directly compared strength measures between groups with and without scapular dyskinesis in a population of asymptomatic overhead athletes.10 While significant weakness of the lower trapezius was demonstrated in the scapular dyskinesis group, the authors limited their strength measurements to only the lower trapezius and serratus anterior.10 Additional studies are needed that examine strength data of the scapular stabilizers and rotator cuff to gain a better understanding of the clinical relevance of scapular dyskinesis, as well as providing additional means to diagnose, monitor, and measure patient outcomes during the rehabilitation process. Therefore, the primary aim of this study was to compare strength measures of the shoulder complex between healthy individuals with and without scapular dyskinesis. It was hypothesized that healthy individuals with scapular dyskinesis would demonstrate decreased strength when compared to healthy individuals without scapular dyskinesis.

METHODS Participants A convenience sample of 40 participants volunteered to participate in the study (age = 22.2 ± 2.4 years; height = 169.9 ± 8.7 cm; mass = 68.7 ± 13.0 kg; body mass index (BMI) = 23.7 ± 3.1 kg/m2; sex

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= 12 males, 28 females; arm dominance = 3 left, 37 right). Participants were recruited from the School of Health Sciences at Duquesne University. All participants were included that met the following inclusion criteria: 1) between the ages of 18 and 40, and 2) no history of neck or dominant shoulder injury or pathology. Shoulder dominance was determined by which arm the participant would use to throw a ball. Exclusion criteria included 1) the presence of any neurological condition that affected muscular strength and consequent upper extremity range of motion, 2) inability to achieve ≥ 140° of shoulder elevation, 3) any previous surgery on the dominant shoulder, 4) diagnosis of rheumatoid arthritis, and 5) if the participant was currently pregnant. The University’s institutional review board approved the study and all participants were required to provide written informed consent prior to participation.

To ensure adequate statistical power, a power analysis was performed using G*Power 3.1.9.2. Based on preliminary data from 10 subjects, an effect size was calculated (f = .313), and operating at a power of 80% and α = .05, it was determined that an estimated sample size of 22 participants was needed to detect significant differences in strength.33 While collecting data, an apparent disparity was revealed in the number of participants with and without scapular dyskinesis. Scapular dyskinesis, as defined by the methods described in this study, was observed in 68% (10/13 males, 17/27 females) of the participants. Therefore, a matched-pairs analysis was utilized, which yielded 13 matched-pairs from the sample. (Table 1) The participants were matched according to sex and BMI. The remaining 14 participants from the sample were excluded from the study because suitable pairings were unavailable.

Procedures All participants completed the Physical Activity Readiness Questionnaire (PAR-Q)34 to establish general health fitness. If participants checked “yes” for any of the listed items they were disqualified from the study. To confirm a healthy shoulder status, all participants completed the patient self-report section and underwent the physical examination section of the American Shoulder and Elbow Surgeons Standardized Shoulder Assessment (ASES).35 Any presence of decreased range of motion, strength,

or other clinical findings that suggested shoulder pathology upon examination would have resulted in exclusion from the study.

Scapular Dyskinesis Test Participants were evaluated for scapular dysfunction of the dominant shoulder utilizing the scapular dyskinesis test.36 The participants performed separate trials of bilateral shoulder flexion and abduction while holding either a 1.4 kg or 2.3 kg weight: 1.4 kg for body masses < 68.1 kg and 2.3 kg for body masses > 68.1 kg.36,37 The test was modified by having the participants perform 10 repetitions for each movement. Movement velocity was standardized across all participants by way of a metronome set at 80 beats per minute resulting in a movement velocity of approximately 120°/s; therefore, each trial lasted 30 seconds. Performance of the test was digitally recorded from a standardized distance and height for documentation purposes.

The presence of scapular dyskinesis was determined by scapular winging, dysrhythmia, or both as defined by McClure et al.37 Scapular winging was defined as any posterior displacement of the medial border and/or inferior angle of the scapula away from the thorax.37 Dysrhythmia was defined as any early or excessive elevation or protraction, non-rhythmical motion while raising or lowering the arm, or rapid downward rotation while lowering the arm.37 A dichotomous method (yes/no) was used to categorize those with and without scapular dyskinesis.38 One investigator, with 14 years of clinical experience as an athletic trainer, evaluated all participants and determined the presence of scapular dyskinesis. Test-retest reliability (coefficient of agreement = .99) was assessed using digital recordings of 10 subjects that were randomly chosen from the sample. Reassessment occurred within a period of 48 hours. The investigator was blinded to the original scoring, and subject ordering was randomized to decrease bias.

Manual Muscle Tests Participants underwent eight manual muscle tests of muscles around the shoulder complex: upper trapezius (two methods), middle trapezius, lower trapezius, serratus anterior, supraspinatus, and the medial and lateral rotators of the humerus. The

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order of the strength tests were randomized. A handheld dynamometer (ergoFET 300, Hogan Health Industries©, West Jordon, UT), with a manufacturer’s reported accuracy of +/- 2%, was used to assess the peak force (N) exerted during the tests. Measures of force captured by the handheld dynamometer during the manual muscle tests were used to quantify measures of strength. Prior to data collection, the dynamometer was assessed for accuracy by comparing known loads applied to the dynamometer and its recorded values (r = .9998). For each muscle test, the participants were asked to generate a maximal effort against the resistance being applied by the investigator. Thus, participants performed a “make test” rather than a “break test” as it is commonly used in handheld dynamometry studies.24-28 Participants were asked to gradually build up their effort over a two-second period and maintain a maximum effort for three seconds. Three trials were performed for each manual muscle test with a 30-second rest period between each trial, and approximately one minute of rest between each muscle. Prior to performing the manual muscle tests, participants were provided instruction on proper performance of the test. Additionally, participants performed two to three sub-maximal efforts in order to become accustomed to the testing procedures.

Two different methods were used to evaluate the upper trapezius. The first method (UT1) was performed as described by Hislop et al39 (Figure 1). The participant was seated with the hands resting on the thighs, and the shoulder girdle was positioned at the midrange of elevation. The dynamometer was placed on the acromion process and the resistance was directed inferiorly. The second method (UT2) was performed with the participant standing atop of a modified rake handle while grasping the dynamometer with the dominant hand (Figure 2).

For this test, the manufacturer’s handle and hook accessories were affixed to the dynamometer. The dynamometer was attached to the modified rake handle by a metal chain. A screen was placed immediately adjacent to the participant on the non-dominant side to aide in limiting extraneous lateral trunk motion. The dynamometer was affixed to the chain at a height that positioned the participant’s shoulder girdle in the midrange of elevation. The participant was instructed to shrug their shoulder superiorly,

Figure 1. Test position for the upper trapezius, method 1.

Figure 2. Test position for the upper trapezius, method 2.

while maintaining an extended elbow, against the resistance.

The serratus anterior (SA) was tested as described by Kendall et al40 (Figure 3). The participant was seated with the dominant arm positioned in 120° of shoulder flexion with the thumb pointed in an upward direction. The dynamometer was positioned on the humerus at the level of the deltoid insertion, and the resistance was applied in a downward direction that was perpendicular to the humerus.

Strength of the middle trapezius (MT) was measured as described by Kendall et al40 (Figure 4). The participant was positioned prone on a plinth with the shoulder abducted to 90° and the humerus laterally rotated where the thumb pointed toward the ceil-

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Figure 3. Test position for the serratus anterior.

Figure 5. Test position for the lower trapezius.

2/3 of the distance from the root of the spine to the posterolateral angle of the acromion. Collecting strength measures of the lower trapezius by placing the dynamometer on the spine of the scapula has been determined to be a valid method of assessment.24 The resistance was applied in a superior and anterolateral direction in line with the humerus.

Figure 4. Test position for the middle trapezius.

ing. The location of the resistance force applied by the tester was modified whereby the dynamometer was positioned on the spine of the scapula approximately 2/3 of the distance from the root of the spine to the posterolateral angle of the acromion. The position was modified in an effort to isolate the measured forces to the scapulothoracic musculature and prevent the involvement of other muscular forces (e.g., rotator cuff).24 The resistance was applied in an anterolateral direction in line with the humerus.

The lower trapezius (LT) was tested as described by Hislop et al39 (Figure 5). The participant was positioned prone on a plinth with the shoulder abducted to 140° and the humerus laterally rotated where the thumb pointed toward the ceiling. Again, the location of the dynamometer was modified and positioned on the spine of the scapula approximately

The supraspinatus (SS) was evaluated as described

by Celik et al25 (Figure 6). The participant was seated with the dominant arm positioned in 90° of shoulder scaption (30° anterior to the frontal plane) with the thumb pointed toward the ceiling. The dynamometer was positioned on the upper arm just proximal to the elbow, and the resistance was applied in a downward direction.

Figure 6. Test position for the supraspinatus.

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The medial (MR) and lateral (LR) rotators were tested as described by Riemann et al26 (Figures 7 and 8). The participant was seated with a bolster placed between the dominant upper arm and thorax to maintain a position of 30° abduction and 30° flexion of the shoulder. The elbow was positioned at 90° of flexion, while the forearm was positioned in 0° pronation/supination and aligned parallel to the sagittal plane to achieve approximately 30° of lateral rotation of the shoulder. The dynamometer was placed over the distal radioulnar joint on the volar and dorsal surfaces for the medial and lateral rotators, respectively.

The same investigator performed all the manual muscle tests in this study. For each test, the peak force (N) from three trials was averaged, normalized

Figure 7. Test position for the medial rotators.

Figure 8. Test position for the lateral rotators.

to body weight (N), and used for data analysis. Excellent within-session, intrarater reliability (ICC3,1 = .920 – .970) was demonstrated for all manual muscle tests over the duration of data collection. In addition to the normalized strength data, strength ratios (UT/ LT, UT/MT, LT/MT, SA/UT, SA/MT, SA/LT, and LR/ MR) were calculated by dividing the averaged peak force of one muscle by the other.

Statistical Analyses Descriptive statistics were calculated for demographic data. A two-way mixed analysis of variance was used to determine differences in strength between those with and without scapular dyskinesis, with manual muscle tests (UT1, UT2, SA, MT, LT, SS, MR, and LR) being the repeated factor. If a significant main effect for manual muscle tests was detected, pairwise comparisons were made using a Bonferonni adjustment. Also, a two-way mixed analysis of variance was used to determine differences in strength ratios between those with and without scapular dyskinesis, with strength ratios (UT/LT, UT/MT, LT/MT, SA/UT, SA/MT, SA/LT, and LR/MR) being the repeated factor. If a significant interaction was detected, pairwise comparisons were made between groups for each repeated factor, and a Bonferonni adjustment was made for multiple comparisons. All statistical analyses were calculated using SPSS version 22 (IBM Corporation, Armonk, NY), and the level of significance was set a priori at α = .05.

RESULTS Demographic data for the 13 matched-pairs are presented in Table 1. For strength comparisons (Table 2), no significant interaction effects (F1.825,43.794 = 1.03, p = .343) were observed between manual muscle tests and scapular dyskinesis. Also, no significant main effects were demonstrated for scapular dyskinesis (F1,24 = .380, p = .543); however, significant main effects for manual muscle tests were revealed (F1.825,43.794 = 239.582, p < .001). For the strength ratios analysis (Table 3), no significant interaction effects (F1.834,44.015 = 1.933, p = .160) or main effects for scapular dyskinesis (F1,24 = 2.517, p = .126) were observed. Although significant main effects for strength ratios were revealed, these effects were not a focus of this study.

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Table 1. Participant Demographics for Matched-Pairs Analysis Variable Age (y ± SD) Height (cm ± SD) Mass (kg ± SD) BMI (kg/m2 ± SD) Sex (n) Arm Dominance (n) BMI = body mass index.

With Dyskinesis 21.5 ± 1.2 170.1 ± 9.0 72.7 ± 14.6 24.9 ± 3.4 3 males; 10 females 0 left; 13 right

Without Dyskinesis 22.5 ± 2.6 167.5 ± 7.1 69.3 ± 11.9 24.6 ± 2.8 3 males; 10 females 2 left; 11 right

p .188 .420 .523 .770

Table 2. Manual Muscle Test Data for Matched-Pairs Analysis Muscle With Dyskinesis Without Dyskinesis Total Upper Trapezius 1 0.292 ± 0.046 0.328 ± 0.085 0.310 ± 0.069* Upper Trapezius 2 0.271 ± 0.047 0.277 ± 0.099 0.274 ± 0.076* Serratus Anterior 0.145 ± 0.029 0.149 ± 0.036 0.147 ± 0.032† Middle Trapezius 0.137 ± 0.013 0.135 ± 0.022 0.136 ± 0.018* Lower Trapezius 0.105 ± 0.013 0.109 ± 0.028 0.107 ± 0.022‡ Supraspinatus 0.097 ± 0.015 0.105 ± 0.028 0.101 ± 0.022§ Medial Rotators 0.089 ± 0.017 0.091 ± 0.028 0.090 ± 0.023* Lateral Rotators 0.060 ± 0.012 0.060 ± 0.014 0.060 ± 0.013 Data are presented as normalized strength values (M ± SD) calculated by averaging the maximum force (N) of three trials then dividing by body weight (N) for each muscle, respectively. *Significantly greater than those listed below it. †Significantly greater than lower trapezius, supraspinatus, medial and lateral rotators. ‡Significantly greater than medial and lateral rotators. §Significantly greater than lateral rotators.

DISCUSSION It was hypothesized that strength differences would exist between healthy individuals with and without scapular dyskinesis, which may serve as a causative factor for scapular dyskinesis. However, the results of this study demonstrated no significant differences in strength or strength ratios of the scapular stabilizers and rotator cuff when compared between those healthy shoulders with and without scapular dyskinesis. To the authors’ knowledge, this was the first study to compare strength measures collected from a sample of healthy participants with and without scapular dyskinesis.

Scapular dyskinesis is commonly associated with numerous pathologies of the shoulder; however, it is not well understood if scapular dyskinesis is the cause or result of the injury.8 Muscle performance, specifically muscular weakness, has been implicated as a causal factor of scapular dyskinesis based on studies involving symptomatic patients.7,8 Rehabilitation programs focused on restoring muscle imbalances of the scapular stabilizers have been demonstrated to restore strength of the rotator cuff in symptomatic overhead athletes.22,23 Therefore, if muscular performance is in fact a contributory factor then it is

plausible that strength deficits would be observed in healthy individuals with scapular dyskinesis. However, the results of the current study challenge the idea that healthy individuals with scapular dyskinesis have strength deficits. The results of this study are further supported in that strengthening programs designed to improve shoulder complex strength do not appear to resolve scapular dyskinesis.41 Therefore, it may be suggested that gross strength is not a contributory factor in the development of scapular dyskinesis. While the intent of this study was to determine if any strength differences existed, it was interesting to find such a disproportionate number of those with scapular dyskinesis. The disproportionate number of those with scapular dyskinesis along with no differences in strength in a sample of healthy college-aged individuals calls into question the clinical relevance of scapular dyskinesis as a movement impairment. These data may suggest that scapular dyskinesis in healthy individuals is no more than a normal variation of scapular motion. Furthermore, these data may explain the common occurrence and inconsistent patterns of scapular dyskinesis that occur in symptomatic individuals. Nonetheless, these data should not detract from evaluating and considering the role that scapular dyskinesis plays

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in symptomatic patients. Furthermore, there is sufficient evidence to support the use of a rehabilitation program focused on restoring scapular stabilizer recruitment and neuromuscular control.7 The prevalence of scapular dyskinesis is unknown in the healthy population, but it appears to be quite common, if not more common, than what is presently considered to be “normal” scapular motion. In the present study, 68% (27/40) of the overall sample presented with aberrant scapular motion, which led to the utilization of a matched-pairs analysis. According to the literature, scapular dyskinesis has been shown to be present in 50 – 61% of healthy overhead athletes.9,10,14,42 McClure et al37 used overhead athletes that were moderately healthy (included individuals with pain rated up to seven using a 10-point pain scale) to establish reliability of the scapular dyskinesis test, and reported 85% of participants displayed obvious scapular dyskinesis. While their study did not account for arm dominance, it adds to the argument that aberrant scapular motion is present more often than not in healthy populations.

Thus, further investigations are warranted to determine the prevalence of scapular dyskinesis in the healthy population.

Significant differences were observed in strength between several of the muscles tested when the two scapular dyskinesis groups were combined (Table 2). Due to a lack of significant differences between the muscles tested, a specific rank order could not be produced. However, several trends were identified that resulted in the following generalized order: the UT generated the greatest amount of force, followed by the SA and MT, LT, SS, MR, and the LR generated the least amount of force. Interestingly,

this generalized order is nearly identical to normative data collected via handheld dynamometry using similar testing procedures.26,27 In addition to strength data, strength ratios (Table 3) were calculated that have been reported in normative studies,26,27 or have been the focus of rehabilitation programs aimed at restoring balance of the scapular stabilizers.7,22,23 No significant differences were revealed for any of the strength ratios between the scapular dyskinesis groups (Table 3). The scapular stabilizer ratios calculated from the present study correspond well to those reported by Turner et al.27 However, the LR/ MR ratios (0.675 – 0.676) appear to be smaller than those reported by Riemann et al,26 which ranged from 0.86 – 0.92.

It has commonly been suggested that decreased muscle performance of the shoulder musculature is present in individuals with scapular dyskinesis.6-8 However, the authors of these papers primarily reference studies that did not control for scapular dyskinesis, but were based on electromyographic data that demonstrated altered activation patterns of the scapular stabilizers in symptomatic shoulders (e.g., impingement).6-8 Few studies have demonstrated strength deficits of the shoulder musculature in individuals with scapular dyskinesis.10,22,23 Merolla and colleagues reported infraspinatus (IS)22,23 and SS22 strength deficits in symptomatic overhead athletes with scapular dyskinesis. In both studies, participants completed similar six-month rehabilitation programs designed to improve balance and control of the scapular stabilizers. Significant improvements (p < .01) in IS and SS strength were reported at 3 (IS = 42%,22 36%,23 SS = 23%22) and 6 (IS = 43%,22 43%,23 SS = 24%22) months. Based on these results, Merolla and colleagues22,23 speculated that imbalances in the

Table 3. Strength Ratios for Matched-Pairs Analysis Strength Ratio With Dyskinesis Without Dyskinesis Total UT/LT 2.791 ± 0.386 3.092 ± 0.668 2.941 ± 0.556 UT/MT 2.145 ± 0.333 2.423 ± 0.394 2.284 ± 0.384 LT/MT 0.771 ± 0.080 0.800 ± 0.117 0.785 ± 0.099 SA/UT 0.503 ± 0.105 0.461 ± 0.055 0.482 ± 0.085 SA/MT 1.059 ± 0.162 1.106 ± 0.158 1.082 ± 0.159 SA/LT 1.383 ± 0.229 1.403 ± 0.237 1.393 ± 0.228 LR/MR 0.676 ± 0.097 0.675 ± 0.118 0.675 ± 0.106 Strength Ratios (M ± SD) were calculated by dividing the averaged peak force of one muscle by the other, respectively. UT = upper trapezius, MT = middle trapezius, LT = lower trapezius, SA = serratus anterior, LR = lateral rotators, and MR = medial rotators.

No significant differences were revealed between groups for any of the strength ratios.

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scapular musculature led to an acquired scapular dyskinesis, which compromised the length-tension relationship of the rotator cuff muscles that resulted in weakness of the IS and SS, secondarily. However, the results of these studies should be interpreted cautiously as muscle performance measures were not collected for the scapular stabilizers. Additionally, while all participants were cleared for labroligamentous injuries, chondral lesions, and rotator cuff tears via magnetic resonance imaging, they were all symptomatic at baseline. Therefore, it is purely speculative that scapular dyskinesis was acquired, especially with the growing evidence that scapular dyskinesis is commonly found in healthy overhead athletes.9-11 Others have speculated the same regarding muscle imbalances of the scapular stabilizers, which has led to the development of a scapular repositioning maneuver to test for weakness of the IS and SS.30,31 During this maneuver, the clinician retracts the scapula and provides external stabilization that results in the ability of the rotator cuff in symptomatic individuals with scapular dyskinesis to produce greater strength output when compared to traditional manual muscle testing procedures. Yet, strength improvements have been observed in healthy, asymptomatic individuals when utilizing the repositioning maneuver as well.31,32 In contrast, Smith and colleagues43 demonstrated significantly lower measures of shoulder elevation strength when the scapula was positioned in retracted and protracted positions as compared to the normal resting position in a sample of healthy individuals without scapular dyskinesis. Nonetheless, these studies indicate scapular positioning has an impact on shoulder strength. The scapular repositioning maneuver was not utilized in the current study, and no significant differences were revealed between the scapular dyskinesis groups. These findings suggest that healthy individuals may position their scapula optimally for strength output regardless of the presence of scapular dyskinesis. Therefore, the clinical usefulness of the repositioning maneuver is debatable and should be interpreted with caution.

In addition to the current study, only one other study has compared strength measures of the MT and LT in asymptomatic individuals with and without scapular dyskinesis. Seitz et al10 reported weakness of the LT by 4% (p = .031) body mass in those

with scapular dyskinesis in a sample of asymptomatic overhead athletes. Interestingly, the group with scapular dyskinesis in the current study demonstrated weakness by 4% body mass, but was not found to be significant. The conflicting results may be explained by differences in populations studied as stronger scapular muscles of the dominant shoulder,28,44 and asymmetrical positioning of the scapula are known to occur in healthy overhead athletes.45,46 Additionally, testing methods differed for the manual muscle test as Seitz et al10 applied resistance just proximal to the wrist, whereas the resistance was applied directly to the scapula in the current study. It was thought that a better representation of the strength capabilities of the scapular stabilizers would be achieved by positioning the dynamometer directly over the scapula, which is supported by others.24 In fact, Michener et al24 demonstrated that assessing strength of the lower trapezius with a handheld dynamometer placed over the scapula yielded valid measures when compared against electromyography. However, no data exist that compares strength measures of the scapular stabilizers collected with the dynamometer placed in the two different positions. Nonetheless, by positioning the dynamometer at the wrist, additional factors (e.g., glenohumeral strength) contribute to force generation that may disguise the true strength capabilities of the targeted musculature.

When evaluating the results of the current study, several limitations were identified that warrant acknowledgment. First, the generalizability of the results are limited to healthy, college-aged individuals, which consisted mostly of females (77%) and may or may not have included overhead athletes.

Additionally, only data from the dominant arm was used in this study. Inclusion of data from the nondominant arm in future studies would aid in the generalizability of the results and in determining the prevalence of scapular dyskinesis. A second limitation is the large amount of variability that is inherent to scapular kinematics, yet a dichotomous method was utilized to categorize those with and without scapular dyskinesis. Other investigators have subcategorized movements of the scapula as normal, subtle, or obvious to maximize the detection of differences.47,48 However, for the purposes of this study, the subtle and obvious categories were combined

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and the yes/no method38 was utilized as it was speculated that clinicians are more likely to treat symptomatic patients the same regardless of the “degree” of scapular dyskinesis. Studies36,38 have indicated better measures of agreement in identifying scapular dyskinesis utilizing a dichotomous method over other sub-categorization methods as defined by Tate et al36 and Kibler et al.49 Regardless of the fact that the presence of scapular dyskinesis was based upon an established criteria and the implementation of that criteria by a single observer, a large amount of variability was noted in the scapular motion in the scapular dyskinesis group. Through the implementation of the match pair’s criteria and merely by chance alone, those with a lesser degree of scapular dyskinesis were not included in the matched-pairs. This adds merit to the current findings because excluding those participants should have maximized any potential differences between the groups. Lastly, a ceiling effect was observed with the UT1 method as a few of the male participants were able to lift the investigator from the floor, which negated the ability to collect a maximum effort by these individuals.

This, along with a similar experience by Turner et al,27 prompted the use of the UT2 method. While significant differences were revealed between the two methods, the overall results in the matched-pairs analysis were not likely affected as neither measure revealed significant differences between the two scapular dyskinesis groups.

CONCLUSION The results of this study indicate that no differences in shoulder strength exist between individuals with and without scapular dyskinesis in a healthy population of college-aged individuals with no history of neck and shoulder pathology. As such, gross strength is not likely to be a contributing factor to the development of scapular dyskinesis, whereas other muscle performance factors, such as neuromuscular control, may be. Moreover, this study adds to a growing body of evidence that scapular dyskinesis is commonly found in healthy individuals.

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45. Myers JB, Laudner KG, Pasquale MR, et al. Scapular position and orientation in throwing athletes. Am J Sports Med. 2005;33(2):263-271.

46. Oyama S, Myers JB, Wassinger CA, et al.

Asymmetric resting scapular posture in healthy overhead athletes. J Athl Train. 2008;43(6):565-570.

47. Lopes AD, Timmons MK, Grover M, et al. Visual scapular dyskinesis: kinematics and muscle activity alterations in patients with subacromial impingement syndrome. Arch Phys Med Rehabil.

2015;96(2):298-306.

48. Seitz AL, McClure PW, Lynch SS, et al. Effects of scapular dyskinesis and scapular assistance test on subacromial space during static arm elevation. J Shoulder Elbow Surg. 2012;21(5):631-640.

49. Kibler WB, Uhl TL, Maddux JW, et al. Qualitative clinical evaluation of scapular dysfunction: a reliability study. J Shoulder Elbow Surg.

2002;11(6):550-556.

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IJSPT

ORIGINAL RESEARCH

ANODAL TRANSCRANIAL DIRECT CURRENT STIMULATION (TDCS) INCREASES ISOMETRIC STRENGTH OF SHOULDER ROTATORS MUSCLES IN HANDBALL PLAYERS Fuad Ahmad Hazime1,4 Ronaldo Alves da Cunha2 Renato Rozenblit Soliaman2 Ana Clara Bezerra Romancini2 Alberto de Castro Pochini2 Benno Ejnisman2 Abrahão Fontes Baptista3

ABSTRACT Background: Weakness of the rotator cuff muscles can lead to imbalances in the strength of shoulder external and internal rotators, change the biomechanics of the glenohumeral joint and predispose an athlete to injury. Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique that has demonstrated promising results in a variety of health conditions. However few studies addressed its potential approach in the realm of athletics.

Hypothesis/Purpose: The purpose of this study was to investigate if transcranial direct current stimulation (tDCS) technique increases the isometric muscle strength of shoulder external and internal rotators in handball athletes.

Study Design: Randomized, double-blind, placebo-controlled, crossover study.

Methods: Eight female handball players aged between 17 and 21 years (Mean=19.65; SD=2.55) with 7.1 ± 4.8 years of experience in training, participating in regional and national competitions were recruited. Maximal voluntary isometric contraction (MVIC) of shoulder external and internal rotator muscles was evaluated during and after 30 and 60 minutes post one session of anodal and sham current (2mA; 0.057mA/cm2) with a one-week interval between stimulations.

Results: Compared to baseline, MVIC of shoulder external and internal rotators significantly increased after real but not sham tDCS. Between-group differences were observed for external and internal rotator muscles. Maximal voluntary isometric contraction of external rotation increased significantly during tDCS, and 30 and 60 minutes post-tDCS for real tDCS compared to that for sham tDCS. For internal rotation MVIC increased significantly during and 60 minutes post-tDCS. Conclusions: The results indicate that transcranial direct current stimulation temporarily increases maximal isometric contractions of the internal and external rotators of the shoulder in handball players.

Level of Evidence: 2 Key words: Isometric contraction, handball, shoulder rotator muscles, Transcranial direct current stimulation (tDCS)

1

Department of Physical Therapy. Federal University of Piauí, Piauí, Brazil.

2 Sports Traumatology Center. Federal University of São Paulo, São Paulo, Brazil.

3 Laboratory of Functional Electrical Stimulation, Department of Biomorphology, Federal University of Bahia, Salvador, Brazil.

4 Department of Physical Therapy, Speech-Language and Hearing Science and Occupational Therapy of the Medical School, University of São Paulo, Brazil. Postgraduate Program in Rehabilitation Sciences of the Medical School, University of São Paulo, Brazil.

Conflict of interest The authors have no conflicts of interest to declare.

Funding No funding was provided for this study.

CORRESPONDING AUTHOR Fuad Ahmad Hazime 1 Department of Physical Therapy. Federal University of Piauí Piauí, Brazil E-mail: fuad@ufpi.edu.br.

Phone: +55863323-5209

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INTRODUCTION Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique for modulation of brain activity and excitability that has demonstrated promising results in a variety of health conditions, such as chronic pain,1,2 depression3 and chronic stroke.4 For healthy athletes, tDCS is potentially useful due to the possibility of ergogenic or facilitatory effect in muscle performance and sports’ skills.5 Previous authors have shown that an application of anodal tDCS (a-tDCS) over primary motor cortex (M1) of healthy individuals improves muscle endurance6,7; enhances pinch force in the lower leg (grip force of the great toe and the second toe)8 and enhances the consolidation of ballistic thumb movement.9 Other researchers investigated the effect of tDCS over the left premotor cortex and found an improvement performance of a dexterity-demanding task.10 Specifically for muscle performance tasks, the effect of tDCS seems to be related to alterations in motor unit recruitment strategies.7,11,12 Taken together these results suggest that tDCS could be useful as an auxiliary tool for physical and motor performance training.

However despite some evidence of the benefits of tDCS in healthy volunteers, few studies have addressed its potential approach in the realm of athletics.

Increase in muscle capabilities even at minimum levels can be useful for athletes, especially for sports demanding excessive and repetitive efforts. For instance, in throwing athletes such as handball players, muscle weakness of external shoulder rotators is associated with shoulder injury.13 Muscle imbalance between the external and internal rotator muscles is also observed in handball players.14 Thus optimal muscle function is highly desired to avoid shoulder injury and impairment in sports performance. The possibility of identifying a safe ergogenic aid to optimize muscle recruitment and muscle strength is of extreme interest to athletes, coaches and researchers, and modulation of the motor cortex by tDCS may be an easy and helpful strategy in this condition. The purpose of this study was to investigate whether tDCS technique increases the isometric muscle strength of shoulder external and internal rotators in handball athletes. Maximal voluntary isometric contraction (MVIC) was evaluated during and after the application of anodal and sham current

to test the modulatory and plastic effects of tDCS on isometric muscle strength, respectively.

METHODS Subjects This randomized, double-blind, placebo-controlled crossover study included eight female handball athletes participating in regional and national competitions (Table 1). All participants were in the preseason training period and were instructed not to perform any kind of strenuous exercise and not to ingest alcoholic or caffeinated drinks during the two weeks of data collection. Athletes with suspected or confirmed pregnancy, complaints of pain in the upper limbs with intensity ≥ 3, evaluated by numerical pain rating scale (NPRS 0-10), medical history or personal report of epilepsy or convulsive event, or the use of drugs with central action were excluded.

The study was approved by the local Research Ethics Committee under the protocol number 269.011 and the participants signed the informed consent.

Experimental paradigm The study was conducted in two weeks. In the first week, the participants were randomly distributed based on an online generating random numbers software (www.randomization.com) into two groups: (1) real anodal tDCS or (2) sham anodal tDCS. The randomization and allocation concealment were carried out by an external collaborator, not involved in the study, through individual opaque envelopes containing the identification number of the participants and their type of stimulation (real / sham). In the second week the type of stimulus was inverted between the participants. Muscle performance evaluation was carried out (1) immediately pre-tDCS, (2) during tDCS (after 13 min); (3) 30 minutes posttDCS, and (4) 60 minutes post-tDCS. Evaluations during and after the application of anodal current Table 1. Participant’s characteristics

Variable

Mean (SD)

Age (years) Body Mass (Kg) Height (m) Handball experience (years) Week training (hours)

19.7 (2.3) 64.9 (7.9) 1.66 (0.5) 7.8 (4.5) 31 (10.0)

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were designed to test the modulatory and plastic effects of tDCS, respectively. The same researcher performed all the evaluations. He did not know the characteristics of the applied stimulations (real or simulated), nor did the participants.

Muscle Strength Evaluation Initially, the participants were instructed to perform warm-up exercise for five minutes on an upper body ergometer. Afterwards, they made two attempts of submaximal isometric voluntary contraction of the external and internal rotator muscles, in the dominant limb, to familiarize themselves with the methods of muscle strength evaluation. One minute of rest was allowed between contractions. The maximum voluntary isometric contractions of the internal and external rotator muscles in the dominant limb were collected. To minimize the risks of muscle fatigue during MVIC tests, all participants were allowed a rest interval of one minute between contractions.15 Counter-balancing of the rotator muscles was performed to minimize the participant’s learning factor. To perform the tests, the hand held dynamometer (MIcroFet2, Hoggan Health industries, USA) was positioned at the athlete’s wrist area (2cm below the radial styloid process) on the dorsal aspect of the wrist to test the lateral rotators, and ventral aspect to test the internal rotators.16 A rigid band was used to stabilize the dynamometer.

The participants remained in the supine position, with shoulder at 90° of abduction and the elbow was flexed to 90°.17 During the test the assessor stabilized the participant’s shoulder to avoid accessory movements (Figure 1).

Anodal tDCS Anodal tDCS was applied through a battery powered DC generator (Activadose II, USA) using two electrodes measuring 5 x 7cm (35cm2) (Ibramed, Brazil) covered with an electrode sponge, saturated with physiological saline solution, and fixed onto the head by means of velcro straps. The electrodes were mounted in accordance with the International 10-20 EEG System18 for optimal focalization of the primary motor cortex.

The electrode with the positive charge (anode – excitatory pole) was positioned at C3 or C4 (contra-

Figure 1. Manual muscle testing with a hand-held dynamometer during tDCS application. Anodal pole positioned over M1 contralateral to the evaluated upper limb. Cathodal pole positioned over ipsilateral supraorbital contralateral to anode pole.

lateral to the dominant limb), and the electrode with the negative charge (cathode – inhibitory pole) in the ipsilateral supraorbital region of the dominant limb (Figure 1). Real tDCS was applied with electric current amplitude of 2 mA, electric current density of 0.057 mA/cm2, for 20 minutes. Sham tDCS was applied with the same parameters, maintaining the electrodes in place for 20 minutes over the head, but stimulation was on for only the first 30 seconds.19 During the application of tDCS the participants remained seated. After 13 minutes of stimulation, they laid down on the stretcher for the MVIC evaluation, corresponding to time interval 2 (during tDCS).

The decision was made to wait until 13 minutes of stimulation had passed, because previous studies have demonstrated that this was the minimum time required to obtain an increase in cortical excitability for up to 1.5 hours.20 The adverse effects were evaluated after each application through spontaneous reports of any unpleasant sensations such as burning, tingling, itching, headache, or nausea.

Statistical Analysis The averages of three maximum contractions in each time interval were analyzed separately with regards to the external and internal rotator muscles.

Normalization of the data was performed by using

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the body mass (kg) of each participant.21 Differences in the MVIC of the rotator muscles within evaluation time points and between real and sham stimulation were calculated using linear mixed models by using group, time and group-versus-time interaction terms.

Post hoc tests with Bonferroni corrections were used when necessary. Mean differences of MVIC at baseline between the first and second week were analyzed by paired t-tests for external and internal rotator muscles. Level of significance was established at p < 0.05. The analyses were performed using the software program IBM SPSS v.20 for Windows.

RESULTS No adverse events were reported during and after application of the intervention protocols. Paired t-tests showed no differences between the means of MVIC in the baseline interval between the first and second week, for external (t(7) = 0.03, p = 0.98) and internal (t(7) = 10.50, p = 0.18) rotator muscles.

Intraclass correlation coefficient (ICC) showed good to excellent intra-rater reliability between week 1 and week 2 for baseline measures of external rotation (ICC = 0.94; 95%CI = 0.72 to 0.99). For internal rotation ICC showed poor to excellent intra-rater reliability (ICC = 0.72; 95%CI = 0.37 to 0.94).

Significant differences within time intervals were observed for external and internal rotator muscles.

Compared to baseline, MVIC increased significantly during, after 30 and 60 minutes for real but not for sham tDCS for external rotation. Internal rotation increased significantly after 30 and 60 minutes for

real but not for sham tDCS (Table 2). Between-group differences were observed for external and internal rotator muscles. Maximal voluntary isometric contraction increased significantly during tDCS, and 30 and 60 minutes post-tDCS for real tDCS than during sham tDCS (Table 2).

DISCUSSION The aim of this study was to investigate whether anodal tDCS applied to the motor cortex has ergogenic effects on isometric strength of shoulder muscles in handball players. The results showed that anodal tDCS can induce a temporary and progressive increase in MVIC of shoulder rotator muscles, which did not happen in sham tDCS intervention.

Compared to baseline muscle strength, real tDCS improved 10.2, 18.6 and 19.3% for external rotation during and after 30 and 60 minutes post-stimulation, respectively. Internal rotation muscles showed improvement of 5.6%, 11.1% and 15.1%, respectively.

For sham tDCS no improvements were observed for external and internal rotation in all time frames analyzed. When compared to sham tDCS, stimulation results also showed increases in MVIC during and after tDCS for external and internal rotator muscles.

These results indicate that tDCS can temporarily induce an incremental increase in maximal isometric strength of shoulder rotators in previously physically conditioned subjects.

There is some evidence in the literature that tDCS influences fatigue and muscle strength in normal

Table 2. Mean (SD) for external and internal muscle strength (N/Kg) across intervals and mean difference (95% CI) within and between groups External Rotation Real tDCS

Sham tDCS

Between-group differencesa

Within-group differences

tDCS intervals T0

T20

T50

T80

T20-T0

T50-T0

T80-T0

0.9

1.0

1.1

1.1

0.1*

0.2*

0.2*

(0.1)

(0.1)

(0.2)

(0.2)

(0.0 to 0.2)

(0.1 to 0.3)

(0.1 to 0.3)

0.9

0.9

0.9

0.9

0.0

0.0

0.0

(0.2)

(0.2)

(0.1)

(0.1)

(-0.1 to 0.1)

(-0.1 to 0.1)

(-0.2 to 0.1)

T20

T50

T80

0.1* (0.0 to 0.2)

0.2* (0.1 to 0.3)

0.2* (0.1 to 0.3)

0.1* (0.0 to 0.2)

0.1* (0.0 to 0.2)

0.1* (0.0 to 0.2)

Internal Rotation Real tDCS

Sham tDCS

0.9

1.0

1.1

1.1

0.1

0.1*

0.1*

(0.1)

(0.1)

(0.1)

(0.1)

(0.0 to 0.2)

(0.0 to 0.2)

(0.0 to 0.2)

0.9

0.9

0.9

0.9

0.0

0.0

0.0

(0.1)

(0.1)

(0.2)

(0.2)

(-0.1 to 0.1)

(-0.1 to 0.1)

(-0.1 to 0.1)

tDCS: Transcranial direct current stimulation. T0: Baseline; T20: 20min of stimulation; T50: 30min post-stimulation; T80: 60min post-stimulation. aBetween-group differences are adjusted. *Significant difference (p<0.05).

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volunteers. Cogiamanian et al. found increased isometric force endurance in a submaximal isometric contraction of elbow flexors after 10 minutes of anodal but not cathodal tDCS applied over the motor areas of the cerebral cortex (1.5mA, 0.043mA/ cm2).6 In a similar protocol of submaximal contraction of elbow flexors, Williams et al. demonstrated that anodal, but not sham tDCS (1.5mA, 0.043mA/ cm2) enhanced time to task failure during but not at the end of task execution. For lower limbs, Tanaka and collaborators demonstrated that 10 minutes of real but not sham or cathodal tDCS applied to the motor cortex (2mA, 0.057mA/cm2) could temporarily enhance maximal leg pinch.

A reasonable explanation for these improvements in muscle strength is that the enhancement of corticospinal excitability via tDCS may alter motor unit recruitment strategies.7,11,12 Hence, as more motor units are recruited, more muscle strength is generated. Although the authors’ did not measure muscle activation, the current results are likely to be more related to optimization of neuromuscular function than other effects (such as motivational effects), as the same participants were assessed in both conditions in the crossover design.

In the current study, changes in MVIC during real stimulation indicated that tDCS technique could positively modulate the isometric strength of external and internal shoulder rotators in handball players. Muscle imbalance, as represented by the ratio of external to internal rotators, is often present in handball players14 and may lead to injury.22 tDCS could be applied as a complementary tool in muscle strengthening programs to help counteract these imbalances in combination with specific exercises, as this transitory increment in muscle strength per se does not necessarily result in improved sports skills if considered as an unique intervention.5 In this context, tDCS could act to increase sports performance through facilitating the activation of corticospinal tract and potentiating the entire motor pathway. Favorable results have been demonstrated when tDCS is associated with active exercises. Anodal tDCS (2mA, 0.08mA/cm2) combined simultaneously with voluntary exercise produces a two-fold increase in the amplitude of motor excitability compared with

tDCS or exercise alone.23 Nonetheless, the effect of tDCS combined with exercise seems to be dependent on the characteristic of exercises, such as type of muscle contractions.24 It is possible that tDCS has a relevant effect in specific physical fitness and in specific conditions. The “ideal” protocols for motor cortex modulation that fit the needs of athletes and coaches still need further investigation.

The present study has some limitations and factors that may have influenced the results. (1) Small sample size: Given the high variability between subjects during and after tDCS application these results must be replicated with large samples; (2) Variability in muscle representation in the primary motor cortex: transcranial magnetic stimulation was not utilized to determine the hot spot for external and internal muscle rotators in the cortex, which would have helped to potentiate the effects of the intervention; (3) The authors did not include cathodal stimulation. Although many studies have demonstrated that cortical excitability is polarity-dependent,20,25 other studies have verified that anodal polarity may exert an inhibitory effect during motor tasks26 just as cathodal polarity may exert an excitatory effect according to the intensity of stimulation.27 Future studies should include cathodal stimulation to investigate if the effects of tDCS on muscle strength are dependent on the polarity.

CONCLUSION The results of this randomized, crossover trial indicate that transcranial direct current stimulation temporarily increases the isometric strength of the shoulder rotator muscles in handball players.

REFERENCES 1. O’Connell NE, Wand BM, Marston L, Spencer S, et al.

Non-invasive brain stimulation techniques for chronic pain. Cochrane Database Syst Rev. 2014;4:CD008208.

2. Vaseghi B, Zoghi M, Jaberzadeh S. Does anodal transcranial direct current stimulation modulate sensory perception and pain? A meta-analysis study.

Clin Neurophysiol. 2014;125(9):1847-1858.

3. Meron D, Hedger N, Garner M, Baldwin DS. Transcranial direct current stimulation (tDCS) in the treatment of depression: Systematic review and meta-analysis of efficacy and tolerability. Neurosci Biobehav Rev. 2015;57:46-62.

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4. Kang N, Summers JJ, Cauraugh JH. Transcranial direct current stimulation facilitates motor learning post-stroke: a systematic review and meta-analysis. J Neurol Neurosurg Psychiatry. 2016;87(4):345-355.

5. Banissy MJ, Muggleton NG. Transcranial direct current stimulation in sports training: potential approaches. Front Hum Neurosci. 2013;7:129.

6. Cogiamanian F, Marceglia S, Ardolino G, Barbieri S, et al. Improved isometric force endurance after transcranial direct current stimulation over the human motor cortical areas. Eur J Neurosci.

2007;26(1):242-249.

7. Williams PS, Hoffman RL, Clark BC. Preliminary evidence that anodal transcranial direct current stimulation enhances time to task failure of a sustained submaximal contraction. PLoS One. 2013;8(12):e81418.

8. Tanaka S, Hanakawa T, Honda M, Watanabe K. Enhancement of pinch force in the lower leg by anodal transcranial direct current stimulation. Exp Brain Res. 2009;196(3):459-465.

9. Koyama S, Tanaka S, Tanabe S, Sadato N. Dualhemisphere transcranial direct current stimulation over primary motor cortex enhances consolidation of a ballistic thumb movement. Neurosci Lett.

2015;588:49-53.

10. Pavlova E, Kuo MF, Nitsche MA, Borg J. Transcranial direct current stimulation of the premotor cortex: effects on hand dexterity. Brain Res. 2014;1576:52-62.

11. Krishnan C, Ranganathan R, Kantak SS, Dhaher YY, et al. Anodal transcranial direct current stimulation alters elbow flexor muscle recruitment strategies.

Brain Stimul. 2014;7(3):443-450.

12. Dutta A, Krishnan C, Kantak SS, Ranganathan R, et al. Recurrence quantification analysis of surface electromyogram supports alterations in motor unit recruitment strategies by anodal transcranial direct current stimulation. Restor Neurol Neurosci.

2015;33(5):663-669.

13. Clarsen B, Bahr R, Andersson SH, Munk R, et al.

Reduced glenohumeral rotation, external rotation weakness and scapular dyskinesis are risk factors for shoulder injuries among elite male handball players: a prospective cohort study. Br J Sports Med. 2014;48(17):1327-1333.

14. Andrade MS, Vancini RL, de Lira CA, Mascarin NC, et al. Shoulder isokinetic profile of male handball players of the Brazilian National Team. Braz J Phys Ther. 2013;17(6):572-578.

15. Wong OM, Cheung RT, Li RC. Isokinetic knee function in healthy subjects with and without Kinesio taping. Phys Ther Sport. 2012;13(4):255-258.

16. Marcondes FB, de Jesus JF, Bryk FF, de Vasconcelos RA, et al. Posterior shoulder tightness and rotator cuff strength assessments in painful shoulders of amateur tennis players. Rev Bras Fisioter.

2013;17(2):185-194.

17. Donatelli R, Ellenbecker TS, Ekedahl SR, Wilkes JS, et al. Assessment of shoulder strength in professional baseball pitchers. J Orthop Sports Phys Ther. 2000;30(9):544-551.

18. Klem GH, Luders HO, Jasper HH, Elger C. The ten-twenty electrode system of the International Federation. The International Federation of Clinical Neurophysiology. Electroencephalogr Clin Neurophysiol Suppl. 1999;52:3-6.

19. Gandiga PC, Hummel FC, Cohen LG. Transcranial DC stimulation (tDCS): a tool for double-blind sham-controlled clinical studies in brain stimulation.

Clin Neurophysiol. 2006;117(4):845-850.

20. Nitsche MA, Paulus W. Sustained excitability elevations induced by transcranial DC motor cortex stimulation in humans. Neurology. 2001;57(10):18991901.

21. Hurd WJ, Morrey BF, Kaufman KR. The effects of anthropometric scaling parameters on normalized muscle strength in uninjured baseball pitchers. J Sport Rehabil. 2011;20(3):311-320.

22. Page P. Shoulder muscle imbalance and subacromial impingement syndrome in overhead athletes. Int J Sports Phys Ther. 2011;6(1):51-58.

23. Kim GW, Ko MH. Facilitation of corticospinal tract excitability by transcranial direct current stimulation combined with voluntary grip exercise. Neurosci Lett.

2013;548:181-184.

24. Thirugnanasambandam N, Sparing R, Dafotakis M, Meister IG, et al. Isometric contraction interferes with transcranial direct current stimulation (tDCS) induced plasticity: evidence of state-dependent neuromodulation in human motor cortex. Restor Neurol Neurosci. 2011;29(5):311-320.

25. Nitsche MA, Paulus W. Excitability changes induced in the human motor cortex by weak transcranial direct current stimulation. J Physiol. 2000;527 Pt 3:633-639.

26. Antal A, Terney D, Poreisz C, Paulus W. Towards unravelling task-related modulations of neuroplastic changes induced in the human motor cortex. Eur J Neurosci. 2007;26(9):2687-2691.

27. Batsikadze G, Moliadze V, Paulus W, Kuo MF, et al.

Partially non-linear stimulation intensity-dependent effects of direct current stimulation on motor cortex excitability in humans. J Physiol. 2013;591(Pt 7):19872000.

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IJSPT

ORIGINAL RESEARCH

LOAD-ENHANCED MOVEMENT QUALITY SCREENING AND TACTICAL ATHLETICISM: AN EXTENSION OF EVIDENCE Stephen M. Glass, PhD1 Randy J. Schmitz, PhD, ATC2 Christopher K. Rhea, PhD2 Scott E. Ross, PhD, ATC2

ABSTRACT Background: Military organizations use movement quality screening for prediction of injury risk and performance potential. Currently, evidence of an association between movement quality and performance is limited. Recent work has demonstrated that external loading strengthens the relationship between movement screens and performance outcomes. Such loading may therefore steer us toward robust implementations of movement quality screens while maintaining their appeal as cost effective, field-expedient tools.

Purpose: The purpose of the current study was to quantify the effect of external load-bearing on the relationship between clinically rated movement quality and tactical performance outcomes while addressing the noted limitations.

Study Design: Crossover Trial.

Methods: Fifty young adults (25 male, 25 female, 22.98±3.09 years, 171.95±11.46 cm, 71.77±14.03 kg) completed the Functional Movement Screen™ with (FMS™W) and without (FMS™C) a weight vest in randomized order. Following FMS™ testing, criterion measures of tactical performance were administered, including agility T-Tests, sprints, a 400meter run, the Mobility for Battle (MOB) course, and a simulated casualty rescue. For each performance outcome, regression models were selected via group lasso with smoothed FMS™ item scores as candidate predictor variables.

Results: For all outcomes, proportion of variance accounted for was greater in FMS™W (R2=0.22 [T-Test], 0.29 [Sprint], 0.17 [400 meter], 0.29 [MOB], and 0.11 [casualty rescue]) than in FMS™C (R2=0.00 [T-Test], 0.11 [Sprint], 0.00 [400 meter], 0.19 [MOB], and 0.00 [casualty rescue]). From the FMS™W condition, beneficial performance effects (p<0.05) were observed for Deep Squat (sprint, casualty rescue), Hurdle Step (T-Agility, 400 meter run), Inline Lunge (sprint, MOB), and Trunk Stability Push Up (all models). Similar effects for FMS™C item scores were limited to Trunk Stability Push Up (p<0.05, all models).

Conclusions: The present study extends evidence supporting the validity of load-enhanced movement quality screening as a predictor of tactical performance ability. Future designs should seek to identify mechanisms explaining this effect.

Level of Evidence: 3 Key Words: Movement quality, tactical athlete, talent identification, screening

1

Department of Physical Therapy, Temple University, Philadelphia, PA, USA 2 Applied Neuromechanics Research Group, Department of Kinesiology, The University of North Carolina at Greensboro, Greensboro, NC, USA.

CORRESPONDING AUTHOR Stephen M. Glass, PhD Temple University 1947 N Broad St. Room 702C Philadelphia, PA, 19122 E-mail: stephen.glass@temple.edu

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INTRODUCTION Recent recruiting cycles have been remarkably successful for the U.S. military.1,2 Accession goals with respect to quantity and quality were exceeded, in many cases by substantial measure. Such a favorable recruiting environment largely eliminated the need for consideration of pre-accession performance screening systems.3 However, the same reports that extol the recruiting successes of recent years also express concern about potential future challenges.1,2 Owing to a combination of defense budget cuts and economic alternatives for the recruitment population, it will likely be more difficult for the military to meet its accession goals over the next decade.

This prospect of future austerity has accordingly renewed focus on the discussion of minimizing preventable attrition due to substandard fitness or injury. Because multi-faceted performance batteries can be cumbersome, consideration is warranted for efficient clinical tools that can identify at-risk military candidates in pre-accession settings.

One solution that may hold promise as a cost effective and field-expedient option for preventing performance-related personnel loss is movement quality screening. The use of such screens has increased substantially in recent years.4-7 In addition to classifying individuals by injury risk, movement screens have also been applied as a method of predicting performance in tactical athletes8,9 and other populations.10-12 In this endeavor, most research has failed to show a relationship between clinically rated movement scores and performance outcomes9-13â&#x20AC;&#x201D;a lack of association which likely stems from two sources.

First, relatively undemanding movement tests may not present a challenge sufficient to highlight deficiencies relevant to athletic performance. Accordingly, it has been suggested that adjusting screening practices to increase specificity or difficulty may increase the likelihood of detecting deficiencies clinically.9,13,14 The second limitation of movement screening as a correlate of physical performance relates to current methods for scoring and analyzing data. Item scores are most commonly rated on an ordinal scale and summed into a total. While a composite representation of test performance has its appeal, this practice is appropriate only if the construct underlying the

total score is unidimensional. In the case of clinical movement screens, a growing body of evidence would suggest this is not the case.15-17 More detailed information can be found in the item scores themselves, although certain considerations must be addressed concerning their analysis. In addition to a rank order structure which is difficult to accommodate in linear or logistic regression,18 direct analysis of component score data in existing clinical movement screens would substantially increase the dimensionality of a prediction model.

A recent investigation in young, recreationally active non-service members demonstrated that Functional Movement Screenâ&#x201E;˘ (FMSâ&#x201E;˘) tests under load show increased predictive validity with respect to criterion performance measures specific to the tactical athlete.14 In the same context, that study also demonstrated the utility of regularization techniques designed to accommodate high-dimensional regression problems with ordered predictors. The intention in combining these two modifications in approach was to help bring the sports medicine community closer to a field-expedient, feasible means of conducting pre-accession screening for performance deficits.

While the above-mentioned study showed promising results, certain factors limit the generalizability of their findings. First, it was conducted using a relatively small sample size (n = 19). Second, this sample did not contain an even balance of men and women. The purpose of the current study was to quantify the effect of external load-bearing on the relationship between clinically rated movement quality and tactical performance outcomes while addressing the noted limitations.

METHODS Data were collected in a laboratory setting by a single investigator experienced in the required measurement techniques. Participation was limited to individuals between 18-34 years of age in order to reflect the recruitment pool for military and tactical occupations. Subjects were additionally required to be free from recent (< six months) injury and to accumulate a minimum of 90 minutes/week of physical activity.

All subjects provided written consent to participate and completed a physical activity readiness questionnaire (PAR-Q) before data collection.

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Procedures This study was approved by the Institutional Review Board at The University of North Carolina at Greensboro. A total of fifty recreationally active adults participated in the study (25 female: 22.00±2.02 years, 165.40±10.24 cm, 63.98±11.07 kg; 25 male: 23.96±3.74 years 178.82±7.51 cm, 79.66±12.66 kg).

Subjects reported to the laboratory for a single data collection session. Following consent and completion of the PAR-Q, the Functional Movement Screen™ was administered under two conditions (wearing a weight vest: FMSW, and not wearing a weight vest: FMSC) in randomized order. Finally, participants completed a battery of physical performance tests.

Functional Movement Screen™ Following a familiarization round, the FMS™ 19,20 was administered both with and without an 18.10 kg weight vest (MiR Vest Inc., San Jose, CA). This is comparable to loads used in previous investigations on the topic of tactical athleticism,21,22 as well as those used in clinical screens designed to predict physical performance.6 Testing conditions were administered back-to-back in randomized order by an investigator proficient in the use of FMS™ testing.

Scores for component tests were assigned based on a 1-3 scale according to the criteria outlined in the FMS™ protocol.19,20 Physical Performance Tests Following completion of the FMS™ in both testing conditions, participants performed a 10-minute cycle ergometer warm up during which they were instructed to target an RPE of 13 (“Somewhat Hard”).

They then began a series of five performance tests comprising assessments from previous tactical performance work.22,23 Instructions were to complete each individual test as quickly as possible. Physical performance tests were administered in the following order for all subjects: 1) T-Agility test, 2) 27.43 meter sprints, 3) 400 meter run, 4) Mobility for Battle (MOB), and 5) simulated casualty rescue.

Completion time for both the Agility T-Test and sprints was recorded using an infrared timing gate (Brower Timing Systems, Draper, UT). Subjects began on the starting mark with one foot positioned on a start-on-release trigger. When directed, subjects performed the following sequence: forward sprint

9.14 m (10 yds), right side-shuffle 4.57 m (5 yds), left side-shuffle 9.14 m (10 yds), right side shuffle 4.57 m (5 yds), back peddle 9.14 m (10 yds). The timing gates were applied similarly in the 27.43 m sprints.

For both the Agility T-Test and the 27.43 sprint, each effort was followed by approximately 60 seconds of rest regardless of whether performing another trial of the same test or proceeding to the next task.

Because of logistical restrictions, completion time for the remaining tests was recorded using a handheld stopwatch. Courses for the 400 m run and Mobility for Battle23 (MOB) were mapped with cones in an indoor gymnasium. The 400 m run was administered as a series of 4.5 laps around the periphery of the gym space. The MOB, designed as a multifaceted test incorporating several soldier-relevant field maneuvers, was organized in stations according to the methods described in Crowder et al.23 Participants were allotted up to five minutes of recovery time upon finishing each of the 400 m and MOB tests.

The final test was a simulated partner rescue, in which subjects were required to drag a 68.04 kg (150 lbs.) dummy across a distance of 45.72 m (50 yds).

The dummy was fashioned from sandbags wrapped in carpet with a handle attached to one end. Completion time was recorded after the final bag crossed the finishing line.

Statistics Several researchers have noted the limitations of analyzing the FMS™ composite score.14-16 The item scores themselves are likely the better source of information, although extra care must be taken to select appropriate prediction models from a multitude of candidate predictor variables. Further, more of the information contained in the item scores can be preserved by using methods that account for their ordinal structure. Each of these challenges can be addressed via penalization. Application of regression penalization algorithms is common in, for example, genome-wide association studies (GWAS),24 in which the number of predictors often greatly exceeds the number of observations. The effect of penalization is to shrink large coefficients and thereby reduce bias toward data characteristics, which are unique to a given sample. Additional penalization can be applied to smooth the differences between successive levels

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of a predictor.18 Thus, these techniques offer an attractive solution to the problems that arise when analyzing FMS™ item score data.

In the current analyses, a group lasso penalty was first applied to select an appropriate model. Differences between neighboring levels within the retained predictors were then smoothed using a second penalization algorithm. The same penalty parameter (Λ) was used in each step, identified as the value of Λ, which minimized cross-validation error in the group lasso.

The final step after model selection and smoothing was to construct bootstrap 95% confidence intervals of the estimated coefficients using the bias-corrected and accelerated method. Each of these steps was completed using R v3.1.0 with ordPens 0.3-4218 and grpreg 2.825 packages.

RESULTS Descriptive statistics regarding physical performance outcomes are presented in Table 1. Model summaries are presented in Table 2 while smoothed and unsmoothed coefficients, along with their respective bootstrap confidence intervals, are presented in Tables 3 (Agility T-Test, Sprint, and 400 meter outcomes) and 4 (MOB and Partner Rescue outcomes).

A non-zero R2 was observed in only three of the models corresponding to the unweighted condition. The first of these was the Sprint model, in which penal-

Table 1. Descriptive Summary of Performance Outcomes.

Test Time (s) T-test 12.81 ± 1.55 Sprint 3.98 ± 0.54 400m 93.88 ± 16.60 MOB 145.74 ± 28.39 RSQ 23.17 ± 9.48 T-test = T-Agility test Sprint = 27.43 meter sprint 400m = 400 meter run MOB = Mobility for Battle assessment RSQ = simulated casualty rescue

ized FMS™ item scores accounted for 11% of the variance in time to completion. The second and third were the penalized and unpenalized MOB models which, respectively, accounted for 19% and 9% of the variance in time to completion. In contrast, nonzero R2 values were observed in all models featuring scores from the weighted condition, with variance explained ranging from 11% - 29%.

In the unweighted condition, higher Trunk Stability Push Up scores were predictive of faster completion times for the Sprint and MOB tests. A similar influence was observed for the remaining three performance outcomes, though variation in scores was not

Table 2. Summaries of Penalized and Unpenalized Model Solutions. FMS™C (unweighted) models are shown on the left and FMS™W (weighted) models are shown on the right. Each is presented both with optimized penalization (top) and no penalization (bottom) in adjacent rows. The “Features” column indicates the number of predictors retained at the given level of penalization.

Unweighted Weighted Λ CVE R2 Features Λ CVE R2 Features Agility 0.31 2.48 0.00 1 0.16 1.84 0.22 3 0.00 3.14 0.00 7 0.00 2.22 0.05 7 Sprint 0.09 0.25 0.11 2 0.02 0.20 0.29 7 0.00 0.29 0.00 7 0.00 0.21 0.27 7 400m 4.12 285.68 0.00 1 1.01 223.15 0.17 6 0.00 294.19 0.00 7 0.00 227.78 0.16 7 MOB 4.46 637.21 0.19 1 2.99 559.84 0.29 3 0.00 720.13 0.09 7 0.00 606.77 0.23 7 RSQ 1.27 90.06 0.00 3 1.46 78.21 0.11 3 0.00 93.32 0.00 7 0.00 95.79 0.00 7 Agility = T-Agility test, Sprint = 27.43 meter sprint, 400m = 400 meter run, MOB = Mobility for Battle assessment, RSQ = simulated casualty rescue, Λ = regression model penalty parameter, CVE = Cross-validation error

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Table 3. Coefficients and bootstrap (BCa method) 95% confidence intervals for retained predictors of time to completion of Agility, sprint, and 400 meter. Level indicates the FMS™ item score, for which the reference condition (“1”) is not shown.

Test DS HS ILL SM ASLR TSPU RS

Level 2 3 2 3 2 3 2 3 2 3 2 3 --

Coef ----------0.41 -1.40 --

Agility 95% CI ----------(-0.91, 4.27) (-1.97, -1.78)* --

Coef ---------0.01 0.21 0.00 -0.64 --

Sprint 95% CI --------(-1.63, 0.53) (-0.26, 0.94) (-0.63, 1.10) (-0.94, -0.94)* --

Coef -----------1.21 -11.62 --

400m 95% CI ----------(-12.10, 8.57) (-30.41, -12.86)* --

Weighted Condition Agility Sprint 400m Level 95% CI 95% CI 95% CI Coef Coef Coef 2 ---0.23 (-1.12, -0.02)* -1.95 (-16.19, 7.51) 3 ---0.15 (-0.95, 0.32) -6.02 (-28.49, 3.61) HS 2 -1.13 (-6.49, 0.00)* -0.04 (-2.54, 0.34) -28.84 (-50.70, -29.29)* 3 -1.95 (-5.96, -1.51)* -0.35 (-3.00, 0.08) -37.03 (-49.89, -42.12)* ILL 2 ---0.29 (-2.53, 0.15) --3 ---0.43 (-2.69, -0.02)* --SM 2 0.43 (-0.26, 1.96) 0.25 (0.03, 1.16)* 6.74 (1.75, 19.52)* 3 -0.20 (-2.90, 1.89) 0.21 (-0.28, 2.49) 16.89 (6.47, 51.08)* ASLR 2 --0.12 (-0.66, 1.12) --3 --0.15 (-0.63, 1.25) --TSPU 2 -1.62 (-2.08, -2.06)* -0.43 (-0.95, -0.36)* -12.67 (-24.17, -13.18)* 3 -1.57 (-2.49, -1.79)* -0.50 (-1.51, -0.46)* -11.19 (-25.65, -7.67)* RS -------DS = Deep Squat, HS = Hurdle Step, IL = Inline Lunge, SM = Shoulder Mobility, ASLR = Active Straight Leg Raise, TSPU = Trunk Stability Push Up, RS = Rotary Stability Test DS

explained at the model level. Higher Trunk Stability Push Up scores from the weighted condition were predictive of faster completion times for all measures. Additionally in the weight vest condition, a Hurdle Step score of 3 was predictive of faster Agility T-Test times while a score of 2 or 3 was predictive of faster 400 meter run times. Higher weighted Inline Lunge scores were also associated with performance, with a score of 3 predicting faster Sprint times and a score of 2 or 3 predicting faster MOB times. Interestingly, a weighted Inline Lunge score of 3 was also predictive of slower time to completion on the partner rescue simulation. A similar inverse relationship was observed between 400 m times and scores of 2 or 3 in the weighted Shoulder Mobility test. Finally, a weighted Deep Squat score of 2 was

predictive of faster sprint times while a score of 2 or 3 was predictive of faster partner rescue times.

DISCUSSION This study sought to quantify the effect of external load-bearing on the relationship between cost-efficient movement quality screens and tactical performance outcomes. The current findings support the conclusion that external load-bearing strengthens the relationship between movement quality and tactical athleticism. The vast majority of these results demonstrate that better movement quality on the weighted Trunk Stability Push-up, Hurdle Step, Inline Lunge, and Deep Squat tests is predictive of faster completion of the physical performance tests. Very few predictive relationships exist

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Table 4. Coefficients and bootstrap (BCa method) 95% confidence intervals for retained predictors of time to completion of MOB and Partner Rescue. Level indicates the FMS™ item score, for which the reference conditions (“1”) is not shown.

Test DS HS ILL SM ASLR TSPU RS

Level 2 3 2 3 2 3 2 3 2 3 2 3 --

Coef -----------6.30 -31.05 --

MOB Obstacle 95% CI ----------(-37.33, 3.88) (-52.60, -52.60)* --

Coef ----0.00 3.54 -1.36 2.98 ---1.39 -6.01 --

RSQ 95% CI ----(0.00, 0.00) (1.50, 9.01)* (-34.51, 6.22) (-7.19, 12.92) --(-10.34, 6.52) (-14.65, -4.63)* --

W ei g h t ed C o n di t i on MOB Obstacle RSQ Level 95% CI 95% CI Coef Coef 2 ---4.40 (-16.25, -2.37)* 3 ---4.57 (-17.39, -1.03)* HS 2 ----3 ----ILL 2 -25.34 (-78.57, -14.32)* --3 -29.59 (-80.03, -21.00)* --SM 2 ----3 ----ASLR 2 ----3 --TSPU 2 -28.81 (-28.88, -28.88)* -9.39 (-9.90, -9.90)* 3 -30.54 (-28.88, -28.88)* -10.83 (-11.54, -11.54)* RS -----MOB = Mobility for Battle assessment, RSQ = simulated casualty rescue, DS = Deep Squat, HS = Hurdle Step, IL = Inline Lunge, SM = Shoulder Mobility, ASLR = Active Straight Leg Raise, TSPU = Trunk Stability Push Up, RS = Rotary Stability Test DS

between unweighted movement quality and performance tasks. These observations parallel previously reported increases in the predictive validity of FMS item scores related to testing under a standardized external load.14 The combination of the present findings with similar results derived from an unrelated sample establishes strong evidence in support of this effect. Before continuing the discussion of the present findings, it should be noted that the authors consider the correlation between movement quality and performance as a function of the common factors that underlie both outcomes. The factors in question are derived from physical fitness models found in the U.S. Army Physical Fitness School

doctrine.26 As will be detailed later, this conceptual framework may have implications for how movement quality assessments are applied.

In this protocol, the expected finding was that external loading during movement quality assessments would improve prediction of physical performance.

While this improvement in prediction was observed, it is interesting to note that the test items driving that improvement were not necessarily the same as those observed previously. Among the items that overlap, weighted Trunk Stability Push Up predicted better performance in all outcomes, as did the unweighted Trunk Stability Push Up for the Sprint.

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Also common to both datasets, weighted Hurdle Step predicted faster 400m run times. The previously published data14 contains several unique effects in the weighted condition. These include relationships between the Deep Squat and 400m run, the Deep Squat and MOB, and the Hurdle Step and MOB. Two unique performance-inhibiting effects were also noted. Specifically, a 3 on the Inline Lunge or Shoulder Mobility tests predicted slower times in the Partner Rescue task.

Several unique effects were also observed in the current data set. These included the relationships between weighted Inline Lunge and sprint speed, weighted Inline Lunge and MOB times, and weighted Deep Squat and Partner Rescue times. Each of these positive effects might be explained by qualities like muscular strength and balance, which arguably become more critical to movement execution in the weighted condition. Additional beneficial effects specific to the present analysis were observed in the relationships between unweighted Trunk Stability Push Up and all outcomes other than sprint speed.

Again, muscular strength is likely a factor, as this test requires a high degree of upper body strength even in the unweighted condition.

Apparently detrimental effects of movement quality in the current dataset included those between weighted Shoulder Mobility and sprint speed, weighted Shoulder Mobility and 400 m times, and unweighted Inline Lunge and Partner Rescue times.

In those effects related to the weighted Shoulder Mobility test, it is possible that certain qualities that enable an individual to achieve a high score are beneficial only to a point. For example, an individual who is able to touch fists behind his/her back despite wearing a weight vest might be hypermobile to an extent that interferes with performance.

Alternatively, this degree of mobility might reflect a lack of movement restriction associated with typical muscle development. The negative association between unweighted Inline Lunge scores and Partner Rescue times is more difficult to explain and may require further consideration. One possibility is that this reflects a tradeoff between muscular strength/power and coordination in performing this relatively novel movement. In any case, because the current results are based on a larger sample size that

is split evenly between men and women, these findings may be more generalizable than previous work.

In many cases, the hypothesized relationship between clinically rated movement behaviors and physical performance has eluded investigators.9-11,13 The difficulty in demonstrating this association may be rooted in the relatively low demand of most screening tools or improper analysis. Steps were taken in the present study to address these concerns.

Specifically, we incorporated an external loading condition and modeled the effects of item scores on performance outcomes with well-suited statistical techniques. The current results suggest that the relationship between movement and performance can be observed under the proper conditions. These findings may have considerable implications for preaccession screening strategies in a time during which the cost of performance failure has the potential to increase substantially. Specifically, an inexpensive and easily administered movement assessment could help prevent attrition and washback by complementing existing accession standards.

A natural follow-up question might seek to explain the mechanisms driving this relationship between movement patterns and performance outcomes. Different interpretations of the present findings could be taken to support vastly different approaches to training. Proponents of movement screening frequently consider movement behaviors themselves to be a kind of stand-alone functional criterion.5,27 This understanding has recently inspired efforts to identify intervention protocols capable of improving screening scores.28,29 An alternative interpretation proposed here would suggest that the utility of clinical screens in this context is that they allow us to see evidence of performance-relevant attributes using a convenient, field-expedient test. Understanding which attributes mediate the relationship between movement and performance may therefore be the more appropriate focus of training and is the subject of ongoing research in our laboratory.

Two limitations should be noted regarding this study. First, participants were recruited primarily from a civilian undergraduate population without regard to tactical occupational experience or aspirations. As such, it is possible that this sample failed to

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represent certain characteristics of individuals likely to pursue such careers. Second, as has been noted by other researchers,30 an individual’s behavior in response to standardized FMSTM instructions is not necessarily a reflection of his/her preferred technique. To the extent that the latter is a better indicator of movement quality, the FMSTM may be limited in its ability to capture this quantity.

CONCLUSION In conclusion, the results of this study support previously observed increases in the validity of clinically rated movement as a predictor of tactical athlete performance outcomes, specifically when movement quality is rated in conjunction with external loading.

Clinicians and recruiters might consider screening for performance-relevant movement dysfunction using adjunct weight. Future research should focus on refining testing methods to increase feasibility and information gained, as well as identifying modifiable factors that best explain this relationship.

REFERENCES 1. Kapp L. Recruiting and Retention: An Overview of FY2010 and FY2011 Results for Active and Reserve Component Enlisted Personnel. Congressional Research Service;2013.

2. Kapp L. Recruiting and Retention: An Overview of FY2012 and FY2013 Results for Active and Reserve Component Enlisted Personnel. Congressional Research Service;2014.

3. Molloy JM, Feltwell DN, Scott SJ, Niebuhr DW. Physical training injuries and interventions for military recruits. Mil Med. 2012; 177(5):553-558.

4. Lubans DR, Smith JJ, Harries SK, Barnett LM, Faigenbaum AD. Development, test-retest reliability, and construct validity of the resistance training skills battery. J Strength Cond Res. 2014; 28(5):1373-1380.

5. Kritz M. Development, reliability and effectiveness of the Movement Competency Screen (MCS), Auckland University of Technology; 2012.

6. McKeown I, Taylor-McKeown K, Woods C, Ball N. Athletic ability assessment: a movement assessment protocol for athletes. Int J Sports Phys Ther. 2014; 9(7):862.

7. Tarara DT, Hegedus EJ, Taylor JB. Real-time testretest and interrater reliability of select physical performance measures in physically active collegeaged students. Int J Sports Phys Ther. 2014; 9(7):874887.

8. Bock C, Orr R, Stierli M, Hinton B. The Functional Movement Screen as a predictor of police occupational task performance. J Sci Med Sport.

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9. McGill S, Frost D, Andersen J, Crosby I, Gardiner D. Movement quality and links to measures of fitness in firefighters. Work. 2013; 45(3):357-366.

10. Parchmann CJ, McBride JM. Relationship between functional movement screen and athletic performance. J Strength Cond Res. 2011; 25(12):33783384.

11. Okada T, Huxel KC, Nesser TW. Relationship between core stability, functional movement, and performance. J Strength Cond Res. 2011; 25(1):252-261.

12. McGill SM, Andersen JT, Horne AD. Predicting performance and injury resilience from movement quality and fitness scores in a basketball team over 2 years. J Strength Cond Res. 2012; 26(7):1731-1739.

13. Lockie R, Jalilvand F, Jordan C, Callaghan S, Jeffriess M. Research-Grade Scoring for the Functional Movement Screen and Relationships with Athletic Performance Tests in Team Sport Athletes. J Athl Enhanc. 2015; 4(1):1-8.

14. Glass SM, Ross SE. Modified functional movement screening as a predictor of tactical performance in recreationally active adults. Int J Sports Phys Ther.

2015; 10(5):612-621.

15. Li Y, Wang X, Chen X, Dai B. Exploratory factor analysis of the functional movement screen in elite athletes. J Sports Sci. 2014:1-7.

16. Kazman JB, Galecki JM, Lisman P, Deuster PA, O’Connor FG. Factor structure of the functional movement screen in marine officer candidates. J Strength Cond Res. 2014; 28(3):672-678.

17. Koehle MS, Sinnen N, Safferm BY, Saffer BY. Factor Structure and Internal Validity of the Functional Movement Screen in Adults. J Strength Cond Res. Publish Ahead of Print.

18. Gertheiss J, Tutz G. Penalized regression with ordinal predictors. Int Stat Rev. 2009; 77(3):345-365.

19. Cook G, Burton L, Hoogenboom B. Pre-participation screening: The use of fundamental movements as an assessment of function–Part 2. N Am J Sports Phys Ther. 2006; 1(3):132.

20. Cook G, Burton L, Hoogenboom B. Pre-participation screening: The use of fundamental movements as an assessment of function–Part 1. N Am J Sports Phys Ther. 2006; 1(2):62.

21. Heller MF, Challis JH, Sharkey NA. Changes in postural sway as a consequence of wearing a military backpack. Gait & Posture. 2009; 30(1):115117.

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22. Harman EA, Gutekunst DJ, Frykman PN, et al.

Prediction of simulated battlefield physical performance from field-expedient tests. Mil Med. 2008; 173(1):36-41.

23. Crowder TA, Ferrara AL, Levinbook MD. Creation of a criterion-referenced military optimal performance challenge. Mil Med. 2013; 178(10):1085-1101.

24. Hoffman GE, Logsdon BA, Mezey JG. PUMA: a unified framework for penalized multiple regression analysis of GWAS data. PLoS Comput Biol. 2013; 9(6):e1003101.

25. Breheny P, Huang J. Penalized methods for bi-level variable selection. Stat Interface. 2009; 2(3):369-380.

26. Knapik JJ, Rieger W, Palkoska F, Van Camp S, Darakjy S. United States Army physical readiness training: rationale and evaluation of the physical training doctrine. J Strength Cond Res. 2009; 23(4):1353-1362.

27. Cook G. Movement: Functional movement systems: Screening, assessment, and corrective strategies. Aptos, California: On Target Publications; 2010.

28. Bodden JG, Needham RA, Chockalingam N. The Effect of an intervention program on Functional Movement Screen test scores in mixed martial arts athletes. J Strength Cond Res. 2013.

29. Frost DM, Beach TA, Callaghan JP, McGill SM. Using the functional movement screen to evaluate the effectiveness of training. J Strength Cond Res. 2012; 26(6):1620-1630.

30. Frost DM, Beach TA, Callaghan JP, McGill SM. FMS Scores Change With Performers’ Knowledge of the Grading Criteria—Are General Whole-Body Movement Screens Capturing “Dysfunction”? J Strength Cond Res. 2015; 29(11):3037-3044.

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IJSPT

ORIGINAL RESEARCH

EMG OF SHOULDER MUSCLES DURING REACTIVE ISOMETRIC ELASTIC RESISTANCE EXERCISES Michael J. Mullaney, DPT, SCS1 Christine Perkinson, PT1 Ian Kremenic, M.Eng1 Timothy F. Tyler, PT, ATC1 Karl Orishimo, MS,CSCS1 Christopher Johnson, MPT, MCMT1

ABSTRACT Background: Traditionally, shoulder isometrics are introduced in the early stages of shoulder rehabilitation. A patient’s isometric torque output is based on a subjective perception of force generation. By utilizing elastic resistance elongation (strain) to standardize force output, clinicians could prescribe shoulder therapeutic isometrics based on % maximum voluntary contraction (%MVC).

Purpose/Hypothesis: The purpose of this study was to measure electromyographic (EMG) activity and determine the %MVC during shoulder flexion, external rotation and abduction isometrics at varying lengths of TheraBand® elastic resistance. It was hypothesized that increased elongation of progressive resistance bands would proportionately increase the %MVC of the shoulder musculature.

Study Design: Laboratory design using healthy subjects.

Methods: Eight healthy subjects (16 shoulders) (5 females, 3 males; avg. age 29.2) were tested. Surface EMG electrodes were placed over the anterior deltoid, middle deltoid, and infraspinatus muscles. A force transducer was anchored to a stable surface with its corresponding end in series with an extremity strap securely holding the elastic band. Subjects were asked to maintain shoulder position for the proper isometric contraction (flexion, abduction and external rotation) while taking incremental steps away from the anchored elastic resistance, to the beat of a metronome to clearly marked distances on the floor (50, 100, 150, 200 and 250% of band elongation). This was repeated with yellow, red, green, and blue TheraBand® resistance levels. Maximum voluntary contractions for both force and EMG were collected for each subject in all three test positions. EMG data were normalized and expressed as a %MVC. Results: For external rotation and flexion, the infraspinatus and anterior deltoid activity increased with band elongation (p<0.01) and progressive colors (p<0.01). The increases in EMG activity with elongation plateaued with the yellow and red bands but continued to increase with the green and blue bands (p<0.01). The increase in infraspinatus and anterior deltoid EMG activity with progressive band color was more apparent for green and blue bands compared with yellow and red band (p<0.01). For the abduction exercise, middle deltoid activity increased with band elongation (p<0.01) and progressive color (p<0.01). In all three exercises, there was an increase in force exerted by the band with increasing length and band color (p < 0.001). However, while there were clear increases in force from red to green to blue, there was no difference in force between yellow and red regardless of elongation (p<0.01).

Conclusion: Isometric flexion, external rotation and abduction muscle activity can be accurately prescribed clinically by adjusting the elongation and resistance associated with progressive colors of resistance bands.

Level of Evidence: 3 Key words: Elastic resistance, isometric exercise, electromyography

1

Nicholas Institute of Sports Medicine and Athletic Trauma Lenox Hill Hospital, New York, NY, USA

CORRESPONDING AUTHOR Michael J. Mullaney DPT, SCS Nicholas Institute of Sports Medicine and Athletic Trauma Manhattan Eye Ear and Throat Hospital - A division of Lenox Hill Hospital 210 East 64 Street New York, New York 10065 732-970-4974 E-mail: mullaneypt@gmail.com

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INTRODUCTION Rehabilitation programs for various shoulder conditions such as rotator cuff repair, stabilization procedures and glenohumeral impingement, emphasize the importance of a progressive rotator cuff strengthening program. Several authors have documented the electromyographic (EMG) activity of the glenohumeral musculature during common therapeutic shoulder exercises.1,2,3,4,5,6,7,8,9,10 Rehabilitation guidelines for glenohumeral pathologies are typically divided into multiple phases.9,11,12 Within each phase there is a gradual progression of rotator cuff loading based on muscle activation during specific exercises.4,5,9,12,13 These programs progress from early isometric exercises to more advanced isotonic exercises in an effort to return the patient to full function.11,13 Isometric exercises are regularly implemented by physical therapists for rehabilitation because they can often provide a controllable and safe training stimulus for patients with limited range of motion. 10,14,13 The challenge with performing these early-stage isometric exercises is the ability of the patient to accurately estimate the force being used to complete an exercise. The reported force production may be influenced by the sincerity, motivation and pain level of the patient. 15,16 A person’s ability to continually reproduce a target muscle contraction, regardless if it is maximal or submaximal, is inconsistent.17 The biomechanical factors that determine muscle force include muscle length, shortening velocity, activation history and current activation.17 Patients will typically utilize their sense of “effort” rather than their sense of “force” when trying to produce a submaximal contraction.17 Patients’ perceptions of their effort may not always correlate with the force that they are actually producing. Therefore, it is proposed that using an active isometric technique with elastic resistance can assist in accurately predicting what percent of maximum voluntary contraction (% MVC) will be produced during isometric flexion, abduction, and external rotation of the upper extremity.

Actual force production and muscle activation, as measured by EMG levels using elastic resistance during isometrics, has not been described and needs to be examined. The purpose of this study was to measure EMG activity and %MVC during shoulder flexion, external rotation and abduction isometrics

at varying lengths of consecutive resistance levels of elastic resistance. It was hypothesized that an increased elongation of progressive resistance bands would proportionately increase the %MVC of the shoulder musculature.

METHODS Participants Eight healthy participants (16 shoulders: 6 males and 2 females; avg age 29.2) volunteered to participate in EMG testing of the glenohumeral joint during reactive isometric exercises. A reactive isometric utilizes elastic resistance as the external force opposing an isometrically held contraction. The external force is increased as the stationary segment (isometrically contracting muscle and joint) is moved further from the fixed end of the elastic resistance, causing increased elongation of the elastic resistance. Participants were excluded if they had a history of shoulder injury within one year or presented with pain during the testing protocol. All participants gave written informed consent. This study was approved by the Lenox Hill Hospital Institutional Review Board.

Testing Prior to testing, yellow, red, green and blue elastic resistance bands (TheraBand®, Performance Health, Akron, Ohio) were cut to 50cm and pre-stretched 50 times to 100% elongation to pre-condition and develop an initial resting length of the bands.18,19 Different colors represent progressive thickness of bands, which result in increasing levels of resistance.

The elastic resistance bands were attached to a TheraBand® extremity strap at one end and secured to a stable surface with an in-line force transducer (Kistler Instrument Corp, Amherst, NY). Following skin prep (shaving, if necessary, skin abrasion and cleaning with alcohol), circular bipolar Ag-AgCl surface electrodes (Noraxon Dual Electrodes, Noraxon USA, Scosttsdale, Arizona; diameter, 1 cm; interelectrode distance, 2 cm) were applied bilaterally on the anterior deltoid, middle deltoid and infraspinatus muscles according to the recommendations of Perotto.20 Muscle activity was recorded at 960 Hz using an 8-channel telemetry system with a bandwidth of 10 to 500 Hz (Noraxon Telemyo, Noraxon USA, Scottsdale, Arizona). Participants performed three, fivesecond MVCs in standing (one minute rest between

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contractions) with a force transducer (Kistler Instrument Corp, Amherst, NY) for shoulder flexion (anterior deltoid), shoulder abduction (middle deltoid) and external rotation (infraspinatus). The average of the maximum force produced during each of the three contractions was used as the MVC. For MVC testing for flexion, the participants were placed in approximately 10-20° of shoulder abduction, 0° of shoulder flexion and 0° of elbow extension and was instructed to forward flex their shoulder. For shoulder abduction, the participants were placed in approximately 10-20° of shoulder abduction, 5-10° of shoulder flexion and 0° of elbow extension and instructed to maximally abduct their shoulder. For shoulder external rotation, participants were placed with elbow in 90° of flexion and the shoulder in neutral glenohumeral rotation with a towel roll placed between the humerus and the trunk bringing the shoulder to approximately 10° of shoulder abduction. These positions were chosen to keep in line with the stationary force transducer for consistent measurements during MVC tests and reactive isometric recording. These MVCs were performed on both dominant and non-dominant shoulders to develop % MVCs at each testing position.

Participants were then instructed in the three reactive isometric test positions. For external rotation, participants were placed with elbow in 90° of flexion and the shoulder in neutral glenohumeral rotation with a towel roll placed between the elbow and the trunk bringing the shoulder to approximately 10° of shoulder abduction, to help ensure the participant maintained the test position.(Figure 1) Participants were fitted with an extremity strap around the wrist for all isometric test positions. Participants were then instructed to step out laterally to clearly identified distances on the floor of 50%, 100%, 150%, 200% and 250% elongation (i.e., each being that percentage greater than the resting length) of the elastic band. Participants ensured they were stepping out the correct distance and maintaining the appropriate shoulder positioning by holding a laser pointer in their test hand that pointed towards the percent elongation marking on the floor. To test shoulder flexion, participants were placed in approximately 10-20° of shoulder abduction, 0° of shoulder flexion and 0° of elbow extension. (Figure 2) Participants were placed in 10-20° of abduction to prevent any soft tissue

Figure 1.

between the thorax and humerus from interfering with the position. Participants then stepped anteriorly to each of the five elongation positions, resisting the posterior force of the elastic resistance. Once again, participants held a laser pointer to ensure elongation distances were consistent with each step. To test shoulder abduction, participants were also placed in approximately 10-20° of shoulder abduction, 5-10° of shoulder flexion and 0° of elbow extension. (Figure 3) Participants were placed into 5-10° flexion to clear any abdominal or hip soft tissue that could impede the elastic resistance band. Participants then stepped laterally to each of the five elongation positions, resisting the medial directed force of the elastic resistance. Subjects performed these five step distances sequentially from 50% to 250% stopping at each percent elongation position for approximately 3-4 seconds using a metronome. The metronome pace was set at 12 beats per minute to allow for enough contraction time at each elongation without risking

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Figure 2.

Figure 3.

increased fatigue and loss of proper positioning. All three of these test positions were randomly ordered and performed with the yellow, red, green, and blue elastic resistance, also in random order.

RESULTS Initial analysis showed no effect of side on any muscle activity or force measurement (p=0.155); therefore, dominant and non-dominant arms were grouped together for purposes of analysis. The % MVC for each position and resistance in flexion, external rotation and abduction are listed in the Appendix. Most notable is the change of %MVC in each position from 50% elongation in the yellow to 250% elongation using the blue elastic resistance.

Anterior deltoid %MVC increased from 11.2±1.3% at 50% elongation of yellow to 26.3±2.3% at 250% elongation of blue. Infraspinatus %MVC increased from 16.2±2.1% at 50% elongation of yellow to 29.5±5% at 250% elongation of blue. Middle deltoid %MVC increased from 22.5±2.7% at 50% elongation of yellow to 36.7±4.5% at 250% elongation of blue.

Data Analysis All EMG data were rectified and smoothed using a root mean square process with a 50-millisecond smoothing window. The maximum value for each contraction was used for analysis. Additionally, all data from the tested exercises were normalized and are presented as %MVC. For each exercise, data were analyzed using repeatedmeasures ANOVA to examine the effects of arm side (dominant vs. non-dominant), band elongation (five percentages) and band resistance (four colors) on the primary muscle activated for that exercise: the infraspinatus for isometric external rotation, the anterior deltoid for isometric flexion and the middle deltoid for isometric abduction. Statistical significance was set at p<0.05.

For external rotation (Figure 4a) and flexion exercises (Figures 5a and 5b), the infraspinatus and anterior deltoid activity increased with elongation (p<0.01)

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Figure 5.

Figure 4.

and progressive band color (p<0.01). The increases in EMG activity with elongation plateaued with the yellow and red bands, but continued to increase with the green and blue bands (p<0.01). Additionally, the increase in infraspinatus (Figure 5a) and anterior deltoid (Figures 5a and 5b) EMG activity with progressive band color was more apparent for green and blue bands compared with yellow and red bands (p<0.01). For the abduction exercise, middle deltoid activity (Figure 6a) increased with elongation (P<0.01) and progressive band color (p<0.01).

In all three exercises, there was an increase in band force (Figures 4a, 4b, and 4c) with increasing elongation and progressive color (p< 0.001). However, while there were clear increases in force production from red to green to blue, there was no difference in force production between yellow and red regardless of percent elongation (p<0.01).

DISCUSSION This study offers insight into the utilization of elastic resistance in prescribing reactive isometrics for

Figure 6.

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shoulder rehabilitation. The force exerted by elastic resistance depends on percentage of elongation.

In work by Page et al,21 the slope of the force-elongation curve of elastic bands varies with changes in the thickness of elastic material; specifically, the force-elongation slope of progressive colors slightly increases with increasing thickness. Because elastic resistance is normally prescribed by color, one cannot assume that changes in resistance (color) will cause a standard gradual increase in muscle activation when proceeding from one color resistance to the next in the progression. This concept is clearly seen in the present study as each band was elongated from 50% to 250%. Although the trend shows gradual band force and %MVC increase at each percent elongation, the changes are not of equal percentages based on band color. This study highlights the fact that the greater the resistance supplied by the bands (blue and green) during reactive isometrics, the faster both exerted forces and EMG activity went up, which is consistent with increasing slopes of force-elongation.

In contrast, for the bands supplying less resistance (yellow and red) during reactive isometrics, exerted forces and EMG activity increased more slowly.

Previous studies have highlighted the use of elastic resistance during shoulder exercises and shoulder rehabilitation programs.6,22,23,24,25 This is the first study on progressive reactive isometric exercise prescription utilizing elastic resistance bands. These findings highlight an increase in muscle activity for each exercise based on band elongation and progressive color. As utilization of isometrics is often limited based on patientsâ&#x20AC;&#x2122; sincerity, motivation, and pain level,15,16 this study provides insight into muscle activity and resistance one can expect to see using reactive isometric resistance exercises with a variety of elastic band resistances.

Clinically, this allows physical therapists to further understand the load placed on shoulder muscles during specific exercises. The data provided offers guidance when prescribing these types of exercises.

Clinically, the most important factor is the color (resistance level) of the band. The color of the band drives the increased resistance during longer elongations of reactive isometrics. The absence of this effect for the middle deltoid may indicate that the middle deltoid is not as much of a prime mover as

was assumed for the abduction isometric exercise, at this range of motion, with the muscles of the rotator cuff potentially working more than expected. Subjectively, subjects indicated that the task became difficult during the higher elongations, particularly for the higher resistance bands; thus, it is logical to assume there is a large degree of co-contraction of agonist muscles while performing these reactive isometrics at higher loads.

Of note is that all exercises produced muscle activity measured as less than 40% MVC, with the vast majority being under 30% MVC. This should be considered when prescribing therapeutic exercises during the early stages of rehabilitation. Many authors recommend exercising at <20% MVC muscle activation during the early stages following rotator cuff repair. 3,7,10,23 Utilization of the yellow, red, and green reactive isometrics for flexion at 250% elongation falls below this 20% MVC threshold for early stages of rehabilitation. Utilization of reactive isometrics for external rotation fall within this <20% threshold for anterior deltoid for yellow and red up to 150% elongation. Abduction reactive isometrics appear to initiate at >20% MVC of the middle deltoid and should be used with caution during the earlier stages of rehabilitation, and reserved for the middle stages of rehabilitation. Dockery et al3 have shown that the use of pulleys for â&#x20AC;&#x153;passive motionâ&#x20AC;? can activate the deltoid up to 25% MVC. This study presents with areas of limitations. It is important to note that these values are in normal, healthy population and should be considered during exercise prescription for patients with shoulder pathology.

Patients with pathology may present with an altered neuromuscular firing patterns that may not necessarily reflect that of a non-pathological shoulder. This study utilized surface EMG and it is possible that kinesiologic fine wire EMG may have different results. Standardization of test positions/movements were achieved with floor marking, the use of a laser pointer, and a metronome pace; however, subject movement during testing is often a variable that is difficult to control.

CONCLUSIONS Isometric flexion, external rotation and abduction muscle activity progressively increases when using varied colors of elastic resistance band (increas-

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ing resistance by color) and increasing the percent elongation. The higher resistance bands (green and blue) produced forces faster and EMG activity went up faster than in the lower resistance bands (yellow and red). Using varied choices of elastic resistance to increase the muscle activation during isometric exercises is a novel approach that can allow clinicians to accurately prescribe these exercises.

REFERENCES 1. Ballantyne BT, O’Hare SJ, Paschall JL, Pavia-Smith MM et al. Electromyographic activity of selected shoulder muscles in commonly used therapeutic exercises. Phys Ther. 1993;73(10):668-77 2. Blackburn TA, White B. EMG analysis of posterior rotator cuff exercises. Athl Train. 1990;25:40-45.

3. Dockery ML, Wright TW, LaStayo PC. Electromyography of the shoulder: an analysis of passive modes of exercise. Orthopedics.1998;21(11): 1181-1184.

4. Escamilla RF, Yamashiro K, Paulos L, Andrews JR. Shoulder muscle activity and function in common shoulder rehabilitation exercises. Sports Med. 2009;8(39):663-685.

5. Jenp Y, Malanga GA, Growney ES etal. Activation of the rotator cuff in generating isometric shoulder rotation torque. Am J Sports Med. 1996;24(4):477-485.

6. Kibler WB, Sciascia AD, Uhl TL, Tambay N, Cunningham T. Electromyographic analysis of specific exercises for scapular control in early phases of shoulder rehabilitatioin. Am J Sports Med. 2008;36(9):1789-1798.

7. McCann PD, Wootten ME, Kadaba MP, Bigliani LU. A kinematic and electromyographic study of shoulder rehabilitation exercises. Clin Orthop. 1993:179-188.

8. Moseley JB, Jobe FW, Pink M, Perry J, Tibone J. EMG analysis of the scapular muscules during a shoulder rehabilitation program. Am J Sports Med. 1992;20:128-134.

9. Reinold MM, Wilk KE, Fleisig GS, Zheng N, Barrentine SW, Chmielewski T, Cody RC, Jameson GG, Andrews JR. Electromyographic analysis of the rotator cuff and deltoid musculature during common shoulder external rotation exercises. J Orthop Sports Phys Ther. 2004;34(7):385-394.

10. Uhl TL, Muir TA, Lawson L. Electromyographical assessment of passive, active assistive and active shoulder rehabilitation exercises. Phys Med Rehabil.

2010;2:132-141.

11. Brewster C, Moynes-Schwab DR. Rehabilitation of the shoulder following rotator cuff injury or surgery.

J Orthop Sports Phys Ther. 1993;18:422-426.

12. Reinold MM, Macrina LC, Wilk KE, Fleisig GS, Dun S, Barrentine SW, Ellerbusch MT, Andrews JR. Electromyographic analysis of the supraspinatus and deltoid muscles during 3 common rehabilitation exercises. J Athl Train. 2007;42(4):464-469.

13. Van der Meijden OA, Westgard P, Chandler Z, Gaskill TR, Kokmeyer D, Millett PJ. Rehabilitation after arthroscopic rotator cuff repair: current concepts review and evidence based guidelines. Int J Sports Phys Ther. 2012;7(2):197-218.

14. Lee JH, Park SJ, Na SS. The effect of proprioceptive neuromuscular facilitation therapy on pain and function. J Phys Ther Sci. 2013;26:713-718.

15. Ha S, Cynn H, Kwon O, etal. A reliability of electomyographic normalization methods for the infraspinatus muscle in healthy subjects. J Hum Kin. 2013;36:69-76.

16. Marras WS, Davis KG. A non-mvc emg nomalization technique for the trunk musculature; part 1 method development. J Electromyogr Kinesiol. 2001;11:1-9.

17. Simon AM & Ferris DP. Lower limb force production and bilateral force asymmetries are based on sense of effort. Exp Brain Res. 2008;187:129-138.

18. Patterson RM, Jansen CW, Stegink H etal. Material properties of thera-band tubing. Phys Ther.

2001;81(8):1437-1445.

19. Simoneau GG, Bereda SM, Sobush DC etal.

Biomechanics of elastic resistance in therapeutic exercise programs. J Orthop Sports Phys Ther.

2001;31(1):16-24.

20. Perotto A. Anatomical Guide for the Electromyographer. 3rd ed. Springfield, IL: Charles C. Thomas; 1994.

21. Page P, Labbe A, Topp R. Clinical force production at Thera-Band elastic bands. J Orthop Sports Phys Ther.

2000;30(1):A47-48.

22. Fernanadez-Fernanadez J; Ellenbecker T, Sanz-Rivas D etal. Effects of a 6-week junior tennis condition program on service velocity. J Sport Sci Med. 2013;12:232-239.

23. Hintermeister RA, Bey MJ, Lange GW etal.

Electromyographic activity and applied load during shoulder rehabilitation exercises using elastic resistance. Am J Sports Med. 1998;26(2):210-220.

24. Hughes CJ, Hurd K, Jones A etal. Resistance properties of Thera-Band tubing during shoulder abduction exercise. J Orthop Sports Phys Ther.

1999;29(7):413-420.

25. Page PA, Lamberth J, Abadie B; etal. Posterior rotator cuff strengthening using Theraband® in a functional diagonal pattern in college baseball pitchers. J Athl Train. 1993;28:346-354.

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Appendix. Percent MVC for each position

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IJSPT

ORIGINAL RESEARCH

THE EFFECT OF ELECTRICAL STIMULATION VERSUS SHAM CUEING ON SCAPULAR POSITION DURING EXERCISE IN PATIENTS WITH SCAPULAR DYSKINESIS Deborah L. Walker, PT, DPT, OCS, GCS1 Cheryl J Hickey, PT, MPT, MS, Ed.D1 Mason B. Tregoning1

ABSTRACT Background: Conventional therapeutic exercise programs are commonly used to treat patients with scapular dyskinesis. There are no studies that have examined traditional therapeutic exercise programs with the addition of remote triggered electrical stimulation (ES) to affect the position of the scapula (using spine to scapular border distance as a reference point) during the performance of exercises that have lower upper trapezius (UT) to lower trapezius (LT) ratio exercises.

Purpose: The purpose of this pilot study was to compare scapular position after performance of three low UT/LT ratio therapeutic exercises in two conditions, electrical stimulation (ESTherex) and sham electrical stimulation (ShamTherex) in asymptomatic persons who were positive for scapular dyskinesis.

Study Design: Randomized trial, single-blinded Methods: Eleven asymptomatic university students representing 15 scapulae with a positive Scapular Dyskinesis Test were recruited as subjects. Participants were randomized into exercise and electrical stimulation (ESTherex) or exercise and sham electrical stimulation (ShamTherex). Subjects performed side-lying shoulder external rotation and flexion, and prone horizontal abduction with external rotation in both conditions. Scapular position was assessed during active abduction at four angles before and after performance of these exercises.

Results: There were no significant differences in scapula to spine distance between ESTherex and ShamTherex groups at 0, 45, 90 and 120 degrees of shoulder abduction. A between group difference (ESTherex and ShamTherex) approached significance at 45 degrees (p= 0.089, CI=-.152 to 1.88 cm) with the post mean measurement of the ShamTherex group (6.44 cm) greater than the post mean measurement of the ESTherex group (5.57 cm). The ESTherex showed a significant pre-to-post mean within group improvement in spine to scapula distance at 120 degrees (mean 2.76 cm, t=4.89, p=.003).

Conclusions: Electrical stimulation with exercises for scapular dyskinesis showed improvements in spine to scapula distance at 120 degrees of shoulder abduction.

Level of evidence: Therapy, level 1b Key words: Electrical stimulation, lower trapezius, scapular dyskinesis,

1

California State University, Fresno, CA, USA.

CORRESPONDING AUTHOR Deborah L. Walker, PT, DPT, OCS, GCS California State University, Fresno 5315 Campus Drive M/S PT 29 Fresno, CA 93740 559-278-0491 E-mail: dewalker@mail.fresnostate.edu

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BACKGROUND The scapula and the shoulder are a highly interconnected functional unit with lifetime prevalence estimates of shoulder pain, although imprecise, due to varying degrees of motion loss and symptom duration, that range from 6.7% to 66.7% for the general population.1 Because the scapula and shoulder function as a unit, a change in normal kinematics of either will result in aberrant shoulder complex mechanics, termed scapular dyskinesis.2 Aberrant shoulder complex mechanics result in an increased risk for upper extremity range of motion limitations, upper extremity deficits, or upper quarter pain syndromes.3-6 For example, over activation of the upper trapezius (UT) in conjunction with delayed activation of the lower trapezius (LT) results in limited posterior tilt of the scapula.7,8 Limited posterior scapular tilt has been postulated to lead to a loss of acromial elevation that may predispose an individual to impingement.9,10 A systematic review by Kibler et al. links changes in scapular kinematics during arm elevation to a change in glenoid angle that creates an increased risk of shoulder instability.11 Shoulder instability and impingement are two of many potential shoulder pain syndromes that may result from altered scapular kinematics.6,12 Scapular dyskinesis (defined as altered scapular motion and position) can be a precursor to an abnormal relationship between the glenohumeral joint and the scapula during movement, and it is therefore critical that dyskinesia be addressed.13 Dyskinesis describes aberrant scapular position at rest, such as winging of the scapula6 (excessive prominence of the medial scapular border) and a deviation from normal scapular motion during arm elevation manifesting as a lack of smooth coordinated movement.6,9 For example, an individual with observable shoulder shrugging during arm elevation is indicative of lack of coordination between the upper, middle and lower trapezius muscles.14 Alternatively, Kibler15 defines a Type II pattern of scapular dyskinesis (Scapular Dyskinesis Classification System) as the presence of a prominent medial scapular border which is most evident during eccentric lowering of the humerus creating rapid downward rotation of the scapula during arm lowering. Excessive shoulder shrugging and rapid downward rotation of the scapula during arm lowering, demonstrate uncoordinated scapular movement, described as scapular dyskinesis.

It is common for physical therapists to treat patients with shoulder pain and scapular dyskinesis. Treatment techniques to address dyskinesis include manual neuromuscular facilitation, tactile cueing, visual feedback, electrical stimulation, supervised exercise, mobilization, strengthening, electromyography, and other interventions.16 RESEARCH INCONSISTENCIES REGARDING SCAPULAR DYSKINESIS Studies linking shoulder pathology and scapular dyskinesis have shown contradictory findings. One example is the inconsistent recruitment timing of scapular muscles noted in a systematic review by Struyf et al.17 In this systematic review electromyographic studies were used for assessment of scapular patterns in patients with impingement and glenohumeral (GH) instability, compared to healthy controls.

Regardless of shoulder pathology (impingement or GH instability) findings were conflicting with regard to recruitment of scapular musculature. Of the six studies that assessed EMG in patients with impingement, three reported increased recruitment of the UT,18-20 while three showed no difference in UT activity when compared to healthy controls.21-23 Furthermore, of the two studies that compared EMG in the UT of those with and without GH instability, results were also conflicting. One study showed increased UT activity24 while the other study found no difference in UT activity in individuals with instability compared to healthy controls.25 Lack of consensus regarding the combined behavior of muscle recruitment and timing, in the treatment of impingement and glenohumeral instability, leave a gap in the literature that can lead to clinical decisions guided by experience rather than evidence. Based on the findings from the systematic review, Struyf et al., recommend assessing and addressing individual motor pattern deficits.17 LOWER TRAPEZIUS ROLE IN SCAPULAR DYSKINESIS One motor pattern deficit noted in scapular dyskinesis is an over active UT combined with an under active LT. Seitz et al. used rehabilitative ultrasound imaging to assess differences in LT muscle thickness in persons with and without scapular dyskinesis.26 Lower trapezius muscle thickness was

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increased in persons with scapular dyskinesis compared to individuals without dyskinesis. According to the researchers this change in thickness can be associated with abnormal scapular muscle contractile behavior because of weakness or delayed timing of the muscle. The same trend did not occur when thickness of the serratus anterior muscle was assessed in persons with and without dyskinesis.26 Cools et al.27 used EMG to identify three exercises that address this type of scapular dyskinesis by identifying low UT to high lower and middle trapezius (UT/LT) activation patterns.27 Three exercises were identified: side lying external rotation, side lying shoulder flexion (beginning at 90degrees), and prone horizontal abduction at 90 degrees of abduction. The exercises found to have a low UT/LT ratio address the voluntary muscle recruitment of the LT while minimizing UT firing. These exercises however, do not address the muscle fiber loss from disuse.

MUSCLE BEHAVIOR AND DISUSE ATROPHY RELATED TO LOWER TRAPEZIUS DYSKINESIS Disuse results in a selective muscle fiber loss.28 When an individual performs voluntary muscle activation, motor fibers are recruited in an asynchronous fixed pattern with the recruitment of slow conducting, slow twitch, fatigue-resistant small muscle fibers (SSFR) before fast conducting, fast twitch, fatigable, large (FFF) muscle fibers. In contrast, when an individual performs high intensity exercise, fast conducting, fast twitch, fatigable muscle fibers are recruited.29,30 When electrical stimulation (ES) is coupled with voluntary muscle contraction the result is the recruitment of all muscle fibers synchronously, regardless of muscle fiber size and speed of conduction.31 Because of the advantage of this coupled mechanism, electrical stimulation may offer a more comprehensive approach in the treatment of muscles that exhibit alteration in recruitment timing that lead to movement dysfunction.

STUDIES ON THE EFFECT OF ELECTRICAL STIMULATION Four Cochrane systematic reviews have explored the effect of electrical stimulation in rehabilitation.

The reviews differ from the current study in the fol-

lowing ways: one review assessed the effect of ES on central nervous system injuries (CNS)32, while the population in the current study had intact central nervous systems; two reviews assessed the effect of ES on orthopedic shoulder pathologies (rotator cuff disease and adhesive capsulitis),33,34 however both of these were applied to address pain and had very different protocols and purposes compared to this study; the final review assessed electrotherapeutics for chronic pain and again, was not applicable to this study.35 To the knowledge of the authors, the application of stimulation in the current study does not appear in the published literature.

Electrical stimulation has resulted in consistent positive outcomes in varied orthopedic and neurologic patient populations.36-39 A systematic review assessing the effect of neuromuscular electrical stimulation (NMES) after anterior cruciate ligament reconstruction reported improved quadriceps strength 16 weeks post operatively with an exercise and NMES condition, compared to exercise alone.40 Authors suggest that peripheral ES changes motor behavior.31,41 Additional examples of the benefit of ES with an exercise program include a study by Scott et al that supported therapeutic ES at the maximum tolerated stimulation intensity for strength improvements in the quadriceps.36 The consistent positive outcomes of ES are also demonstrated in neurologic populations. A 2015 systematic review by Howlett et al. found moderate improvement in walking speed when ES was compared to no intervention and training alone for functional activity improvement following stroke.37 These studies lend support for underlying mechanisms of ES as a treatment, however no studies directly use ES in the manner being explored in the current study.

RESEARCH DEFINING THE PHYSIOLOGICAL EFFECTS OF ELECTRICAL STIMULATION Although all the effects that ES has on the body are not completely understood, there is clear support for proposed mechanisms. These mechanisms include the following: 1) the effect on central nervous system (CNS) generated frequency pattern41, 2) excitation of potential selective fiber types42, and 3) dose repeatability (e.g. the same motor response

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every time with the same ES set up and parameters, regardless of voluntary patient input). Scapular dyskinesis, which has an involuntary component that may require new CNS input and, which may respond to selective fiber recruitment to correct, could respond to ES as an additional intervention.

ES may allow for an individual to internalize proper scapular position more quickly as compared to other contemporary treatments THE EFFECT ON CENTRAL NERVOUS SYSTEM (CNS) GENERATED FREQUENCY PATTERN With regard to CNS generated frequency patterns, electrical stimulation is known to modulate ascending and descending input to motor systems. Sugawara et al. found increased primary motor cortex motor evoked potentials (MEPs) in the extensor carpi radialis (ECR) when ES was combined with voluntary muscle contraction compared to ES or voluntary contraction alone. The combination of ES and voluntary muscle contraction of the ECR also resulted in decreased MEPs of the flexor carpi radialis when compared to the condition of ES or voluntary contraction alone.31 In addition to increased primary motor cortex excitability of the electrically stimulated muscle groups, ES recruits (whether the individual chooses to or not) muscle fibers that the patient often does not know how to recruit, or is not able to recruit with his or her voluntary muscle contraction alone. These are also the same muscles that therapists spend a lot of time in treatment trying to get the patient to recruit. Therapist facilitation methods not employing ES do not have the same physiological effects as those using ES. Henderson et al. speculate that there is no difference in motor unit recruitment order based on conduction time in response to ES, but that variability of motor unit pool recruitment is dependent upon the stimulation threshold of the peripheral nerve, the location of axon within the nerve and various other axon characteristics such as hyperpolarization following ES.42 Electrical stimualtion that assists in repositioning of the scapula may have the potential to address dyskinesis related disuse as could be associated with an elongated and or weakened lower or middle trapezius. For example,

Cools et al. report â&#x20AC;&#x153;abnormal recruitment timingâ&#x20AC;? in the middle and lower trapezius in overhead ahtletes with impingement.14 If a delay in the onset of muscle recruitment is a reflection of stretch weakness43 and the stretch weakness persists, and it leads to atophy (as occurs in innervated skeletal muscle with an intact but unused alpha motor neuron),43 and ES may address this weakness peripherally.

SELECTIVE FIBER TYPE ACTIVATION WITH ELECTRICAL STIMULATION A motor unit refers to a motor neuron and the associated skeletal muscle fibers,44 a shift in fiber type as result of disuse from dyskinesis, may respond more rapidly to ES combined with voluntary contraction than ES or exercise alone. Specifically, SSFR fibers may be more susceptible to disuse atrophic signaling resulting in a shift in muscle fiber ratios.28,45 When there has been a shift in muscle fiber type, as a result of disuse, aging, and/or disease,28 voluntary muscle contraction may be inadequate to address motor pattern deficits. Efficacious treatments for these patient populations are critically important in a fast-paced payer driven healthcare environment.

The upper and lower trapezius are made up of different muscle fiber types, which allows for the various functional roles of the trapezius.46 The lower trapezius is predominantly SSFR (Type I) muscle fiber whereas the upper trapezius is comprised of more FFF (Type II) muscle fiber possibly making the entire muscle complex at risk for shifts in muscle fiber type from disuse.47 However, this same varied fiber composition of the upper and lower trapezius make the trapezius a prime candidate for ES to address ill effects of disuse related muscle atrophy.

ELECTRICAL STIMULATION DOSE REPEATABILITY The introduction of ES to comprehensively address motor pattern deficits, results in electrically induced muscle contractions, which produce a predictable muscle fiber recruitment that is impossible to achieve with therapist facilitated motor cueing or voluntary muscle contraction alone. Because the training effect is consistently replicable, void of therapist expertise, or void of patient motivation, it may be an optimal training condition. In short, ES adds

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consistent training conditions (reproducible intervention, recruitment of all muscle fiber types, and regulation at supraspinal levels). When applied to the dyskinetic scapula it provides a non-volitional, repositioning of the scapula, prior, to the patient performing targeted exercise.

The purpose of this pilot study was to compare scapular position after performance of three low UT/LT ratio therapeutic exercises in two conditions, electrical stimulation (ESTherex) and sham electrical stimulation (ShamTherex) in asymptomatic persons who were positive for scapular dyskinesis.

It was hypothesized that the addition of electrical stimulation to the lower trapezius during low UT/LT ratio therapeutic exercise would produce a greater change in scapular to spine measurements compared to sham electrical stimulation condition during the same low UT/LT ratio exercises.

METHODS Subjects Subjects were recruited from a sample of convenience comprised of student volunteers recruited from the Department of Physical Therapy at Fresno State University. Subject recruitment included students with any of the following: scapular winging, excessive scapular motion or prominent scapulae.

Inclusion criteria included: aged 18 to 35 years with a positive Scapular Dyskinesis Test (SDT). Positive SDT tests were noted by winging or medial border prominence noted visually at rest, lack of smooth coordinated movement (early scapular elevation or shrugging while raising the arm into forward flexion, and/or rapid downward scapular rotation during arm lowering from full flexion). The motion was characterized as dyskinesis as “yes” (presence of deviation or dysrhythmia/asymmetry) or “no” (no dyskinesis)47 by an orthopedic certified specialist physical therapist with twenty-six years of clinical experience.

The subjects were assessed for visual winging of the scapula at rest and during active flexion and abduction following completion of an intake questionnaire.

Subjects meeting any of the following criteria were excluded: non-intact skin or rash in the electrode area, impaired sensation, impaired cognition, ballistic movements, spastic movements, rheumatoid

arthritis, osteoporosis, osteoarthritis, fever, flu-like symptoms, current infection, pregnancy, scoliosis, cancer, thoracic outlet syndrome, myelopathy, diagnosis of fibromyalgia, evidence of any upper quadrant orthopedic cervical disorder or pathology, central nervous system involvement, cervical stenosis, cervical thoracic surgery, chronic migraines, fracture, past or current use of corticosteroids. Exclusion criteria were based on an interview and intake questionnaire review by principal investigators. All subjects provided informed consent before participation. The Department Review Board of Fresno State University in Fresno California approved the study. Eleven subjects representing fifteen scapulae were randomized into ESTherex or ShamTherex group.

Measurement Procedures Thoracic spinous process (between T7-T10)48 to inferior scapular angle distance was measured with the arm positioned at varying degrees of shoulder abduction, (0, 45, 90, and 120), in standing. Pre-data collection, intra-rater reliability for the manual measures was established (r=.60).

During the manual measurement, the patient stood facing a wall mounted large diagrammed goniometer. A surgical marker was used to mark the center of rotation at the glenohumeral joint as assessed by two physical therapists. The blinded physical therapist (OCS with 26 years of experience) provided palpation of bony landmarks (kneeling/head down position) while a second physical therapist passively placed the subjects arm in the correct position (abduction with external rotation) so that it was aligned with either the 45, 90, or 120 degree marking on the wall goniometer and the subject actively held the arm once aligned correctly with corresponding angle on the wall goniometer. A trained Doctor of Physical Therapy (DPT) student recorded the tape measured SSD distance. The measurement readings were unknown to the orthopedic certified specialist physical therapist who palpated the bony landmarks. Measurements were taken at the beginning of week 1, and the end of weeks 2 and 3.

Exercise: Protocol and Subject Education The number of treatments, in addition to repetitions and sets of exercises chosen, are those seen in

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usual care outpatient physical therapy settings (2x per week, 3-week duration). Three exercises were selected. The exercises included side lying external rotation at 90 degrees (with a towel roll under the distal humerus), side lying forward flexion from 90 degrees to nose-level (at 120-130 degrees of flexion), prone horizontal abduction with external rotation at 90 degrees abduction (Figures 1-3).

The ESTherex group received ES to the lower trapezius triggered by a second physical therapist (with 20 years of experience teaching electrotherapeutics at Fresno State University), using a remote trigger switch to coordinate the ES immediately prior to the patient initiated movement. In order to ascerFigure 3. Prone horizontal abduction with electrical stimulation to the lower trapezius

Figure 1. Sidelying shoulder external rotation with electrical stimulation to the lower trapezius

Figure 2. Sidelying shoulder flexion with electrical stimulation to the lower trapezius

tain optimal scapular retraction and depression from electrical stimulation, the subject’s arm was placed in a manual muscle test position for the LT and given slight resistance so lower trapezius fibers were visualized for proper electrode placement.49 The electrode placement was slightly adjusted until the optimal scapular retraction and depression was obtained. Once the desired electrode placement was established, the electrode was outlined with a surgical marker for reproducibility between exercise sessions. The frequency and pulse width were 30pps and 250usec respectively. A pulse with of 250usec was used to guarantee a fused muscle contraction (however not a strengthening contraction). Rates greater than 30pps were not used to avoid any signs of muscle fatigability. The intensity was set high enough to produce visible scapular pull with appropriate scapular retraction and depression combined.

Once set, the intensity was not changed between treatment sessions. The intensity within the intervention group varied between 23 milliamps (mA) and 29 mA. Stimulation intensity was recorded and reproduced on each subsequent treatment session.

The comfort of all contractions was confirmed by the subject’s verbal approval. The ESTherex group performed the three exercises with ES. Each exercise was performed three sets of 15 repetitions with a one-minute rest between exercise repetitions. The electrical stimulation was used during clinic exercise sessions only. A biphasic-pulsatile current was used.

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The ShamTherex groups received no ES. The machine was turned on only to show the lights change when the remote trigger was pressed. As with the intervention group, the ShamTherex group also received sham ES via remote trigger application by a physical therapist, beginning just prior to patient initiated movement and stopping with cessation of patient voluntary movement.

Table 1. Group Statistics: ShamTherex and ESTherex Shoulder Abduction Angle

Group

N

Mean (cm)a

Pre0

ShamTherex ESTherex ShamTherex ESTherex ShamTherex ESTherex ShamTherex ESTherex ShamTherex ESTherex ShamTherex ESTherex ShamTherex ESTherex ShamTherex ESTherex

8 7 8 7 8 7 8 7 8 7 8 7 8 7 8 7

6.1375 5.4714 6.2500 5.5.000 6.3875 5.4857 6.4375 5.5714 7.6625 7.1429 6.4125 6.9286 8.4375 10.171 6.9625 7.4143

Post0 Pre45 Post45

One educational session, for exercise program instruction and practice, was provided to both groups, prior to beginning the exercise protocol.

Participants received home exercise program (HEP) handouts that included pictures of the three exercises and written instructions. Participants also received HEP logs to record HEP compliance. Participants were instructed to perform all exercises at home in the same manner as performed during the intervention sessions (3x15) without the addition of resistance. Both groups were seen for two treatments per week for three weeks after the initial assessment and set-up visit, for a total of 7 sessions. Participants completed exercise logs during the 3-week treatment duration, and provided a self-report of exercise compliance. All participants reported compliance with the HEP (performed 2 additional days outside of the treatment sessions). All but two HEP logs were maintained by participants, and turned in at the end of the treatment trial. The missing two HEP logs were from participants in the ShamTherex group. Two physical therapists performed all interventions with one DPT student to assist set-up and recording of data.

RESULTS With regard to between group comparisons, spine to scapula distance was assessed in 15 scapulae to compare ESTherex to ShamTherex. Independent t-tests indicated no significant differences in spine to scapula distance between ESTherex and ShamTherex at 0, 45, 90 and 120 degrees of standing shoulder abduction at the end of the six treatment sessions (Table 1). Independent t-tests comparing post-mean differences (ESTherex and ShamTherex) approached a statistically significant difference at 45 (p=.089, CI=-.152 to 1.88 cm) with the post mean measurement of the ShamTherex group (6.44 cm) greater than the post mean measurement of the ESTherex group (5.57 cm) (Table 2).

Pre90 Post90 Pre120 Post120 a Inferior

medial scapular angle to spine distance (at T7-T10) in centimeters

For purposes of a learning effect, within group differences were also analyzed. A trend was noted within the ShamTherex and ESTherex groups at 0 and 45 degrees when compared to trends seen within each group at 90 and 120 degrees. In other words, the higher abduction angles (90 and 120) showed closer mean spine to scapula distance compared to the lower angles (0 and 45). At 0 and 45 degrees both the ShamTherex and ESTherex spine to scapula mean SSD scores were larger (further from the spine). A similar trend was noted in the mean scores within the ShamTherex group and the ESTherex group at 90 and 120 with the mean score differences being lower in both conditions at the greater abduction angle. Of significance is the pre-post within group difference of the ESTherex group at 120 degrees of abduction.

At 120 degrees of abduction, despite the small sample size, there was a statistically significant decrease in means pre-measurement to post-measurement at 120 for the ESTherex group (mean 2.76 cm, t=4.89, p=.003) (Table 3). This is even more important to note because the ShamTherex group started with 1.73 cm less spine to scapula distance (better positioning) than the ESTherex group at 120 degrees (ShamTherex 8.44 cm and 6.96 cm, ESTherex -10.17 cm and 7.41 cm) (Tables 3 and 4). Although there was not a significant difference in between group, post-test measures, the within group pre-to-post mean changes of the ESTherex group (measured by SSD distances, as an

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Table 2. Independent Samples Test ESTherex and ShamTherex Post Mean Differences t-test for Equality of Meansa Shoulder Angle

t

Pre0 Post 0 Pre 45 Post 45 Pre 90 Post 90 Pre 120 Post 120

1.034 1.517 1.289 1.838 .639 -.902 -1.451 -.625

2 â&#x20AC;&#x201C;tailed

.320 .153 .220 .089 .534 .383 .171 .543

Mean Difference

Std. Error

95% Confidence Interval of the Difference Lower Upper

.66607 .75000 .90179 .86607 .51964 -.51607 -1.7339 -.45179

.64439 .49434 .69935 .47114 .81271 .57207 1.1951 .72239

-.7270 -.3179 -.6091 -.1518 -1.236 -1.752 -4.316 -2.012

2.058 1.812 2.413 1.884 2.275 .7198 .8478 1.109

a Inferior

medial scapular angle to spine distance (T7-T10) in centimeters Note: No statistically signi icant difference between ESTherex (intervention) & ShamTherex (control) group scapula to spine distance (SSD) in centimeters.

Table 3. Paired Samples T Test ESTherex (post mean scores)

Pair No.

Pair 1 Pair 2 Pair 3 Pair 4

Pair angle

pre0-post0 pre45-post45 pre90-post90 pre120post120

Mean

-.0286 -.0857 .2143 2.757

95% Con idence Interval of the Difference -1.115 1.057 -1.003 .8321 -.9475 1.376 1.376 4.138

t

-.064 -.229 .451 4.88

Sig (t-tailed)

.951 .827 .668 .003*

*Statistically signi icant difference in pre-measurement to post-measurement within group SSD means

Table 4. Paired Samples T Test ShamTherex (post mean scores)

Pair No. Pair 1 Pair 2 Pair 3 Pair 4

Pair angle Pre0-post0 Pre45-post45 Pre90-post90 Pre120-post120

Mean -.11250 -.05000 1.2500 1.4750

indicator of greater scapular excursion) exceeded that of the ShamTherex group. Although the ESTherex group initially started with more scapular excursion compared to the ShamTherex group at the same angle, their within group change was significant even though their scapular position started with more excursion than the ShamTherex group at 120.

DISCUSSION No statistically significant between group difference was found between the ESTherex and ShamTherex group in SSD at different degrees of standing shoulder abduction. There was significant spine to scapula change in distance in the ESTherex group at 120 pre-measurement to final post-treatment measurement. Of note, the pre-measurement of 120,

t -.348 -.101 1.754 2.220

Sig (t-tailed) .738 .922 .123 .062

the ESTherex scapula to spine distance was further from the spine in comparison to the ShamTherex group, although the difference was not statistically significant. The significant within group effect for the ESTherex group demonstrates a sustained scapular reposition (measurements taken after ES completed). This finding may reflect the improvement in resting muscle state associated with the addition of electrical stimulation to voluntary drive.49,50 The same within group effect was not seen in the ShamTherex group. In order to understand the meaning of this within group effect, it will be necessary in subsequent studies to not only look at SSD change but to add clinical measures for pain and function in clients with shoulder pain in the presence of dyskinesis, in order to truly understand

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the implication of a SSD change. However, because these subjects were positive for dyskinesis but not symptomatic for pain, this could not be assessed during this pilot study.

The absence of a between group effect may be explained by low power in this small pilot sample.

Because the intervention specifically addressed LT activation via the addition of ES, the finding that the ESTherex group showed the most improvement at 120 degrees (when the lower trapezius would be most active) may indicate a change in motor pattern.

However, this cannot be construed from the one significant outcome of this limited sample population.

While both groups (ESTherex and ShamTherex) did not show improvements at 0 and 45, within group changes in SSD were observed from initial to final measurement at 90 and 120; although the finding at 90 degrees was not statistically significant. This is consistent with typical firing patterns seen in the lower trapezius.

The other finding that may be notable and will require further research, is the between group statistic at 45 degrees of abduction (p = 0.089). This finding at 45 degrees abduction, although not significant, in spite of the small sample size, may suggest an improvement in the starting position of the scapula for the ESTherex group. Borsa et al. reported that the scapula downwardly rotates prior to humeral elevation 0 to 30 degrees.51 Since all scapulae in the study were dyskinetic, a larger sample may change this non-significant observation and answer the question regarding scapular set position prior to elevation in dyskinetic scapulae.

Another important consideration is firing behavior of the LT. Lower trapezius firing is greatest between humeral elevation angles 90 and 120 degrees, with the largest demand at 120 of elevation.52 In fact, that is what is noted for the within groupsâ&#x20AC;&#x2122; mean changes observed at 90 and 120, when increased LT activation would start to affect scapular excursion. The greatest mean difference was seen in the ESTherex group at 120. Based on this, a few things may be occurring. At the most demanding LT position (120), the scapula showed the greatest gains in excursion differences with the addition of ES cueing. This was not the case again, for the ShamTherex group (ESTherex 2.76 cm, ShamTherex -1.51 cm). In the case of scapular dyski-

nesis, as a result of the dis-coordinated recruitment of UT to LT firing, the addition of ES to a targeted exercise program may result in less LT hypoactivity.

Although it is important to note that at this time, this idea is only conjecture.

The benefit of adding ES to the LT as an adjunct to three low UT/LT exercises may be multifaceted.

Electrical stimulation assists in repositioning of the scapula, ES non-selectively recruits all muscle fiber subtypes,44 and ES demonstrates positive effects on M1 cortical levels when combined with voluntary muscle contraction.41 In this study, investigators observed repositioning of the scapula (increased retraction and depression) as a result of ES cueing. Repositioning of the scapula creates a change in length of the scapular muscles that more closely resembles a non-dyskinetic scapula. This repositioning effect would be applicable for example, in cases such as an elongated LT combined with a shortened pectoralis minor muscle as is seen in scapular protraction. Electrical stimulation facilitated repositioning of the scapula (improved retraction and depression) places the LT and pectoralis minor in a position that more closely approximates non-dyskinetic scapula (in the absence of contracture), compared to scapular protraction alone. This change in position may artificially restore the normal length tension relationships of adjacent soft tissues. Normal length of the scapular muscles can improve the timing of muscle firing, resulting in improved quality of movement, and addresses one aspect of the Scapular Algorithm as proposed by Cools et al,53 in the treatment of scapular dyskinesis. Additionally, scapular repositioning can create a change in the position of the glenohumeral joint.11 A change in glenohumeral position will change the soft tissue relationships of the peri-glenoid muscles and ligaments, and in addition, positively affect the scapular muscles.

Electrical stimulation provides a non-selective, synchronous recruitment of muscle fibers that recruits a greater number of muscle fibers than voluntary muscle contraction alone.30,31,42 Electrical stimulation recruits all muscle fiber subtypes (type I, IIa, IIx/d, IIb)44,49 including oxidative Type I muscle fibers (SSFR) normally recruited in activities of daily

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living. If in the case of disuse related dyskinesis, it is the oxidative subtype of muscle fiber that is atrophied, then hypothetically exercise alone should adequately address the muscle fiber imbalance.

However, selectivity for muscle atrophy remains a mystery28,44 therefore in the absence of understanding the etiology of the disuse, ES may be an essential addition to a comprehensive rehabilitation program.

In addition to possibly reestablishing muscle fiber balance between SSFR fibers and FFF fibers, ES provides input to Type II (FFF) fibers in a standardized and reproducible manner. This type of facilitation is unattainable by conventional physical therapy facilitation techniques alone. When disuse atrophy from aging or disease results in the loss of FFF fibers, ES can assist with the restoration of muscle fiber loss without requiring high levels of exercise or ES induced maximal muscle contractions that can be painful and are likely unachievable in some patients. Not only does ES provide a more complete muscle fiber recruitment; it minimizes practitioner imposed variability by providing a consistent replicable cue. Electrical stimulation produces a highly reproducible positional change of the scapula (with respect to spine to scapular border distance) as a new reference point, which may facilitate improved coordination of upper, middle, and lower trapezius muscle recruitment.

Lower trapezius firing at humeral elevation angles less than 30 degrees of abduction is minimal.2 In the case of dyskinesis, the potential exists for LT firing at angles less than 30 degrees when setting of the scapula should occur. Premature muscle firing may represent a premature activation of adjacent scapular muscles. Electrical stimulation to the LT at the initiation of shoulder flexion at 90 degrees in sidelying and prone, provides a correctly timed motor cue to the LT to facilitate accurate muscle firing. It is likely that this could carry over into functional positions.

Of note, all subjects in the intervention group stated that their scapula felt different after electrical stimulation. No subjects in the control group reported a different feeling in the scapula at any time during the treatment protocol. The participant descriptor word, “different”, was in response to the question posed to all participants at the beginning of each treatment session, “how do you feel?” (asked at the same time HEP logs were checked). Premature firing of the LT (during

the scapula setting phase) in dyskinetic scapulae may provide one plausible explanation for the approaching significance between groups at 45 degrees abduction.

Visual inspection of the scapula is a clinically relevant method for assessing scapular dyskinesis.8,47,54,55 Interestingly however, consistent assessment of the scapula for dyskinesis may not be incorporated into typical physical therapy assessment of the upper quarter. Screening for dyskinesis requires no equipment and can be performed in less than one minute.

LIMITATIONS The following limitations are noted in this research.

This pilot addresses only scapular position as affected

by ES of the LT in patients with scapular dyskinesis.

It is the recommendation of the authors that continued ES studies should also explore serratus anterior recruitment and/or timing deficits. Second, the use of inferior medial scapular angle to thoracic spinous process distance (SSD), as a predictor of scapular dyskinesis, is an imprecise and overly simplified psychometric that utilizes frontal plane distance to describe impairments that occur in three planes. It is an overly simplified, but clinically useful psychometric to describe static and dynamic positioning of the scapula. SSD was chosen in an attempt to incorporate a tool that is accessible and efficient to administer in busy outpatient settings. The investigators made the assumption that decreased scapula-spine distance indicates less scapular dyskinesis. In the presence of shortened middle trapezius, rhomboid, or levator scapulae muscles, the inferior angle to spinous process distance may also be decreased. Of additional consideration was the limited number of scapulae assessed in this pilot study. Further research with larger and more diverse samples is indicated.

CONCLUSIONS No statistically significant between group difference was found between the ESTherex and ShamTherex group in SSD at various degrees of shoulder abduction.

The significant within group SSD change pre to final post treatment measurement in the ESTherex group at 120 degrees is promising. This finding supports the continued exploration of the effect of ES to the LT combined with low UT/LT ratio exercises in persons with scapular dyskinesis and an increased SSD.

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IJSPT

ORIGINAL RESEARCH

RELIABILITY AND VALIDITY OF A BIOMECHANICALLY BASED ANALYSIS METHOD FOR THE TENNIS SERVE Natalie L. Myers, PhD, ATC, PES1 W. Ben Kibler, MD, FACSM2 Leah Lamborn, MS, ATC1 Belinda J. Smith, MPhty3 Tony English, PhD, PT1 Cale Jacobs, PhD, ATC1 Tim L. Uhl, PhD, PT, ATC, FNATA1

ABSTRACT Background: An observational tennis serve analysis (OTSA) tool was developed using previously established body positions from three-dimensional kinematic motion analysis studies. These positions, defined as nodes, have been associated with efficient force production and minimal joint loading. However, the tool has yet to be examined scientifically.

Purpose: The primary purpose of this investigation was to determine the inter-observer reliability for each node between two health care professionals (HCPs) that developed the OTSA, and secondarily to investigate the validity of the OTSA. Methods: Two separate studies were performed to meet these objectives. An inter-observer reliability study preceded the validity study by examining 28 videos of players serving. Two HCPs graded each video and scored the presence or absence of obtaining each node.

Discriminant validity was determined in 33 tennis players using video taped records of three first serves. Serve mechanics were graded using the OSTA and categorized players into those with good (≥ 5) and poor (≤ 4) mechanics.

Participants performed a series of field tests to evaluate trunk flexibility, lower extremity and trunk power, and dynamic balance.

Results: The group with good mechanics demonstrated greater backward trunk flexibility (p=0.02), greater rotational power (p=0.02), and higher single leg countermovement jump (p=0.05). Reliability of the OTSA ranged from K=0.36-1.0, with the majority of all the nodes displaying substantial reliability (K>0.61).

Conclusion: This study provides HCPs with a valid and reliable field tool used to assess serve mechanics. Physical characteristics of trunk mobility and power appear to discriminate serve mechanics between players. Future intervention studies are needed to determine if improvement in physical function contribute to improved serve mechanics.

Level of Evidence: 3 Key words: Functional testing, kinematic analysis, tennis serve 1

University of Kentucky, Lexington, KY, USA Shoulder Center of Kentucky, Lexington Clinic Orthopedics Sports Medicine Center, Lexington, KY, USA 3 Women’s Tennis Association, St Petersburg, FL, USA 2

The authors wish to thank Dennis Van der Meer, Bruce Elliott PhD, Mark Kovacs PhD, Kathleen Stroia MS, ATC, PT, Todd Ellenbecker DPT, Paul Lubbers PhD, Raphael Bahamonde PhD, Murphy Jensen, and the Women’s Tennis Association Sport Sciences & Medicine staff for their contributions to the development of the serve analysis tool.

CORRESPONDING AUTHOR Natalie L. Myers 210c Charles T Wethington Building 900 South Limestone Lexington, KY 40506-0200 E-mail: natalie.myers@uky.edu

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INTRODUCTION An effective serve is a key component and can be a major weapon for success in tennis. Many coaches and health care professionals (HCPs) would agree that primary outcomes when developing and teaching the serve are to improve performance (specifically serve velocity) and to prevent injury.1 Since the serve is the shot that initiates the start of each point, and it accounts for 60% of all strokes it is arguably the most important and predominant shot of the service game.2 The complex sequence of movements involved in the serve along with its repetitive nature makes it one of the most commonly researched strokes in the game of tennis. A player showing true mastery of the stroke is able to utilize the kinetic chain through a sequence of motions that originate at the lower limbs. These lower limb actions are followed by trunk rotation that ultimately leads to upper limb rotation.3 However, alterations in the kinetic chain during the serve may have implications on injury and performance.

Researchers investigating the biomechanical demands associated with the tennis serve have successfully targeted the threats to serve performance and upper limb loads that contribute to upper extremity injury.1,3-11 Each of these researchers utilized three-dimensional (3D) motion analysis to investigate the kinematics and kinetics that accompany the serve. 3D analysis has been widely accepted by researchers as the gold standard in movement analysis.12 However this technique cannot be easily utilized on court (outside environment) and is costly and time-consuming for HCPs and coaches who implement screening programs to plan protocols.13-15 Consequently, a field-based observational analysis may be more practical for HCPs and coaches to evaluate tennis serve mechanics.

A field-based observational analysis must be quick, easy to use, allow a HCP or coach to provide almost immediate feedback, and demonstrate reliability and validity. With an understanding of the biomechanical demands required during the tennis serve, researchers created a clinically applicable observational tennis serve analysis (OTSA) tool to evaluate the mechanics of the serve. The tool, initially described in 2008,16 and later updated in 201317 provided a detailed framework of specific positions representing normal mechanics, abnormal mechanics,

and potential strategies to improve altered mechanics.17 The OTSA was refined in 2013 to be performed on the court and to include video, in order to help improve the effectiveness and applicability of the analysis. The analysis assesses key body positions and motions throughout the kinetic chain that have been found to be associated with optimal ball speed and efficient force production for creating maximal energy with minimal energy expenditure. Additionally, these body positions help to mitigate joint loading to protect against injury. These specific body positions and motions have been defined as “nodes” and have been compiled through 3D motion analysis studies.1,3-11,18 The framework can be used visually to evaluate the presence or absence of the nodes during the service motion.

The investigations reported in this paper were accordingly designed to determine the reliability and validity of the OTSA tool. The primary purpose was to determine the inter-observer reliability for each node between two health care professionals that developed the OTSA. It was hypothesized that the reliability would be greater than 0.4119 for the majority of the nine nodes of the OTSA. The secondary purpose was to investigate the validity of the OTSA by determining if a series of field tests to evaluate trunk flexibility and power, lower extremity power, and dynamic balance would discriminate between players with good and poor serve mechanics as assessed by the OTSA. The authors’ hypothesized that players demonstrating good serve mechanics would perform better on a series of musculoskeletal field tests compared to those with poor serve mechanics.

METHODS Two separate studies were undertaken to meet the objectives of performing a validation and reliability study. In order to be transparent in the methods and for clarity, the studies methods and results sections have been subdivided into two components.

Subjects Two samples of participants were used to document the reliability and validity of the OTSA. To determine the inter-observer reliability of the OTSA video data from 28 professional women’s tennis players were analyzed. All players were actively participating on the professional tour. Players were excluded

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if diagnosed with a neurological disorder, or had a history of fracture and/or surgeries within a year of the video collection. The research team received a waiver of consent from The Lexington Clinic Orthopedic Research Review Board.

To investigate the validity of the OTSA a cross-sectional study was implemented on 33 healthy nonprofessional tennis players. Player characteristics are detailed in Table 1. Players were considered eligible if they participated in tennis at least once a week (college, high school, or recreational), had a United States Tennis Association National Tennis Rating (USTA NTR), and were not under medical care for a musculoskeletal condition that affected tennis play. Players were excluded if any of the players had been diagnosed with a neurological disorder, or had a history of fractures and/or surgery within the past year. Prior to participation, all players gave informed consent approved by the University of Kentucky Institutional Review Board.

Procedures Observational Tennis Serve Analysis (OTSA) Tool The Women’s Tennis Association (WTA) in conjunction with the Shoulder Center of Kentucky (Lexington, KY) developed the OTSA as a field-based tool that can be used to assess tennis serve mechanics.

The OTSA is divided into nine components, the first eight components are called nodes, and the last component is as assessment of motion. The first eight nodes are evaluated at maximal knee flexion while the last component is assessed during the entire serve motion, and represents the composite motion Table 1. Demographic characteristics for players enrolled in validity study G o o d S er v e Mechanics Sex M al e 12 Female 4 Age* 23 ± 9 Body Mass Index* 23 ± 2 Arm Length* 0.64 ± 0.08 m USTA Ranking* 6 ± 0.6 OTSA Composite 6±1 Score* *Represented with mean ± standard deviation m = meters USTA = United Stated Tennis Association OTSA = Observational Tennis Serve Analysis

Poor Serve Mechanics 6 11 3 8 ± 16 24 ± 3 0.57 ± 0.03 m 4 ± 1.0 2±1

of the entire serve. Each of the eight nodes and the composite motion are graded separately as present or absent, using specific criteria that define efficient and inefficient mechanics (Table 2). If a node is graded as present a score of one is recorded for that particular node, whereas a node that is graded absent is recorded as zero. A composite score is totaled by taking the sum of the individual nodes, with a maximum score of nine representing excellent mechanics, and a zero representing poor mechanics.

INTER-OBSERVER RELIABILITY A retrospective analysis was performed to determine the inter-observer reliability of the OTSA. Twentyeight service videos were supplied independently to two observers, an orthopedic surgeon (WBK) and a licensed physiotherapist (BS). Each video contained one service trial from the deuce court during match play. The digital camera was placed at the back corner of the court at approximately 45° angle to the player’s back. The observers were blinded to player name. Both observers were experienced in tennis sports medicine (combined experience of 40 years) and were instrumental in creating the OTSA tool.

Each observer independently evaluated each serve, using a standardized scoring sheet. The observers reviewed the videos as much as needed using slow motion and freeze-frame during maximal knee bend. The two observers recorded categorical data for each of the nine components on each player.

VALIDITY Prior to all data collection for the validity portion of this study each player underwent a standardized 10-minute warm-up period that included jogging, lower and upper extremity mobility drills, and no more than 10 practice serves from the deuce court.

Following the warm-up, players were asked to perform three of their best first serves. Each service trial was captured using two digital cameras (Panasonic HDC-HS60, Hamburg, Germany). One camera was positioned anteriorly to the participant, 20 feet from the baseline “T” of the court at a 20° angle. The second was positioned posterolaterally to the participant, 14 feet from the baseline “T” of the court at a 45° angle (Figure 1). These two camera positions were chosen as they elicited the best angles for viewing all nine components associated with the OTSA.

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Table 2. Observational Tennis Serve Analysis Tool Grading Scale Efficient Mechanics

Picture of Good Mechanics

Inefficient Mechanics

Node 1: Foot Good: Back foot stays behind front foot

Bad: Back foot stays in front of front foot

Node 2: Knee

Good: Both knees to bend greater than 15°

Bad: Both knees bend less than or equal to 15°

Node 3: Counterhip Rotation

Good: The hip on back side is rotating away from the net

Bad: The hip on back side is not rotating away from the net

Node 4: Posterior hip tilt

Good: The hip on back side is dropping towards the ground

Bad: The hip on back side is not dropping towards the ground

Node 5: Hip Lean

Good: The hip on front side is not leaning forward towards the net

Bad: The hip on front side is leaning forward towards the net

Node 6: XAngle

Good: x-angle describes the relationship between the shoulders and the hips and should be ≈ equal to 30°

Shoulders don’t rotate behind the hips

Node 7: Trunk

Good: Trunk rotation around a vertical axis

Picture of Bad Mechanics

Bad: the x-angle is less than 30° Shoulders rotate too far behind the hips Bad: the x-angle is greater than 30° Bad: No trunk rotation, lateral trunk bending only, lumbar hyperextension, hyper-rotation, or hypo-rotation

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Table 2. Observational Tennis Serve Analysis Tool Grading Scale (continued) Efficient Mechanics

Picture of Good Mechanics

Node 8: Arm Good: Shoulder in line with the plane of scapula

Inefficient Mechanics

Picture of Bad Mechanics

Bad: Hypercocking – shoulder behind plane of scapula

Hypococking – shoulder in front of plane of scapula

Assessment of Motion 9: Composite Motion of Kinetic Chain

Good: Use knee flexion and back leg drive to maximize ground reaction forces that push the body upward from the cocking position into ball impact

Bad: Use trunk muscles to pull the trunk and arm from cocking into ball impact

Picture Picture represents end represents end stage of motion stage of (motion to be motion assessed (motion to be dynamically) assessed dynamically) *Note: Evaluate nodes 1-8 at maximum knee bend. Composite motion of kinetic chain should be evaluated throughout entire motion.

Copyright © WTA Tour Inc., The Shoulder Center of Kentucky. All Rights Reserved

One member of the research team assessed serve mechanics of all participants’ using the OTSA. This member of the research team was familiar with the OTSA and had previously developed substantial intraobserver reliability (Table 3). Players were categorized into two groups based on their OTSA score; those with a composite score of ≥ 5/9 on the OTSA were considered to have good serve mechanics (n=16), whereas those with a score of ≤ 4/9 were considered to have poor serve mechanics (n=17). Serve videos were reviewed one week apart, and the intra-observer reliability for the composite score was excellent (ICC=0.95, 95% Confidence Interval: 0.84, 0.98). Following the recording of the serves each player underwent a series of field tests that measure aspects of kinetic chain functional capability: trunk flexibility,20 single and double leg countermovement vertical jump (CMJ),21 trunk rotational power,22 and dynamic balance.23 TRUNK FLEXIBILITY A variation of Aragon et al20 trunk rotation flexibility measure was adopted for this study. Two polyvinyl

chloride (PVC) pipes were used to create an angle to record trunk flexibility. One PVC pipe (1 meter long) was placed on the ground in between the foot and the knee in the coronal plane. Another PVC pipe was placed behind the players back and between the arms while the hands were placed on the hips. Trunk flexibility was expressed by the direction in which the serving shoulder was moving (backward or forward). For example, backward rotation for a right-handed server was performed by kneeling on the left knee while positioning the right foot in front of the kneeling leg and instructed to rotate the serving arm backwards. Forward flexibility was performed in an exact manner except players were kneeling on the right leg and instructed to rotate the serving arm forwards. Participants were asked to rotate as far as possible without losing balance and maintaining correct posture. The examiner stood behind and above the players and took a snapshot using a digital camera at the end range of motion.

ImageJ, an open source imaging processing system (https://imagej.net) was used to calculate the

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for each subject. Excellent inter-rater reliability of the measurements were established prior to starting data collection using the data of six participants for both forward (ICC = 0.99, 95%CI=0.93-1.00) and backward flexibility (ICC = 0.99, 95%CI= 0.99-1.00).

Figure 1. Anterior and posterior camera position for tennis serve video capture.

angle of rotation using the PVC pipes as landmarks (Figure 2). The averages of three trials for both backward and forward flexibility were used for data analysis. Total arc of motion was calculated by adding backward and forward rotation angles together

TRUNK ROTATIONAL POWER The field test of Cowley and Swensen22 for the power component of core stability was modified so that in addition to measuring the distance the medicine ball traveled, power was calculated by power (Watts) = (force x distance)/time.24 Players’ arm lengths were measured bilaterally from the tip of the acromion process to the radial styloid process.25 Each player was instructed to sit with both feet flat on the ground shoulder width apart. The elbows were extended and supinated, and the 5th digits from the left and the right hands were touching. A 2.72 kg medicine ball was placed in the participants’ hands. Each player was then instructed to maintain a flat back and to lower the torso to a 45° hip angle; this position was confirmed with a standard goniometer. Lastly, players were asked to rotate the trunk to approximately 90° so the serving arm moved backwards (Figure 3a), and to perform an explosive contraction of the core musculature using the arms as levers to project the medicine ball to the opposite side of rotation. The medicine ball was released from the hands when the player reached the opposite knee (Figure 3b).

Participants were given up to five practice trials. A one to two minute rest period was given between practice and actual testing. The average of the three trials were used for data analysis.

Table 3. Intra-observer reliability performed by one experienced sports medicine professional evaluating the service videos of 13 professional players Node

Description

Kappa Coefficient 1.0a 0.75b 0.63b 0.75b 0.83a 0.64b 1.0a 0.75b 0.58c

Node 1 Foot Position Node 2 Knee Position Node 3 Counterhip Rotation Node 4 Posterior Hip Tilt Node 5 Hip Lean Node 6 X-Angle Node 7 Trunk Position Node 8 Arm Position Assessment Composite Motion of of Motion 9 Kinetic Chain a Indicates almost perfect level of agreement (≥ 0.81) b Indicates substantial level of agreement (0.61 to 0.80) c Indicates moderate level of agreement (0.41-0.60)

Level of Agreement (%) 100 92 92 92 92 85 100 92 85

95% Confidence Intervals 1.00, 1.00 0.29, 1.21 -0.07, 1.33 0.29, 1.21 0.51, 1.15 0.20, 1.10 1.00, 1.00 0.29, 1.21 0.05, 1.11

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Figure 2. Angle of rotation for backward trunk flexibility on a right handed server.

A standard video camera was placed anteriorly to each player so the entire movement was filmed (medicine ball release to ground contact). All videos were uploaded and analyzed using video motionanalysis software (Dartfish 8 ProSuite; Dartfish, Fribourg, Switzerland) where distance in meters and time in seconds were calculated. The video camera was calibrated using a reference distance prior to the task. A meter stick was placed horizontally next to the player to calibrate the video recording of the ball toss. This step was essential in measuring distance within video motion-analysis as it provided a known distance in order to compute the distance each person threw. The start time of the movement was defined as the point in which the medicine ball crossed over the opposite leg just before release and ended at ball contact with the ground. The duration of the event was used to calculate power. A member of the research team used these same time points to measure the distance the medicine ball traveled in meters. The weight of the medicine ball was converted into 26.64 newtons, and represented force, the distance was represented in meters, and the time in seconds. Excellent inter-rater reliability of the measurements was established using the data of six participants for trunk rotational power (ICC = 0.98, 95%CI: 0.90-0.99).

Figure 3. a. Trunk rotational power starting position for a right handed server. b. Trunk rotational power ending position for a right handed server

COUNTERMOVEMENT VERTICAL JUMP Lower extremity power was assessed with double and single leg CMJ.21 All players were asked to maintain an upright position followed by a quick crouching action to propel the body into a maximal vertical jump. The participants were instructed to jump vertically as high as possible while keeping the legs straight in the air. The use of the arms to reach as high as possible was permitted as part of the movement. A familiarization period consisted of up to three practice jumps for both the double and single CMJ. A rest period of two minutes was given in between double and single legged jumps. The single leg jump was performed on the dominant leg (defined as the ipsilateral leg as serving arm).

A standard video camera was placed perpendicular to the plane of motion. All video motion-analysis data were analyzed using the same Dartfish software. To determine vertical jump height the following equation was used.21

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TIA (time in air) jump height = ½ g (t/2)2 t = time in air, determined by time difference from the video recording from takeoff to landing as determined by foot contact. g = 9.8 m · sec−2 Excellent inter-rater reliability of the measurements was established using the data of six participants for both double leg (ICC =0.99, 95%CI= 0.98-1.00) and single leg (ICC = .97, 95%CI=0.80-0.99). The average of the three double leg and single leg CMJs were used for data analysis.

DYNAMIC BALANCE Dynamic balance was measured using the anterior direction of the Star Excursion Balance Test.26,27 Each player was given standardized verbal instructions along with a visual demonstration, followed by four practice trials.23,26 While barefoot, the participants then performed three test trails in the anterior direction for each leg. A member of the research team measured leg length on each limb while the participants lay supine. The distance in centimeters (cm) was recorded from the Anterior Superior Iliac Spine to the center of the ipsilateral medial malleolus. Reach distance was normalized to each participant’s limb length by dividing by the players’ leg length (cm) and multiplying by 100. The average normalized percent leg length score among the trials for each stance leg was used for data analysis. Excellent inter-rater reliability of the anterior reach Star Excursion Balance Test has been previously established (ICC = 0.92).23 Statistical Analysis Percentage of observed agreement and kappa (K) coefficients were used to investigate inter-observer reliability for each of the nine components of the OTSA. K was interpreted using the following scale: ≤ 0 = poor agreement, .01-.20 = slight agreement, .21-.40 = fair agreement, .41-.60 = moderate agreement, .61-.80 = substantial agreement, and .81-1 = almost perfect agreement.19 A final composite score was calculated for each of the 28 players by summing together the individual scores of each of the nine components. To determine the inter-rater reliability of the total composite score, an Intraclass Correlation Coefficient (ICC) was utilized.

In combination with the reliability statistics, several researchers have suggested the proportion of positive agreement be calculated to provide readers with a clearer understanding of reliability. 28-32 Furthermore, this proportion should be considered when a kappa paradox is present, in which a low kappa statistic accompanies a high level of observed agreement between observers.28,30 When this paradox is present, interpretation of the kappa on its own may not be meaningful, and calculation of the proportion of positive agreement should be generated to interpret the results.29 The following equation was used to calculate the proportion of positive agreement using the same data within the 2 x 2 contingency tables exported from SPSS when generating Kappa statistics.

Ppos = 2a / (N + a – d) N = # of observations a = true positive d = true negative The dependent measures from the field tests (trunk flexibility, rotational power/distance, CMJ, and dynamic balance) were analyzed separately using an analysis of covariance (ANCOVA) to determine if physical characteristics would demonstrate differences between those with good and poor serve mechanics. One player from the good serve mechanics group was unable to perform forward trunk flexibility; therefore this player was removed from flexibility analyses (forward, backward, and total motion) leaving 15 players data for statistical analysis in this group. All other analyses used data from all 17 players in the poor mechanics group and 16 players in the good mechanics group. An ANCOVA was utilized to remove bias that may contribute differences present within the two groups (Table 1).33 Chi square analysis was used for binomial data and independent T-test was used for continuous data. A chi-square revealed sex differences between the two groups (p=0.04), and independent t-test revealed a difference in age between the two groups (p<0.001).

Arm length was found to be different between groups (p=0.006). All analyses incorporated sex and age as a covariate to account for group differences.

Additionally, arm length was incorporated into trunk

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rotational power and distance comparisons. All data were analyzed using Statistical Program for the Social Sciences (SPSS) version 21.0 (IBM Corp. Armonk, NY, USA). A α level of p ≤ 0.05 was considered significant.

RESULTS Reliability The percentage of observed agreement between the two observers varied by node and is presented in Table 4. The kappa scores ranged from 0.36 to 1.0, and the level of agreement ranged from 78 to 100% agreement. Five out of the nine nodes scored K>0.61. The average composite score for Rater 1 was 7 ± 2.1 and Rater 2 was 7 ± 2.2. There was excellent inter-observer reliability between the two raters using the composite score (ICC = 0.90, 95% CI: 0.847-0.985). The kappa paradox was present in the other four nodes (2, 5, 7, 8) with lower Kappa scores. The proportions of positive agreement for these four nodes range from 0.57 to .96 and are also presented in Table 4.

Validity Trunk flexibility and power measures discriminated between the two groups (Table 5). Backward trunk flexibility and total arc of motion were significantly greater in those with good mechanics compared to those with poor mechanics when adjusting for age and sex. Similarly, trunk rotational power and

distance were greater in those with good mechanics compared to poor mechanics when adjusting for age, sex, and arm length. Dominant single leg CMJ was also greater in those with good mechanics by 10cm. There were no significant differences between groups for forward trunk flexibility, double leg CMJ, or dynamic balance (Table 5).

DISCUSSION The OTSA was developed using kinematic findings from 3D motion analysis studies. The developers of this tool suggested the analysis might be practical for coaches and HCPs to evaluate serve mechanics in the absence of costly 3D biomechanical equipment.

However, the practicality of such a tool cannot be suggested without basic psychometric properties.

Therefore, the current study investigated the validity and inter-observer reliability between the two HCPs that helped to create the OTSA. It was hypothesized that players demonstrating good serve mechanics would perform better on a series of musculoskeletal field tests compared to those with poor serve mechanics. The hypothesis was partially supported as five measures were found to differentiate those with good and poor mechanics. Players with good mechanics demonstrated approximately 11° more backward trunk flexibility and 23° more total trunk rotational motion. Those with good serve mechanics generated 46 more watts of trunk rotational power,

Table 4. Inter-observer reliability between two experienced sports medicine professionals evaluating 28 tennis serve videos Node

Percentage of Observed Agreement (%) 89 78 96

Kappa Coefficient

Node 1: Foot Position 0.77b Node 2: Knee Position 0.43c Node 3: Counterhip 0.84a Rotation Node 4: Posterior Hip 100 1.0a Tilt Node 5: Hip Lean 89 0.36d Node 6: X-angle 96 0.78 b Node 7: Trunk Position 92 0.47 c Node 8: Arm Position 85 0.51c Assessment of Motion 9: 96 0.86a Composite Motion of Kinetic Chain a Indicates almost perfect level of agreement (≥ 0.81) b Indicates substantial level of agreement (0.61 to 0.80) c Indicates moderate level of agreement (0.41-0.60) d Indicates fair level of agreement (0.21-0.40)

95% Confidence Intervals

Proportion of Positive Agreement

0.53, 1.01 0.02, 0.84 0.53, 1.15

0.85 0.57 0.97

1.00, 1.00

1.00

-0.54, 1.26 0.20, 1.36 -0.24, 1.18 0.07, 0.95 0.61, 1.11

0.94 0.98 0.96 0.91 0.97

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Table 5. Means ± standard deviations for all dependent measures between groups Good Serve Mechanics

Poor Serve Mechanics

Trunk Flexibility Measuresa (degrees) Backward Trunk Flexibility 60.71 ± 10.82° 49.39 ± 14.85° Forward Trunk Flexibility 57.97 ± 14.28° 46.31 ± 18.25° Total Arc of Motion 118.68 ± 23.39° 95.70 ± 28.36° Power Measures Trunk Rotational Power 165.20 ± 30.90 118.76 ± 22.25 (Watts)a,b Trunk Rotation for Distance 5.02 ± 1.35 2.68 ± 0.70 (meters)a,b 0.41 ± 0.11 0.26 ± 0.08 Double Leg CMJ (meters)a Single Leg CMJ (meters)a 0.22 ± 0.05 0.12 ± 0.05 Dynamic Balance a Dominant Anterior Leg Reach 66.17 ± 5.52% 63.32 ± 7.09% (reach distance in cm/leg length in cm*100) Non-Dominant Anterior Leg 67.03 ± 5.02% 63.53 ± 6.87% Reach (reach distance in cm/leg length in cm*100) a ANCOVA model corrected for age, and sex b ANCOVA model corrected for age, sex, and arm-length

had a greater throwing distance on average of two meters (m) during the trunk rotational power test, and jumped an average 10cm higher on the dominant single leg CMJ compared to players with poor mechanics. Additionally, it was hypothesized that the inter-observer reliability would be greater than 0.41 for the majority of the nine nodes. This study supported that hypothesis as 89% of the nodes generated moderate to almost perfect agreement. However, caution must be taken when interpreting the kappa values of the nodes generating fair to moderate agreement, as the kappa paradox was present within these four nodes.

The kappa is “affected by the prevalence of the finding under consideration much like prediction values are affected by the prevalence of the disease under consideration.”30 p.362,32 For example, the low kappa value (0.36) associated with node five presents with a percentage of observed agreement of 89% (two observers in agreement 25 out of 28 observations). This occurred because 24 out of the 25 agreed responses were that players did exhibit forward hip lean, and only one time did the raters agree that the athlete did not exhibit forward hip lean during the serve. Therefore, there is much agreement among the observers, but there is an uneven distribution of observations within the contingency table. With the proportion of positive

p-Value

Cohen D Effect Size

0.02 0.09 0.02

0.94 0.71 0.88

0.02

1.73

0.002

2.20

0.33 0.05

1.57 2.00

0.30

0.45

0.31

0.58

agreement value reaching near one, (0.94 in this case) it can be interpreted that the decline in kappa is a result of the high prevalence of “yes” responses (24 responses) compared to “no” responses (one response) between the observers.29 The kappa value representing nodes five, seven, and eight seems to be underestimating the true agreement between these two raters as the proportion of positive agreement is large providing an additional method to interpreting the data that may help to provide a clearer picture.29 Results of the present study suggest that trunk flexibility and power capacity of both the trunk and lower extremity are key contributions to good serve mechanics. Tennis researchers have investigated the relationship between rotational trunk kinematics during the serve and serve velocity. Elite players displaying trunk rotation about the anteroposterior and transverse axis early in the service motion had improved serve speeds compared to those demonstrating rotation later in the motion.1 Consistent with the findings of this study, lower handicapped golfers demonstrated 10° more torso flexibility than those with higher handicaps.34 Previous authors have indicated that poor torso flexibility may inhibit the mechanics of the golf swing, specifically the X factor (or x-angle), thus diminishing drive distance and decreasing velocity.35,36 The role of torso rotation has also been demon-

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strated to contribute to enhanced throwing velocity in baseball players.37 Additionally, multi-modal training regimes incorporating the lumbopelvic hip complex and torso have shown to be effective for improving serve velocity,38 throwing accuracy,39 and ball velocity in overhead athletes.40,41 The results of this study are consistent with literature pertaining to other rotational sports, and should encourage tennis professionals to consider trunk flexibility as an important screening tool for the assessment of serve mechanics.

If deficits are present, a training regimen concentrating on trunk mobility should be considered, as trunk rotation movement appears to be a contributing factor in players exhibiting improved performance and as this study showed good serve mechanics.

Tennis is considered a rotational power sport requiring explosive movements in the transverse plane.42 Trunk rotation is an imperative motion necessary for generating power during all three of the major strokes to create velocity at ball impact. To the authorâ&#x20AC;&#x2122;s knowledge, this is the first study to date that has calculated power output in Watts using a previously established field based measure that assessed the power component of core stability.22 Previous research investigated the effects of a power stability training intervention integrating multi-planar rotational torso movement on ball velocity and muscular power in collegiate throwing athletes.40 Palmer and colleagues40 found that power stability training improved throwing velocity by 5 km/h and muscular power by 85W when compared to an endurance training protocol. Although the testing procedures for trunk power was different in the two studies, the power values of 165 Âą 31 watts in good performers are comparable to the pre-intervention trunk power values of 248 Âą 128 Watts. Differences between the actual averages in this study and the Palmer et al study may also be attributed to participant population and the differences in testing maneuvers.40 While the current study did not include an intervention component, a field test identifying significant trunk rotational power differences could be valuable in future intervention and performance assessments. Therefore, assessing dynamic trunk power may be helpful in determining players that need future intervention as trunk rotational power is positively correlated with performance in rotational sports.40,43

In this study, single leg CMJ height on the dominant leg revealed a 10-centimeter difference between the two groups while the double leg CMJ showed no difference between the groups. While this study did not measure lower extremity forces, these findings may suggest that those with good mechanics are able to maximize back leg drive up and through the serve, as this is the basis for proper hip motion and subsequent acceleration. This is consistent with the work of Girard et al,44 who showed elite tennis players activate the dominant leg muscles earlier in the tennis motion than less skilled players, and of Whiteside et al11 who showed elite adult female tennis players to have greater dominant leg triple extension velocities and racquet velocities at impact compared to prepubescent elite players. The importance of this finding is that each leg should be independently evaluated when screening players for potential lower extremity power deficits.

There are several advantages to this type of observational analysis. First, it is portable to practice or tournament sites, and can be implemented by using a standard video camera. Second, it allows coaches and HCPs to easily identify mechanical flaws within the service motion to improve performance and diminish possible injury risk. Third, by specifically demonstrating failures to achieve specific nodes, it can highlight areas for more comprehensive musculoskeletal evaluation, treatment, and conditioning. In turn, coaches and HCPs may evaluate specific body regions that aid in the improvement of the serve technique. With the identification of node deficiencies it may be possible to develop programs to improve mechanics, performance, and ultimately reduce injury risk.

These investigations have limitations. First, serve mechanics and power were not assessed using 3D kinematic and kinetic analysis. However, the protocol used to measure kinematics and power reflects practical field tests. Second, the outcomes of the tennis serves were not recorded. The authors did not document if the three service trials were considered playable points. Future studies should document the outcome of each service trial to combat this limitation. Third, two experienced sports medicine professionals who were involved in the development of the method performed the analysis. Future research is underway to address this specific limitation by incor-

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porating more HCPs and tennis coaches that have not developed the OTSA tool into a larger reliability study. Lastly, future research should investigate if a standardized training intervention can improve the mechanics of the tennis serve. Based on the current results, an intervention should likely incorporate trunk flexibility and both trunk and lower extremity interventions as these components were able to differentiate those with good and poor serve mechanics.

CONCLUSION The OTSA has a high agreement between two experienced observers, indicating good to excellent reliability. This system has the potential to help coaches, players, and HCPs better analyze the tennis serve motion. This study demonstrated that specific physical characteristics can differentiate players with good and poor serve mechanics as defined by the OTSA scores. Specifically, trunk rotation and power capacity of the trunk and lower extremity are key areas that may contribute to poor serve mechanics and may be reasonable starting points to address in interventions that may enhance serve mechanics and performance.

REFERENCES 1. Martin C, Kulpa R, Ropars M, Delamarche P, Bideau B. Identification of temporal pathomechanical factors during the tennis serve. Med Sci Sports Exerc.

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3. Elliott B, Fleisig G, Nicholls R, Escamilia R. Technique effects on upper limb loading in the tennis serve. Aust J Sci Med Sport. Mar 2003;6(1):76-87.

4. Campbell A, Straker L, O’Sullivan P, Elliott B, Reid M. Lumbar loading in the elite adolescent tennis serve: link to low back pain. Med Sci Sports Exerc.

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8. Martin C, Kulpa R, Delamarche P, Bideau B. Professional tennis players’ serve: correlation between segmental angular momentums and ball velocity. Sports Biomech. 2013;12(1):2-14.

9. Martin C, Bideau B, Ropars M, Delamarche P, Kulpa R. Upper limb joint kinetic analysis during tennis serve: Assessment of competitive level on efficiency and injury risks. Scand J Med Sci Sports.

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10. Martin C, Bideau B, Bideau N, Nicolas G, Delamarche P, Kulpa R. Energy Flow Analysis During the Tennis Serve: Comparison Between Injured and Noninjured Tennis Players. Am J Sports Med. Aug 28 2014.

11. Whiteside D, Elliott B, Lay B, Reid M. The effect of age on discrete kinematics of the elite female tennis serve. J Appl Biomech. Oct 2013;29(5):573-582.

12. Ford KR, Myer GD, Hewett TE. Reliability of landing 3D motion analysis: implications for longitudinal analyses. Med Sci Sports Exerc. Nov 2007;39(11):20212028.

13. Ferrarello F, Bianchi VA, Baccini M, et al. Tools for observational gait analysis in patients with stroke: a systematic review. Phys Ther. Dec 2013;93(12):16731685.

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17. Kibler WB, Wilkes T, Sciascia A. Mechanics and Pathomechanics in the Overhead Athlete. Clin Sports Med. 2013;32(4):637-651.

18. Reid M, Elliott B, Alderson J. Shoulder joint loading in the high performance flat and kick tennis serves. Br J Sports Med. Dec 2007;41(12):884-889; discussion 889.

19. Landis JR, Koch GG. The measurement of observer agreement for categorical data. Biometrics.

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20. Aragon VJ, Oyama S, Oliaro SM, Padua DA, Myers JB. Trunk-rotation flexibility in collegiate softball players with or without a history of shoulder or elbow injury. J Athl Train. Sep-Oct 2012;47(5):507513.

21. Moir GL. Three Different Methods of Calculating Vertical Jump Height from Force Platform Data in Men and Women. Meas Phys Educ Exerc Sci. 2008;12(4):207-218.

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22. Cowley PM, Swensen TC. Development and reliability of two core stability field tests. J Strength Cond Res. Mar 2008;22(2):619-624.

23. Gribble PA, Kelly SE, Refshauge KM, Hiller CE. Interrater reliability of the star excursion balance test. J Athl Train. Sep-Oct 2013;48(5):621-626.

24. Kreighbaum E BK. Biomechanics: A Qualitative Approach for Studing Human Movement. 4th ed ed. Needham Heights, MA: Simon & Schuster Company; 1996.

25. Myers NL, Toonstra JL, Smith JS, Padgett CA, Uhl TL. Sustained Isometric Shoulder Contraction on Muscular Strength and Endurance: A Randomized Clinical Trial. Int J Sports Phys Ther. Dec 2015;10(7):1015-1025.

26. Earl JE, Hertel J. Lower-extremity muscle activation during the Star Excursion Balance Tests. J Sport Rehab. 2001;10(2):93-104.

27. Gribble PA, Hertel J, Plisky P. Using the star excursion balance test to assess dynamic posturalcontrol deficits and outcomes in lower extremity injury: a literature and systematic review. J Athl Train. 2012;47(3):339-357.

28. Cicchetti DV, Feinstein AR. High agreement but low kappa: II. Resolving the paradoxes. J Clin Epidemiol.

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29. Cunningham M. More than Just the Kappa Coefiicient: A Program to Fully Characterize InterRater Reliability between Two Raters. SAS Global Forum 2009; 2009.

30. Feinstein AR, Cicchetti DV. High agreement but low kappa: I. The problems of two paradoxes. J Clin Epidemiol. 1990;43(6):543-549.

31. Sim J, Wright CC. The kappa statistic in reliability studies: use, interpretation, and sample size requirements. Phys Ther. Mar 2005;85(3):257-268.

32. Viera AJ, Garrett JM. Understanding interobserver agreement: the kappa statistic. Fam Med. May 2005;37(5):360-363.

33. Henderson Jr CR. Analysis of covariance in the mixed model: higher-level, nonhomogeneous, and random regressions. Biometrics. 1982:623-640.

34. Keogh JW, Marnewick MC, Maulder PS, Nortje JP, Hume PA, Bradshaw EJ. Are anthropometric, flexibility, muscular strength, and endurance variables related to clubhead velocity in low-and

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high-handicap golfers? J Strength Cond Res. 2009;23(6):1841-1850.

Myers J, Lephart S, Tsai YS, Sell T, Smoliga J, Jolly J. The role of upper torso and pelvis rotation in driving performance during the golf swing. J Sports Sci. Jan 15 2008;26(2):181-188.

Lephart SM, Smoliga JM, Myers JB, Sell TC, Tsai Y-S. An eight-week golf-specific exercise program improves physical characteristics, swing mechanics, and golf performance in recreational golfers. J Strength Cond Res. 2007;21(3):860-869.

Stodden DF, Fleisig GS, McLean SP, Lyman SL, Andrews JR. Relationship of Pelvis and Upper Torso Kinematics to Pitched Baseball Velocity. J Appl Biomech. 2001;17(2):164-172.

Fernandez-Fernandez J, Ellenbecker T, Sanz-Rivas D, Ulbricht A, Ferrautia L. Effects of a 6-week junior tennis conditioning program on service velocity. J Sports Sci Med. 2013;12(2):232-239.

Lust KR, Sandrey MA, Bulger SM, Wilder N. The Effects of 6-Week Training Programs on Throwing Accuracy, Proprioception, and Core Endurance in Baseball. J Sport Rehab. 2009;18(3):407-426.

Palmer T, Uhl TL, Howell D, Hewett TE, Viele K, Mattacola CG. Sport-Specific Training Targeting the Proximal Segments and Throwing Velocity in Collegiate Throwing Athletes. J Athl Train. Jun 2 2015;50(6):567-577.

Saeterbakken AH, van den Tillaar R, Seiler S. Effect of Core Stability Training on Throwing Velocity in Female Handball Players. J Strength Cond Res. 2011;25(3):712-718.

Earp JE, Kraemer WJ. Medicine ball training implications for rotational power sports. Strength Cond. 2010;32(4):20-25.

Freeston JL, Carter T, Whitaker G, Nicholls O, Rooney KB. Strength and Power Correlates of Throwing Velocity on Subelite Male Cricket Players.

J Strength Cond Res. Jun 2016;30(6):1646-1651.

Girard O, Micallef JP, Millet GP. Lower-limb activity during the power serve in tennis: effects of performance level. Med Sci Sports Exerc. Jun 2005;37(6):1021-1029.

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IJSPT

ORIGINAL RESEARCH

DO GENERAL MEDICAL PRACTITIONERS EXAMINE INJURED RUNNERS? Videbaek, S.1 Jensen, A.V.2 Rasmussen, S.1 Nielsen, R.O.3

ABSTRACT Background: General Medical Practitioners (GMP) in Denmark perform clinical examinations of patients with musculoskeletal pain. However, the prevalence proportion of examinations caused by running-related injuries remains unknown.

Purpose: The primary purpose of the present study was to estimate the prevalence proportion of consultations in general medical practice caused by running-related injuries. The secondary purpose was to estimate the prevalence proportion of injured runners, who consult their GMP, that are referred to additional examinations or treatments.

Study Design: A survey-based study.

Methods: An online survey was distributed in October and November 2015 to more than 370 GMPs in Denmark and completed by 27.

Results: The median prevalence proportion of consultations caused by running-related injuries in the prior two weeks was 0.80% [25th percentile = 0.00%; 75th percentile = 1.43%]. Ten (37%) GMPs reported to refer between 0-24% of the injured runners to additional examination or treatment, whereas thirteen (48%) of GMPs referred between 25-49% and four (15%) referred 50-74% of injured runners.

Conclusion: Although a very small part (<1%) of the GMPs consultations were related to running injuries, this result suggests that injured runners seek advice in the primary health-care system in Denmark. As a consequence, physiotherapists willing to treat runners with running-related injuries may inform the GMPs in their local community about the treatment possibilities they offer. The low response-proportion highlights the challenges recruiting GMPs willing to respond to questionnaires on running-related injuries. It is plausible to assume that the estimates reported in the present study are overestimated owing to selection bias.

Level of Evidence: 3 Key words: Family medicine, injuries, physiotherapy, running

1

Orthopaedic Surgery Research Unit, Science and Innovation Center, Aalborg University Hospital, Aalborg University, Denmark 2 Department of Political Science, Aarhus University, Denmark 3 Department of Public Health, Section for Sport Science, Aarhus University, Denmark

CORRESPONDING AUTHOR Solvej VidebĂŚk Section of Sport Science, Department of Public Health, Faculty of Health Science, Aarhus University, Dalgas Avenue 4, room 438, 8000 Aarhus C., Denmark Phone: +4561685110 E-mail: solvejandersen@hotmail.com

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INTRODUCTION Physical activity plays an important role in prevention of lifestyle diseases, which affect large segments of the population and account for comprehensive socioeconomic burden.1,2 Therefore, an effort to increase physical activity should be considered a public-health priority.3 Running has been shown to be a popular form of physical activity among less active people seeking a healthier lifestyle and persistent running practice remains fundamental to obtaining well-established individual and socioeconomic benefits.4,5 Running-related injuries (RRIs) are a common problem, since a recent meta-analysis,6 revealed a weighted incidence rate of 17.8 injuries (95 % confidence interval [CI] 16.7;19.1) per 1,000 hours of running in novice runners and 7.7 (95 % CI 6.9;8.7) per 1,000 hours of running in recreational runners. Patello-femoral pain, iliotibial band syndrome, medial tibial stress syndrome, Achilles tendinopathy and plantar fasciitis are running injuries commonly diagnosed by health-care professionals.7,8 General Medical Practitioners (GMPs) are primary care providers and are usually the first point of contact for a runner in the health-care system. GMPs in Denmark use the International Classification of Primary Care 2 (ICPC-2) coding system to document the health issues of each patient. An ICPC-2 code consists of a letter and two numbers, and represents a disease or a symptom, and registers musculoskeletal problems by anatomical region, e.g. L15 symptoms/complaints knee or L77 ankle sprain. In Central Denmark Region, 14.5% of the consultations performed by GMPs in 2009 were reported as musculoskeletal problems.9 The causative factors for these musculoskeletal problems are not registered due to the organization of the ICPC-2 coding system. As a consequence, it is impossible to conduct a registerbased study to investigate the prevalence proportion of consultations in GMP practices caused by RRIs. In a study of novice runners participating in a Dutch “Six-week start to run program”, Hespanhol et al. reported a prevalence proportion of 9.6% of the injured runners consulting their GMP.10 In addition, amongst marathon runners, Van Middelkoop et al. reported a prevalence proportion of 16.4% of the

injured runners consulting a GMP because of their RRI.11 In a study on the Dutch population, Baarveld et al. found 8.6% of sports-related consultations to be due to running/jogging as injury-prone activity.12 Finally, amongst injured road runners, 24% consulted a GMP.13 Although interesting, these data do not clarify the prevalence proportion of RRI consultations in general practice. The primary purpose of the present study was to estimate the prevalence proportion of consultations in general medical practice caused by running-related injuries. The secondary purpose was to estimate the prevalence proportion of injured runners, who consult their GMP, that are referred to additional examinations or treatments.

METHODS Ethics and protection of data The Scientific committee, North Denmark Region, evaluated the protocol but waived the request for approval because observational studies, according to the Danish law, do not require an ethical approval.

The study was approved by the Danish Data Protection Agency (J. nr. 2008-58-0028).

Recruitment of general practitioners In order to estimate the prevalence proportion of consultations amongst GMPs in Denmark caused

by RRI, an online survey was distributed in October and November 2015. To reach as many GMPs as possible, the questionnaire was widely distributed: (i) via the newsletter of NordKAP, an organization that encompasses ∼340 GMPs in the North Denmark Region; (ii) GMPs were contacted face-to-face at an annual national conference (Lægedage 2015) held in Copenhagen; (iii) Danish GMPs were contacted by phone and encouraged to respond; (iv) and face-toface contact in their practices was used to further support participation (Figure 1).

Questionnaire development and pilot testing Qualitative interviews with runners and GMPs were conducted in advance of constructing the electronic questionnaire. Standardized questionnaire methodology was used to inform the design of the questionnaire. The preliminary questionnaire was pilot tested and modified in two phases in order to analyze the questionnaire comprehensibility and adequacy in achieving targeted data collection goals as defined in

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Pilot version 1 Development of ques onnaire based on predefined research ques ons. A thourough process performed in coopera on with a professional expert in ques onnaire development in order to secure the op mal sequence of ques ons together with ideal wording.

Test and evalua on Feedback interviews with four independent GMPs

Pilot version 2 Sugges ons from the four GMPs incorporated.

Content: Modifica on of ques on regarding the three most frequent RRI diagnoses, due to risk of recall bias Exclusion of a ques on examining the propor on of runners being seen >3 mes per RRI Exclusion of two ques ons examining details of the typical runner seen with RRI in GMP Addi on of ankle sprain in the eligible category of frequent RRI Uni ng and regrouping ques ons regarding diagnos cs and treatments of RRIs Defini ons: Linguis c modifica ons of the introductory remarks to certain ques ons Rewording of available op ons of treatments and type of prac ce.

Test and evalua on Performed by GMPs

Final Ques onnaire Design op miza on and con nuous scale ques ons changed to eligible intervals in aim for increased compliance

Distribu on

(i) NordKAP ∼ 340 asked* 14 fulfilled

(ii) GMP conference 16 asked 3 fulfilled

(iii) GMPs contacted by phone 17 asked 6 fulfilled

(iv) GMPs contacted face-to-face 5 asked 4 fulfilled

Respondents n = 27 n = 3 of these were contacted to confirm or correct suspicious and missing answers

Final number of completed ques onnaire replies n = 27

Figure 1. Flowchart showing questionnaire development, distribution, and responses.

GMP = General Medical Practitioner, RRI = Running-related injury. *Number of GMPs in the North Denmark Region The International Journal of Sports Physical Therapy | Volume 12, Number 3 | June 2017 | Page 452

the purpose of the present study. In pilot study one, an interview was conducted independently with each of four GMPs upon completion of the questionnaire.

The interview was aimed at collecting feedback on the level of comprehensibility of the questionnaire instructions and questions, as well as specific suggestions for improvements or modifications of the questions. Pilot study two was performed by two independent GMPs and carried out in a similar manner as the procedure in pilot study one. In each phase, the questionnaire was thoroughly modified according to the feedback, and after pilot study two the final questionnaire was distributed. Details concerning the evaluation and modification upon completion of each pilot study are visualized in Figure 1.

Description of main questions in survey First, two questions focused on the number of overall consultations in GMP practice caused by both RRIs and non-RRIs: “1) How many consultations do you have per day in an average working week? (State in whole numbers)” and “2) How many consultations have you had in total during the last period of two working weeks? (State in whole numbers)”. Secondly, three questions were targeting consultations caused by RRIs: “3) Have you had at least one consultation concerning a person with a RRI over the past year?”, “4) How many consultations regarding RRIs have you had in total during the last period of two working weeks?” (State in whole numbers)” and “5) How many consultations regarding RRIs have you had per month over the past year? (State in whole numbers)”. The GMPs where informed that all questions should be answered to the best of their assessment. When combining the continuous scale data from the question asking about the GMPs total number of consultations during the last period of two working weeks and the question about the total number of consultations regarding RRIs during the last period of two working weeks, the prevalence proportion of consultations caused by RRIs was estimated using the following equation:

The time frame of the prior two working weeks were chosen as the basis for the primary estimate of this study to reduce the risk of subjective recall bias. The question about monthly number of consultations regarding RRIs over the past year was included in order to be able to test the robustness of the primary estimate to this choice of time frame.

The secondary purpose of the study was to estimate the proportion of injured runners referred to additional examinations or treatments. To investigate this, a questionnaire section with the following two questions was designed: “What is the proportion of the RRIs which you refer to secondary examinations and/or treatment?”, with the eligible answers: “0-24%”; “25-49%”; “50-74%”; “75-100%” or “Don’t know”; and “If you refer the patient, to whom do you refer? (select all that apply)”, with the eligible options: “Physiotherapist”; “Chiropractor”; “Orthopaedic surgeon”; “Specialist in sports medicine”; “Acupuncturist” and “Other”.

Data management and statistical analysis: Data were analysed using Stata/IC version 14.1 (StataCorp, College Station, Texas, USA). Continuous data were evaluated using quartile-quartile plots to evaluate if data were normally distributed, and since they did not follow a normal distribution, we used the median- instead of the mean estimate.

Descriptive statistics were used to present the data according to questionnaire categories. In some questions, respondents had the opportunity to include more than one response; therefore the number of responses could exceed 100%.

Trial registration This was a survey-based study. No trial registration was made.

RESULTS In total, 27 GMPs completed the questionnaire. Baseline characteristics of the responding GMPs together with the representativeness according to gender,

Total number of consultations caused

by RRI in the last two working weeks .100=%consultations caused by RRI in the last tw wo working weeks ultations in the Total number of consu last two working weeks The International Journal of Sports Physical Therapy | Volume 12, Number 3 | June 2017 | Page 453

seniority, type of practice and number of listed patients were compared to all GMPs in the Central Denmark Region (Table 1).9 According to gender, seniority and type of practice no significant differences were found. The number of listed patients was significantly different, as the included GMPs had a higher number of listed patients than the average of all GMPs in the Central Denmark Region.

All the responding GMPs have had at least one consultation concerning a person with a RRI in the past

year. The median proportion of consultations caused

by RRIs in the last period of two working weeks was 0.80% [25th percentile = 0.00%; 75th percentile = 1.43%]. The median of the monthly proportion of consultations caused by RRIs was 0.71% [25th percentile = 0.23%; 75th percentile = 1.20%] (Table 2).

A proportion of 25-49% of the consulting injured runners, were referred to additional examination and/or treatment by 48% (n = 13) of the GMPs. None of the GMPs referred 75-100% of the consulting injured runners to additional examination and/ or treatment (Figure 2). In case of referral, more

Table 1. Representativeness of participating general medical practitioners (GMPs) with regard to gender, seniority, type of practice, number of listed patients per GMP, interest in sports medicine, qualifications in sports medicine, personal interest in running Participating GMPs % (n) n total = 27

All GMP in one Region in DK % (n) n total = 871

p-value

Gender Male Female

59.3% (16) 40.7% (11)

61.1% (532) 38.9% (339)

0.84

Number of years in practice* <5 5-10 10-20 >20

34.6% (9) 7.7% (2) 26.9% (7) 30.8% (8)

24.1% (210) 18.4% (160) 32.0% (279) 25.9% (222)

0.36

Type of practice Single-handed Group

18.5% (5) 81.5% (22)

24.7% (215) 75.3% (656)

0.46

Number of list patients per GMP* <1000 1000-1499 1500-1999 >1999

0.0% (0) 19.2% (5) 53.8% (14) 26.9% (7)

8.0% (70) 50.9% (443) 36.2% (315) 4.9% (43)

<0.05

63% (17) 30% (8) 7% (2)

na

GMP characteristics

Interest in sports medicine** “Yes” “No” “Don’t know” Qualifications in sports medicine*** “Yes” “No”

37.1% (10) 62.9% (17)

Runner “No, never” “No, but I used to” “Yes, once a week” “Yes, twice a week” “Yes, several times a week”

0.0% (0) 11.1% (3) 14.8% (4) 7.4% (2) 66.7% (18)

na

na

n = number of GMPs na = not available * One GMP did not provide an answer to this question ** “Do you have a particular interest to sports medicine?” *** “Do you have specific qualifications in diagnostics and treatments of running-related injuries (courses, scientific experience, ultrasound, other)?”

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Table 2. Proportion of consultations in general medical practice caused by running-related injuries Median (%)

25th percentile (%)

75th percentile (%)

Min (%)

Max (%)

Period of 2 weeks

0.80 %

0.00 %

1.43 %

0.00 %

2.50 %

Monthly

0.71 %

0.23 %

1.20 %

0.00 %

2.00 %

Period of 2 weeks = the last period of two working weeks Monthly = per month over the past year

Central Denmark Region revealed no differences in gender, seniority and type of practice. It is impossible to compare these results with existing data, since no other study has investigated the proportion of consultations because of RRIs in GMP practices. In addition, comparison to data in registries is impossible since RRIs are not registered specifically in the ICPC-2 coding system in Denmark.

Figure 2. Distribution of general medical practitioners (GMPs) with regard to the proportion of running-related injuries, which they refer to additional examination and/or treatment.

Y-axis denotes the number of GMPs selecting the category.

than 90% of the GMPs reported to refer the injured runner to a physiotherapist.

DISCUSSION The present study revealed a median proportion of consultations in the prior period of two working weeks and a median monthly proportion of consultations caused by RRIs of 0.80% and 0.71%, respectively. If these proportions of consultations amongst the 27 GMPs submitting questionnaires is generalizable to all 3,495 GMPs in Denmark, RRIs have a considerable impact on the primary health-care system.

However, these results should be interpreted with caution, since the estimates reported in the present study might be overestimated owing to selection bias. GMPs interested in the running injury thematic and those who diagnose runners on a regular basis may have been more willing to respond to the questionnaire than those unfamiliar with running.

However, this remains speculative and the comparison of the included GMPs and the average GMP in

The secondary purpose of the study was to investigate the proportion of injured runners, whom the GMP chose to refer to additional examination and/ or treatment. Nearly 40% of the GMPs referred between 25% and 49% of the injured runners to physiotherapists, orthopaedic surgeons and specialists in sports medicine. Again, this estimate might be overestimated because of selection bias. In addition, it is unknown how many runners that used the referral for further diagnostics and/or treatment.

In comparison, Moth et al.9 reported that 6.6% of patients consulting a GMP with a sports-related injury were referred to the hospital.

The present study reveals an impact of running injuries in primary care and that the GMPs recommended injured runners to seek physiotherapy in more than 90% of the cases where the GMP made a referral. According to Figure 2, many of these injured runners are not referred to additional examination and/or treatment. Reasons for this could be many and were not addressed by the survey. The authors suggest that it may be that the GMPs do not believe there is a need for a referral since the runners should be able to handle their injury on their own. Secondly, the GMPs may recommend the runners to seek treatment but refrains from providing a referral, since the cost for the treatment is then partly covered by the health-care system. Finally, it may be that the GMPs are unaware of the pos-

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sibilities for additional examination and treatment options for injured runners in the local community.

Assuming the latter case is true, stronger dialogue between physiotherapists working with runningrelated injuries and GMPs in their local community is indicated. In a survey amongst competitive distance runners, 70% of the runners felt the advice and/or treatment from a physiotherapist was valuable in resolving injury.14 Although this was better than other health-care professionals that were listed in the survey, there is room for improvement. Referral of the injured runner to a physiotherapist with expertise in running-related injuries may be one important step.

Strength and limitations The most important strength of the present study was the sampling of data directly from the population of GMPs in Denmark. Little is known about the impact of RRIs on GMP practices, and most other studies concerning the topic are based on data collected from the population of injured runners.12,13 In addition, the responding sample of GMPs was representative according to gender, seniority and type of practice when compared to the general population of GMPs in the Central Denmark Region.

However, the present study had some limitations.

First, the number of responses (n=27) was low, which, given that more than 370 GMPs were provided with the possibility to respond the electronic questionnaire, leading to a response proportion lower than 7.3%. The response proportion might have been higher if the GMPs had received a compensation for the time-consuming task (approximately 2-3 minutes) of filling out the electronic questionnaire. Second, the majority (66.7%) of the responding GMPs practiced running several times a week, thus presumably having a greater interest in running than the non-responding GMP. This could possibly induce a selection bias (overestimation of the prevalence proportion), since GMPs with a greater interest in running might have a higher number of patients consulting them because of a running-related injury.

Further studies â&#x20AC;&#x201C; Ideas for data collection In future studies, the authors suggest to the provision of minimal compensation to the GMPs responding to

the questionnaire in order to improve the response proportion. In addition, to overcome the challenges of one-year recall period, which is difficult to respond to without recall problems, or two-week snapshot, which is affected by seasonal variation, future prospective studies are needed. The present ICPC-2 coding system does not register the causative factors of musculoskeletal problems, and therefore prospective data would have to be collected separately, by for instance using a logbook method, which would enable the GMP in registering precisely each time a consultation is caused by a RRI. CONCLUSION The median prevalence proportion of consultations caused by running-related injuries in the past two weeks was 0.80% [25th percentile = 0.00%; 75th percentile = 1.43%]. A proportion of 25-49% of the consulting injured runners, were referred to additional examination and/or treatment by 48% (n = 13) of the GMPs. The low response-proportion highlights the challenges recruiting GMPs willing to respond to questionnaires on running-related injuries. Therefore, these results should be interpreted with caution since the estimates reported in the present study might have been overestimated due to selection bias. If the prevalence proportion of consultations caused by running injuries is generalizable to all 3,495 GMPs in Denmark, the results from the present study suggest that injured runners seek advise in the primary health-care system in Denmark. As a consequence, physical therapists willing to treat runners with running-related injuries may inform the GMPs in their local community about treatment possibilities.

REFERENCES 1. Ekelund U, Steene-Johannessen J, Brown WJ, et al.

Does physical activity attenuate, or even eliminate, the detrimental association of sitting time with mortality? A harmonised meta-analysis of data from more than 1 million men and women. Lancet.

2016;388(10051):1302-1310.

2. Lee IM, Shiroma EJ, Lobelo F, et al. Effect of physical inactivity on major non-communicable diseases worldwide: An analysis of burden of disease and life expectancy. Lancet. 2012;380(9838):219-229.

3. Ding D, Lawson KD, Kolbe-Alexander TL, et al. The economic burden of physical inactivity: A global

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4.

5.

6.

7.

8.

analysis of major non-communicable diseases.

Lancet. 2016;388(10051):1311-1324.

Hespanhol Junior LC, Pillay JD, van Mechelen W, Verhagen E. Meta-analyses of the effects of habitual running on indices of health in physically inactive adults. Sports Med. 2015;45(10):1455-1468.

Hespanhol Junior LC, van Mechelen W, Postuma E, Verhagen E. Health and economic burden of running-related injuries in runners training for an event: A prospective cohort study. Scand J Med Sci Sports. 2016;26(9):1091-9.

Videbaek S, Bueno AM, Nielsen RO, Rasmussen S. Incidence of running-related injuries per 1000 h of running in different types of runners: A systematic review and meta-analysis. Sports Med. 2015;45(7):1017-1026.

Nielsen RO, Ronnow L, Rasmussen S, Lind M. A prospective study on time to recovery in 254 injured novice runners. PLoS One. 2014;9(6):e99877.

Taunton JE, Ryan MB, Clement DB, McKenzie DC, Lloyd-Smith DR, Zumbo BD. A retrospective casecontrol analysis of 2002 running injuries. Br J Sports Med. 2002;36(2):95-101.

9. Moth G, Olesen F, Vedsted P. Reasons for encounter and disease patterns in danish primary care: Changes over 16 years. Scand J Prim Health Care.

2012;30(2):70-75.

10. Hespanhol Junior LC, Huisstede BM, Smits DW, et al. The NLstart2run study: Economic burden of running-related injuries in novice runners participating in a novice running program. J Sci Med Sport. 2016;19(10):800-804.

11. Van Middelkoop M, Kolkman J, Van Ochten J, Bierma-Zeinstra SM, Koes BW. Course and predicting factors of lower-extremity injuries after running a marathon. Clin J Sport Med. 2007;17(1):25-30.

12. Baarveld F, Visser CA, Kollen BJ, Backx FJ. Sportsrelated injuries in primary health care. Fam Pract.

2011;28(1):29-33.

13. Furman S. Sport injuries and family practice: Who do roadrunners consult? S Afr Med J. 1986;69:108-110.

14. Rendall EO, Mohtadi NG. Survey of competitive distance runners in alberta: Satisfaction with health care services with respect to running injuries. Clin J Sport Med. 1997;7(2):104-112.

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IJSPT

CASE SERIES

IMPAIRMENT BASED EXAMINATION AND TREATMENT OF COSTOCHONDRITIS: A CASE SERIES Richard A. Zaruba, PT, PhD1 Eric Wilson, PT, DSc2

ABSTRACT Background: Costochondritis is commonly encountered in primary care, but is not routinely referred to PT. Costochondritis can last from several weeks to several months, limiting the patient’s ability to perform tasks at work and home.

Purpose: Identify common impairments and examine the effects of treatment in subjects with costochondritis.

Study Design: Retrospective case series Case Description: Eight subjects were referred to physical therapy for costochondritis (mean duration of condition 6.3±1.3 months) and reported that their condition restricted their ability to participate in occupational and fitness activities. The numerical pain rating scale (NPRS) and patient-specific functional scale (PSFS) were administered at the initial evaluation and at discharge. The Global Rating of Change (GROC) scale was only administered at discharge.

All subjects received treatment directed at the cervicothoracic spine and ribcage and consisting of manual therapy and exercise.

Outcomes: Subjects were seen 4.8±0.9 (mean±standard deviation) times. All subjects showed clinically meaningful changes at discharge. The mean NPRS decreased by 5.1±1.7 points; the mean PSFS increased by 5.3±1.4 points; and the mean GROC was 5.9±1.1 points. All subjects were able to return to participation in previous activities without restrictions at discharge.

Discussion - Conclusion: The results of this case series suggests that PT utilizing an impairment based examination and treatment approach including manual therapy and therapeutic exercise may facilitate the resolution of costochondritis.

Level of Evidence: Level IV Key words: Breathing, chest, manual therapy, ribs, thoracic

1

Physical Therapy Program, University of Jamestown, Fargo, ND, USA 2 Tactical Sports OMPT Fellowship, United States Airforce Academy, Colorado SpringsCO, USA The University of Jamestown Institutional Review Board approved this study and informed consent was obtained from the subjects prior to the collection of data. The authors certify that they have no affiliations or financial involvement with any organization or entity with a direct financial interest in the subject matter or materials discussed in the article.

CORRESPONDING AUTHOR Richard A. Zaruba University of Jamestown, Physical Therapy Program 4190 26th Ave S Fargo, ND E-mail: rzaruba@uj.edu

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INTRODUCTION Subjects with costochondritis are commonly encountered in primary care, but are not routinely referred to physical therapy (PT).1-5 Whereas there is some speculation, the actual etiology of this condition remains unknown.3 Pain is most commonly localized unilaterally to the second through fifth costochondral junctions, with more than one junction generally affected.3 Typically, local swelling is not noted in costochondritis, unlike Tietze syndrome.3 Whereas this condition is considered selflimiting and normally resolves within one year,1,6 it can last from several weeks to several months7 or be recurring,8 limiting the patient’s ability to function in occupational demands and activities of daily living. Pain is often associated with repetitive activities involving the upper extremities or deep breathing, including exertional activities, such as lifting heavy objects or cardiovascular exercise.3,9,10 When subjects are referred to PT, their condition has often progressed to a chronic stage with additional impairments, such as reduced endurance and difficulty performing moderate to heavy manual labor duties, have arisen secondary to compensation for costochondritis. Compounding this difficulty is the current lack of evidence/consensus as to the most effective way to manage this condition.

Current recommendations for medical treatment are analgesics and nonsteroidal anti-inflammatory drugs, heat/ice, and possibly anesthetic/steroid injections.3,4,8,11,12 The infrequent referral of subjects with costochondritis to rehabilitation has made it difficult for research to be performed regarding the effects of manual therapy or exercise. At this time only a single research trial exists that supports stretching as an intervention using the visual analog scale for an outcome.13 All other publications regarding manual therapy and/or exercise specifically for costochondritis have been case reports or case series of no more than two subjects.14-18 Whereas the results of the stretching study are promising, it was a limited retrospective study with a large number of confounding variables that may have affected the results.13 The remaining case reports used an impairment-based approach, which included manual therapy and exercise directed at the upper thoracic vertebrae, rib cage, and surrounding

soft tissues, with significant improvement noted in two or more of the following patient outcomes, the Numeric Pain Rating Scale (NPRS),14,15,18 Visual Analog Scale,16,17 Dallas Pain Questionnaire,14 Functional Rating Scale,14 Patient-Specific Functional Scale (PSFS),18 and return to previous performance/activity level.14-18 Given the limited research and lack of a clear consensus regarding optimal treatment strategies, a retrospective review of a series of subjects utilizing an impairment-based approach may provide further insight. It may also provide a better indication of where more formal investigation and research should be directed. The purpose of this case series is to identify common impairments and examine the effect of treatment in subjects with costochondritis.

CASE DESCRIPTIONS The University of Jamestown Institutional Review Board approved this study and informed consent was obtained from the subjects prior to the collection of data. Eight subjects with costochondritis were retrospectively reviewed for similarities in their evaluative findings and interventions. The subjects were referred to physical therapy by their primary care physicians over a four-month period after having been screened for non-musculoskeletal causes of their symptoms. All subjects had undergone a full medical evaluation for cardiopulmonary issues, including electrocardiography secondary to their reports of “chest pain”. All subjects were referred to PT secondary to demonstrated inability to perform full military duties and participate in mandatory fitness training, particularly push-ups and running, without exacerbation of symptoms. Subject demographics are shown in Table 1. The majority of cases were due to either physical activity or respiratory infection. In two subjects, there was an insidious onset and additional questioning during the patient interview and examination did not suggest any possible causes. Patient’s primary pain was isolated to the costosternal junctional area on at least two unilateral consecutive costosternal joints of the second through seventh ribs. The common primary aggravating factors reported by the subjects were any activity that caused heavy breathing and/or endrange horizontal abduction and adduction of the shoulder.

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Table 1. Patient Demographics Patient

Age (years)

Sex

Military Occupation

Duration (months)

Dominant Hand

Cause

1

23

Male

Security forces

7

Right

Fitness Activity

2

38

Male

Aircraft Maintenance

5

Right

Respiratory infection

3

23

Female

Security forces

8

Right

Insidious Onset

7

Left

Fitness Activity

4

37

Female

Munitions technician

5

28

Male

Security forces

6

Right

Respiratory infection

6

32

Male

Aircraft Maintenance

7

Left

Insidious Onset

7

28

Female

Security forces

4

Right

Fitness Activity

8

31

Male

Security forces

6

Right

Respiratory infection

Mean

30.0

62.5% Male

SD

5.7

6.3 1.3

SD, standard deviation.

INITIAL EVALUATION All subjects were screened and evaluated using a standardized PT examination for cervicothoracic conditions.19 All examination, evaluation and treatment was conducted by a single physical therapist with six years of clinical experience, board certified as an orthopedic clinical specialist, and fellowship trained in orthopedic manual physical therapy.

Outcomes Instruments None of the subjects reported any radicular or referred symptoms. The subjects reported an average of the best, worst and current rating in the prior 24 hours on NPRS of 5.6 (range, 4–8) with specific activities noted to increase pain by an average of 2.0 points. The NPRS has been demonstrated to be valid in chronic musculoskeletal pain conditions with a change of 1.0 point, or 15%, identified as the minimal clinically important difference (MCID)20 and excellent (r=0.79–0.92) test-retest reliability when administered at least two times during the week.21,22 The NPRS was completed by all subjects at each visit to monitor condition.

The PSFS was administered to all eight subjects with an average score of 4.5 (range, 3–6). The PSFS has been demonstrated to be valid in neck pain and cervical radiculopathic conditions, with a change of 2.0–2.2 points as the MCID22,23 and excellent (r=0.82–0.92) test-retest reliability.23-25 The PSFS was

completed per standard operating procedures at initial evaluation and discharge. Two common patient specific functions noted with all subjects were to be able to perform all duties without restriction and to be able to participate in fitness training without restriction.

The Global Rating of Change (GROC) was administered to all eight subjects at the last appointment prior to the cessation of the episode of care. The GROC has been demonstrated to be valid in cervical and upper extremity conditions. A score between ±1 and ±3 indicates a small change; a score between ±4 and ±5 indicates a moderate change; and a score between ±6 and ±7 indicates a large change.26 If treatment duration had lasted longer than four weeks a formal re-evaluation and completion of the PSFS and GROC would have been completed at that time per clinic standard operating procedures.

Observations/Palpations All subjects positioned themselves with varying degrees of a forward head, shoulder protraction, and increased upper (T3–5) and middle (T5–10) thoracic kyphosis.27,28 Additionally, all subjects performed splinting of upper torso by the upper extremities when seated for symptomatic relief if an elevated surface such as chair arms or a table was available.

Palpation with anterior to posterior pressure up to

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the point of initiation of rib movement at the costosternal joints reproduced the subjects’ symptoms and demonstrated tenderness of at least two consecutive costosternal junctions from the second to the sixth ribs unilaterally, with pain present on the patient’s dominant side in six of the eight cases.29 All subjects reported reproduction of pain with deep inhalation and six of eight-reported pain with normal exhalation (Table 2).

Palpation with pressure to the point of fingernail blanching applied to the pectoralis major/minor, latissimus dorsi, upper trapezius, and scalene muscles did not reproduce subjects’ symptoms. No active trigger points were identified corresponding to the subjects’ pain patterns and symptoms; however, it is noteworthy that the pectoralis minor is deep to the pectoralis major, making it difficult to detect trigger points if they are present.30 Range of Motion Active range of motion was tested for cervical spine, thoracic spine, ribcage, and shoulders bilaterally as described by Flynn et al.19 Cervical active range of motion was reported to be associated with “stiffness” or “discomfort” at end-range cervical flexion and rotation to the noninvolved side in 50% of subjects. All subjects reported symptom reproduction with overpressure applied with rotation to the noninvolved side. Thoracic extension was observed to be limited both actively and passively in all subjects with symptom reproduction and “stiffness” or “discomfort” at end-range. Excursion of ipsilateral upper and middle ribs was diminished during the subjects’ respiratory cycle. Ipsilateral horizontal shoulder

adduction past 10 degrees reproduced symptoms intermittently in all subjects.

Accessory Motions Unilateral posterior anterior glides of the cervicothoracic junction (C7–T1)27,28 and upper thoracic (T1–7) spine29 were hypomobile and reproduced symptoms in all subjects when tested ipsilateral to corresponding symptomatic costosternal joints. The first and/or second ribs were hypomobile in six subjects, with partial replication of subjects’ symptoms.

Hypomobility in the costovertebral joint of ribs 3–7 was present in only four subjects; however, symptom reproduction, including pain, occurred in all subjects when the symptomatic costosternal joint area was assessed29 (Table 2).

Muscle Length All subjects were assessed for length of pectoralis major/minor, latissimus dorsi, upper trapezius, and scalene muscles.27,28 All eight subjects were found to have increased tightness and/or guarding in the pectoralis major/minor and upper trapezius muscles, with greater tone on the involved side. Six subjects had increased tone/tightness in the scalene muscles of the involved side and 50% of the subjects demonstrated increased tightness in the latissimus dorsi on the involved side (Table 3).

Special Tests The Upper Limb Tension Test A (ULTT),27,28,31 Spurling’s Test,27,28,31,32 and the Cervical Distraction Test27,28,31,33 were performed to rule out any cervical referral and were negative for all subjects, with a negative ULTT decreasing the possibility of the

Table 2. Palpation of Costosternal Joints and Symptom Provocation with Movement Thoracic Deep Full CPA Costotransverse Extension Inhalation Exhalation C7–T7 PA 1–7 Yes C7–T4 Yes Rt 1–2 Yes 1 Yes Yes Yes C7–T6 Lt 2–7 2 Yes C7–T4 Yes Rt 1–2 Yes 3 Yes Yes No T3–5 Lt 3–5 4 Yes C7–T4 Yes Yes Rt 1–2 5 Yes Yes No T3–6 Rt 4–5 6 Yes Yes C7–T4 Rt 1–2 Yes 7 Yes Yes Yes C7–T6 Rt 2–7 8 75.0% 100.0% 100.0% Mean 0.0% 0.0% 46.3% SD SD, standard deviation. Rt, right. Lt, left. R, rib. CPA, central posterior anterior glides. PA, posterior anterior glides.

Patient

Palpation Rib Tenderness Rt R2–4 Lt R3–6 Rt R3–4 Lt R4–5 Rt R2–4 Rt R4–5 Rt R3–4 Rt R3–6

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Table 3. Muscle Length and CRLF Test Latissimus Pectoralis Pectoralis Minor Dorsi Major Tightness Tightness Tightness Yes Yes Yes 1 Yes Yes Yes 2 Yes Yes No 3 Yes Yes No 4 Yes Yes Yes 5 Yes Yes No 6 Yes Yes No 7 Yes Yes Yes 8 100.0% 100.0% 50.0% Mean 0.0% 0.0% 53.5% SD SD, standard deviation. CRLF, cervical rotation lateral flexion Patient

patient’s condition being related to cervical radiculopathy to less than 10%.31 The Cervical Rotation Lateral Flexion (CRLF) Test was performed, and six subjects demonstrated restriction in motion and an early firm end feel, with symptom reproduction in four of the six subjects, indicating a possible dysfunction that was contributing to the patient’s condition at the first/second rib.34-36 (Table 3) As costochondritis is normally a diagnosis of exclusion, no special tests have been identified as valid for differential diagnosis. Palpation of the involved costochondral segments with symptom reproduction is the only recommended physical examination technique cited at this time.3 INTERVENTION Intervention was an impairment-based model addressing the individual findings for each patient, prioritized according to the approach of treating thoracic spine prior to ribcage.37 Each manual–therapybased intervention was matched with an appropriate home exercise to improve carry-over (Table 4). All subjects were seen one to two times per week, determined by the subjects’ availability and duties, and treated four to six times (average 4.8) over a three to four week period.

The cervicothoracic junction and upper thoracic vertebral region were treated first with a seated manipulation directed toward the identified region of dysfunction. Up to three attempts were made, rechecking of thoracic gross and accessory movement after each attempt, if successful PT progressed to next prioritized area of impairment. All subjects were instructed in performance of a home exercise

Upper Trapezius Tightness Yes Yes Yes Yes Yes Yes Yes Yes 100.0% 0.0%

Levator Scapulae Tightness Yes Yes Yes Yes Yes Yes Yes Yes 100.0% 0.0%

Scalenes Tightness

CRLF

Yes Yes Yes No Yes No Yes Yes 62.5% 51.8%

Right Left Right No Right No Right Right 75.0% 46.3%

consisting of thoracic/rib cage self-mobilization for extension and flexion timed with breathing (Figure 1).

First and second rib restrictions were treated with seated mobilization/manipulation and affected subjects were instructed on self-mobilization with a belt for their home exercise. First/second rib dysfunction received grade 3 to 4 mobilizations for up to three sets of 30 seconds each, unless an appropriate end feel was noted, at which time the technique progressed to a high-velocity low-amplitude manipulation for the appropriate area with a maximum of two attempts. The CRLF was used as asterisk sign and rechecked between sets of mobilizations or attempts at manipulation. The self-mobilization exercise previously instructed for thoracic dysfunctions also provides a self-mobilization for first/second rib dysfunctions, so no specific exercise was matched with this manual intervention (Table 4).

Hypomobile third to seventh ribs were treated with Grade 3 to 4 posterior to anterior mobilization techniques directed toward the costotransverse and/or anterior to posterior mobilization techniques directed toward the costosternal joints for up to three sets of 30 seconds each. Rib mobility was assessed prior to mobilization and reassessed after each set. Subjects were then instructed on an upper thoracic/rib cage extension/flexion/rotation self-mobilization exercise timed with breathing for their home exercise (Figure 2).

Tight muscles, including the pectoralis major/ minor, latissimus dorsi, upper trapezius, and scalenes, were treated according to their assessment findings. Contract/relax soft–tissue-release tech-

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Figure 1. Thoracic flexion/extension self-mobilization timed with breathing. (A) Patient begins exercise in thoracic flexion sitting on low-back chair with hands interlocked behind cervicothoracic junction and elbows pointing toward ipsilateral knees with full exhale. (B) Patient then performs thoracic extension over back of chair in conjunction with horizon abduction of elbows and full inhalation timed with movement. Return to starting position.

Table 4. Impairment-Based Findings, Prevalence, and Interventions Impairment Finding

Prevalence Intervened

Manual Therapy

Hypomobile C7–T1

8/8

8/8

Seated distraction cervicothoracic junction mobilization/manipulation

Hypomobile T2–7

8/8

8/8

Seated distraction upper/mid thoracic mobilization/manipulation

Tight pectoralis major/minor

8/8

8/8

Contract-relax soft-tissue release for pectoralis major/minor

Tight upper trapezius

8/8

8/8

Contract-relax soft-tissue release for upper trapezius

Hypomobile rib 1/2

6/8

4/8

Seated first/second rib mobilization/manipulation

Tight anterior/middle/ posterior scalene

6/8

4/8

Contract-relax soft-tissue release for anterior/ middle/posterior scalenes

Hypomobile rib 3–7

4/8

2/8

Supine costovertebral joint manipulation

Tight latissimus dorsi

3/8

1/8

Contract-relax soft-tissue release for latissimus dorsi

Therapeutic Exercise Thoracic flexion/extension selfmobilization timed with breathing (Figure 1) Thoracic flexion/extension selfmobilization timed with breathing (Figure 1) Corner stretch for pectoralis major/minor Self-mobilization/stretch with belt/ towel for first/second rib, anterior/middle/posterior scalenes and upper trapezius Self-mobilization/stretch with belt/ towel for first/second rib, anterior/middle/posterior scalenes and upper trapezius Self-mobilization/stretch with belt/ towel for first/second rib, anterior/middle/posterior scalenes and upper trapezius Thoracic flexion/extension with unilateral rotation self-mobilization timed with breathing (Figure 2) Kneeling prayer stretch with bench for latissimus dorsi

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Figure 2. Thoracic flexion/extension with unilateral rotation self-mobilization timed with breathing. (A) Patient begins exercise in thoracic flexion sitting on low-back chair with one hand placed behind cervicothoracic junction with elbow pointing toward contralateral knee; opposite hand is holding chair seat with full exhale. (B) Patient then performs thoracic extension over back of chair in conjunction with rotation and horizon abduction of elbow to point posteriorly, timed with full inhalation. Return to starting position.

niques were directed at the pectoralis major/minor, anterior/middle/posterior scalene, and/or latissimus dorsi muscles for up to three sets of 30 seconds each, with approximately 25% resistance applied by the patient. Subjects were then instructed in the corresponding self-stretch for their home exercise programs for the affected muscles (Table 4).

Subjects were reassessed at each visit for all previous positive findings to modify each patient’s plan

of care based on response to the previous treatment interventions. Manual therapy for specific impairments was discontinued if impairment was no longer present, whereas the specific exercises for the impairment were continued three times per day at home and/or in clinic for a minimum of two weeks after manual therapy intervention for specific impairment was discontinued, to reinforce and maintain the improvements in the patient’s condition (Table 5).

Table 5. Number of Times Intervention was Applied to Patient Patient

Cervicothoracic Junction

Upper Thoracic

Pectoralis Major/Minor

Upper Trapezius

Rib 1/2

Ant/Mid/Post Scalene

Rib 3–7

Latissimus Dorsi

1

3

3

4

3

2

4

0

0

2

4

4

5

4

4

4

3

3

3

3

3

3

3

0

0

0

0

4

3

3

3

3

0

0

0

0

5

3

3

4

3

2

3

0

0

6

3

3

3

3

0

0

3

0

7

2

2

3

2

2

2

0

0

8

4

4

5

4

0

0

0

3

Ant, anterior; Mid, middle; Post, posterior.

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Table 6. Visits and Outcomes NPRS PSFS PSFS (Pre) PSFS (Post) GRC Change Change 5 10 6 1 5 6 +6 4 1 6 6 0 6 6 10 4 +7 2 4 10 4 0 4 7 +6 3 3 4 5 1 4 5 9 4 +5 4 5 7 0 7 10 4 +7 6 5 4 5 2 3 5 9 4 +4 6 4 10 4 0 4 3 7 +5 7 6 8 0 8 4 10 6 +7 8 4.8 5.1 9.8 5.6 0.5 4.5 5.3 +5.9 Mean 0.9 1.4 0.8 1.7 1.2 0.5 1.4 1.1 SD N, number; NPRS, numerical pain rating scale; PSFS, patient-specific functional scale; GRC, global rating of change; SD, standard deviation.

Patient

Visits (N)

NPRS (Pre)

NPRS (Post)

OUTCOMES All patient outcome measures indicated clinically meaningful improvements in an average of 4.8 total sessions including the initial evaluation (Table 6).

All subjects were able to resume normal duties and military fitness training without symptoms, including running and push-ups, after a standardized 45-day reconditioning phase for fitness training (as directed by USAF instructions), initiated after discharge from physical therapy.

DISCUSSION This case series provides preliminary evidence that an impairment-based approach addressing motion impairments at the cervicothoracic spine may be beneficial to subjects with costochondritis. All subjects reported the typical signs and symptoms of costochondritis, including tenderness at the costosternal junction of the second to fifth ribs unilaterally, with symptom exacerbation secondary to exertion, and/or horizontal abduction/adduction.

An impairment-based approach was effective with the subjects in this case series, but it remains to be seen if there is a more effective approach to treatment secondary to the limitations presented by a case series, including lack of comparison and control groups. It has been shown that the biomechanics of the thoracic vertebrae and rib cage are interdependent.38,39 This interdependence, combined with the patient presentations, provides face validity to the interventions directed to these regions. Seated thoracic manipulation was chosen due to the effectiveness, efficacy, and safety of these techniques.40-42 Manual therapy techniques were selected based on

the authorsâ&#x20AC;&#x2122; experience because they are specific to the identified impairment, easy to perform, safe, and well tolerated by most subjects.43 Manual therapy techniques also allow the clinician to carry on a running dialogue with the patient during treatment, thus permitting a continuous assessment of symptoms and a corresponding modification of amplitude and/or cadence. A maximum of three attempts at manipulation were chosen based on previously published pragmatic studies.40-42 Four subjects required interventions directed only at the cervicothoracic junction and upper thoracic vertebrae for resolution of their impairments and condition, and there was no need to address the first to seventh ribs. Six of the subjects also had hypomobility and symptom reproduction noted in the first and second ribs, which was addressed with interventions in four subjects when not resolved by intervention at the cervicothoracic junction and upper thoracic vertebrae. This can be explained by the biomechanical interdependence of the ribs and vertebrae in the upper thorax.38,39 Home programs were prescribed based on their ability to address one or more impairments, while being simple to perform and requiring minimal equipment. This ensured that no more than five exercises were prescribed for any of the home exercise programs, in order to improve patient compliance.44,45 It is unclear as to why there was a delay in referral to physical therapy for these subjects of an average duration of 6.3 months. It could be hypothesized, that given the high number cases seen in primary care that clear naturally, that the referring physi-

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cians believe that physical therapy intervention was unnecessary for this condition. Another possible hypothesis is that with these subjects presenting with “chest pain” a referral was thought to be inappropriate. However, the exact reason for the delayed in referral of the subjects is still unclear at this time.

Limitations As is typical in case reports or case series, the study design does not allow for the determination of cause and effect due to lack of a control group. Some methods used in this study, such as accessory motion assessment and symptom provocation, may be significantly limited in their reliability and diagnostic utility, but may be of assistance in directing an impairment based treatment approach. A properly designed randomized controlled study would provide additional information that may help overcome the significant limitations of this case series. Future research also should attempt to identify the MCID of the NPRS and PSFS for this population as well as determine the most appropriate type and dose of manual therapy and home exercise program.

CONCLUSION The results of this case series suggest that an impairment based approach to examination and treatment of individuals with costochondritis was effective for pain reduction, and patient specific improvements in function. The question remains: “Are the symptoms experienced with costochondritis due to direct injury at the costochondral region or are they the result of compensation for changes in other areas of the axial skeleton? Further research and investigation will be required to answer this question.

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2. Fam AG. Approach to musculoskeletal chest wall pain. Prim Care. 1988;15(4):767-782.

3. Proulx AM, Zryd TW. Costochondritis: diagnosis and treatment. Am Fam Physician. 2009;80(6):617-620.

4. Semble EL, Wise CM. Chest pain: a rheumatologist’s perspective. South Med J. 1988;81(1):64-68.

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Harkonen M. Tietze’s syndrome. Br Med J. 1977;2(6094):1087-1088.

Freeston J, Karim Z, Lindsay K, Gough A. Can early diagnosis and management of costochondritis reduce acute chest pain admissions? J Rheumatol.

2004;31(11):2269-2271.

Ayloo A, Cvengros T, Marella S. Evaluation and treatment of musculoskeletal chest pain. Prim Care.

2013;40(4):863-887, viii.

Habib PA, Huang GS, Mendiola JA, Yu JS. Anterior chest pain: musculoskeletal considerations. Emerg Radiol. 2004;11(1):37-45.

11. How J, Volz G, Doe S, Heycock C, Hamilton J, Kelly C. The causes of musculoskeletal chest pain in patients admitted to hospital with suspected myocardial infarction. Eur J Intern Med. 2005;16(6):432-436.

12. Spalding L, Reay E, Kelly C. Cause and outcome of atypical chest pain in patients admitted to hospital. J R Soc Med. 2003;96(3):122-125.

13. Rovetta G, Sessarego P, Monteforte P. Stretching exercises for costochondritis pain. G Ital Med Lav Ergon. 2009;31(2):169-171.

14. Aspegren D, Hyde T, Miller M. Conservative treatment of a female collegiate volleyball player with costochondritis. J Manipulative Physiol Ther.

2007;30(4):321-325.

15. Cubos J, Cubos A, Di Stefano F. Chronic costochondritis in an adolescent competitive swimmer: a case report. J Can Chiropr Assoc.

2010;54(4):271-275.

16. Grindstaff TL, Beazell JR, Saliba EN, Ingersoll CD. Treatment of a female collegiate rower with costochondritis: a case report. J Man Manip Ther.

2010;18(2):64-68.

17. Ian Rabey M. Costochondritis: Are the symptoms and signs due to neurogenic inflammation. Two cases that responded to manual therapy directed towards posterior spinal structures. Man Ther.

2008;13(1):82-86.

18. Westrick RB, Zylstra E, Issa T, Miller JM, Gerber JP. Evaluation and treatment of musculoskeletal chest wall pain in a military athlete. Int J Sports Phys Ther.

2012;7(3):323-332.

19. Flynn T, Cleland J, Whitman J. Users’ Guide to the Musculoskeletal Examination: Fundamentals for the Evidence-Based Clinician. 1st ed. Buckner, KY: Evidence in Motion; 2008.

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20. Salaffi F, Stancati A, Silvestri CA, Ciapetti A, Grassi W. Minimal clinically important changes in chronic musculoskeletal pain intensity measured on a numerical rating scale. Eur J Pain. 2004;8(4):283-291.

21. Jensen MP, McFarland CA. Increasing the reliability and validity of pain intensity measurement in chronic pain patients. Pain. 1993;55(2):195-203.

22. Young IA, Cleland JA, Michener LA, Brown C. Reliability, construct validity, and responsiveness of the neck disability index, patient-specific functional scale, and numeric pain rating scale in patients with cervical radiculopathy. Am J Phys Med Rehabil.

2010;89(10):831-839.

23. Cleland JA, Childs JD, Whitman JM. Psychometric properties of the Neck Disability Index and Numeric Pain Rating Scale in patients with mechanical neck pain. Arch Phys Med Rehabil. 2008;89(1):69-74.

24. Westaway MD, Stratford PW, Binkley JM. The patient-specific functional scale: validation of its use in persons with neck dysfunction. J Orthop Sports Phys Ther. 1998;27(5):331-338.

25. Cleland JA, Fritz JM, Whitman JM, Palmer JA. The reliability and construct validity of the Neck Disability Index and patient specific functional scale in patients with cervical radiculopathy. Spine (Phila Pa 1976). 2006;31(5):598-602.

26. Jaeschke R, Singer J, Guyatt GH. Measurement of health status. Ascertaining the minimal clinically important difference. Control Clin Trials.

1989;10(4):407-415.

27. Hanney WJ, George SZ, Kolber MJ, Young I, Salamh PA, Cleland JA. Inter-rater reliability of select physical examination procedures in patients with neck pain. Physiother Theory Pract. 2014;30(5):345352.

28. Cleland JA, Childs JD, Fritz JM, Whitman JM. Interrater reliability of the history and physical examination in patients with mechanical neck pain.

Arch Phys Med Rehabil. 2006;87(10):1388-1395.

29. Heiderscheit B, Boissonnault W. Reliability of joint mobility and pain assessment of the thoracic spine and rib cage in asymptomatic individuals. J Man Manip Ther. 2008;16(4):210-216.

30. Alvarez DJ, Rockwell PG. Trigger points: diagnosis and management. Am Fam Physician. 2002;65(4):653660.

31. Wainner RS, Fritz JM, Irrgang JJ, Boninger ML, Delitto A, Allison S. Reliability and diagnostic accuracy of the clinical examination and patient self-report measures for cervical radiculopathy. Spine (Phila Pa 1976). 2003;28(1):52-62.

32. Shabat S, Leitner Y, David R, Folman Y. The correlation between Spurling test and imaging

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studies in detecting cervical radiculopathy. J Neuroimaging. 2012;22(4):375-378.

Viikari-Juntura E. Interexaminer reliability of observations in physical examinations of the neck.

Phys Ther. 1987;67(10):1526-1532.

Lindgren KA. Thoracic outlet syndrome with special reference to the first rib. Ann Chir Gynaecol.

1993;82(4):218-230.

Lindgren KA, Leino E, Hakola M, Hamberg J. Cervical spine rotation and lateral flexion combined motion in the examination of the thoracic outlet.

Arch Phys Med Rehabil. 1990;71(5):343-344.

Lindgren KA, Leino E, Manninen H. Cineradiography of the hypomobile first rib. Arch Phys Med Rehabil. 1989;70(5):408-409.

Flynn T. Direct treatment techniques for the thoracic spine and rib cage: muscle energy, mobilization, high-velocity thrust, and combined techniques. In: Flynn T, ed. The Thoracic Spine and Rib Cage: Musculoskeletal Evaluation and Treatment. 1st ed.

Boston: Butterworth-Heinemann; 1996:171-210.

Mannen EM, Anderson JT, Arnold PM, Friis EA. Mechanical analysis of the human cadaveric thoracic spine with intact rib cage. J Biomech.

2015;48(10):2060-2066.

39. Mannen EM, Anderson JT, Arnold PM, Friis EA. Mechanical Contribution of the Rib Cage in the Human Cadaveric Thoracic Spine. Spine (Phila Pa 1976). 2015;40(13):E760-766.

40. Boyles RE, Ritland BM, Miracle BM, et al. The short-term effects of thoracic spine thrust manipulation on patients with shoulder impingement syndrome. Man Ther. 2009;14(4):375380.

41. Cleland JA, Childs JD, McRae M, Palmer JA, Stowell T. Immediate effects of thoracic manipulation in patients with neck pain: a randomized clinical trial.

Man Ther. 2005;10(2):127-135.

42. Cross KM, Kuenze C, Grindstaff TL, Hertel J. Thoracic spine thrust manipulation improves pain, range of motion, and self-reported function in patients with mechanical neck pain: a systematic review. J Orthop Sports Phys Ther. 2011;41(9):633-642.

43. Puentedura EJ, O’Grady WH. Safety of thrust joint manipulation in the thoracic spine: a systematic review. J Man Manip Ther. 2015;23(3):154-161.

44. Posavac E, Sinacore J, Brotherton S, Helford M, Turpin R. Increasing compliance it medical treatment regimens: a meta-analysis of program evaluation. Evaluation & The Health Professions.

1985;8(1):7-22.

45. Becker MH. Patient adherence to prescribed therapies. Med Care. 1985;23(5):539-555.

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IJSPT

CASE REPORT

DRY NEEDLING INCREASES MUSCLE THICKNESS IN A SUBJECT WITH PERSISTENT MUSCLE DYSFUNCTION: A CASE REPORT Kevin M. Cross, PhD, PT, ATC1 Michael McMurray, DPT, OCS, FAAOMPT1

ABSTRACT Background and purpose: Muscle dysfunction is very common following musculoskeletal injury. There is very little evidence to suggest that muscle function may be positively impacted by soft tissue interventions, such as dry needling. The purpose of this case report is to describe the immediate effect of dry needling on muscle thickness in a subject after shoulder surgery.

Case Description: A 22 year-old competitive gymnast presented seven months post shoulder surgery with significant impairments and functional limitations. Previous physical therapy focused on restoration of range of motion and strength using general exercise interventions, but the subject had persistent tightness and weakness of musculature of the shoulder complex. A subject-specific physical therapy program including manual physical therapy resulted in significant initial improvement, but lack of flexibility and weakness of the rotator cuff limited progress. Dry needling was used to address persistent myofascial trigger points.

Outcomes: Immediately after dry needling the infraspinatus, the muscleâ&#x20AC;&#x2122;s thickness was significantly improved as measured by rehabilitative ultrasound imaging. There was a corresponding increase in force production of external rotation at 90 degrees of abduction.

Discussion: Minimal research exists that validates the potential of dry needling on muscle function, as assessed by muscle thickness measured using rehabilitative ultrasound imaging. The results of this case report suggest that dry needling contributed to improvement in muscle thickness and strength in a subject with muscle dysfunction following an injury.

Level of Evidence: 4 Key words: Dry needling, muscle thickness, trigger points

1

UVa-Healthsouth Sports Medicine and Rehabilitation Center, Charlottesville, VA, USA

CORRESPONDING AUTHOR Kevin M. Cross PO Box 801005 Ray C. Hunt Drive #2100 Charlottesville, VA 22903 Phone: 434-243-0311 Fax: 434-243-0320 E-mail: kevin.cross@healthsouth.com

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BACKGROUND AND PURPOSE Muscle dysfunction is commonly identified among subjects with persistent pain syndromes and musculoskeletal injuries.1,2 Myofascial trigger points (MTrPs) develop within muscles associated with musculoskeletal pathology and may create a variety of symptoms and impairments including local and referred pain, decreased range of motion, muscle stiffness, and altered muscle function.3-12 MTrPs are hypothesized to occur as a consequence of muscle overload either from prolonged low-level exertion (occupational posturing), repetitive eccentric and concentric contractions (throwing a ball), or direct traumatic overload (whiplash).13 Specifically, muscle inhibition following a musculoskeletal injury is a limiting factor to impairment resolution and functional progression. The exact mechanism of muscle inhibition has not been definitively identified, but appears to be due to deactivation of the muscle by the central nervous system in response to an injury, pain, or both.14 This response occurs as a protective means to prevent further injury to the damaged structure. 14-16 However, even after the body has repaired the injured tissue, persistent muscle weakness and fatigue results when the muscle inhibition is left unaddressed, and ultimately, the muscle atrophies.16 The sequelae of not treating muscle inhibition may include poor functional outcome and poor subject satisfaction.

A relatively novel mode of measuring muscle function in the clinic is with rehabilitation ultrasound imaging (RUSI). Measurement of the muscle thickness during contraction, relative to its resting thickness, provides an indirect measure of the muscle’s function.17 Muscle function is implied to be greater if there is an increase in muscle thickness during the contracted state as compared to the resting state.

While the clinimetrics of RUSI are still developing, it appears to be a very promising tool for indirect measurement of muscle function in the trunk17 and shoulder region.18,19 Most interventions that target muscle inhibition following a joint injury have focused on influencing the joint’s mechanoreceptors, the peripheral nervous system, or the central nervous system.15 A comprehensive systematic review15 of interventions that combat

muscle inhibition of the quadriceps revealed that TENS application had the strongest and most consistent benefit for improving muscle contractibility.

Manual therapy had weak immediate effects, however, as only one study was identified that directly manipulated the soft tissue.20 Specifically, the performance of active release technique for subjects with anterior knee pain did not reduce muscle inhibition or increase muscle strength immediately or within 20 minutes after the intervention.20 Variable findings are reported when considering soft tissue mobilization on a more general measure of muscle function such as force production.8,21-24 Direct intervention of the MTrP may be required to improve the function of the pathological muscle.

Dry Needling (DN) has become a recognized and accepted form of treatment of MTrPs among many different medical professionals.3,25 DN has been defined by the American Physical Therapy Association as “a skilled intervention that uses a thin filiform needle to penetrate the skin and stimulate underlying myofascial trigger points, muscular and connective tissues for the management of neuromusculoskeletal pain and movement impairments”.26 While this intervention has received increasing attention as a modality for treatment of musculoskeletal disorders, quality research is limited with regard to its influence on MTrP symptoms, especially motor function.10 The purpose of this case report is to describe the immediate effect of dry needling on muscle thickness in a subject after shoulder surgery.

CASE DESCRIPTION: SUBJECT HISTORY AND SYSTEM REVIEW A 22-year-old female former collegiate gymnast presented to the physical therapy clinic seven months post surgical repair of a posterior labral tear of the right shoulder. She injured her shoulder during gymnastics practice five months prior to the surgery. However, because the competitive season had already started, she elected conservative management and participated in gymnastics with activity modifications. Immediately after the competitive season, the subject had surgery to repair the posterior labrum. She initially participated in physical therapy for six months, and the focus of therapy was self-directed restoration of range of motion (ROM)

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and standard strengthening exercises. She was frustrated with her continued limitation in shoulder mobility and strength which disrupted routine daily activities that required her to reach overhead. Therefore, the subject sought treatment at the authors’ facility. The subject had no other significant medical conditions.

CLINICAL IMPRESSION #1 After taking a thorough history, the exact cause of the subject’s limited range of motion (ROM) and strength could not be specified. Given that the surgical procedure was a posterior Bankart repair without involvement of other static or dynamic structures, there was no suspicion of iatrogenic involvement such as excessive tightening of the capsule or rotator cuff contracture. Also, given that the subject was young and had excellent health without any comorbidities, it seemed unlikely that she had developed any capsular adhesions from pathologies such as metabolic disorders.

The authors’ experience suggests that patients who have joint instability frequently develop muscle dysfunction in response to extreme muscle guarding of the shoulder musculature as they attempt to improve dynamic stability. Her description of the post-operative rehabilitation program also implied a non-specific exercise regimen that did not address specific limitations of muscle and capsular restrictions, such as inferior capsular restrictions, which limit shoulder elevation.

Examination Posture: The subject had an endomorphic body type.

Her BMI was 19.39 kg/m2, and she had good general muscle definition and tone. She had a minimal forward head and anteriorly tilted scapulae, but the right scapula presented with a predominant Type 3 dysfunction as defined by Kibler et al.27 Cervical Screen: The cervical spine had full ROM without restriction or pain. There was no reproduction of symptoms with assessment.

Range Of Motion (ROM): Examination revealed significant limitations in active (AROM) and passive (PROM) ROM of the left shoulder. The limitations were especially remarkable with shoulder elevation (Table 1) as there was observable scapular elevation as a compensation strategy during AROM, and PROM required manual scapular stabilization. All end ranges of ROM were painful with stiff capsular endfeels.

Joint Mobility: Glenohumeral and scapulothoracic articulations were significantly restricted and stiff in all planes. Joint restrictions varied between Grade 1 and Grade 2 hypomobility.

Strength: Left shoulder complex musculature demonstrated strength deficits per manual muscle testing (Table 1). 28 Palpation: Palpation revealed a generalized decrease in soft tissue mobility in all muscles adjacent to

Table 1. Clinical measurements taken at initial evaluation, three weeks, and six weeks after the initial evaluation Shoulder ROM

Ini al Evalua on

3 Weeks Post IE

6 Weeks Post IE

Flexion

AROM = 145 PROM = 160 AROM = 130 PROM = 145 AROM = 35 PROM = 50 Immediate Scapular Compensa on

AROM = 170 PROM = 180 AROM = 150 PROM = 170 AROM = 50 PROM = 70 AROM = 70 PROM = 90

AROM = 170 PROM = 180 AROM = 160 PROM = 180 AROM = 60 PROM = 80 AROM = 85 PROM = 110

PROM = 35 MMT: Flexion =4/5 Abduc on = 4-/5 ER @ 0 abd =4/5 IR @ 0 abd = 5-/5

PROM = 45 MMT: Flexion =4+/5 Abduc on = 4/5 ER @ 0 abd =4+/5 IR @ 0 abd = 5/5

PROM = 55 HHD (% opposite): Flexion = 78% Abduc on = 72% ER @ 0 abd = 86% ER @ 90 abd = 64% IR @ 0 abd = 85%

Abduc on ER at 0 ER at 90 IR at 90 Strength

IE=Ini al evalua on; AROM= Ac ve range of Mo on; PROM= Passive range of mo on; ER= External rota on

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the scapulothoracic and glenohumeral articulations. Highly irritable active and latent MTrPs were present throughout the region, specifically in the rotator cuff muscles. The most significant MTrPs were noted in the muscle belly of the infraspinatus. They were identified by point tenderness that replicated the subject’s pain and were associated with a taut band within the muscle. Several of the MTrPs responded to palpation with a local twitch as described by Simons, Travell and Simons. 29 N e u r o logical: Sensory was intact to light touch throughout the upper extremity. Reflexes and myotomes were unremarkable.

Pain Score: The visual analog scale was used to assess pain with 0 representing no pain and 10 representing the worst pain imaginable.30 The patient’s average Numeric Pain Rating Scale was 3/10 with her current pain=2/10, worst pain=5/10, and her least pain=2/10.

Functional Outcome: The QuickDASH was used to assess the patient’s function.31 There are three sections to the questionnaire: the Disability/Symptom section, the Work section, and the Sports section.

Each section is scored 0-100 with 0 representing no disability and 100 representing complete disability. The subject’s score on the Disability/Symptom section was 47%, the Work section was 0% and the Sports/Performing Arts module was 100%.

CLINICAL IMPRESSION #2 Given the longevity of the post-surgical impairments, one hypothesis was that the surgical procedure had failed and the patient still had joint pathology. However, due to the lack of trauma or reinjury to the shoulder, joint derangement as a cause of ROM and strength limitations was low on the list of differential diagnoses. Neurologically, there were no indications of sensory or reflex deficits. Shoulder complex musculature was diminished in all planes and was associated with shoulder discomfort. Moreover, resistance testing of the distal extremity did not indicate nerve root or peripheral nerve involvement.

Palpation of the shoulder musculature revealed multiple active and latent MTrPs, most notably within the infraspinatus muscle belly, which replicated glenohumeral joint pain that was reported during

ROM and resistance testing. ROM was restricted in all planes with stiff with capsular endfeels. (Table 1) The presence of palpation findings with concordant ROM restrictions and strength deficits verified the presence of MTrPs as described by Simons, Travell and Simons.29 Assessment of joint mobility within the midrange of ROM confirmed stiffness of the joint capsule. Specifically, inferior glide, anterior glide and posterior glide demonstrated Grade I hypomobility. Based on the results of the examination, the subject appeared to have generalized soft tissue restrictions in the glenohumeral joint, scapulothoracic articulation and the surrounding musculature as well as extensive MTrP activation which influenced muscle function.

INTERVENTION #1 Physical therapy focused on an individualized program to improve shoulder mobility, strength and scapular stabilization. ROM limitations were specifically addressed with various manual therapies including joint mobilization, instrumented soft tissue mobilization, MTrP release, and manual stretching. Within three weeks, there were dramatic improvements in ROM and strength (Table 1).

CLINICAL IMPRESSION #3 After the initial gains from the individualized program, impairment and functional progress plateaued. Although ROM improved immediately following a treatment, the subject continued to complain of weakness at the endranges of motion and consequently, the stiffness and immobility returned quickly after each session. Given the perpetuation of highly irritable trigger points in the scapulohumeral muscles, DN was incorporated into her treatment plan for a more direct, targeted, and time-efficient intervention for the MTrPs . Due to the complexity of dysfunction in the shoulder complex muscles, the infraspinatus was chosen to evaluate the influence of DN on muscle thickness given its influence on shoulder stability and function.32 INTERVENTION #2 A physical therapist certified in dry needling performed the additional interventions. In the state of Virginia a dry needling certified physical therapist must have completed at least 54 hours of post pro-

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fessional training including providing evidence of meeting expected competencies that include demonstration of cognitive and psychomotor knowledge and skills.33 Prior to the intervention the subject was educated on dry needling and signed a consent form. For the treatment, a clean needle technique was utilized, as per facility policy and procedures, and universal precautions were used by the treating PT. Seirin No. 8 (0.30) x 60mm needles were used (Seirin Corporation, Shizuoka, Japan). The subject was placed in a prone position with her arm slightly abducted, and the therapist identified active and latent MTrPs in the infraspinatus. The therapist performed a pistoning technique in the active and latent MTrPs. Fast repetitive needle movements in a cone pattern were performed to elicit local twitch responses. Once a twitch response was elicited the needle was removed. If no twitch response was elicited at a certain MTrP after multiple attempts the needle was removed. This procedure was repeated once at three distinct MTrPs in the infraspinatus.

The patient received DN as part of her physical therapy treatment for three successive visits.

OUTCOME MEASURES Before the first DN, the subjectâ&#x20AC;&#x2122;s external rotation isometric force (as a measure of strength) was assessed using a hand held dynamometer (HHD) (MicroFet2, Hoggan Health Industries, Salt Lake City Utah) with the subject placed in prone with the shoulder passively placed at 90 degrees of abduction and neutral external rotation.18 In the same position, the infraspinatus thickness was also assessed in both shoul-

ders using rehabilitative ultrasound imaging (RUSI).

18 The RUSI device used to take images was the Interson SR 7.5 MHz (Interson Corporation, Pleasanton, California) with a linear array transducer. Images were taken at the superior-medial margin of the infraspinatus18 and the inferior aspect of the infraspinatus. Because the subject had prominent latent MTrPs in the inferior aspect of the infraspinatus, which was to be a focus of DN, we chose to also measure the thickness of this part of the muscle. The superior border of the RUSI soundhead was placed 5 cm distal from the intersection of the spine of the scapula and the medial border of the scapula. The medial border of the soundhead was parallel and immediately adjacent to the medial border of the scapula. A marker was used to outline the sound head on the patientâ&#x20AC;&#x2122;s skin to improve the accuracy of measuring the same area of the muscle when subsequent measurements were performed. Three images were taken of each shoulder at rest and at a 50% MVIC of external rotation, as measured by a HHD. On the right shoulder, 50% MVIC images were also taken after the DN. OUTCOMES Immediately prior to DN, the thickness of the right inferior infraspinatus was at an approximate 20% deficit compared to the left with a consequent strength deficit of 35% as measured with HHD. There was no difference in muscle thickness of the superior infraspinatus between the left and right shoulders. Immediately following the DN, external rotation strength increased by approximately 30%, and the RUSI measurement of the inferior infraspinatus thickness increased by 25%. (Figure 1) This

Figure 1. a. Right inferior infraspinatus image at rest. b. Right inferior infraspinatus image at 50% MVIC before dry needling. c. Right inferior infraspinatus image at 50% MVIC after dry needling The International Journal of Sports Physical Therapy | Volume 12, Number 3 | June 2017 | Page 472

Table 2. Infraspinatus thickness (mm) at rest and at 50% MVIC before and after dry needling Rest

Pre-Treatment 50% MVIC

Post-Treatment 50% MVIC

Right Inferior Infraspinatus

10.5

15.2

18.9

Le Inferior Infraspinatus

10.4

19.1

-

Right Superior Infraspinatus Le Superior Infraspinatus

9.8 10.6

17.8 18.6

18.2 -

value was comparable to the thickness of the left infraspinatus. (Table 2) There was no immediate change in the pain scale, but the patient did report increased muscle “soreness” in the treatment location with active motion. She reported the “soreness” as different from the typical pain.

DISCUSSION Muscle dysfunction is a common component of musculoskeletal injuries. MTrPs have been proposed as a primary contributor to muscle dysfunction and are associated with a variety of signs and symptoms.3 DN is an emerging intervention used to address the motor dysfunction caused by MTrPs. Unfortunately, there is limited evidence assessing the efficacy of DN, specifically on motor function.4-7,34 This case report provides an addition to the evidence that demonstrated a change in muscle thickness, (a surrogate measure of motor function) following DN in a patient with long-term post-operative shoulder complex dysfunction.

Lucas et al 4,5 evaluated the effect of latent MTrPs on muscle function as indirectly measured by the timing of muscle activation. Shoulder muscle activation during active scaption was compared between pain-free subjects with and without identifiable latent MTrPs in scapular stabilizing muscles. The infraspinatus of subjects with latent MTrPs activated much earlier, and the upper trapezius significantly later. Additionally, compared to the control group, all shoulder muscles of the subjects with latent MTrPs were not activated within a consistent timeframe. The increased variability of muscle activation in conjunction with delayed upper trap activation and prolonged duration of infraspinatus activation may be responsible for inconsistent shoulder complex mechanics that results in glenohumeral joint pathology. 5

Given the effect of latent MTrPs on activation patterns, Lucas et al 5 assessed the effects of DN and passive stretching of the latent MTrPs on activation patterns during scaption. Following the treatment, the activation of the infraspinatus and the upper trapezius significantly changed to resemble the timing of the control group. The timing of activation also became more consistent for all of the shoulder complex muscles. The authors suggest that the MTrPs are part of a neurological loop that when successfully diminished allow for normalization of muscle function as assessed by activation patterns and thus proficiency of movement.5 Koppenhaver et al34 evaluated the effect of DN on infraspinatus function among subjects diagnosed with subacromial pain syndrome. No significant changes in muscle function were identified immediately after DN to three general locations of common MTrPs. Similar to the current report, the authors measured the thickness of the infraspinatus by RUSI, but only the superior-medial aspect of the infraspinatus was measured. Their findings confirm that DN of the inferior aspect of the muscle did not result in a change of thickness in the superior-medial infraspinatus. As Koppenhaver et al34 stated, this may have been an important limitation of their study because the measurement occurred at a section of the muscle that was distant from the treatment site. Although the boundaries of the sound head were marked over the inferior infraspinatus in the current study in attempt to accurately relocate its position before and after DN, definitive anatomical boundaries must be identified to provide reliable RUSI measurements of this region between subjects and treatment dates.

With regard to the subject, the portion of the infraspinatus adjacent to the focal region of DN demonstrated a large increase in thickness equal to

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the infraspinatus of the asymptomatic shoulder.

Similar results following DN have been previously described in the lumbar multifidus.35 However, the changes in multifidus muscle function did not occur uniformly across all subjects, and increased function was only observed at one week post-treatment, unlike the findings of the current case report. The factors underlying the differences in a pathological muscleâ&#x20AC;&#x2122;s response to DN are unknown, but certainly differences in DN technique and treatment of associated MTrPs in the region may impact the treatment success.

The presence of MTrPs also appears to influence the intensity of muscle function. Celik and Yeldan7 reported that subjects who had MTrPs in selected shoulder and scapular stabilizing muscles had approximately 20% strength deficits in flexion and 15% strength deficits in scaption. In a case series, Osborne and Gatt 6 report similar qualitative findings of decreased external rotation strength at 90 degrees of abduction among elite volleyball players with shoulder pain and MTrPs. Following DN to MTrPs in the infraspinatus and teres minor, strength of external rotation at 90 degrees of abduction was significantly increased as measured by manual muscle testing. This finding occurred in conjunction with a decrease in perceived pain and increased abduction ROM with no pain in the impingement zone.

As with all case reports, limitations exist which restrict the applicability of the conclusions. The subject was seven months after a labral repair. The prolonged period of her impairments after surgery is not typical for most patients. Therefore, these findings may not be generalized to all patients with shoulder complex dysfunctions or those in the immediate post-operative timeframe. The results indicate a simultaneous increase in infraspinatus muscle thickness and external rotation strength immediately following DN. However, these findings may have been the result of a placebo effect or other physiological responses. Although infraspinatus muscle thickness increased immediately following DN, the lack of long term follow up is another limitation because the duration of this change in muscle morphology is unknown. Additional larger studies are required to investigate the relationship between changes in activation, morphology, and strength following DN.

CONCLUSION The results of this case report highlight the potential benefit of DN on muscle function as measured by RUSI (muscle thickness) and force production (handheld dynamometry). After a prolonged period of nonspecific rehabilitation, the subject demonstrated significant muscle dysfunction associated with MTrPs. DN of the MTrPs in the infraspinatus resulted in an immediate increase in muscle thickness and a concurrent increase in strength. Healthcare practitioners should consider DN as an adjunctive intervention to promote improvements in muscle function when muscle dysfunction is present.

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3. Dommerholt J. Dry needling - peripheral and central considerations. J Man Manip Ther. 2011;19(4):223227.

4. Lucas KR, Rich PA, Polus BI. Muscle activation patterns in the scapular positioning muscles during loaded scapular plane elevation: The effects of latent myofascial trigger points. Clin Biomech.

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5. Lucas KR, Polus BI, Rich PA. Latent myofascial trigger points: Their effects on muscle activation and movement efďŹ ciency. J Bodyw Mov Ther. 2004;8:160166.

6. Osborne NJ, Gatt IT. Management of shoulder injuries using dry needling in elite volleyball players. Acupunct Med. 2010;28(1):42-45.

7. Celik D, Yeldan I. The relationship between latent trigger point and muscle strength in healthy subjects: A double-blind study. J Back Musculoskelet Rehabil. 2011;24(4):251-256.

8. Pavkovich R. Effectiveness of dry needling, stretching, and strengthening to reduce pain and improve function in subjects with chronic lateral hip and thigh pain: A retrospective case series. Int J Sports Phys Ther. 2015;10(4):540-551.

9. Passigli S, Plebani G, Poser A. Acute effects of dry needling on posterior shoulder tightness. a case report. Int J Sports Phys Ther. 2016;11(2):254-263.

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10. Boyles R, Fowler R, Ramsey D, et al. Effectiveness of trigger point dry needling for multiple body regions: A systematic review. J Man Manip Ther.

2015;23(5):276-293.

11. Calvo-Lobo C, Pacheco-da-Costa S, Martinez-Martinez J, et al. Dry needling on the infraspinatus latent and active myofascial trigger points in older adults with nonspecific shoulder pain: A randomized clinical trial. J Geriatr Phys Ther. 2016;00:1-13.

12. Clewley D, Flynn TW, Koppenhaver S. Trigger point dry needling as an adjunct treatment for a patient with adhesive capsulitis of the shoulder. J Orthop Sports Phys Ther. 2014;44(2):92-101.

13. Dommerholt J, Bron C, Franssen J. Myofascial trigger points: An evidence-informed review. J Man Manip Ther. 2006;14:203-221.

14. Rice DA, McNair PJ. Quadriceps arthrogenic muscle inhibition: Neural mechanisms and treatment perspectives. Semin Arthritis Rheum. 2010;40(3):250-266.

15. Harkey MS, Gribble PA, Pietrosimone BG. Disinhibitory interventions and voluntary quadriceps activation: A systematic review. J Athl Train. 2014;49(3):411-421.

16. Hopkins JT, Ingersoll CD. Arthrogenic muscle inhibition: A limiting factor in joint rehabilitation. J Sport Rehabil. 2000;9:135-159.

17. Teyhen DS, Koppenhaver S. Rehabilitative ultrasound imaging. J Physiother. 2011;57:196.

18. Koppenhaver S, Harris D, Harris A, et al. The reliability of rehabilitative ultrasound imaging in the measurement of infraspinatus muscle function in the symptomatic and asymptomatic shoulders of patients with unilateral shoulder impingement syndrome. Int J Sports Phys Ther. 2015;10(2):128-135.

19. Temes WC, Temes CA, Hilton V, et al. Reliability and validity of thickness measurements of the supraspinatus muscle of the shoulder: An ultrasonography study. J Sports Rehabil. 2014;8:20132023.

20. Drover JM, Forand DR, Herzog W. Influence of active release technique on quadriceps inhibition and strength: A pilot study. J Manipulative Physiol Ther. 2004;27(6):408-413.

21. Haser C, Stoggl T, Kriner M, et al. Effect of dry needling on thigh muscle strength and hip flexion in elite soccer players. Med Sci Sports Exerc.

2017;49(2):378-383.

22. Shin MS, Sung YH. Effects of massage on muscular strength and proprioception after exercise-induced muscle damage. J Strength Cond Res. 2015;29(8):22552260.

23. Forman J, Geertsen L, Rogers ME. Effect of deep stripping massage alone or with eccentric resistance

24.

25.

26.

27.

on hamstring length and strength. J Bodyw Mov Ther.

2014;18(1):139-144. van den Dolder PA, Ferreira PH, Refshauge KM. Effectiveness of soft tissue massage and exercise for the treatment of non-specific shoulder pain: A systematic review with meta-analysis. Br J Sports Med. 2014;48(16):1216-1226.

Tough EA, White AR, Cummings TM, et al.

Acupuncture and dry needling in the management of myofascial trigger point pain: A systematic review and meta-analysis of randomised controlled trials.

Eur J Pain. 2009;13(1):3-10.

APTA Public Policy, Practice, and Professional Affairs Unit. Description of dry needling in clinical practice: An education resource paper, page 2.

Alexandria, VA: American Physical Therapy Association; 2013.

Kibler WB, Uhl TL, Maddux JW,et al. Qualitative clinical evaluation of scapular dysfunction: A reliability study. J Shoulder Elbow Surg.

2002;11(6):550-556.

28. Hislop H, Avers D, Brown M. Daniels and Worthingham’s Muscle Testing: Techniques of Manual Examination and Performance Testing. 9th ed. St. Louis, Missouri: Elsevier; 2014.

29. Simons DG, Travell JG, Simons LS. Myofascial Pain and Dysfunction: The Trigger Point Manual. 2nd ed.

Philadelphia, PA: Lippincott Williams and Wilkins; 1999.

30. Michener LA, Snyder AR, Leggin BG. Responsiveness of the numeric pain rating scale in patients with shoulder pain and the effect of surgical status. J Sport Rehabil. 2011;20:115-128.

31. Macdermid JC, Khadikar L, Birmingham TB, et al.

Validity of the QuickDASH in patients with shoulderrelated disorders undergoing surgery. J Orthop Sports Phys Ther. 2015;45:25-36.

32. Sharkey NA, Marder RA. The rotator cuff opposes superior translation of the humeral head. Am J Sports Med. 1995;23(3):270-275.

33. Virginia Board of Physical Therapy. Guidance on dry needling in the practice of physical therapy. page 112-119. Richmond, VA: 2010.

34. Koppenhaver SL, Embry R, Ciccarello J, et al. Effects of dry needling to the symptomatic versus control shoulder in patients with unilateral subacromial pain syndrome. Man Ther. 2016;26(12):62-69.

35. Koppenhaver SL, Walker MJ, Su J, et al. Changes in lumbar multifidus muscle function and nociceptive sensitivity in low back pain patient responders versus non-responders after dry needling treatment.

Man Ther. 2015;20(6):769-776.

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IJSPT

CASE REPORT

AORTIC INJURY DUE TO PARAGLIDING: A CASE REPORT Kazuhiko Omori, MD, PhD1 Kei Jitsuiki, MD1 Takashi Majima, MD1 Ikuto Takeuchi, MD1 Toshihiko Yoshizawa, MD1 Kouhei Ishikawa, MD1 Hiromichi Ohsaka, MD, PhD1 Keiichi Tambara, MD, PhD2 Youichi Yanagawa, MD, PhD1

ABSTRACT A 64-year-old male fell from an altitude of 10 m while paragliding after stalling due to the wind. The purpose of this case report is to describe the outcomes after multiple injuries sustained during a paragliding accident, including a potentially life-threating injury to the thoracic aorta. The subject sustained a bite wound on his tongue, injuries to his chest (left side) and back, and a right forearm deformity. Enhanced whole body computed tomography (CT) revealed fractures of the bilateral laminae of the second and third cervical bones, right first rib, the tenth thoracic vertebral body (compression type), second lumbar vertebral body (burst type) and the right radius, Other injuries included an injury to the thoracic aortic arch and the presence of intraabdominal fluid collection without perforation of the digestive tract. Endovascular treatment was selected for the aortic injury because of multiple injuries. Immediate management included hypotensive rate control therapy using calcium and a beta blocker. On the fourth hospital day, the subject underwent deployment of a stent-graft to the aorta and subsequent surgical immobilization for the lumbar burst fracture. He also underwent surgical immobilization of the radial fracture and was discharged on the 28th hospital day. First responders or physicians should consider the possibility of aortic injury when treating patients who suffer falls while paragliding and provide appropriate management. Failure to provide appropriate management of an aortic injury could result in death.

Level of Evidence: 4 Key words: Aortic injury; multiple fractures; paragliding

1

Department of Acute Critical Care Medicine, Shizuoka Hospital, Juntendo University 2 Department of Cardiovascular Surgery, Shizuoka Hospital, Juntendo University

CORRESPONDING AUTHOR Youichi Yanagawa 1129 Nagaoka, Izunokuni City, Shizuoka, Japan 410-2295 Tel: 81-55-948-3111 E-mail: yyanaga@juntendo.ac.jp

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INTRODUCTION Paragliding is an increasingly popular hobby, as people try to find new and more adventurous activities.1 There are many recreational and competitive paragliding events held throughout the world. However, there is also substantial and inherent danger with this sport. For this reason, as well as the inexperience of many operators, injuries occur frequently.1 The role of the sports physical therapist (PT) is typically as a part of the sports medicine team, often being present during performance of recreational sports. The PT can assume the role of an emergency medical responder (EMR) whose primary role is the management of individuals in emergency type situations.2 In this role, the PT must be prepared to handle any type of emergency situation, which may occur related to medical conditions and/or acute orthopedic/sports injuries.2 Injuries sustained while paragliding tend to occur at the spine, pelvis and lower extremities.3-5 Lautenschlager et al analyzed 86 injuries associated with paragliding in a prospective study and found that 60% of all accidents happened during the landing phase, 26% at launching and 14% while in-flight.3 The purpose of this case report is to describe the outcomes after multiple injuries sustained during a paragliding accident, including a potentially lifethreating injury to the thoracic aorta.

Enhanced whole body computed tomography (CT) revealed fractures of the lamina at the second and third cervical vertebrai, right first rib, tenth thoracic vertebral body (compression type), second lumbar vertebral body (burst type) and right radias, Additionally, a thoracic aortic arch injury and intraabdominal fluid collection were noted. (Figure 1) Immediate management included hypotensive rate control therapy using calcium and a beta blocker, targeting a systolic blood pressure of 80 mmHg for prevention of rupture of the aorta. Endovascular treatment was also selected for the aortic injury because of the presence of multiple injuries. On the day of his injury, the subject was restless and therefore was intubated using a sedative. On the fourth hospital day, he underwent deployment of a stent-graft into the aortic arch by an endovascular specialist who was invited from another hospital.

The following day, he underwent posterior fixation of the lumbar burst fracture by the orthopedic surgeons and was extubated on the sixth hospital day.

Follow up ultrasound and CT imaging showed that the fluid collection in his abdomen had resolved, so the subject was allowed to begin eating and also to begin inpatient rehabilitation including muscle strength training, balance training and ambulation training. Of note, rehabilitation was not the emphasis of this case report, thus, is not described in detail.

After undergoing plate fixation for the radial frac-

CASE PRESENTATION The subject of this case report is a 64-year-old male fell who from an altitude of 10 m while paragliding, after stalling due to the wind. A physician-staffed helicopter was called to transport the subject after his accident. On arrival at the hospital, the subject was conscious with a blood pressure of 140/98 mmHg, heart rate of 78 beats per minute, SpO2 of 100% under 10 L/minute of oxygen delivered via a reservoir mask, and a body temperature of 36.5°C. He had a bite wound on his tongue, displayed tenderness to palpation of the left side of the chest and the back, as well as a right forearm deformity.

Sonographic assessment for trauma showed fluid collection in his mesentric interval. A biochemical analysis of the blood revealed leukocytosis (12,600/ μL) and increased creatinine phosphokinase level (401 IU/L) and D-dimer levels (135.7 μg/mL).

Figure 1. Enhanced chest computed tomography (CT) on arrival. The CT scan shows pseudo-aneurysm at the aortic arch (arrow).

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ture, he was discharged on the 28th hospital day to home, independently.

DISCUSSION Cause of injury By necropsy, approximately 10% of automobile accidents or falls from aircrafts result in fatal aortic injury, indicating that aortic injury must be considered in fatal high-energy accidents.6,7 Regarding the natural history of aortic injury, Parmley evaluated 296 cases of blunt aortic injury in young soldiers and found that about 15% survived long enough to get to a hospital.8 Of this 15%, 99% would have died without surgical intervention; 15% of these subjects would have survived only the first hour, 30% the first six hours, 49% the first 24 hours. Seventytwo percent would have died within eight days, and 90% within 4 months.8 The mechanism of blunt aortic injury remains the most important factor in establishing the diagnosis, with falls from over three meters representing a major source of this injury.

During paragliding, pilots fly well over three meters from the ground, so falling while paragliding carries a risk of sustaining blunt aortic injury. In a previous report concerning fatal accidents due to paragliding, aortic injury was reported in addition to head, cervical cord injury, and lung rupture.3,5,9 Blunt trauma can damage the thoracic aorta by several mechanisms. The most commonly described cause of rupture is the differential forces set up within the chest by deceleration in either the horizontal or vertical plane.6,10 The descending aorta remains fixed to the posterior chest wall, while the heart and ascending aorta swing forward and tear free at the isthmus. Given that the present subject had thoracic and lumbar fractures, which are frequently induced by energy through the vertical plane, the aortic injury was presumably caused by a mainly vertical trauma due to a fall from a height.11 Aortic arch injury has been reported following a fall due to an airplane accident.7 Signs and Symptoms of Aortic Arch Injury in the Prehospital Setting Some clinical features that suggest the presence of blunt thoracic aortic injury include hypotension, upper extremity hypertension, bilateral lower

extremity pulse deficit, and initial chest tube output of >750 mL of blood.12 Patients with this presentation have a high incidence of other significant injuries. However, these clinical features are unreliable for diagnosis of aortic injury as their absence cannot exclude the presence of the blunt aortic injury.12 Thirty percent of patients with this injury have no external signs of chest trauma while 75% have rib fractures that draw attention away from the concomitant intrathoracic injury.12 The subject of the present case had chest pain due to rib fracture and multiple significant spinal injuries due to the highenergy accident, thus any first responder should have treated this case as a potential blunt thoracic aortic injury.

Appropriate Care of the Victim in the Prehospital Setting A first responder treating a patient who sustained injury due to paragliding must consider some important key points. Michetti et al reported that overall mortality with aortic injury was 92% and prehospital mortality was 63%.13 Thus, first the provider should always consider the possibility of an aortic injury, which can be lethal. Second, the provider should address the patientâ&#x20AC;&#x2122;s airway, breathing, and circulatory status. If the patients goes into cardiac arrest, immediate basic life support must be provided, and the automated external defibrillator be used as indicated, after activating the emergency response system. Third, if able, induce hypotension by limiting prehospital intravenous fluid administration and using nitrates, which may result in increase of survival rates for this type of patient with a rupture of the aorta.14 Providing pain control and gentle treatment during stabilization so that he patient does not sustain an increase blood pressure. Finally, transport the patient to a trauma center as quickly as possible, as patients with aortic injury taken to a trauma center had significantly lower mortality than patients taken to a non-trauma medical center.13 The Radiologic Findings Upon Hospital Admission The first examination is typically includes plain radiography. A widened mediastinum, blurred aortic contour, and irregular aortic arch may be visible on chest X-ray, and are typical image findings in cases

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of thoracic aortic injury. However, the sensitivity of chest X-ray in the detection of aortic injuries is not high.15,16 Thus, additional imaging is warranted, and Computerized Tomography (CT) of the chest with intravenous contrast is strongly recommended for the diagnosis of clinically significant thoracic aortic injury.17 In the present subject, the chest X-ray only showed minor aortic arch irregularity; however, enhanced CT clearly demonstrated the greater extent of the aortic arch injury.

APPROPRIATE CARE IN THE EMERGENCY ROOM For all traumatized patients, vital signs should be stabilized by initiating appropriate supportive therapy, rapidly identifying life-threatening injuries using radiography, ultrasound imaging, and enhanced CT. Organizing the trauma team within the emergency room to administer definitive therapy efficiently is of utmost importance. The subject of this case report had stable vital signs but significant, potentially lethal injuries were found on the whole body enhanced CT. The thoracic aortic injury was prioritized for treatment, as it is potentially the most lethal. Accordingly, the management included permissive induced hypotension and rate control therapy, in addition to pain control in the emergency room.

TREATMENT PLAN Among the multiple injuries in the present case, the thoracic aortic injury was the most lethal; thus, the immediate goal was to repair the aortic injury.

Blunt aortic injury used to be treated by open repair.

Recently, however, less-invasive treatment via endovascular stent graft has been performed.18 A metaanalysis of retrospective cohort studies indicated that the procedure-related mortality, overall 30-day mortality and the risk of postoperative paraplegia were significantly lower with endoluminal repair than with open repair.19 This treatment is especially indicated in the presence of multiple injuries, as open repair requires an artificial heart lung apparatus with heparin administration, which can induce bleeding in other traumatic injury sites.20 Accordingly, endovascular treatment was selected and obtained a favorable outcome. After repairing the aortic injury, a lumbar burst fracture was the next obstacle to obtaining early functional rehabilitation.

Accordingly, immobilization of the lumbar spine was performed soon after confirming the absence of complications of the endovascular stent graft. In the present subject, the intraabdominal fluid collection suggested an intraabdominal injury which was of concern to the medical team, however, this resolved spontaneously. The radial fracture was subsequently stabilized in an elective surgery.

REHABILITATION PLAN Before the repair of the aortic injury in the present case, the patient was strictly confined to bed because a rupture of the aortic injury had the potential to result in sudden death. In addition, the subject had sustained a lumbar burst fracture; thus, postural change was not allowed based on the instructions of the orthopedist.

A pressure dispersing bed was used to prevent integumentary break down. After repairing the aortic injury, passive motion of upper extremities was started by nurses to prevent contracture. After the surgical stabilization of the lumbar fracture, postural change and passive motion of all extremities commenced (subject remained in a cervical orthosis) by nurses. After extubating the patient and confirming the disappearance of the fluid collection in his abdomen, physical therapy ensued to increase the subjectâ&#x20AC;&#x2122;s, sitting balance, transfer abilities, standing balance and gait, and muscle strength. Each of these interventions was provided depending on recovery of the subjectâ&#x20AC;&#x2122;s function and degree of pain. The rehabilitation program, which was determined based on thorough individualized assessment of his specific problems, allowed the patient to obtain functional ambulatory independence by the time that he was discharged.

CONCLUSION A first responder or physicians should pay attention to the possibility of lethal aortic injury when treating patients who suffer falls while paragliding (or from subststantial heights in other circumstances) and provide appropriate management. Although not common, such an injury could be life threatening and should be considered a priority in post-traumatic management.

REFERENCES 1. Fasching G, Schippinger G, Pretscher R. Paragliding accidents in remote areas. Wilderness Environ Med. 1997;8(3):129-33.

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2. Smith DD, Schuemann T, Hoogenboom BJ. The role of the sports physical therapist-marathon events. Int J Sports Phys Ther. 2013;8(4):531-6.

3. Lautenschlager S, Karli U, Matter P. Paragliding accidents--a prospective analysis in Swiss mountain regions. Z Unfallchir Versicherungsmed. 1993;Suppl 1:55-65. in German 4. Fasching G, Schippinger G, Pretscher R. Paragliding accidents in remote areas. Wilderness Environ Med. 1997 ;8(3):129-33.

5. Rekand T. The epidemiology of injury in hanggliding and paragliding. Med Sport Sci. 2012;58:44-56.

6. O’Conor CE. Diagnosing traumatic rupture of the thoracic aorta in the emergency department. Emerg Med J. 2004 ;21(4):414-9.

7. Pezzella AT. Blunt traumatic injury of the thoracic aorta following commercial airline crashes. Tex Heart Inst J. 1996;23(1):65-7.

8. Parmley LF, Mattingly TW, Manion WC, Jahnke EJ. Nonpenetrating traumatic injury of the aorta.

Circulation. 1953;17:1086–101.

9. Sato T, Maze Y, Tenpaku H. Delayed surgical treatment of traumatic injury of the thoracic aorta.

Kyobu Geka. 2004 ;57(12):1117-20. in Japanese 10. Schrøder Hansen K, Våge V, Morild I. Vertical shear forces and their influence on disruption of the diaphragm and thoracic aorta. Eur J Surg.

2001;167(7):548-51.

11. Postma IL, Oner FC, Bijlsma TS, et al. Spinal injuries in an airplane crash: a description of incidence, morphology, and injury mechanism. Spine. 2015 ;40(8):530-6.

12. Ho AF, Chua TW, Seth P, et al. Atypical presentation of traumatic aortic injury. Case Rep Emerg Med. 2014;2014:864301.

13. Michetti CP, Hanna R, Crandall JR, Fakhry SM. Contemporary analysis of thoracic aortic injury: importance of screening based on crash characteristics. J Trauma. 2007;63(1):18-24.

14. van der Vliet JA, van Aalst DL, Schultze Kool LJ, et al. Hypotensive hemostatis (permissive hypotension) for rupturedabdominal aortic aneurysm: are we really in control? Vascular. 2007;15(4):197-200.

15. Gutierrez A, Inaba K, Siboni S, et al. The utility of chest X-ray as a screening tool for blunt thoracic aortic injury. Injury. 2016 ;47(1):32-6.

16. Ekeh AP, Peterson W, Woods RJ, et al. Is chest x-ray an adequate screening tool for the diagnosis of blunt thoracic aortic injury? J Trauma. 2008 ;65(5):1088-92.

17. Fox N, Schwartz D, Salazar JH, et al. Evaluation and management of blunt traumatic aortic injury: a practice management guideline from the Eastern Association for the Surgery of Trauma. J Trauma Acute Care Surg. 2015 ;78(1):136-46.

18. Khoynezhad A, Azizzadeh A, Donayre CE, et al.

RESCUE investigators: Results of a multicenter,prospective trial of thoracic endovascular aortic repair for blunt thoracic aortic injury(RESCUE trial). J Vascular Surg 2013; 57(4):899905.

19. Xenos ES, Abedi NN, Davenport DL, et al. Metaanalysis of endovascular vs open repair for traumatic descending thoracic aortic rupture. J Vasc Surg.

2008;48(5):1343-51.

20. Brand S, Breitenbach I, Bolzen P, Petri M, Krettek C, Teebken O. Open repair versus thoracic endovascular aortic repair in multiple-injured patients: Observations from a level-1 trauma center.

Arch Trauma Res. 2015;4(4):e27183.

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IJSPT

CLINICAL COMMENTARY

SUPERIOR CAPSULE RECONSTRUCTION FOR MASSIVE ROTATOR CUFF TEARS - KEY CONSIDERATIONS FOR REHABILITATION Jonas Pogorzelski, MD, MHBA1 Brooke M. DelVecchio, PT, DPT, OCS2 Zaamin B. Hussain, BA1 Erik M. Fritz, MD1 Jonathan A. Godin, MD, MBA1,3 Peter J. Millett, MD, MSc1,3

ABSTRACT Superior capsule reconstruction is a recently-developed surgical technique for the treatment of massive, irreparable rotator cuff tears. So far, biomechanical cadaveric studies and clinical outcomes results have been promising concerning integrity, stability, and ROM after superior capsule reconstruction. As this technique has only been recently developed, an evidence-based rehabilitation protocol has not been previously designed. Thus, the purpose of this clinical commentary is to provide an overview of superior capsule reconstruction and to propose a rehabilitation program based on the available scientific evidence. The existing evidence is supplemented by the experience of the senior author who has performed more than forty superior capsule reconstruction procedures to date. This proposed rehabilitation protocol consists of four distinct phases, focusing on maximal protection, range of motion and muscular endurance, muscular strength and return to activity.

Level of Evidence: 5 Key words: Irreparable rotator cuff tears, rehabilitation, shoulder, superior capsule reconstruction

1

Steadman Philippon Research Institute, Vail, CO, USA Howard Head Sports Medicine Center, Vail, CO, USA 3 The Steadman Clinic, Vail, CO, USA 2

CORRESPONDING AUTHOR Peter J. Millett, MD, MSc Steadman Philippon Research Institute The Steadman Clinic 181 West Meadow Drive, Suite 400 Vail, Colorado 81657 E-mail: drmillett@thesteadmanclinic.com

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INTRODUCTION AND BACKGROUND The prevalence of massive rotator cuff tears has been reported to be as high as 40% of all rotator cuff tears.1, 2 If not treated in a timely manner, muscle atrophy and fatty infiltration often ensue, resulting in irreparable tears.3 But even if treated in time, the failure rates of massive rotator cuff repairs are higher than those following the repair of smaller tears.4 Once a tear is irreparable, a spectrum of treatment options exists. Non-operative management may be indicated in patients with low demands and symptoms that occur predominantly with use, but it has been shown to lead to the progression of osteoarthritis.5, 6 Partial rotator cuff repair and debridement have shown good results;7-10 however, there is limited long-term outcome data of 10 years or more to support its use, as well as the risk of continued pain, loss of motion and function, and worsening arthritic changes.7-10 In elderly patients with advanced shoulder osteoarthritis, reverse total shoulder arthroplasty may be indicated to address cuff tear arthropathy.2 However, limited implant longevity and activity restrictions from high-impact activities make joint replacement a less desirable option in younger patients. Therefore, additional options have been developed for younger patients. Latissimus dorsi tendon transfers have been shown to be a reasonable treatment method for posterosuperior massive rotator cuff tears. However, high complication rates, difficult revisions following failure, and poor outcomes in certain patient populations make stringent patient selection for this procedure particularly important.11 Less invasive than latissimus dorsi tendon transfer, the superior capsule reconstruction (SCR) procedure is a novel technique developed in Japan by Mihata et al.12 as reverse arthroplasty was not approved in Japan at the time. The original technique used fascia lata autograft to reconstruct the superior capsule in the presence of an irreparable rotator cuff tear. Today, a number of allograft options, including a human acellular dermal allograft (Arthroflex, Arthrex, Naples, FL), can be used instead of fascia lata autograft. As demonstrated both biomechanically and clinically by Mihata et al.,12, 13 the graft design and surgical placement prevents the humeral head from migrating superiorly and thus enables efficient biomechanics of the shoulder. Additionally, the graft acts as a mechanical spacer between the

humeral head and the undersurface of the acromion.

Improved range of motion, joint space, and American Shoulder and Elbow Surgeons (ASES) scores following SCR have been reported.13 This arthroscopic technique has a low complication rate and shortterm follow-up at a minimum of two years postoperatively shows limited progression of osteoarthritis and rotator cuff muscle atrophy.13 As this innovative technique is only emerging from its infancy, an evidence-based rehabilitation protocol has not been previously designed since the technique was only developed in 2007.12, 14 Therefore, the purpose of this clinical commentary is to provide an overview of SCR for the treatment of massive rotator cuff tears and to propose a rehabilitation program based on the available scientific evidence.

ANATOMY / BIOMECHANICS / PATHOBIOMECHANICS Movement at the shoulder complex arises from a combination of glenohumeral and scapulothoracic motion. The scapula provides a muscle attachment site and allows load transfer from the upper limb to the thorax. The bony architecture, labrum, joint capsule, ligaments and negative pressure within the glenohumeral joint space all provide passive stability. In addition, the rotator cuff and long head of the biceps tendon center the humeral head on the glenoid and provide active stability, thereby allowing effective shoulder function. The rotator cuff consists of four muscles working synergistically: the supraspinatus, infraspinatus, teres minor, and subscapularis.

Each muscleâ&#x20AC;&#x2122;s origin and insertion sites determine its function. The supraspinatus forms the superior aspect of the rotator cuff and initiates abduction.

The infraspinatus and teres minor comprise the posterior aspect of the rotator cuff and contribute to abduction and function primarily to initiate external rotation. The subscapularis makes up the anterior portion of the rotator cuff and is primarily responsible for internal rotation. In healthy shoulders, a balanced force couple for the glenohumeral joint in both the coronal and the axial planes is maintained by the synergistic action of the deltoid and rotator cuff muscles. In the axial plane, the subscapularis and infraspinatus/teres minor complex maintain a balanced force couple, while the deltoid and rotator cuff inferior to the humeral head equator form a bal-

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anced force couple in the coronal plane. As such, the rotator cuff muscles function as primary dynamic stabilizers to maintain concentric joint reduction during rotation of the humeral head on the glenoid.1 Small to medium size rotator cuff tears involving the supraspinatus and the anterior portion of the infraspinatus do not affect stability in the coronal and axial planes because the balanced force couples are maintained. These can be differentiated from massive tears involving at least two tendons including the postero-inferior part of the rotator cuff where the balance of the force couple in the coronal plane is lost, thereby compromising the fulcrum that is necessary for normal glenohumeral mechanics.1, 15-20 To restore normal kinematics in patients with massive tears of the postero-superior rotator cuff tendons, greater forces are required by both the deltoid and the intact rotator cuff muscle-tendon units, particularly the subscapularis, to achieve stable abduction.21 The progression of a rotator cuff tear leads to disruption of the axial force couple and subsequent superior subluxation of the humeral head and shoulder dysfunction.19 The force required to move the arm increases with tear size making the biomechanics less efficient. The tensile load on the intact fibers increases because the torn tendons cannot contribute to load sharing, and this leads to tear propagation, especially if the remaining tendon is of poor quality.

Additionally, with initiation of abduction, superior subluxation of the humeral head can occur as a result of muscle weakness or tendon retraction, leading to increased cuff impingement between the greater tuberosity and the inferior aspect of the acromion.16, 22 This increased cuff impingement can cause medial extension of supraspinatus tears, leading to a cycle of superior humeral head migration and tear propagation. Usually, a massive rotator cuff tear involving at least two torn tendons is needed to provoke superior migration of the humeral head.23 Non-anatomical superior subluxation of the humeral head against the glenoid produces shear forces at the articular surfaces that cause cartilage destruction. Without early intervention, pain and loss of function ensue, along with the development of disabling osteoarthritis that often progresses to rotator cuff arthropathy.22

SURGICAL TREATMENT Many operative procedures, including those previously outlined, have been used to treat massive rotator cuff tears, but this commentary focuses on SCR (Figure 1) of which the senior author has performed more than 40 to date. The arthroscopic SCR technique has previously been described in detail

by Katthagen et al.24 The retracted, deficient supraspinatus tendon is arthroscopically confirmed and extensively debrided. After the superior glenoid and greater tuberosity bony surfaces are prepared, three anchors are inserted into the glenoid at the 10, 12, and 2 oâ&#x20AC;&#x2122;clock positions. The rotator cuff defect is measured to determine the size of the human acellular dermal allograft. The patch is then introduced into the shoulder through the anterolateral portal, and the graft is fixed medially. On the humeral side, two anchors are inserted for medial-row fixation at the articular cartilage margin. Two lateral anchors are then inserted for lateral-row fixation. Finally, the lateral part of the graft is compressed down onto the footprint using a suture bridge technique (Figure 2).

The native rotator cuff tissue may require margin convergence and is then sutured into the graft for additional stability.

POST-OPERATIVE REHABILITATION Post-operative rehabilitation following SCR begins with close communication between the surgeon

Figure 1. Diagram from superolateral view of a left shoulder illustrating the ďŹ nal superior capsule reconstruction (SCR) construct, using a human dermal acellular allograft.

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range of motion exercises with scapular stabilization for the first eight weeks.

Phase I â&#x20AC;&#x201C; Maximal Protection The rehabilitation goals of Phase I include protecting the surgical repair, minimizing pain and inflammation, maintaining mobility of accessory joints and providing patient education. Physical therapy typically begins on post-operative day one in order to review post-operative restrictions and precautions, rehab protocol and progressions, and initial home exercise program, as well as to discuss expected functional outcomes.

Figure 2. Arthroscopic photograph in a left shoulder taken from the lateral portal, showing the ďŹ nal SCR construct.

and the physical therapy team. This communication continues throughout the recovery process and is an essential component to ensuring a successful outcome. The physical therapist should discuss expected functional outcomes as well as specifics of the surgery with the surgeon prior to discussing expectations with the patient in order to gain a better understanding of each individualâ&#x20AC;&#x2122;s prior level of function, chronicity of injury, tissue integrity, and goals. The authors always promote a high level of activity in their patients post-operatively while making them aware of the risks of certain activities and sports, particularly contact or overhead sports. Moreover, the authors make patients aware of the limited evidence that currently exists regarding long-term outcomes or risk factors for failure after SCR. The protocol detailed below is consistent with that suggested by Petri et al.,14 allowing limited and protected PROM initially. However, progression is not as gradual as that suggested by Mihata et al.13 who, after using a fascia lata allograft, advocate for four weeks immobilization, then four weeks of passive and active assisted exercises and finally gradual strengthening beginning at eight weeks. On the other hand, the protocol described herein is not as aggressive as Gupta et al.25 (surgical procedure with a xenograft) who advocate allowing unrestricted passive

Post-operatively, patients are immobilized in a sling limiting passive range of motion (PROM) as much as possible. This is in order to protect the surgical repair by allowing sufficient time for healing to occur prior to introducing controlled, progressive load to the graft. The patient is placed in a sling with abduction pillow to support the glenohumeral joint in the scapular plane, which is worn for six weeks.

Patients are instructed to wear compression stockings for two weeks and to perform ankle pumps for up to six weeks post-operatively in order to reduce the risk of deep vein thrombosis.

Although the patient is not initially allowed PROM of the glenohumeral (GH) joint, it is important to ensure maintenance of accessory joint mobility throughout the six-week immobilization period of the shoulder. Patients are instructed on proper performance of active range of motion (AROM) of the cervical spine as well as AROM of the elbow, wrist and hand outside of the sling. Concurrent scapular retraction and depression is also initiated at this time in order to facilitate activation of postural musculature and prevent tightness of the anterior shoulder musculature. Patients are also encouraged to perform gentle ball squeezes using the hand on the involved side in order to facilitate circulation throughout the upper extremity while immobilized in the sling.

Instruction is provided to the patient and caregiver, if present, regarding donning/doffing of the sling as well as how to properly don and doff clothing.

It is recommended that patients use a second sling to support their shoulders while showering. Five to six times daily, patients are encouraged to apply

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cryotherapy and compression for no more than 30 minutes to the involved shoulder the first two weeks post-operatively in order to assist with minimizing pain and inflammation and to provide comfort while sleeping.26 Phase II – Range of Motion and Muscular Endurance The range-of-motion (ROM) and muscular endurance phase is typically introduced 6 weeks post-operatively. The rehabilitation goals of Phase II consist of restoring passive and active range of motion while managing pain, improving rotator cuff endurance, establishing normal scapulohumeral rhythm and returning to light functional activities of daily living.

Following six weeks of immobilization, the patient is cleared by the surgeon to begin restoring full PROM and AROM of the GH joint without restrictions other than patient tolerance. Rehabilitation of the shoulder at this point generally follows a rehabilitation program typical of a post-operative massive rotator cuff repair. This includes both healing timelines and criteria-based progression as outlined by the multi-disciplinary Level V consensus statement by Thigpen et al.27 allowing for special considerations specific to SCR rehabilitation. It is important to remember the SCR procedure is indicated for massive, irreparable rotator cuff tears in select patients with a functioning deltoid and at least a partially functioning subscapularis and that not all rotator cuff musculature is repaired with this procedure. Moreover, the patient who has undergone SCR may not meet the criteria for rehabilitation progression at the same rate as a patient who has undergone a rotator cuff repair.

Most candidates for SCR present pre-surgically with a retracted, full thickness tear of the supraspinatus and a partial- to full-thickness tear of the infraspinatus and teres minor. Emphasis should be placed on muscle activation of the deltoid, specifically the middle and posterior fibers, along with on regaining as much external rotation function as possible.

The external rotators of the glenohumeral joint may be difficult to activate initially, and activation is dependent upon the amount and tissue integrity of the retracted infraspinatus/teres minor surgically attached to the superior capsule graft. Along with the superior capsule graft, the deltoid and internal and

external rotation musculature make up the primary force couples about the glenohumeral joint.28 Force couples result in rotational movement; the balance of muscular forces creates dynamic stabilization of the glenohumeral joint through humeral head compression.28 The graft will prevent superior migration of the humeral head during active elevation of the glenohumeral joint. The deltoid and internal/external rotation musculature provide the force couple to approximate the humeral head in the glenoid throughout active and resisted range of motion.

Pain-free glenohumeral PROM is initiated in the supine position prior to beginning active assisted range of motion (AAROM), which typically commences during the seventh post-operative week if PROM is progressing appropriately and pain is properly managed. Generally, AAROM is initiated in positions that place less gravitational demand on the musculature, such as supine, prone or side-lying positions, and can be progressed to seated or standing positions as tolerated. PROM and AAROM exercises should focus on planes of glenohumeral motion including forward elevation, scaption, and internal and external rotation. Supine AAROM forward elevation to 90° and external rotation are initiated utilizing a dowel or the contralateral upper extremity for assistance. Based on the authors’ experience, a slideboard can also be utilized in the supine (Figure 1), side-lying, or prone (Figure 2) positions in order to facilitate deltoid activation with scaption and forward elevation movements. Open chain proprioception, pendulums (i.e. Codman’s exercise) and gentle aquatic therapy can also be initiated at this time in accordance with patient comfort. Emphasis should be placed on maintaining scapular control with all AAROM and AROM therapeutic exercises.

Scapular and glenohumeral isometrics, as well as initial proprioceptive therapeutic exercises, should be incorporated into treatment at this time as the patient is just beginning to re-learn muscle activation patterns associated with movement of the glenohumeral joint. Sub-maximal glenohumeral isometrics should include the deltoid, subscapularis, infraspinatus, teres minor, triceps and biceps. Isometrics are initiated in a supine, neutral scaption position and can be progressed to varying degrees of abduction, forward elevation, and external rotation.

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Biofeedback may be useful with isometrics in order to facilitate neuromuscular re-education of the external rotators. Scapular isometrics are progressed from initial activation in Phase 1 to side-lying or prone positions and should focus on retraction, protraction, depression and elevation from a neutral scapular position. These exercises should begin without resistance before progressing to the application of manual resistance, which provides effective biofeedback regarding scapular proprioception. Progression of scapular isometrics in a side-lying or prone position can be performed with the upper extremity supported in various degrees of external rotation or scaption.

When the patient exhibits effective isometric muscle contraction as well as fair muscle activation with AAROM therapeutic exercises with pain managed effectively, AROM is then initiated. AROM is typi-

cally incorporated into treatment one to two weeks after the initiation of PROM, per proper progression of PROM/AAROM and adequate pain control.

PROM and AAROM should be incorporated into physical therapy sessions as needed in conjunction with AROM in order to restore functional range of motion. Sling use is also discontinued at this time via a gradual progressive weaning process, and patients can begin utilizing the upper extremity with light activities of daily living, typically at and below waist level. AROM is generally initiated in a supine position. Modifications may be necessary based on each individualâ&#x20AC;&#x2122;s progression at this point in their rehabilitation, and side-lying (Figures 3 and 4) and prone (Figure 5) positions may be utilized prior to progression to standing and seated positions as neuromuscular control and endurance improves.

The following exercises have been indicated in the literature to produce the highest electromyographic

Figure 3. Slideboard-assisted scaption for deltoid activation.

Figure 4. Slideboard-assisted forward elevation in the scapular plane.

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Figure 5. Sidelying abduction.

(EMG) activity of the rotator cuff musculature without compensation of larger muscle groups. These exercises may require modification based on each patientâ&#x20AC;&#x2122;s ability to recruit the proper musculature following SCR. Biofeedback can be a beneficial tool to improve functional neuromuscular re-education of the rotator cuff, deltoid, and periscapular musculature in this phase of rehabilitation.

Regarding external rotation of the glenohumeral joint, side-lying external rotation and prone external rotation abduction exercises have been documented to provide the highest EMG activation of the infraspinatus.29-32 Side-lying external rotation with a towel roll in the axilla should be trialed first, as prone external rotation abduction exercises may place excessive tensile load on the repaired tissue due to insufficient muscular strength to perform these exercises effectively. The towel roll places the glenohumeral joint in the scapular plane, which facilitates an adduction moment upon the glenohumeral joint, thereby reducing capsular stress, improving scapular stability and increasing EMG activity of the targeted musculature.30, 33 Initially, patients will lack sufficient strength to move through the available range of motion. The physical therapist can begin with manual placement of the glenohumeral joint in various degrees of external rotation and have the patient perform isometric holds. Alternatively, gentle rhythmic stabilization

may also be utilized. The glenohumeral joint can also be placed at the end range of available external rotation following isometric holds allowing the patient to perform the eccentric portion of the exercise by returning the arm to neutral. Active external rotation can also be performed in a seated position utilizing a slideboard for assistance as needed. Keep in mind the potential limited range of motion with this movement based on each patientâ&#x20AC;&#x2122;s pre-surgical level of function, the availability and integrity of salvageable external rotator cuff tissue.

The subscapularis and pectoralis musculature work in concert with the external rotation musculature to establish the internal/external rotator force couple that functions in concert with the deltoid. Subscapularis activation is initially facilitated with isometrics and external rotation exercises. Alizadehkhaiyat et al. reported increased EMG activity of the subscapularis with prone external rotation and horizontal abduction exercises.34 Deltoid function is imperative following SCR to restore the force couples about the glenohumeral joint. Initially, the deltoid should be activated utilizing multi-angle submaximal isometrics prior to progressing to isotonics. It is beneficial to begin deltoid isotonics with the patient in a sidelying (Figures 3 and 4) or supine (Figure 1) position.

Patients can begin in a side-lying position to perform glenohumeral abduction in the coronal plane of the

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body (Figure 3), as well as horizontal abduction in the transverse plane (Figures 4 and 5). Assisted scaption exercises performed on a slideboard with the patient prone (Figure 2) or supine (Figure 1) are beneficial to facilitate deltoid function in a functional position without excess gravitational resistance prior to progressing to seated or standing scaption exercises.

The prone full-can exercise has been proven to generate good electromyographic activity of the posterior deltoid and the lower trapezius.35, 36 This exercise may need to be performed with slideboard assistance prior to performing it unassisted in a prone position, with the final progression to an upright position.

Another option to promote functional re-training of the deltoid is the patient performing a press to 90° of glenohumeral forward elevation in a supine position (Figure 6), and subsequently progressing to an incline press. The aforementioned exercises facilitate concentric and eccentric muscular endurance of the posterior, middle, and anterior portions of the deltoid. Isotonic external rotation exercises of the glenohumeral joint, as described above, also promote activation of the posterior deltoid.

The serratus anterior, which protracts the scapula, plays a crucial role in establishing normal scapulo-

humeral rhythm and is an integral component of establishing glenohumeral motion above 90°. Serratus anterior isotonics can be performed initially in a supine or prone position with the glenohumeral joint at 90° of forward elevation while performing the serratus “plus” exercise to protract the scapula while maintaining a static glenohumeral position.

Emphasis is placed on proper protraction and retraction to the neutral position of the scapula at 90°, progressing to scapular protraction at various angles of forward elevation and/or scaption in conjunction with the progression to upright positions while promoting neuromuscular control of the glenohumeral joint. Open chain scapular exercise is emphasized during this phase of rehabilitation in order to establish proper scapulothoracic force couples and improve neuromuscular endurance with AROM activities. Closed chain scapular exercise is initiated during Phase III of the rehabilitation process in order to allow sufficient time to develop proper dynamic stability prior to the initiation of compressive forces on the glenohumeral joint.

Establishing scapular stability is imperative to normalize scapulohumeral rhythm to promote optimal function following SCR. Scapular control is initiated in Phase I and is progressed during Phase II by

Figure 6. Horizontal abduction.

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emphasizing proper scapular position, neuromuscular control, and endurance of the serratus anterior, rhomboids, and middle and lower trapezius muscles throughout all AROM exercises while reducing upper trapezius compensation patterns. It is important to establish normal scapulohumeral rhythm with AROM prior to the initiation of resisted ROM in order to promote proper muscle activation and to reduce compensation patterns. Manual therapy techniques can also be utilized throughout this phase as indicated, keeping in mind the repaired tissues and healing timelines. Manual techniques include but are not limited to soft tissue mobilization, joint mobilizations, contract/relax techniques and low load, long duration stretching. These techniques should be appropriately selected to improve mobility and/or decrease pain.

This phase of rehabilitation can potentially require a significant amount of time to properly retrain the remaining rotator cuff musculature, deltoid, and periscapular musculature to function in concert with the superior capsule graft. The level of function exhibited by each patient prior to surgery should be taken into consideration. Massive, chronic rotator cuff tears generally take an extended duration of time to rehabilitate, regardless of the type of surgical intervention performed.

Phase III – Muscular Strength The muscular strength phase is generally introduced at 10-12 weeks postoperatively and consists of progressive resisted ROM and the initiation of closed chain exercises. The rehabilitation goals of phase III

include advancement of strength and restoration of functional ROM, progressing to higher level functional activities.

Strengthening should be initiated with light resistance bands and/or light dumbbell isotonics, and the initiation of closed chain stabilization exercises should incorporate light weights or resistance and have a functional basis. All resisted exercises should be performed with the underlying goal of improving functional ROM and strength, while ensuring normal scapulohumeral rhythm is maintained.

Resistance is initially applied with the addition of light dumbbells or light resistance bands to the nonresisted isotonic exercises previously described in Phase II. Resistance band exercises, which provide concentric and eccentric components, can be incorporated below shoulder level in the scapular plane at this time. Patients may not be able to perform full active motion initially with the addition of resistance; therefore, initial band strengthening may consist of isometric holds or require modified positions for optimal muscle activation without compensation. The internal and external rotators of the glenohumeral joint are commonly strengthened in a standing position with a towel roll under the arm to place the glenohumeral joint in a neutral scaption position. Forward punches to 90° of glenohumeral forward elevation with a “plus” are utilized to promote strengthening of the serratus anterior and for functional strength above waist level (Figures 7 and 8). These may need to be initiated in a seated assisted position prior to transi-

Figure 7. Prone extension with external rotation.

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Figure 8. Forward elevation with resistance band to facilitate external rotation.

Figure 9. Seated, assisted forward elevation with external rotation resistance.

tion to standing. Resisted rows are also commenced at this time, beginning first in a prone position with light dumbbells prior to transitioning to standing position with resistance bands. Resisted biceps and triceps exercises can also be incorporated at this time with either light dumbbell or band resistance, progressing as appropriate. Resisted exercises can be progressed to shoulder height and above as tolerated by the patient.

It is imperative to emphasize proper scapular position in order to maintain proper glenohumeral kinematics with the addition of the resisted load.

Proprioceptive exercises are also progressed within this phase with the addition of a TheraBandTM FlexBarÂŽ (Performance Health, Akron, OH, USA), resistance band, or manual perturbations in various functional positions beginning below shoulder height in the scapular plane, progressing to shoulder height as appropriate. Initial closed kinetic chain exercises are also initiated to improve neuromuscular control, muscular strength and proprioception of the glenohumeral joint. Closed chain exercises are typically initiated in a low load position while standing with hands on a wall,

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Figure 10. Single-arm assisted forward elevation with serratus assisted plus.

progressing to a declined or quadruped position. Plank positions on the floor may be too demanding at this time secondary to strength deficits for patients who have undergone SCR. Initial closed chain activities consist of weight shifts, scapular protraction/retraction “plus,” static holds with and without manual perturbations, double arm to single arm support, and shallow push-ups if appropriate. It is important to consider the functional deficits of each patient when prescribing specific exercises, ensuring they are appropriate for and relate to established functional goals.

This is typically the final phase of rehab prior to discharge from physical therapy depending on each patient’s functional requirements for daily activities, work and recreational activities. Physical therapists should expect to spend an extended duration of time in this phase of rehabilitation for patients who have undergone SCR as compared to those who have undergone massive rotator cuff repair. Patients who do not require high levels of overhead function and exhibit sufficient strength may begin to return to full daily activities and recreational activities below shoulder level. Patients whose activities demand a higher level of function from the shoulder, including repetitive or overhead activities, may find themselves limited initially as preliminary outcome studies following SCR indicate functional improvements up to two years postoperatively.13

Phase IV – Advanced Strength and Return to Activity This phase of rehabilitation typically consists of overhead strengthening, advanced closed chain, proprioceptive and plyometric exercises. Based on the functional status and strength achieved at this point post-operatively, patients may or may not be appropriate for this phase of rehabilitation. The physical therapist should focus on specific functional requirements based on strength deficits.

As patients continue to build strength, treatment should focus on progressing endurance with highexertion daily activities as well as work and recreational activities at or below shoulder height. It may be challenging for patients who undergo SCR to return to work activities requiring heavy lifting or repetitive overhead lifting as they may not demonstrate sufficient strength to support these types of activities. Return to higher level overhead sports may also prove difficult, and patients may not be able to achieve sufficient muscular power required for these types of activities. Physical therapists and patients can instead focus on recreational activities performed at or below shoulder height, including but not limited to cycling, shooting and golfing.

CONCLUSION This clinical commentary describes a rehabilitation protocol following superior capsule reconstruction.

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Post-operative rehabilitation begins with close communication between the surgeon, the patient, and the physical therapy team. A review of surgical findings is mandatory to establish rehabilitation guidelines. Once post-operative restrictions have been established, a rehabilitation protocol is customized based on surgical findings and patient goals. The standard protocol is characterized by four phases and starts with restrictions on movement lasting six weeks. The aim is to minimize stress placed on the implanted graft to facilitate early graft-to-bone healing. Afterwards, Phase II starts with restoring passive and active range of motion, managing pain, and improving endurance of the rotator cuff. Phase III consists of advancement of strength and functional restoration of ROM followed by Phase IV consisting of overhead strengthening, advanced closed chain, proprioceptive and plyometric exercises, as appropriate.

REFERENCES 1. Bedi A, Dines J, Warren RF, Dines DM. Massive tears of the rotator cuff. J Bone Joint Surg Am. 2010;92:18941908.

2. Greenspoon JA, Petri M, Warth RJ, Millett PJ. Massive rotator cuff tears: pathomechanics, current treatment options, and clinical outcomes. J Shoulder Elbow Surg. 2015;24:1493-1505.

3. Laron D, Samagh SP, Liu X, Kim HT, Feeley BT. Muscle degeneration in rotator cuff tears. J Shoulder Elbow Surg. 2012;21:164-174.

4. Galatz LM, Ball CM, Teefey SA, Middleton WD, Yamaguchi K. The outcome and repair integrity of completely arthroscopically repaired large and massive rotator cuff tears. J Bone Joint Surg Am. 2004;86-a:219-224.

5. Yamaguchi K, Tetro AM, Blam O, Evanoff BA, Teefey SA, Middleton WD. Natural history of asymptomatic rotator cuff tears: a longitudinal analysis of asymptomatic tears detected sonographically. J Shoulder Elbow Surg. 2001;10:199-203.

6. Zingg PO, Jost B, Sukthankar A, Buhler M, PďŹ rrmann CW, Gerber C. Clinical and structural outcomes of nonoperative management of massive rotator cuff tears. J Bone Joint Surg Am. 2007;89:1928-1934.

7. Berth A, Neumann W, Awiszus F, Pap G. Massive rotator cuff tears: functional outcome after debridement or arthroscopic partial repair. J Orthop Traumatol. 2010;11:13-20.

8. Burkhart SS, Nottage WM, Ogilvie-Harris DJ, Kohn HS, Pachelli A. Partial repair of irreparable rotator cuff tears. Arthroscopy. 1994;10:363-370.

9. Heuberer PR, Kolblinger R, Buchleitner S, et al.

Arthroscopic management of massive rotator cuff tears: an evaluation of debridement, complete, and partial repair with and without force couple restoration. Knee Surg Sports Traumatol Arthrosc.

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10. Zvijac JE, Levy HJ, Lemak LJ. Arthroscopic subacromial decompression in the treatment of full thickness rotator cuff tears: a 3- to 6-year follow-up.

Arthroscopy. 1994;10:518-523.

11. Namdari S, Voleti P, Baldwin K, Glaser D, Huffman GR. Latissimus dorsi tendon transfer for irreparable rotator cuff tears: a systematic review. J Bone Joint Surg Am. 2012;94:891-898.

12. Mihata T, McGarry MH, Pirolo JM, Kinoshita M, Lee TQ. Superior capsule reconstruction to restore superior stability in irreparable rotator cuff tears: a biomechanical cadaveric study. Am J Sports Med. 2012;40:2248-2255.

13. Mihata T, Lee TQ, Watanabe C, et al. Clinical results of arthroscopic superior capsule reconstruction for irreparable rotator cuff tears. Arthroscopy.

2013;29:459-470.

14. Petri M, Greenspoon JA, Millett PJ. Arthroscopic Superior Capsule Reconstruction for Irreparable Rotator Cuff Tears. Arthrosc Tech. 2015;4:e751-755.

15. Ahmad CS, Kleweno C, Jacir AM, et al.

Biomechanical performance of rotator cuff repairs with humeral rotation: a new rotator cuff repair failure model. Am J Sports Med. 2008;36:888-892.

16. Su WR, Budoff JE, Luo ZP. The effect of anterosuperior rotator cuff tears on glenohumeral translation. Arthroscopy. 2009;25:282-289.

17. Burkhart SS. Arthroscopic treatment of massive rotator cuff tears. Clinical results and biomechanical rationale. Clin Orthop Relat Res. 1991:45-56.

18. Burkhart SS. Fluoroscopic comparison of kinematic patterns in massive rotator cuff tears. A suspension bridge model. Clin Orthop Relat Res. 1992:144-152.

19. Parsons IM, Apreleva M, Fu FH, Woo SL. The effect of rotator cuff tears on reaction forces at the glenohumeral joint. J Orthop Res. 2002;20:439-446.

20. Thompson WO, Debski RE, Boardman ND, 3rd, et al.

A biomechanical analysis of rotator cuff deďŹ ciency in a cadaveric model. Am J Sports Med. 1996;24:286292.

21. Hansen ML, Otis JC, Johnson JS, Cordasco FA, Craig EV, Warren RF. Biomechanics of massive rotator cuff tears: implications for treatment. J Bone Joint Surg Am. 2008;90:316-325.

22. Nam D, Maak TG, Raphael BS, Kepler CK, Cross MB, Warren RF. Rotator cuff tear arthropathy: evaluation,

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Gerber C, Fuchs B, Hodler J. The results of repair of massive tears of the rotator cuff. J Bone Joint Surg Am. 2000;82:505-515.

Katthagen J, Tahal D, Millett P. Arthroscopic Superior Capsule Reconstruction for Irreparable Rotator Cuff Tears. Orthopaedics Today. 2016.

Gupta AK, Hug K, Boggess B, Gavigan M, Toth AP. Massive or 2-tendon rotator cuff tears in active patients with minimal glenohumeral arthritis: clinical and radiographic outcomes of reconstruction using dermal tissue matrix xenograft. Am J Sports Med. 2013;41:872-879.

Osbahr DC, Cawley PW, Speer KP. The effect of continuous cryotherapy on glenohumeral joint and subacromial space temperatures in the postoperative shoulder. Arthroscopy. 2002;18:748-754.

Thigpen CA, Shaffer MA, Gaunt BW, Leggin BG, Williams GR, Wilcox RB, 3rd. The American Society of Shoulder and Elbow Therapistsâ&#x20AC;&#x2122; consensus statement on rehabilitation following arthroscopic rotator cuff repair. J Shoulder Elbow Surg. 2016;25:521535.

Wilk KE, Arrigo C. Current concepts in the rehabilitation of the athletic shoulder. J Orthop Sports Phys Ther. 1993;18:365-378.

Ballantyne BT, Oâ&#x20AC;&#x2122;Hare SJ, Paschall JL, et al.

Electromyographic activity of selected shoulder muscles in commonly used therapeutic exercises.

Phys Ther. 1993;73:668-677; discussion 677-682.

30. Reinold MM, Wilk KE, Fleisig GS, et al.

Electromyographic analysis of the rotator cuff and deltoid musculature during common shoulder external rotation exercises. J Orthop Sports Phys Ther.

2004;34:385-394.

31. Blackburn TA, McLeod WD, White B, Wofford L. EMG analysis of posterior rotator cuff exercises. Athl Train. 1990;25:41-45.

32. Townsend H, Jobe FW, Pink M, Perry J. Electromyographic analysis of the glenohumeral muscles during a baseball rehabilitation program.

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33. Graichen H, Hinterwimmer S, von Eisenhart-Rothe R, Vogl T, Englmeier KH, Eckstein F. Effect of abducting and adducting muscle activity on glenohumeral translation, scapular kinematics and subacromial space width in vivo. J Biomech.

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34. Alizadehkhaiyat O, Hawkes DH, Kemp GJ, Frostick SP. Electromyographic analysis of the shoulder girdle musculature during external rotation exercises.

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35. Ekstrom RA, Donatelli RA, Soderberg GL. Surface electromyographic analysis of exercises for the trapezius and serratus anterior muscles. J Orthop Sports Phys Ther. 2003;33:247-258.

36. Reinold MM, Macrina LC, Wilk KE, et al.

Electromyographic analysis of the supraspinatus and deltoid muscles during 3 common rehabilitation exercises. J Athl Train. 2007;42:464-469.

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IJSPT

CLINICAL COMMENTARY

REHABILITATION FOLLOWING MEDIAL PATELLOFEMORAL LIGAMENT RECONSTRUCTION FOR PATELLAR INSTABILITY Robert C. Manske, PT, DPT, MEd, SCS, ATC, CSCS1,2,3 Daniel Prohaska, MD4,5

ABSTRACT Patellar instability is a common problem seen by physical therapists, athletic trainers and orthopedic surgeons. Although following an acute dislocation, conservative rehabilitation is usually the first line of defense; refractory cases exist that may require surgical intervention. Substantial progress has been made in the understanding of the medial patellofemoral ligament (MPFL) and its role as the primary stabilizer to lateral patellar displacement. Medial patellofemoral ligament disruption is now considered to be the essential lesion following acute patellar dislocation due to significantly high numbers of ruptures following this injury. Evidence is now mounting that demonstrates the benefits of early reconstruction with a variety of techniques. Recently rehabilitation has become more robust and progressive due to our better understanding of soft tissue reconstruction and repair techniques. The purpose of this manuscript is to describe the etiology of patellar instability, the anatomy and biomechanics and examination of patellofemoral instability, and to describe surgical intervention and rehabilitation following MPFL rupture.

Key words: Knee, patellar instability, rehabilitation, surgery Level of Evidence: 5

1

Wichita State University, Wichita, KS, USA Via Christi Sports and Orthopedic Physical Therapy, Wichita, KS, USA 3 Via Christi Department of Family Medicine, University of Kansas School of Medicine Sports Medicine Fellowship Program, Wichita, KS, USA 4 Advanced Orthopedic Associates, Wichita, KS, USA 5 University of Kansas School of Medicine, Wichita, KS, USA. 2

CORRESPONDING AUTHOR Robert C. Manske, PT, DPT, MEd, SCS, ATC, CSCS Professor and Chair Wichita State University Department of Physical Therapy 358 North Main Wichita, KS 67202 E-mail: Robert.manske@wichita.edu

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BACKGROUND AND PURPOSE Patellar instability is a common complaint seen by physical therapists, athletic trainers and surgeons.

Patellar instability in athletes is a general umbrella term used for either patellar subluxation or dislocation.1 Dislocation and subluxations can occur due to repetitive micro trauma over time creating a gradual progression of instability of a chronic nature. However, instability can also occur due to an acute event such as a patellar dislocation in which localized trauma has forced the patella laterally out of the safe confines of the patellar trochlea of the distal femur.

Lateral patellar dislocations are the most common knee dislocation injury among young adults.2 One structure that helps maintain patellar stability is the medial patellofemoral ligament (MPFL). Substantial progress has been made in the understanding of the MPFL and its role as the primary stabilizer to lateral patellar displacement. MPFL disruption is now considered to be the essential lesion following acute patellar dislocation due to significantly high numbers of ruptures following this injury. Evidence is now mounting that demonstrates the benefits of early reconstruction with a variety of techniques.

Actual dislocations of the patella represent a sparse 2%-3% of all knee injuries.3 Historically these injuries have occurred more commonly in females than in males.4 Nonoperative treatment has been recommended for this injury,5.6 however, conservative treatment of this condition is often of little value as recurrent dislocation occurs in up to 15% to 44% of patients who have sustained a traumatic patellar dislocation.7-11 In persons who have had two prior episodes of dislocations the recurrence rate jumps to 49%.8 Maenpaa and Lehto report that in more than half of the patients, a first time patellar dislocation left untreated or treated nonoperatively will lead to instability and recurrent dislocations.12 These findings are similar to those of McManus et al who report that the natural history of a nonoperatively treated patellar dislocation involves re-dislocation in one of six cases; other residual symptoms in two of six, and three of six cases will be asymptomatic.13 Collectively these studies indicate that conservative treatment with a period of immobilization followed by physical therapy is associated with re-dislocation rates of upwards of 63%. Those who do not re-dislocate may

continue to have persistent patellofemoral problems and disability and even femorapatellar osteoarthrosis.14 Risk factors for recurrent instability include young age, immature physes, sports-related injuries, patella alta and trochlear dysplasia.9 Other predisposing factors that can contribute to chronic patellar instability include: femoral anteversion, external tibial torsion, genu valgum, patellar dysplasia, vastus medialis obliquus atrophy, pes plannus, and generalized ligamentous laxity.15 Patellar instability can be the result of multiple problems including structural anatomical abnormalities, or insufficient soft tissue restraints.16 Examples of structural abnormalities and insufficient soft tissue restraints include vastus medialis weakness, tight lateral structures such as the tensor fascia lata/ iliotibial band, and lateral retinaculum. Other anatomical variations that can create this multifactorial problem include patella alta, increased quadriceps angle, excessive tibial tubercle-trochlear groove distance, trochlear dysplasia and ligament hyperlaxity.6,17-19 The purpose of this manuscript is to describe the etiology of patellar instability, the anatomy and biomechanics and examination of patellofemoral instability, and to describe surgical intervention and rehabilitation following MPFL rupture.

ANATOMY Patellar stability is afforded by both active and passive restraints. Active restraints to the anterior knee are the quadriceps muscle group. Both the rectus femoris and the vastus intermedius have a direct line of pull along the long axis of the femur. The vastus lateralis and the vastus medialis both have, although at slightly different angles, an oblique insertion onto the patella which allows for medial and lateral patellar stabilization. Collectively these muscles provide dynamic patellofemoral stability.

Passive patellar stability is provided by several soft tissue structures including the patellar tendon and the patellar retinaculum. The patellar tendon is the distal component of the quadriceps tendon. The patellar retinaculum is different on the lateral and medial sides. The lateral complex is more intricate and includes two different structures: the superficial oblique retinaculum and the deep transverse retinaculum.20 The medial side of the retinacular

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structures are quite different and include the medial meniscopatellar ligament and the MPFL. In the three-layer description of the medial side of the knee, the MPFL lies in the second layer.21 The MPFL was originally thought to be present in only 29%89% of knees.22,23 It is now commonly accepted that this structure is present in all knees and that it is the major medial static stabilizer of the patellofemoral joint.24-27 The MPFL is unique in that the anterior portion interdigitates with the deep fibers of the vastus medialis obliquus (VMO) (Figure 1), suggesting that it might work together with the VMO supplying medial stabilization. The VMO is the oblique, medial portion of the quadriceps that is thought to provide dynamic medial patellofemoral restraint. In concert these two structures appear to draw the patella from its slightly lateralized position in full extension, moving the patella medially toward the trochlea such that the patella enters the trochlea during early knee flexion movements.28 The anatomical origin of the MPFL has been described in multiple locations. Warren and Marshall report that the MPFL is located at the region

of the superficial medial collateral ligament.21 Feller and colleagues report it to be anterior to the medial epicondyle.29 Steensen describes the origin as the actual anterior medial epicondyle,30 while multiple authors report that its origin is simply at the medial epicondyle.27,31-34 BIOMECHANICS Numerous studies have examined the biomechanical contributions and restraint provided by the MPFL. Amis has shown that the native MPFL is not a very robust ligament; when compared to others in the knee it only withstands loads of about 208N when tested to failure at 25 mm of displacement.31 The MPFL provides from 50-60% of the restraint to lateral patellar translation during the ranges of 0-30 degrees of knee flexion.22,24,25 If the MPFL is sectioned, the patella displaces laterally, even with the other medial stabilizers intact.25,26 Amis and colleagues suggest that this ligament is tightest near full extension and loses tension as the knee is flexed.31 However, McCulloch et al report that the actual highest increase in strain occurred between 25-30 degrees of knee flexion.35 This may be biomechanically appropriate as the patella generally enters the trochlea near 15-20 degree of knee flexion and thus has improved bony support and congruence in that range and further into flexion.

The MPFL rupture at a mean elongation of 26 +/-7 mm in cadaveric specimens.36 Because the mean length of the MPFL is 53 mm, ruptures occur at approximately 49% strain.37 The average width of the MPFL is 1.9 cm.37

Figure 1. A image of the medial aspect of the right knee with the patella at the top. The MPFL, passing over the forceps, links the proximal half of the medial border of the patella to the medial femoral condyle. The superďŹ cial fascia and distal part of the vastus medialis obliquus have been removed. Permission granted by Mountney J, Senavongse W, Amis AA, Thomas NP.Tensile strength of the medial patellofemoral ligament before and after repair or reconstuction. J Bone Joint Surg. 2005;87B(1):36-40.

TEAR CLASSIFICATION Nomura described a classification for tears based on surgical findings from 67 knees following acute or recurrent patellar dislocation.38 Focal injury was seen in 17/18 knees with acute patellar dislocation.

These injuries were categorized into Type I and Type II injuries. Type I are avulsion type or detachments of the ligament from its femoral attachment. Type II injuries are intra-substance tears of the ligament.

The location of these intra-substance tears was usually near the normal femoral attachment of the ligament. In all knees with recurrent patellar dislocation the MPFL was abnormal. Abnormality was

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described as three different types: Type I included no MPFL injury that was seen by gross inspection, but ligament was loose at its femoral attachment; Type II consisted of scar tissue either in the body of the MPFL or between the ligament and its femoral attachment (but both are loose); Type III was termed “absent” type, in which the ligament consisted of a remnant that lacked continuity or could not be identified.

HISTORY As with most knee conditions, obtaining a subjective medical history is critical to the success of any evaluation of musculoskeletal injuries and is never more important than in the knee.39 The medical history should be performed in a consistent and orderly fashion with every patient in order to obtain crucial information without missing important findings.40 Most patients will tell you their problems if you listen closely and ask the appropriate questions. Acute traumatic patellar dislocation can occur due to a single inciting incident; however subluxation of the patella may occur as recurrent patellar instability due to repetitive minor trauma. In some instances there may not be a blow to the knee during the injury mechanism. In general, patellar dislocations or subluxations occur in the lateral direction however, although rare, medial displacement can also occur. In most cases these injuries are the result of a noncontact, quick turning incident, in a single direction with the femur and tibia moving in opposite directions. This can occur during a plant and cut maneuver or trying to fake someone out quickly, in which the femur internally rotates while the tibia remains relatively externally rotated. Regardless of the mechanism, the athlete almost always feels a vivid sensation of bony subluxation. The patient may describe the patella’s position grossly laterally or just a medial prominence. Do not be fooled, as the medial prominence may actually be the uncovered medial femoral condyle that can clearly be seen due the laterally displaced patella. The laterally displaced patella will stay displaced as long as the knee remains flexed. With the help of a sports physician, athletic trainer or therapist movement of the knee into extension will usually cause an abrupt relocation, with which a “clunk” or shifting sensation is felt, providing significant pain relief. Historically a

first time acute patellar dislocation results in significant effusion in the knee. In the athlete with a chronic recurrent dislocation the swelling and effusion may be much more subtle.

EXAMINATION General Examination Any evaluation of a knee disorder should be performed with the patient dressed in shorts with the knees clearly exposed. Physical examination of patellar instability can be done in the face of an acute dislocation, which will be done completely different than that of the athlete with a more chronic condition. Pending the time frame between dislocation and examination the patella may still be dislocated and displaced laterally. Just because the patella presents in its correct position it cannot be assumed that it was not dislocated previously. Within several hours of an acute dislocation, a significant effusion will be present. This may limit the ability to perform a thorough examination due to limited knee mobility due to swelling. There will likely be tenderness along the medial retinaculum, the MPFL and the adductor tubercle. With these described symptoms it is best to assume that the patella has been dislocated until proven otherwise. Swelling, range of knee motion, palpation, and the amount of passive patellar mobility should always be compared to the uninvolved side. A more complete physical examination can be performed on the suspected recurrent patellar dislocation patient as they will not be as irritable as the patient with an acutely dislocated patella.

STANDING EXAMINATION In the standing position the patient should be assessed for multiple things. Equality of weight bearing can be easily viewed in this position, as can varus and valgus alignment. An athlete with miserable malalignment syndrome (MMS) can be predisposed to patellar instability.40 MMS is a constellation of several functional deformities which include internal rotation of the femur, with accompanied bayonet deformity of the tibia, external tibial torsion, and pronated feet. Due to significant swelling, and because maximal capsular volume of the knee is in 25-30 degrees of knee flexion, the patient may stand or walk with the knee in a flexed position.

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SEATED EXAMINATION The seated examination allows the clinician to view the knee in resting position from anterior, medial and lateral aspect. Where is the patella sitting passively in a relaxed seated position? In a patient with a large degree of patella alta the patella will be resting high and laterally in what is called â&#x20AC;&#x153;grasshopper eyesâ&#x20AC;? position. Patella alta can be determined by an Insall-Savalti measurement of greater than 1:1 ratio of patellar tendon length to patellar height. If the length of the patellar tendon is greater than the height of the patella a patella alta exists. This may predispose the athlete to recurrent patellar subluxations or dislocations due to excessive patellar tendon length.

The tibial tubercle sulcus angle can be measured with the athlete sitting over the edge of the treatment table with the knee flexed 90 degrees. The clinician observes the position of the tibial tubercle relative to the patellar center. The first line, a vertical line drawn from the center of the patella while the second is drawn from the center of the patella to the tibial tubercle. The tibial tubercle should be within the femoral trochlea when the knee is flexed 90 degrees. Controversy exists on what a normal angle shoulder be, as ranges from 0 degrees to 10 degrees have been reported.41,42 Passive and active patellar tracking can also be assessed in the seated position. The tripod position, (leaning backwards slightly supported by both hands with a slight posterior pelvic tilt) is assumed to decrease hamstring tightness during testing. The clinician passively extends the relaxed patients knee from flexion to full extension. During this movement the patella translates from a slightly lateral position in flexion to a medial position as the knee extends, and eventually back laterally again near full extension. Slight variations sometime exist between individuals and even between right and left knees of the same individual, so small deviations should not be of great concern. As this is a passive test, it assesses osseous and non-contractive tissues.

Excessive lateral gliding usually indicates tightness of the superficial retinacular fibers, whereas excessive tilting would indicate excessive deep retinacular restraint. Following performance of the passive portion of this test, the clinician should examine

an active component by having the athlete actively extend their knee fully. A similar type of movement should be seen if passive patellar tracking is normal.

The clinician should watch for an abrupt lateral displacement between the range of 20-30 degrees of flexion to full extension as the patella is deviated or subluxed laterally. This may be indicative of a dysfunctional vastus medialis obliquus muscle lacking dynamic medial stability.

Strength can be tested via manual muscle testing of the quadriceps and hamstring muscle groups while seated.

Manual muscle testing of hip muscles can be done in supine, side lying and prone. Adequate strength of all hip muscles and musculature of the trunk/core is needed to ensure proper proximal control.

SUPINE EXAMINATION Supine examination includes examination of passive patellar mobility, knee swelling and effusion and manual muscle testing of proximal hip musculature.

Assessment of passive patellar mobility is done in slight (20-30 degrees) of knee flexion, to engage the trochlea. The patella is then passively translated in both the medial and lateral directions in the frontal plane (Figure 2). Patellar mobility is described in quadrants of movement. The width of the entire patella is four quadrants. Thus two quadrants of movement would indicate movement that is equal to half the patellaâ&#x20AC;&#x2122;s width. Normal patellar mobility is from 1-3 quadrants of passive movement in either direction. Less than 1 quadrant of passive mobility demonstrates hypomobility while passive movement greater than 3 quadrants demonstrates hypermobility.42 Following MPFL reconstruction passive mobility of 2 quadrants is desirable in the medial and lateral directions.

Swelling and joint effusion should be measured in all patients complaining of knee pain. Circumferential measurements can be taken at several different spots around the knee; In particular, measuring at the joint line is suggested for generalized joint effusion. An additional location in a patient with suspected patellar instability would be at an area approximately 10 cm proximal to the knee joint which is the area around the vastus medialis oblique which may be selectively atrophied due to pain and inhibition from knee pain.

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pain, and even medial patellar instability due to iatrogenic causes.47-50 Indications for MPFL reconstruction include recurrent patellar instability that has failed standard nonoperative management. The role of MPFL reconstruction for acute patellar dislocation and isolated trochlear dysplasia has not been clearly determined as of the publication of this manuscript.

SURGICAL TECHNIQUE Surgical reconstruction of the MPFL is performed in the following steps. A thorough examination under anesthesia is performed to assess ligament stability and evaluate the mobility of the patella with special attention to the lateral glide. This is checked both in extension (Figure 3) and in flexion (Figure 4).

Diagnostic arthroscopy is performed to evaluate the patellofemoral articular surfaces evaluating for any chondral damage and treating as indicated (Figure 5). Patellar articular surface injury may require debridement of loose cartilage or if severe may require a osteochondral repair type procedure in addition to the MPFL reconstruction.

Figure 2. Examination of passive patellar mobility. A) The examiner uses thumb to determine midline of patella to determine amount of translation, B) translation of the patella in the lateral direction assessing the amount of passive patellar mobility. Following MPFL reconstruction the desired amount of passive patellar mobility should be approximately 2 quadrants or half the width of the patella.

INDICATIONS FOR SURGERY Conservative treatment is universally attempted in an effort to strengthen the dynamic stabilizers of the anterior knee. When non-operative rehabilitation does not offer a satisfactory outcome regarding stability, surgical reconstruction of the MPFL may be offered. MPFL reconstruction has been shown to be an acceptable method to restore static stabilizing structures.25,43-46 Historically traditional procedures to address patellar dysfunction such as medial retinacular reefing or the lateral release have been utilized to address chronic patellar instability but these often result in continued instability, anterior knee

Reconstruction of the MPFL should attempt to reproduce the native ligament, restore normal anatomy and function and is designed as a “check rein”, but is not intended to be used as a harness to hold the patella centered in the trochlea. Multiple autograft choices exist including: a hamstring

Figure 3. Pre-operative lateral patellar displacement with knee positioned in flexion. Taken from: Manske RC, Lehecka BJ, Prohaska D. Medial patellofemoral ligament reconstruction for patellar instability. SPTS Home Study Course, Indianapolis, IN. 2010.

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Figure 4. Pre-operative lateral patellar displacement with knee positioned in full extension. Taken from: Manske RC, Lehecka BJ, Prohaska D. Medial patellofemoral ligament reconstruction for patellar instability. SPTS Home Study Course, Indianapolis, IN. 2010.

Figure 5. Diagnostic arthroscopy demonstrating patellar instability.

tendon,43,45 the adductor magnus,,51,52 a portion of the quadriceps tendon,53,54 or a medial strip of the quadriceps tendon. Each of these can be used leaving the patellar attachment intact. Allograft tissue has been used, with outcomes that are acceptable, including no undue risk for re-rupture, and no donor site morbidity.55,56 The graft is secured to the patella either by tunnels passing the graft through the patella and anchoring

Figure 6. Location of double incisions used for MPFL reconstruction. Taken from: Manske RC, Lehecka BJ, Prohaska D. Medial patellofemoral ligament reconstruction for patellar instability. SPTS Home Study Course, Indianapolis, IN. 2010.

Figure 7. solating hamstring tendons used for MPFL reconstruction. Taken from: Manske RC, Lehecka BJ, Prohaska D. Medial patellofemoral ligament reconstruction for patellar instability. SPTS Home Study Course, Indianapolis, IN. 2010.

on the far side or with an interference screw, or by looping the graft through the patella with no actual fixation in the patella itself. A double incision is used for proper tunnel and graft placement (Figure 6). When using hamstring autografts, the hamstring tendons must first be isolated and procured (Figure 7). The graft is passed between the soft tissue layers from the patella to its position of attachment on the medial femoral condyle making sure that the graft stays outside the knee capsule.Â

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Figure 8. After graft ďŹ xation, tension is set so that there is no undue tension on the medial side. The graft should become a passive tether, not to create a medial pull. Taken from: Manske RC, Lehecka BJ, Prohaska D. Medial patellofemoral ligament reconstruction for patellar instability. SPTS Home Study Course, Indianapolis, IN. 2010.

It is important to use bony landmarks and often fluoroscopy is employed to ensure that the graft entrance to the femur is in the correct location. After fixation of the graft, tension is set so that there is no excessive strain on the medial side of the knee (Figure 8). The knee is taken through full range of motion to ensure that the graft does not change in length and tighten or loosen. For example, if the femoral site is too proximal, the graft will be tight in flexion, and so the tunnel needs to be repositioned. Failure to change the tunnel may lead to a knee that has excessive loss of flexion after reconstruction. Following graft fixation, lateral patellar translation is again assessed to ensure proper tension (Figure 9).

Fixation on the femur can be done with interference screw, anchors in bone, or distal button fixation.

Post operatively the knee is placed in a compressive soft dressing and cold therapy is utilized. Surgery is done on an outpatient basis.

REHABILITATION FOLLOWING MPFL RECONSTRUCTION Return to activity following MPFL will follow a four phase progression of rehabilitation that gradually allows an increase in range of motion and quadriceps activation, in order to allow a full return to prior

Figure 9. Post-operative lateral patellar translation at 30 degrees of ďŹ&#x201A;exion showing excellent stability. Taken from: Manske RC, Lehecka BJ, Prohaska D. Medial patellofemoral ligament reconstruction for patellar instability. SPTS Home Study Course, Indianapolis, IN. 2010.

activity level. These four phases are typical of other postoperative procedures for the knee and include: Protective Phase (day one to week 6), Moderate Protection Phase (Weeks 7 to 12), Minimum Protection Phase (Weeks 13 to 16), and Return to Full Activity Phase (Weeks 17-20+). Because not all patients heal in the same speed or manner, within the descriptions of each of these postoperative phases, clinical milestones are listed which allow the clinician to better know when the patient can be progressed to another phase.

PHASE I: PROTECTIVE PHASE (DAY 1 TO WEEK 6) Goals for this initial phase following reconstruction include protecting the repair, decreasing pain and inflammation, preventing the negative effects of immobilization, restoring knee range of motion and arthrokinematics, preventing hypomobility, promoting dynamic stability, preventing reflex inhibition and secondary muscle atrophy, developing neuromuscular control of the knee and maintaining core stability.

When MPFL reconstruction is performed independently, Phase I begins within 2-3 days of the surgery. This surgical procedure can also be performed concomitantly with a lateral release or distal

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realignment procedure and may require additional immobilization periods.

non-weight bearing, instructed not to exercise their knee, and were immobilized in a knee brace during the initial postoperative weeks.65

With isolated MPFL reconstruction, ambulation is weight bearing as tolerated and range of motion is progressed as tolerated immediately. Strict immobilization of the knee can result in loss of ground substance and dehydration and approximation of embedded fibers in the extracellular matrix of soft tissues.57 Because the surgical reconstruction of the MPFL requires operating at or near the medial epicondyle of the knee, early motion is indicated. During flexion and extension motion at the knee there is substantial movement of soft tissues around the medial epicondyle and therefore stiffness and loss of motion is common.58 Although some report a restriction of motion and weight bearing are required to protect against additional soft tissue injury following MPFL surgery,59,60 the authors of this manuscript suggest that immobilization is not worth the risk of post-operative stiffness. To decrease this risk of stiffness, range of motion is initiated progressively and early. Immediate range of motion as tolerated is allowed because the MPFL experiences maximal loads near full knee extension and during early knee flexion range of motion.28 As long as the graft is placed isometrically, increases in knee flexion range of motion should not place undue strain on the substitute tissue. Controlled mobilization reverses the effects of immobilization by stimulating collagen synthesis and optimizing alignment of healing tissues.61,62 This is of particular concern in ligaments as studies in animals have clearly shown that following even a few weeks of immobilization results in marked decreases in structural properties.63,64 These decreased properties occur due to subperiosteal bone resorption within the insertion sites as well as microstructural changes within the ligament substance. Remobilization was found to reverse the changes, however it took up to one year to return the properties to normal levels following only nine weeks of immobilization. A systematic review of eight papers of investigations following rehabilitation for MPFL reports that there is little differences in radiological or clinical outcomes between patients who were initially full weight bearing, began immediate active exercises, and were not immobilized in a knee brace, compared to those who were initially

Because post-surgical pain and swelling are known to inhibit quadriceps muscle control, both cryotherapy and electrical stimulation are used to alleviate pain by decreasing nerve conduction velocity and releasing endogenous opiates.66-70 In addition to these modalities the knee should be covered with a compression wrap of some form. The compressive dressing could be an ace wrap or â&#x20AC;&#x153;tube gripâ&#x20AC;? type wrap to decrease existing swelling or prevent the onset of further swelling. The knee should also be kept in elevation early over the first 1-2 days following surgery.

Range of motion is initiated and progressed per surgeonâ&#x20AC;&#x2122;s protocol. The native intact MPFL has a load to failure rate of 208N.36,71,72 When the tibialis anterior is used as a graft substitute, its load to failure strength is 1553N,73 while a single strand of semitendinosus load to failure strength is 1060N.74 Due to the strength of substitute grafts, motion is provided to the knee and patellofemoral joint. After an assessment of passive patellar mobility, patellar mobilizations may be performed in all directions. Because knee motion stiffness and flexion contractures are one of the top complications following MPFL reconstruction,75 the patella can be mobilized if passive mobility is limited. This is in direct opposition to Cheatham and colleagues76 who report that only grade I and II superior and inferior glides are performed at the patellofemoral joint as they feel that medial and lateral glides may stress the surgical site. As long as fixation is appropriate concern regarding the stress of grade III and IV patellar mobilizations is not warranted.

Patellar passive mobility of at least two quadrants in both the medial and lateral directions is desired. If there are less than two quadrants of passive mobility, joint mobilizations are instituted (Figure 10). As with most postoperative knee procedures the first post-operative priority is always gaining full extension to decrease the risk of developing a flexion contracture (Figure 11). Cyclops lesions, as seen with anterior cruciate ligament reconstructions, are not commonly reported following MPFL reconstruction, however capsular and or infrapatellar fat pad contracture, quadriceps inhibition, and poorly placed grafts can lead to motion complications.58

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Figure 10. Treatment of a hypomobile patellofemoral joint following MPFL reconstruction. Lack of passive mobility following reconstruction is one of the most common causes of surgical failure. If the athlete does not have a minimum of 2 quadrants passive patellar mobility, medial and lateral glide patellofemoral joint mobilizations may be required.

Figure 11. Obtain early full knee extension to prevent ďŹ&#x201A;exion contracture.

The patient should ambulate weight bearing as tolerated progressing to full weight bearing for the first two weeks. Empirically, the authors have seen that typically the patient is full weight bearing within one week, however, it is not uncommon to reserve the second week for crutch use if needed or if pain and swelling persists for a longer amount of time.

Early exercises include quadriceps sets, heel slides, hamstring sets and gluteal sets until the patient is

full weight bearing without symptoms. Because the hip and trunk are so important in maintaining proximal control for the knee and the patellofemoral joint, total leg strengthening (TLS) is initiated early. A phased approach is used to progressively strengthen the hip. The exercises used are based on electromyographic (EMG) studies demonstrating the hierarchy of maximal volitional contraction of the surrounding hip musculature.77-80 Bolgla and Boling81 performed a systematic review showing that both quadriceps and hip strengthening exercises are helpful to reduce pain in those with patellofemoral pain syndrome.

They are also the mainstay during MPFL rehabilitation. Please see Table 1 for list of exercise in rank order based on percentage EMG activity.

If quadriceps inhibition occurs during this time frame, evidence has demonstrated neuromuscular electrical stimulation to be helpful in reducing strength loss after knee ligament surgery. Neuromuscular electrical stimulation should be performed with the athleteâ&#x20AC;&#x2122;s volitional contraction in order to work optimally.82-85 Empirically, the authors of this manuscript have found that performing the quadriceps contractions in weight bearing increases contractile output better than when performed supine in long sitting.

Because of the replacement graft immediate strength, a brace or immobilizer is not used. Better understanding of graft mechanics and graft loading has resulted in advancement of rehabilitation. Basic exercises can begin including straight leg raises in all four planes, ankle isotonic strengthening in all planes, heel slides, quadriceps, hamstring and gluteal sets and eventually isotonic hamstring curls.

Once full weight bearing is achieved without issues, closed kinetic chain exercises can begin. These include heel raises, mini-squats, progressive stepups and downs, and balance and proprioception.

Clinical milestones for a safe progression at the end of phase I include full non-painful knee range of motion, full weight bearing without antalgia or limp, no increase in pain or swelling, at least 2 quadrants of patellar mobility, and ability to stand on a single leg.

PHASE II: MODERATE PROTECTION PHASE (WEEKS 7-12) Goals for the moderate protection phase include: 1) maintaining full range of motion, 2) maintain repair,

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Table 1. Rank Order of Mean EMG during Exercises for Gluteus Medius and Gluteus Maximus Muscles80 Exercise

Gluteus Medius

Exercise

Gluteus Maximus

Side-lying hip abduc on 81 Single-limb squat 59 Single-limb squat 64 Single-limb deadli 59 Lateral band walk 61 Transverse lunge 49 Single-limb deadli 58 Forward lunge 44 Sideways hop 57 Sideways lunge 41 Transverse hop 48 Side-lying hip abduc on 39 Transverse lunge 48 Sideways hop 39 Forward hop 45 Clam in 60 hip flexion 30 Forward lunge 42 Transverse hop 35 Clam in 30 hip flexion 40 Forward hop 35 Sideways lunge 39 Clam in 30 hip flexion 34 Clam in 60 hip flexion 38 Lateral band walk 27 All values expressed as a % of MVIC. Data reproduced from: Distefano LJ, Blackburn JT, Marshall SW, Padu DA. Gluteal muscle ac va on during common therapeu c exercises. J Orthop Sports Phys Ther 2009;39(7):532-540.

3) gradual initiation of functional activities. During this phase most restrictions have been lifted.

Range of motion should be fairly well established at this time. If not, emphasis on motion should take precedence so as to not end up with an arthrofibrotic knee. Higher grade mobilizations and gentle overpressure to end ranges should be instituted to normalize the arthrokinematics of knee flexion and extension.

Exercises for strengthening in phase II can include a progression of squats by adding weight or adding proprioceptive component by squatting on balance board (Figure 12). Other closed chain exercises can include lunges starting on level ground and progressing to lunging to labile surface. Leg press exercises should be performed both bilaterally (Figure 13) and unilaterally to ensure adequate stimulus to the post-surgical knee. Lateral band walking places significant load on the hip musculature and is a great exercise to progress proximal hip dynamic stability and control (Figure 14).

Other hip exercises that are effective at strengthening at this time are single leg bridge (Figure 15) and hip hiking (Figure 16 A and B). Balance and proprioceptive exercises provide training for a stable base for the rest of the body to move from. The importance of balance and proprioception in athletics cannot be denied. An attempt to regain lost proprioception,

Figure 12. Performance of squat exercise on a balance board providing not only lower extremity strengthening but also a proprioceptive and balance training effect.

regaining dynamic stability and neuromuscular control should be a priority. Neuromuscular training improves the nervous systems ability to generate optimal and fast muscle firing patterns, increases dynamic joint stability, and decreases joint reaction forces, which allows the muscles surrounding the joint to achieve a state of “readiness” to respond to joint forces and stimulus resulting in enhanced motor control.85 Early forms of balance training can begin in partial weight bearing progressing to full weight bearing. These can occur as weight shifting

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Figure 13. Squatting on a leg press can increase the tolerable load in a controlled fashion.

Figure 15. Hip abductors are recruited highly with the lateral band walking drill.

Figure 14. Lateral band walking provides a method of incorporating additional strengthening effect to the hip abductors which are important proximal stabilizers to the leg and improves knee control.

in all directions. Squatting on a balance board or foam pad can help challenge balance and proprioception. Ultimately single-leg balance exercises can be done by applying a light perturbation or by using distractive elements such as throwing and catching a ball while balancing. In this manner perturbation training is done to induce dynamic knee stability allowing patients to develop their own compensation strategies to maintain stability.86 Single-leg exercises can begin including singleleg squats. These should be assessed critically as

Figure 16. A. Hip hike in the down position, B. Hip hike in the up position.

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compensations can occur. These compensations generally result in increased hip adduction, internal rotation and tibial abduction. These can be seen subjectively when performing a single-leg squat with poor control (Figure 17A). At times this can be improved through strengthening exercises however visual and verbal cues may help improve poor postural control (Figure 17B). The clinical milestones for the moderate protection phase are to maintain previous milestones and to have full strength of hip, quadriceps and hamstrings. These milestones are important to be able to tolerate higher level activities in the minimum protection phase.

PHASE III: MINIMUM PROTECTION PHASE (WEEKS 13-16) The minimum protection phase has the shortest time frame, which lasts from 13 to 16 weeks. The primary goals of this phase are to gradually return the athlete to functional activities.

To allow a gradual return to functional and athletic activities the involved knee has to have loads gradually applied up to that of the level needed to perform these higher functional activities such as running and jumping. This can be achieved by ensuring adequate strength through increased resistance and intensity during previous exercises such as squats, lunges, and leg press. Plyometric activities can begin with small bounding bilaterally such as double- leg jumping in place or double- leg jumping across multiple planes (Figure 18). Lateral and medial bounding can also be initiated which places specific stressors to the medial and lateral knee. Progressions of jumping/hopping should always start bilateral (jumping) and progressing to unilateral (hopping). Progressions to single-leg hopping are initiated in the next phase.

Clinical milestones to move into phase IV include all the prior milestones in addition to confidence in knee.

PHASE IV: RETURN TO ACTIVITY (WEEKS 17-21+) Goals for the return to activity phase include 1) progression of functional activities, 2) full return to all

Figure 17. A. Single-leg squat can be performed to examine more functional movement patterns of the entire lower extremity. A) The patient demonstrates poor frontal, transverse and sagittal control. B) improved control is assisted by visualization in front of mirror and verbal cues.

Figure 18. Bilateral jumping without pain or symptoms.

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prior sports or recreational activities. In this goal the athlete is challenged at even higher levels of lower leg stressors that will determine if they are able to return to their prior sporting activities. This level may not be utilized for every patient. Not all patients that have MPFL reconstruction are higherlevel athletes. If they do not desire or require this level of activity they would not be required to be rehabilitated to this level.

Once the athlete is comfortable with bilateral jumping they can attempt unilateral single-leg hopping on one foot. To start, it may be best to hop off of single affected side and landing on the unaffected side.

Athletes following knee surgery are usually more able to hop from the surgical leg concentrically, but more concerned or afraid when asked to land eccentrically on the affected single-leg. Functional drills or activities such as sidestepping, ladder drills, or carioca can be done in a controlled manner to work on neuromuscular control. It is also at this last stage that the athlete can begin interval type programs such as return to running program.

DISCHARGE AND FULL RETURN TO COMPETITION Discharge and full release and return to competitive sports is based on criteria that include: full range of motion, full strength and ability to achieve norms on standardized functional tests. The single leg step down test should be able to be performed with good form.87 This test is performed with the patient standing near the edge of a 20cm step. The patient is asked to place hands on hips and flex the test knee enough to touch the floor gently with opposite extremity. Five repetitions are scored by giving a single point for 1) using arms to maintain balance, 2) trunk lean either medial or lateral, 3) pelvis rotation or elevation, 4) tibial tubercle moving medial to 2nd toe, 5) unsteady unilateral stance; while two points are given for the tibial tubercle moving medial to the foot. A good score is needed to return to sports.

A good quality score is 0-1 point, medium quality is 2-3 points, and poor quality is 4+ points. The step down test has been shown to have good interrater reliability and has the ability to differentiate those with moderate quality of movement (those with less hip abduction strength and decreased quadriceps

flexibility) compared to those with good movement qualities.88 Additionally, jumping and hopping tests are used.

Criteria to be released for return to sports are for the athlete to be able to jump with both legs together horizontally 100% of height for males and 90% of height for females. Single-leg hop distances should be 90% of height for males and 80% of height for females. These are standardized norms for healthy non injured populations.89 Nomura and colleagues90 followed 24 knees with after MPFL reconstruction for a mean follow-up of 11.9 years. Using the Crosby/Insall criteria and Kellgren/Lawrence grading systems and found that the association of knee osteoarthritis following MPFL reconstruction with or without a lateral release was small over the long-term. This is important as other surgical treatments such as proximal or distal realignments has been proven to be associated with osteoarthritis as early as 10 years following the procedure.91-96 Furthermore, Lippacher and colleagues found that of those who participated in sports prior to MPFL reconstruction, 100% returned to sports.97 Fifty-three percent returned to equal or higher levels, whereas 47% returned at lower levels. In those that returned to lower levels of athletics numerous reasons were cited including physical reasons such as decreased knee function and desire to avoid excessive sports after surgery, but also more psychological reasons too such as lack of time or interest and the fact that they were advised to be aware of the risks of high-pivot sports such as soccer.

PATIENT REPORTED OUTCOMES Patient reported outcomes are instruments and rating scales used to measure outcomes from the patientâ&#x20AC;&#x2122;s perspective. These outcomes may at times be very different from our clinical objective measures. These outcome tools examine many facets of knee health including swelling, giving way, pain and ability to function in activities of daily living. The authors of this manuscript recommend several following MPFL reconstruction. The Activities of Daily Living Scale98 and the Sports Activity Scale99 are both knee specific. The Sports Activity Scale have questions more related to higher levels of physical activity that are pertinent in active populations.

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CONCLUSIONS The science behind MPFL reconstruction and the ensuing rehabilitating continue to evolve as more evidence becomes available. The suggested protocol will help guide the patient to full recovery to sports and/or recreational activities without complications. An early emphasis on range of motion followed by a progression of strengthening exercises allows adequate incorporation of the soft tissue graft to the bony structures utilized during this reconstruction. Clinical milestones have been described to demonstrate when movement to the next phase is to be performed. MPFL reconstruction has been shown to have good results with low risk for major complications. As the surgery and the understanding of the MPFL continue to evolve so will the rehabilitation that follows. At present, clinicians must respect the soft healing tissue constraints but not at the expense of stiffness. Certainly higher levels of clinical research with longer follow up are needed to fully investigate the outcomes following this procedure.

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