2014 v9n3

IJSPT

INTERNATIONAL JOURNAL OF SPORTS PHYSICAL THERAPY

VOLUME NINE issue tHREE june 2014

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

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

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

Manuscript Coordinator Ashley Campbell

Henning Langberg, PT, PhD, MSc Institute of Sports Medicine Copenhagen – Denmark

Managing Editor Mary Wilkinson

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

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

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

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

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

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

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

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

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

Lorrie Maffey, PT, MPT, Dip Manip PT University of Calgary Calgary, Alberta – Canada

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

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

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

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

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

Grethe Myklebust, PT, PhD Oslo Sport Trauma Research Center Norwegian School of Sports Sciences Oslo – Norway

EDITORIAL STAFF & BOARD

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

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

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

Erik Witvrouw, PT, PhD Ghent University Ghent – Belgium

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

IJSPT

international JOURNAL OF 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

Tim Tyler, PT, MS, ATC

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

Robert Manske, PT, DPT, Med, SCS, ATC, CSCS Vice President

Robert Manske, PT, DPT, Med, SCS, ATC, CSCS Wichita State University Wichita, Kansas – USA Associate Editor, Thematic Issues Associate Editors Mario Bizzini, PT, MSc Schulthess Clinic Zürich – Switzerland 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 on its website, www.ijspt.org.

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Teresa L. Schuemann, PT, DPT, SCS, ATC, CSCS Secretary Bryan Heiderscheit, PT, PhD Treasurer Stacey J. Pagorek, PT, DPT, SCS, ATC Representative-At-Large

Administration Mark S. De Carlo, PT, DPT, MHA, SCS, ATC Executive Director Tammy Jackson Executive Assistant Mary Wilkinson Director of Marketing Webmaster Managing Editor, Publications

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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).

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

ISSN 2159-2896

TABLE OF CONTENTS VOLUME 9, NUMBER 3

Page Number Article Title Original Research 289 Consistency of clinical biomechanical measures between three different institutions: implications for multi-center biomechanical and epidemiological research.

Authors: Myer GD, Wordeman SC, Sugimoto D, Bates NA, Roewer BD, Medina McKeon JM, DiCesare CA, Di Stasi SL, Barber Foss KD, Thomas SM, Hewett TE 302 Effect of fatigue on landing performance assessed with the Landing Error Scoring System (LESS) in patients after ACL reconstruction. A pilot study.

Authors: Gokeler A, Eppinga P, Dijkstra PU, Welling W, Padua DA, Otten E, Benjaminse A 312 The activity pattern of the lumbo-pelvic muscles during prone hip extension in athletes with and without hamstring strain injury.

Authors: Emami M, Arab AM, Ghamkhar L 320 Association between quadriceps strength and self-reported physical activity in people with knee osteoarthritis Authors: Pietrosimone B, Thomas AC, Saliba SA, Ingersoll CA 329 Activation deficits do not limit quadriceps strength training gains in patients after total knee arthroplasty Authors: Marmon AR, Snyder-Mackler L 338 Running more than three kilometers during the first week of a running regimen may be associated with increased risk of injury in obese novice runners Authors: Nielsen RO, Bertelsen ML, Parner ET, Sørensen H, Lind M, Rasmussen S 346 A speed distance-based classification system for injury prevention and research in international and domestic youth baseball players Authors: Axe MJ, Strube M, Osinski D, Andrews JR, Snyder-Mackler L 356 Lower extremity balance is improved at time of return to throwing in baseball players after an ulnar collateral ligament reconstruction when compared to pre-operative measurements Authors: Hannon J, Garrison JC, Conway J 365 Clinical outcomes of the addition of eccentrics for rehabilitation of previously failed treatments of golfers' elbow Authors: Tyler TF, Nicholas SJ, Schmitt BM, Mullaney M, Hogan DE Case Report 371 Diagnosis and expedited surgical intervention of a complete hamstring avulsion in a military combatives athlete: a case report.

Author: O'Laughlin SJ, Flynn TW, Westrick RB, Ross MD 377 Upper extremity deep venous thromboembolism following arthroscopic labral repair of the shoulder and biceps tenodesis: a case report Authors: Durant TJS, Swanson BT, Cote MP, Allen DA, Arciero RA, Mazzocca AD Clinical Commentary: Diagnostic Corner 383 Management of acute shoulder pain in an adolescent lacrosse athlete: a case report Author: Malone T Clinical Commentary 388 Considerations and return to swim protocol for the pediatric swimmer after non-operative injury.

Authors: Hamman S 396 Functional Movement Screening: the use of fundamental movements as an assessment of function. Part 1.

Authors: Cook G, Burton L, Hoogenboom BJ, Voight ML Clinical Suggestion 410 Variable resistance training using elastic bands to enhance lower extremity strengthening Author: Lorenz DS

IJSPT

ORIGINAL RESEARCH

CONSISTENCY OF CLINICAL BIOMECHANICAL MEASURES BETWEEN THREE DIFFERENT INSTITUTIONS: IMPLICATIONS FOR MULTICENTER BIOMECHANICAL AND EPIDEMIOLOGICAL RESEARCH Gregory D. Myer1,2,3,4 Samuel C. Wordeman6 Dai Sugimoto1,3,5,7 Nathaniel A. Bates1,4,8 Benjamin D. Roewer6 Jennifer M. Medina McKeon5,9 Christopher A. DiCesare1 Stephanie L. Di Stasi3 Kim D. Barber Foss1 Staci M. Thomas1 Timothy E. Hewett1,2,3,5,4,6,8

ABSTRACT Purpose/Background: Multi-center collaborations provide a powerful alternative to overcome the inherent limitations to single-center investigations. Specifically, multi-center projects can support large-scale prospective, longitudinal studies that investigate relatively uncommon outcomes, such as anterior cruciate ligament injury. This project was conceived to assess within- and between-center reliability of an affordable, clinical nomogram utilizing two-dimensional video methods to screen for risk of knee injury. The authors hypothesized that the two-dimensional screening methods would provide good-to-excellent reliability within and between institutions for assessment of frontal and sagittal plane biomechanics.

Methods: Nineteen female, high school athletes participated. Two-dimensional video kinematics of the lower extremity during a drop vertical jump task were collected on all 19 study participants at each of the three facilities. Within-center and between-center reliability were assessed with intra- and inter-class correlation coefficients.

Results: Within-center reliability of the clinical nomogram variables was consistently excellent, but between-center reliability was fair-to-good.

Within-center intra-class correlation coefficient for all nomogram variables combined was 0.98, while combined between-center inter-class correlation coefficient was 0.63.

Conclusions: Injury risk screening protocols were reliable within and repeatable between centers. These results demonstrate the feasibility of multi-site biomechanical studies and establish a framework for further dissemination of injury risk screening algorithms. Specifically, multi-center studies may allow for further validation and optimization of two-dimensional video screening tools.

Level of Evidence: 2b Keywords: ACL; Injury Prevention; Knee injury; Large scale research projects Multi-site research; patellofemoral pain

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Cincinnati Children’s Hospital Medical Center, Sports Medicine Biodynamics Center and Human Performance Laboratory, Cincinnati, OH, USA Departments of Pediatrics and Orthopaedic Surgery, College of Medicine, University of Cincinnati, Cincinnati, OH, USA The Micheli Center for Sports Injury Prevention, Waltham, MA, USA Sports Medicine, Sports Health and Performance Institute, Department of Orthopaedics, School of Health and Rehabilitation Sciences, The Ohio State University, Columbus, OH, USA Division of Athletic Training, College of Health Sciences, University of Kentucky, Lexington, KY, USA Departments of Physiology & Cell Biology, Family Medicine and Biomedical Engineering, The Ohio State University, Columbus, OH, USA Boston Children’s Hospital, Division of Orthopaedics, Division of Sports Medicine, Boston, MA, USA Department of Biomedical Engineering, College of Engineering and Applied Sciences, University of Cincinnati, Cincinnati, OH, USA Department of Exercise & Sport Sciences, Ithaca College, Ithaca, NY, USA

Acknowledgement of Funding The author’s acknowledge funding support from the National Institutes of Health/NIAMS Grants R01-AR055563. Although no monetary support was

provided, the authors would also like to acknowledge Motion Analysis Corporation’s support of an initiative to accelerate the science for the improvement of child health through the standardization of Global Motion Analysis Networks.

IRB Approval Cincinnati Children’s Hospital Medical Center, The Ohio State University, University of Kentucky.

Conflict of Interest Disclosure There is no potential conflict of interest with any authors on this project.

Specifically, there are no financial relationships with any manufacturers, including, but not limited to grants, honoraria, consulting fees, royalty fees, ownership, or support in preparation of the manuscript.

CORRESPONDING AUTHOR Gregory D. Myer Cincinnati Children’s Hospital 3333 Burnet Avenue; MLC 10001 Cincinnati, OH 45229 Tel: 513-636-0249 Fax: 513-636-6374 Email: greg.myer@cchmc.org

The International Journal of Sports Physical Therapy | Volume 9, Number 3 | June 2014 | Page 289

INTRODUCTION Young female athletes are at two- to ten-fold greater risk than male athletes of sustaining devastating knee injuries such as acute anterior cruciate ligament (ACL) ruptures and chronic patellofemoral pain (PFP).1-4 Screening methods that utilize threedimensional (3D), laboratory-based measures accurately predict the quantifiable risk of sustaining these debilitating knee injuries.5-8 However, this approach is time consuming, costly, and requires extensive training for proper implementation. Accordingly, there are growing efforts to develop equally accurate and more feasible surrogate screening methods that require fewer and less expensive resources. These clinically-based assessments, such as the use of twodimensional (2D) screening, may be more practical (i.e. simpler methods and less technology needed) to implement and have the potential for widespread application, but the reliability of these screening measures performed across multiple institutions has not been tested. While the effectiveness of screening protocols used to identify high-risk athletes have been reported independently by single research groups,6,7,9-11 identification of methodological consistency and subsequent validation between laboratories is a critical step toward widespread injury risk screening using such methods. Ultimately, these clinical screening tools will both enhance the ability of sports medicine practitioners to identify athletes that will benefit from targeted intervention and determine the efficacy of such training.

Multi-center collaborations for prospective, longitudinal investigations provide appealing alternatives compared to single-center study designs. Primarily, a multi-center approach has the capacity to generate large sample sizes and is thus likely to yield more powerful and generalizable results.12 Studies that investigate difficult or relatively uncommon phenomena as their primary outcome of interest, such as ACL injury, may particularly benefit from this approach.13-15 While peer-reviewed reports of multi-center kinematic and kinetic reliability are absent in the literature, the reliability of the drop vertical jump (DVJ) at a single institution has been documented.13 3D analysis of the DVJ has demonstrated excellent within-session reliability for kinetic and kinematic measures

at the hip, knee, and ankle (interclass correlation coefficient (ICC) 0.78-0.99).13 Kinetic and kinematic reliability for the DVJ decreases between sessions (ICCs 0.60-0.92 and 0.59-0.87, respectively).13 A second study also supported excellent within-session 3D reliability for the DVJ with respect to knee abduction angle, knee abduction moment and frontal plane projection angle (ICCs > 0.84).14 Reliability of the frontal plane projection angle from 2D video was also excellent for between- and within-session intra- and inter-rater assessments (ICCs 0.83-0.95).14,15 Therefore, both 2D and 3D video have the potential to reliably assess frontal plane knee motion and loads within a single institution. The excellent reliability of the DVJ task has permitted its use in clinical prediction nomograms that require dependable measures in order to assess relative injury risk.16 A study conducted within a single research institution reported that prospective measures of high knee abduction moment (KAM) during landing predict ACL injury risk in young female athletes.7 Retrospective observations of ACL injuries in female athletes reported knee alignments at the time of injury that have been associated with high KAM.17-19 Previous reports from data collected at a single institution indicated that increased knee abduction angle, increased relative quadriceps recruitment, decreased knee flexion range of motion (ROM), increased tibia segmental length, and increased mass normalized to body height that accompany growth contribute to approximately 80% of the measured variance in KAM during landing (Figure 1).20 Therefore, a clinicbased assessment algorithm using these variables was systematically developed and validated in order to address the limitations of 3D motion capture. The ability to screen for injury risk with a simpler tool provides the opportunity to increase the dissemination and utilization of targeted injury prevention training programs.8,21-24 Preliminary results indicate that this clinic-based assessment tool, used as part of an algorithmic methodology, can precisely quantify 3D kinematics and accurately predict the probability for the critical outcome of high KAM that determines risk of ACL injury in female athlete population.8,22-27 The development of inexpensive, reliable assessment tools that can be administered in a clinic or field testing environment can support screening for injury risk on a more widespread basis.

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Figure 1. Clinician friendly nomogram that was developed from the regression analysis. This nomogram can be used to predict high KAM outcome based on tibia length, knee valgus motion, knee flexion ROM, body mass and quadriceps to hamstrings ratio.

The current study examined the reliability of an affordable, accessible, clinic-based algorithm that uses 2D camcorder-based methods to screen young athletes who may be at high risk of knee injury. The validity, intra-rater reliability, and intra-session reliability of this protocol at a single institution have been reported previously.23 The goal of the current investigation was to measure the within-center and between-center reliability of measures utilized in this protocol at three institutions. Specifically, the authors aimed to measure the within-center and between-center reliability of included testing measures using 2D screening techniques at three different institutions. It was hypothesized that the 2D risk screening methods would provide good-to-excellent reliability within and between institutions for frontal and sagittal plane biomechanics and variables that contribute to high knee abduction loads as predicted by the aforementioned nomogram.

METHODS Subjects Nineteen female, varsity and junior varsity level high school volleyball players participated in this study (Mean age ± 1SD- 15.27 ± 1.0 years; height1.69 ± 0.42 m; mass- 61.08 ± 7.9 kg). A thorough medical history questionnaire was completed by each subject. Any subject with an acute lower extremity injury within the past six months was

excluded. There were no known ACL deficient or reconstructed conditions present among the tested subjects, however participants with anterior knee pain were not excluded from the testing. All subjects were on the current team roster and cleared for full athletic participation. Frontal plane video from each of the subjects was recorded at each of three testing centers. Due to technical errors at one center (Institution III), sagittal plane video at all three testing centers could only be obtained for eight participants (Mean age- 15.83 ± 0.95 years; height- 1.70 ± 0.43 m; mass 63.09 ± 5.7 kg). All subjects were tested as a group at each testing center on separate dates within a three-week period during the preseason.

A research assistant scheduled and coordinated the dates for each of the testing locations. The subjects were initially brought to Cincinnati Children’s Hospital Medical Center Human Performance Laboratory (Institution I). The second location was University of Kentucky Biodynamics Laboratory (Institution II) and finally subjects were tested at The Ohio State University Sport MedicineBiodynamics Laboratory (Institution III). The team’s coach attended all three testing sessions with the athletes.

Screening Stations Prior to the testing sessions, personnel from all three laboratories met with the study coordinators at Institution I to review the testing stations and procedures. A uniform testing protocol was developed

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for use in each of the testing laboratories. The same research assistant coordinated participation of the athletes at all three locations and helped direct their progression between each testing station.

After written informed consent was obtained from parents or legal guardians and assent from the participants, a multi-station protocol, previously approved by the institutional review board at each institution, with six stations was used to implement the injury screening that assessed factors associated with increased risk of ACL injury and PFP. The stations consisted of 1) pubertal maturity and medical history, 2) anthropometrics, 3) flexibility and laxity, 4) alignment, 5) strength, 6) PFP assessment, and 7) 2D and 3D motion analysis. Stations 1, 3, 5 and 6 were not included in this investigation’s reliability analysis.

Anthropometrics Height (cm) for each subject was measured by a research assistant at each site using a standard stadiometer. Tibia length (cm) was measured with a standard measuring tape by a certified athletic trainer at each site and was determined to be the distance between the lateral joint line of the knee and the lateral malleolus. Body mass was measured by a research assistant at each site on a calibrated physician’s scale.

2D Landing Biomechanics Pre-collection Preparation. A total of 42 skin-mounted, retroreflective markers were applied to each subject as part of a larger study using 3D motion testing. Specifically for the 2D motion analysis used in the current investigation, markers were fixed bilaterally on greater trochanter, the medial and lateral epicondyles (medial and lateral knee joint line) and the medial and lateral malleoli were used.

Video Capture. Motion analysis setup consisted of a 2D video capture using two digital cameras, as previously described.24 Both of the cameras were synched using firewire cables directly connected to the data acquisition computer through Cortex (Motion Analysis Corp, Santa Rosa, CA) for Institutions I and II, and through Vicon Nexus (Vicon Motion Systems Ltd, Los Angeles, CA) for Institution III. The 2D video cameras used at Institutions I and III were Panasonic PVGS300 (Panasonic Corporation, Kadoma, Japan). The 2D video cameras used at Institution II were Sony Handycam DCR-HC52 (Sony Electronics, Tokyo, Japan). 2D frontal plane knee kinematic data were collected using standard video cameras during each of the three DVJ trials. Two cameras were positioned three meters from the approximated location of landing at a height of 54.6 centimeters (21.5 inches) to capture sagittal (left side only) and frontal plane lower extremity motion during the DVJ (Figure 2). The frontal plane camera was aligned with the subject’s midline, as determined by standardized foot position on the box prior to beginning the task. The sagittal plane camera was located perpendicular to the frontal plane camera and was centrally located relative to the force platforms where subjects performed the DVJ. Landing sequence images were captured using VirtualDub (virtualdub.org). Coordinate data for the hips, knees, and ankles were captured from the video frame just prior to initial contact and again at maximum medial knee displacement in the frontal view and maximum knee flexion in the sagittal view.

Video Processing. Kinematic data were recorded by a technician from each of the participating institutions. All videos were compiled and analyzed by one tester using ImageJ (http://imagej.nih.gov/ij/). The height of the box used for the DVJ was measured in the video and this distance was converted using

Figure 2. Pictorial presentation of the testing centers.

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the actual known box height. This video correction factor was then used to calibrate coordinate data. In the frontal plane, the hip joint center was estimated relative to a marker placed on the greater trochanter (intersection of the vertical line of the center of the ASIS and knee joint center and the horizontal line between the greater trochanters), the knee joint center was estimated as the mid-point between two markers placed on the medial and lateral knee joint lines and the ankle joint center was estimated as the mid-point between two markers placed on the medial and lateral malleoli (Figure 3). Sagittal plane joint center locations were determined for each subject’s left leg, due to the placement of the sagittal plane camera on the athlete’s left side. The left hip joint center was identified in the sagittal plane view as the marker on the left greater trochanter, the left knee joint center was estimated to be at the location of a marker on the subject’s left lateral knee joint line, and the left ankle joint center was estimated

to be at the location of the marker on the left lateral malleolus (Figure 4).

In the frontal plane view, medial knee displacement (cm) was calculated as the difference between the frontal plane knee joint center at initial contact and at maximum medial knee displacement (Figure 3).

Maximum frontal plane knee angle was calculated from hip, knee and ankle joint centers at maximum medial knee displacement (MMD). Valgus alignment was defined as a positive angle in the frontal plane. In the sagittal-plane view, knee flexion range of motion was calculated as the difference between the knee joint angle at initial contact and at maximum knee flexion. To calculate the nomogram for the right leg, the sagittal-plane measure of knee flexion range of motion was substituted from the left limb video measurement. This substitution was necessary as 2D sagittal plane video was only captured from the leftside profile of each subject. Therefore, calculation of

Figure 3. A. The coordinate position of knee joint center is digitized in the frontal view measured at the frame prior to initial contact is used as the knee valgus position X1. B. The coordinate position of knee joint center is digitized in the frontal view measured at the frame with maximum medial position and is utilized as the knee valgus position X2. C. The calibrated displacement measure between the two digitized knee coordinates (X2–X1) is representative of knee valgus motion during the drop vertical jump.

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Figure 4. A. Knee flexion angle is digitized at the frame prior to initial contact and recorded as the first measure of knee flexion ROM (Θ1 ). B. Knee flexion angle is digitized at the frame with maximum knee flexion and recorded as the second measure of knee flexion ROM (Θ2 ).C. The displacement of knee flexion is calculated as the differences in knee flexion angles at the frame prior to initial contact and maximum knee flexion (Θ1–Θ2 ) and is representative of knee flexion ROM.

the right knee sagittal plane angle would have been inaccurate as the left limb obstructed the view of the contralateral leg.

Surrogate Measure of Relative Quadriceps and Hamstrings Strength: In addition, the prediction nomogram can include a relative measure of quadriceps to hamstrings strength that is prescribed for measurement on an isokinetic dynamometer. For the current project, as is the case with other clinical settings, the same isokinetic testing devices may not be readily available.

In this case, a surrogate measure of the quadriceps to hamstrings ratio can be employed that was defined using a linear regression analysis to predict quadriceps to hamstrings ratio based on the athlete’s body mass. The surrogate quadriceps to hamstrings ratio measure can be obtained by multiplying the athlete’s mass by 0.01 and adding the resultant value to 1.10.8,24 If even greater simplicity is desired, the mean value of 1.53 can be substituted into the prediction algorithm for the quadriceps to hamstring ratio.24 An example of

a completed nomogram for a subject is presented in Figure 5.

Statistical Analysis The nomogram tool used to predict the risk of high knee loads is based on a multivariate logistic regression model developed from previously described data.7,8 The discrete variables and injury risk calculations computed for use in the high knee load risk algorithm were evaluated in the current study for reliability using interclass correlation coefficients (ICC). Within-center (ICC (2,k)) and between-center (ICC (2,1)) reliability was examined for each variable, (height, mass, bilateral tibia length, bilateral knee flexion ROM, bilateral knee valgus excursion).

Reliability was calculated separately for the right and left limbs. Within-center reliability was determined using all three DVJ trials for each subject, whereas between-center reliability was based on mean values calculated from the three DVJ trials for each subject.

ICC calculations were conducted using MATLAB

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Figure 5. Example of predicted probability for high KAM status based on the representative subject’s (figures 4 and 5) clinic-based measurements. Completed nomogram for the representative subject (Tibia length: 35 cm; Knee valgus motion: 8.2 cm; Knee flexion ROM: 75.4 body mass: 52.2 kg; QuadHam: 1.55). Based on her demonstrated measurements this subject would have a 74% (95.5 points) chance to demonstrate high KAM during the drop vertical jump. The actual KAM measurement for the presented drop vertical jump that was quantified simultaneously with 3D motion analysis was 24.2 Nm of knee abduction load.

(version 2010b, The Mathworks, Inc, Natick, MA) and verified with SPSS (Version 20.0, IBM Corporation, Armonk, NY). The range of ICC values were described using the classifications of Fleiss, where ICC < 0.4 was considered poor, 0.4 < ICC < 0.75 was considered fair-to-good, and ICC > 0.75 was considered excellent.28 The approximations of the Fleiss scale are supported by additional literature that has shown frontal and sagittal plane ICC values for 3D knee angles collected between-session on the same subjects with in the same location were 0.616 and 0.855, respectively.13 These values produce an average ICC of 0.735 and suggest that any ICC value above this threshold is excellent as it represents normal biological variability between sessions within the same location. Typical error was also calculated for each variable and used to calculate the nomogram score and risk probability measured between each center.

RESULTS Anatomical Variables Between-center reliability of all anatomical measures was classified as either excellent or fair-to-good (Table 1). Height and mass demonstrated excellent betweencenter reliability with combined ICC values of 0.92 and 0.99, respectively. Tibia length demonstrated fairto-good between-center reliability for both the left and right limb with ICCs of 0.66 and 0.73, respectively.

Frontal Plane Variables The average of all front plane within-center ICC values were higher than the average of all frontal plane between-center ICC values (within ICC = 0.83, between ICC = 0.72; Table 1). The combined ICC values indicate that overall within-center reliability was excellent for the frontal plane, while between-center frontal plane reliability was fair-to-good. Combined frontal plane reliability was excellent within each center, but only one of the between-center comparisons demonstrated excellent agreement for these variables.

Left knee frontal plane excursion consistently demonstrated the lowest reliability of all frontal plane variables for both within and between-center analyses.

Sagittal Plane Variables Within and between-center ICC values for knee flexion range of motion were similar for all measured sagittal plane variables combined (within ICC = 0.83, between ICC = 0.78; Table 1). Sagittal plane reliability was excellent for both the within and betweencenter evaluations. Maximum flexion angle exhibited excellent within and between-center reliability, while flexion angle at initial contact demonstrated excellent within-center and fair-to-good between-center reliability (Table 1). Sagittal plane measures demonstrated consistent reliability between measures within single center and for the same measures between centers.

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Table 1. Between-center and within-center reliability taken individually for each variable BETWEEN-CENTER ICC (2-1) ALL 3 CENTERS I vs II I vs III II vs III Anatomic Measures Height 0.92 0.90 0.96 0.90 Mass 0.99 0.99 1.00 0.99 Left Tibia Length 0.66 0.52 0.70 0.75 Right Tibia Length 0.73 0.63 0.80 0.73 F r on ta l pla n e Left angle at IC (°) 0.79 0.75 0.74 0.86 Right angle at IC (°) 0.81 0.76 0.83 0.83 Left angle at MMD (°) 0.64 0.58 0.65 0.69 Right angle at MMD (°) 0.80 0.75 0.82 0.82 Left excursion (mm) 0.63 0.52 0.73 0.62 Right excursion (mm) 0.68 0.61 0.70 0.71 Sagittal plane Flexion angle at IC (°) 0.71 0.66 0.73 0.75 Maximum flexion angle (°) 0.89 0.91 0.88 0.86 Flexion ROM (°) 0.75 0.71 0.74 0.79 IC = initial contact with ground; MMD = maximum medial displacement; ROM = range of motion

Nomogram Variables Within-center reliability of the variables that comprise the nomogram was consistently classified as excellent, but between-center reliability was classified as fair-to-good. The within-center ICCs for all nomogram variables combined was 0.98 (ICC range 0.95-0.99), while combined between-center ICC was 0.63 (ICC range 0.51-0.78). Typical errors for variables that contributed to the nomogram calculation are represented as the average within-subject differences for within- and between-center analysis (Table 2). The average typical error for frontal plane knee excursion was 2.3 cm for within-center comparisons and 2.5 cm for between-center comparisons.

The average typical error for knee flexion range of motion was 5.9° for within-center comparisons and 6.7° for between-center comparisons. Typical errors

WITHIN-CENTER ICC (2-k) I

II

III

N/A N/A N/A N/A

N/A N/A N/A N/A

N/A N/A N/A N/A

0.82 0.90 0.85 0.93 0.83 0.90

0.85 0.93 0.82 0.90 0.66 0.80

0.91 0.94 0.65 0.90 0.58 0.84

0.93 0.82 0.80

0.80 0.92 0.78

0.61 0.92 0.89

were less than 1% of the mean for height and less than 1.5% of the mean for mass in all betweencenter comparisons. Tibia length typical error was approximately 2.5% of the mean for both the right and left limb.

DISCUSSION In current practice, screening athletes for risk of knee injuries is most often conducted using expensive and technically-daunting 3D motion capture systems. Injury risk assessments using less costly, clinic-based tools have been proposed as an alternative to improve the ability of clinicians to quickly and accurately determine the needs of individual athletes. In addition, these tools must be appropriate for large-scale assessments, as several types of knee injuries are rare and large samples are needed

Table 2. Within-center and between-center typical errors for each nomogram variable

Height (cm) Mass (kg) Left Tibia Length (cm) Right Tibia Length (cm) Flexion ROM (°) Left Valgus Excursion (cm) Right Valgus Excursion (cm) ROM = range of motion

BETWEEN-CENTER TYPICAL ERROR ALL 3 CENTERS I vs II I vs III II vs III 1.1 1.3 1.2 0.7 0.66 0.81 0.75 0.42 0.9 1.0 0.9 0.8 0.7 0.8 0.6 0.8 6.7 8.4 5.7 6.2 2.5 2.5 2.6 2.6 2.5 2.3 2.5 2.5

WITHIN-CENTER TYPICAL ERROR I N/A N/A N/A N/A 6.2 2.0 1.9

II N/A N/A N/A N/A 7.2 2.2 2.0

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III N/A N/A N/A N/A 4.2 3.0 2.5

Figure 6. Frontal plane and sagittal plane measurements of a representative participant tested at each site with an example completed risk nomogram using each sites biomechanical measures.

in order to study these phenomena prospectively. A recently established nomogram (Figure 1) for prediction of knee injury risk has been determined valid and reliable.8,22-27 In order to determine the validity of this approach on a widespread basis, the reliability of this protocol across multiple institutions must be established (Figure 6).

The between-centers reliability needed to be established prior to the pursuit of our multi-center coupled investigations that require the use of biomechanical and neuromuscular testing during dynamic tasks. Therefore, the purpose of this study was to document within- and between-center reliability of a set of clinical screening measures that effectively predict injury risk in youth athletes. The current data indicated that between-center collaboration, using a standardized data collection and analysis protocol can yield consistent results across centers.

Documentation of variability in injury prediction variables between centers will aid the development of rigorous protocols in order to maximize the reliability of variables collected. The between-center reliability of the three centers at frontal plane of the knee joint demonstrated fair-to-good and excellent ICCs with values between 0.63 and 0.81 (Table 2).

Similarly, the between-center reliability in sagittal plane measurements ranged from 0.71 to 0.87 (Table 2), which was rated fair-to-good and excellent ICC values. These values were slightly below the previously reported ICCs for between-session 3D kinematics in the frontal plane and slightly above in the sagittal plane.13 It is important to have the highest reliability possible for each variable since the nomogram consists of a combination of multiple anthropometric and biomechanical variables.8,22,23 Consequently, the nomogram will incorporate and compound the variability from each variable in its calculation.

As expected, the current data confirms that betweencenter measures have greater variability than withincenter measures. Identification of potential sources of between-center variability in a multi-center investigation is imperative for the production of repeatable biomechanical data sets. It was reported that betweensession movement deviations and inconsistency in marker placement have been attributed to variability in kinematic motion data.29 A previous report indicated fair-to-good within-session repeatability and poor between-session repeatability of kinematic data, and suggested that marker placement discrepancy was a primary factor in variability among testing

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centers.30 To reduce error and variability associated with marker placement, marker placement must be undertaken by uniformly trained individuals at each research center who can document their own marker placement reliability in order to further establish known sources of error between centers. Other possible sources of variability in multi-center collaborations can include differences in system accuracy and disparities in the interpretation of results. An important method for control of this inherent variability is the incorporation of a standardized protocol. A study

by Gorton et al.31 reported a reduction in variability of several kinematic variables over 12 centers following the implementation of a standardized testing protocol. The between-center reliabilities were consistent in the current study, which may be attributed to systematic training of all participating investigators using the standardized methods.

The lowest ICC values were observed in left leg frontal plane angle at MMD and left leg tibia length. Tibia length was measured at each institution by experienced, certified athletic trainers using measuring tape.

Therefore, the relatively lower ICCs observed in the measure may indicate a need for more specific and detailed training for standardization of anatomical measurements of the tibia. For frontal plane measures, greater variability has been reported at maximal values rather than initial contact.32 Increased variability reduces reliability, which may explain why the frontal plane angle exhibited lower ICC at MMD than at IC. Increased motion variability may be a result of reduced neuromuscular control. In a population demographic similar to that used in the current study, 93.3% of subjects indicated their right limb to be preferred.33 It has been demonstrated that female subjects tend to exhibit greater neuromuscular control and fewer non-contact ACL injuries in their preferred (right) limbs versus the non-preferred (left) limb.34 This may explain why ICCs of dynamic frontal plane variables were typically lower in the left limb than the right limb.

The time between testing sessions at each institution may have further influenced increased variability and may have reduced the reliability of our clinical measures in multiple ways. First, these athletes had begun their pre-season activities for the upcoming volleyball season. Testing at the initial center (Institution I) was completed within a week of their first week of

training. By the time the athletes performed for final testing session at the third institution (Institution III), they had undergone nearly three weeks of pre-season training. Furthermore, while all athletes were fully participating in their daily practices, five athletes reported mild anterior knee pain in one or both knees at some point throughout the testing period, which is common in this adolescent athletic population.6,35-37 It is well known that anterior knee pain, like PFP, is related to abnormal movement mechanics, but it is unknown whether the severity of symptoms can contribute to variability in that movement. Though the time between the three testing sessions was relatively short, it may be that changes in fitness and injury status may have affected our between-center reliability results. Completion of the current testing protocol at each center within days of each other and avoidance of pre- or in-season training would have been ideal for reducing inter-subject variability. Minimization of the time between biomechanical assessments may have enhanced the between-center reliability of these clinically-based measures.

Single-center studies that aim to examine relatively rare injuries or conditions often have restricted generalizability due to statistical limitations and homogenous participant characteristics. Multi-center collaborative efforts can effectively overcome these limitations by substantially increasing the potential for increased subject enrollment and testing. As an example, a recent investigation that aimed to evaluate several outcomes related to total knee arthroplasty necessitated compilation of data from a total of 90 individual centers in order to have adequate statistical power.38 Only with this large-scale investigation involving 1027 knees from hundreds of patients with total knee arthroplasty, were the authors able to statistically analyze tibiofemoral axial rotation patterns using video fluoroscopy.38 A recent numbers-needed-to-treat (NNT) analysis for ACL injury demonstrated that between 108 (95% CI: 86 to 150) and 120 (95% CI: 74 to 316) female athletes would need to be trained to prevent one noncontact or one overall ACL injury during one competitive season.39 Although a prophylactic effect of NMT has been reported,40 these relatively large NNT indicate a need to screen for high-risk athletes.

As mentioned previously, a prospective cohort study found that a greater KAM during a DVJ was a highly

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specific and sensitive predictor of future ACL injury.7 When predictive modeling of factors was evaluated to determine the propensity for increased external knee abduction moment, several clinically feasible measures had the potential to evaluate ACL injury risk athletes by identification of greater KAM landing mechanics. The reliability of screening methods reported in the current study results support the integrated application of athlete risk assessment algorithms on a widespread basis. Previous authors have indicated that targeted training to athletes with high injury risk biomechanics with the appropriate intervention may more efficiently and effectively reduce injury risk factors. 26,27,41 The applicability of the reported multi-center reliability may be a critical step in the prevention of injury in sports. The long-term goals of future projects will build upon the findings of the current reliability study to determine the mechanisms that underlie the high incidence of knee injury in young female athletes. This knowledge can be readily applied to the development of targeted, affordable and well-disseminated interventions that prevent athletic injuries in female population. In order to apply patient-specific interventions, future work is warranted to continue the development of clinically feasible and reliable tools to predict who is at risk for the development of specific knee injuries such as ACL injury or PFP, in order to apply patient-specific interventions.

Multi-center collaborations for prospective, longitudinal investigations provide an appealing alternative to singlecenter studies. Primarily, a multi-center approach has the capacity to generate large sample sizes and is thus likely to yield more powerful and generalizable results.12 Studies that investigate difficult or rare phenomena as their primary outcome of interest, such as ACL injury, may particularly benefit from this approach.13-15 CONCLUSION The results of this multi-center reliability study demonstrate that the risk screening protocols examined were reliable within centers and repeatable between centers when compared with previously reported measures of 3D motion capture reliability. The current results support efforts to validate and disseminate an injury risk screening algorithm for young athletes. Specifically, the proposed multi-center studies may allow for validation and optimization

of readily accessible and inexpensive 2D camcorder based screening tools to identify younger female athletes at high risk for knee injury. In addition, the screening tools may be a successful practice to support injury prevention training in younger girls thereby allowing them to avoid more severe knee injuries as they mature.35,42 REFERENCES 1. Robinson RL, Nee RJ. Analysis of hip strength in females seeking physical therapy treatment for unilateral patellofemoral pain syndrome. J Orthop Sports Phys Ther. 2007;37:232-8.

2. Fulkerson JP. Diagnosis and treatment of patients with patellofemoral pain. Am J Sports Med. 2002;30:447-56.

3. Fulkerson JP, Arendt EA. Anterior knee pain in females. Clin Orthop Relat Res. 2000:69-73.

4. Malone TR, Hardaker WT, Garrett WE et al.

Relationship of gender to anterior cruciate ligament injuries in intercollegiate basketball players.

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5. Myer GD, Ford KR, Barber Foss KD et al. A predictive model to estimate knee abduction moment: Implications for development of clinically applicable patellofemoral pain screening tool in female athletes. J Athl Train. 2013;In Press.

6. Myer GD, Ford KR, Barber Foss KD et al. The incidence and potential pathomechanics of patellofemoral pain in female athletes. Clin Biomech (Bristol, Avon). 2010;25:700-7.

7. Hewett TE, Myer GD, Ford KR et al. Biomechanical Measures of Neuromuscular Control and Valgus Loading of the Knee Predict Anterior Cruciate Ligament Injury Risk in Female Athletes: A Prospective Study. Am J Sports Med. 2005;33:492-501.

8. Myer GD, Ford KR, Khoury J et al. Development and validation of a clinic-based prediction tool to identify female athletes at high risk for anterior cruciate ligament injury. Am J Sports Med. 2010;38:2025-33.

9. Witvrouw E, Lysens R, Bellemans J et al. Intrinsic risk factors for the development of anterior knee pain in an athletic population. A two-year prospective study. Am J Sports Med. 2000;28:480-9.

10. Kiesel K, Plisky PJ, Voight ML. Can Serious Injury in Professional Football be Predicted by a Preseason Functional Movement Screen? North American journal of sports physical therapy: NAJSPT. 2007;2:147-58.

11. Plisky PJ, Rauh MJ, Kaminski TW et al. Star Excursion Balance Test as a predictor of lower extremity injury in high school basketball players.

J Orthop Sports Phys Ther. 2006;36:911-9.

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12. Brophy RH, Smith MV, Latterman C et al. Multiinvestigator collaboration in orthopaedic surgery research compared to other medical fields. Journal of orthopaedic research: official publication of the Orthopaedic Research Society. 2012;30:1523-8.

13. Ford KR, Myer GD, Hewett TE. Reliability of landing 3D motion analysis: implications for longitudinal analyses. Med Sci Sports Exerc.

2007;39:2021-8.

14. 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.

15. 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.

16. Myer GD, Ford KR, Khoury J et al. ThreeDimensional Motion Analysis Validation of a ClinicBased Nomogram Designed to Identify High ACL Injury Risk in Female Athletes. Physician and Sports Medicine. 2011;39.

17. Olsen OE, Myklebust G, Engebretsen L et al. Injury mechanisms for anterior cruciate ligament injuries in team handball: a systematic video analysis. Am J Sports Med. 2004;32:1002-12.

18. Krosshaug T, Nakamae A, Boden BP et al.

Mechanisms of anterior cruciate ligament injury in basketball: video analysis of 39 cases. Am J Sports Med. 2007;35:359-67.

19. Boden BP, Dean GS, Feagin JA et al. Mechanisms of anterior cruciate ligament injury. Orthopedics.

2000;23:573-8.

20. Myer GD, Ford KR, Khoury J et al. Biomechanics laboratory-based prediction algorithm to identify female athletes with high knee loads that increase risk of ACL injury. Br J Sports Med. 2011.

21. Myer GD, Ford KR, Khoury J et al. Clinical Correlates to Laboratory Based Measures for use in ACL Injury Risk Prediction Algorithm Clinical Biomechanics. 2010;In Press.

22. Myer GD, Ford KR, Khoury J et al. Clinical correlates to laboratory measures for use in non-contact anterior cruciate ligament injury risk prediction algorithm. Clin Biomech. 2010;25:693-9.

23. Myer GD, Ford KR, Khoury J et al. Threedimensional motion analysis validation of a clinicbased nomogram designed to identify high ACL injury risk in female athletes. Phys Sportsmed.

2011;39:19-28.

24. Myer GD, Ford KR, Hewett TE. New method to identify athletes at high risk of ACL injury using

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Myer GD, Ford KR, Khoury J et al. Biomechanics laboratory-based prediction algorithm to identify female athletes with high knee loads that increase risk of ACL injury. Br J Sports Med. 2011;45:245-52.

Myer GD, Ford KR, Brent JL et al. An integrated approach to change the outcome part I: neuromuscular screening methods to identify high ACL injury risk athletes. J Strength Cond Res. 2012;26:2265-71.

Myer GD, Ford KR, Brent JL et al. An integrated approach to change the outcome part II: targeted neuromuscular training techniques to reduce identified ACL injury risk factors. J Strength Cond Res. 2012;26:2272-92.

Fleiss JL. The design and analysis of clinical experiments. New York: Wiley; 1986.

Chambers C, Goode B. Variability in Gait Measurements Across Multiple Sites. Gait Posture.

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Kadaba MP, Ramakrishnan HK, Wootten ME et al.

Repeatability of kinematic, kinetic, and electromyographic data in normal adult gait.

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Gorton GE, 3rd, Hebert DA, Gannotti ME. Assessment of the kinematic variability among 12 motion analysis laboratories. Gait Posture.

2009;29:398-402.

Ford KR, Myer GD, Toms HE et al. Gender differences in the kinematics of unanticipated cutting in young athletes. Med Sci Sports.

2005;37:124-9.

Bates NA, Ford KR, Myer GD et al. Timing differences in the generation of ground reaction forces between the initial and secondary landing phases of the drop vertical jump. Clin Biomech.

2013;28:796-9.

Klimesch W. EEG alpha and theta oscillations reflect cognitive and memory performance: a review and analysis. Brain Res Brain Res Rev. 1999;29:169-95.

Myer GD, Ford KR, Di Stasi SL et al. High knee abduction moments are common risk factors for patellofemoral pain (PFP) and anterior cruciate ligament (ACL) injury in girls: Is PFP itself a predictor for subsequent ACL injury? Br J Sports Med. 2014.

Myer GD, Barber Foss KD, Gupta R et al. Analysis of patient-reported anterior knee pain scale: implications for scale development in children and adolescents. Knee Surg Sports Traumatol Arthrosc.

2014;In Press.

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37. Myer GD, Ford KR, Foss KD et al. A Predictive Model to Estimate Knee-Abduction Moment: Implications for Development of a Clinically Applicable Patellofemoral Pain Screening Tool in Female Athletes. J Athl Train. 2014.

38. Dennis DA, Komistek RD, Mahfouz MR et al. A multicenter analysis of axial femorotibial rotation after total knee arthroplasty. Clin Orthop Relat Res. 2004:180-9.

39. Sugimoto D, Myer GD, McKeon JM et al. Evaluation of the effectiveness of neuromuscular training to reduce anterior cruciate ligament injury in female athletes: a critical review of relative risk reduction and numbers-needed-to-treat analyses. Br J Sports Med. 2012;46:979-88.

40. Myer GD, Sugimoto D, Thomas S et al. The influence of age on the effectiveness of neuromuscular training to reduce anterior cruciate ligament injury in female athletes: a meta-analysis.

Am J Sports Med. 2013;41:203-15.

41. Myer GD, Ford KR, Brent JL et al. Differential neuromuscular training effects on ACL injury risk factors in”high-risk” versus “low-risk” athletes. BMC Musculoskelet Disord. 2007;8:39.

42. Myer GD, Ford KR, Barber Foss KD et al. A predictive model to estimate knee abduction moment: Implications for development of clinically applicable patellofemoral pain screening tool in female athletes. J Athl Train. 2014;In Press.

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IJSPT

ORIGINAL RESEARCH

EFFECT OF FATIGUE ON LANDING PERFORMANCE ASSESSED WITH THE LANDING ERROR SCORING SYSTEM LESS IN PATIENTS AFTER ACL RECONSTRUCTION. A PILOT STUDY Gokeler A.1 Eppinga P.2 Dijkstra P.U.3 Welling W.1 Padua D.A.4 Otten E.1 Benjaminse A.1,5

ABSTRACT Background: Fatigue has been shown to affect performance of hop tests in patients after anterior cruciate ligament reconstruction (ACLR) compared to uninjured controls (CTRL). This may render the hop test less sensitive in detecting landing errors. The primary purpose of this study was to investigate the effect of lower extremity fatigue on landing performance assessed with the Landing Error Scoring System (LESS) in patients after ACLR compared to a CTRL group. It is plausible that fatigue would have an effect on confidence and risk appraisal in the ACLR group. The secondary purpose was to determine the relationship between psychological responses and LESS scores after fatigue.

Methods: Twelve patients following ACLR (6 males, 6 females) who were tested at 10 ± 2.4 months after surgery participated in the current study and were compared to 10 subjects in the control group (5 males, 5 females). Subjects performed a jump-landing task and the landing was assessed using the Landing Error Scoring System (LESS) both before and after fatigue. Digital video camcorders recorded frontal and sagittal plane views of the subject performing the task. The LESS was scored using video replay. Psychological responses in the ACLR group were assessed with the ACL-RSI questionnaire.

Results: Patients after ACLR had a median LESS of 6.5 which reflects a poor result (LESS >6) in the pre-fatigue condition compared to controls who had a LESS of 2.5 which is considered excellent (≤4). In the post-fatigue condition, median LESS in patients after ACLR increased to 7.0 whereas in the control group the LESS increased to 6.0 both of which reflect a poor result. The median increase in LESS was larger in the control (2.0) group compared to patients after ACLR (1.0) but the difference was not significant (p=0.165).

Conclusions: Patients after ACLR have higher LESS scores at baseline compared to a control group. Fatigue resulted in an increase in scores on the LESS in both groups.

Level of Evidence: 3b Keywords: Anterior cruciate ligament, jump landing, fatigue, jump landing, psychology, return to sport

1

University of Groningen, University Medical Center Groningen. Center for Human Movement Sciences.

Groningen, The Netherlands 2 FLYTTA Sports Physical Therapy. Groningen, The Netherlands 3 University of Groningen, University Medical Center Groningen. Center for Rehabilitation. Groningen, The Netherlands 4 Department of Exercise and Sport Science. University of North Carolina. Chapel Hill, NC, USA 5 Hanze University Applied Science, School of Sport Studies.

Groningen, The Netherlands Institutional Review Board The study was approved by the University Medical Center of Groningen Medical Ethics Committee.

Acknowledgements The authors would like to thank Laura Huinink for her invaluable contributions to the development of this study.

CORRESPONDING AUTHOR Alli Gokeler University of Groningen University Medical Center Groningen Center for Human Movement Sciences Antonius Deusinglaan 1 9713 AV Groningen The Netherlands Telephone + 31 50 3611020 E-mail: a.gokeler@rug.nl

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INTRODUCTION Return to sport (RTS) after ACL reconstruction (ACLR) is a frequent subject of debate and patients are usually allowed to return to regular athletic participation approximately six months post-surgery.1,2 The release to full activity is a potential sensitive landmark for the athlete who wants to return to high-level sport participation. Unfortunately, many questions exist and there is a lack of consensus regarding the appropriate criteria for releasing patients to unrestricted sports activities postoperatively.3 Recently, Sward et al suggested that return to a high activity level after an unilateral ACLR was the most important risk factor for sustaining a contralateral ACL injury.4 Injury rates for a second injury exceed 20% for young highly active athletes returning to sports within the first year after surgery.5 Data from the Swedish National Anterior Cruciate Ligament Register indicate that 22% of the 15- to 18-year-old female soccer players underwent a revision or contralateral ACLR during a 5-year period.6 Risk factors acquired secondary to the ACL injury, such as altered neuromuscular function, that affect both the injured and the contralateral leg, most likely further increase the risk of a contralateral ACL injury.4,5 It is common practice to use hop tests in late phase of rehabilitation to ensure safe RTS.7,8 However, hop tests may not be sensitive enough to detect biomechanical deficits, and, typically, kinematics and kinetics are not measured in the clinical setting. As biomechanical changes play an important role in risk for secondary injury, there is a need to develop objective, performance-based assessments designed to identify potential lower extremity biomechanical deficits in the late stage of rehabilitation following ACLR prior to release of the athlete to the high demands of sports. Identification of altered movement patterns post-ACLR may be critical to maximize functional recovery following surgery and reduce risk for a second ACL injury. Based on kinematic and kinetic measurements from jump-landing movement strategies, Padua et al9 developed the Landing Error Scoring System (LESS). The LESS has been shown to possess good criterion validity and reliability as a field-based assessment tool used to identify individuals who exhibit faulty jump-landing biomechanics or high-risk movement patterns dur-

ing jump-landing. It has commonly been assumed that athletes participating in higher levels of competition are more physically fit and have better movement patterns, and that more novice (lower levels of participation) athletes are less fit and poorer movers. Supporting this assumption are data showing that high school athletes demonstrated significantly poorer LESS scores (e.g., higher-risk movement patterns) when compared with college student-athletes.10 More recently, higher level athletes have been shown to have better physical fitness as measured by the Army Physical Fitness Test but as a group did not exhibit better landing technique.11 The implications of this research suggest that “high-risk” movement patterns are prevalent in all levels of athletes. A recent longitudinal study demonstrated that ACL injury and ACLR altered lower extremity biomechanics, demonstrated by increases in frontal plane movement (increased hip adduction and knee valgus). The injured leg of patients after ACLR also exhibited decreased sagittal plane loading (decreased anterior tibial shear force, knee extension moment and hip flexion moment).12 The LESS has not been used in a group of patients after ACLR.

Of all the risk factors associated with ACL injury, neuromuscular control is altered further when the effects of fatigue are combined with unanticipated movements are present.13 A recently published systematic review that investigated effects of fatigue on landing kinematics in a healthy, uninjured population found that neuromuscular fatigue causes various biomechanical alterations that may increase the risk of a noncontact ACL injury during landing.14 Fatigue has been found to increase peak proximal tibial anterior shear force,15 increase peak knee valgus angle,13,16 decrease knee flexion angle,15 decrease hip flexion angle,13 and increase knee internal rotation17 during various tasks. The effect of fatigue has also been studied in patients after ACLR, indicating that 68% of the patients after ACLR showed abnormal hop limb symmetry index (LSI) when tested in a fatigued condition.18 The primary purpose of this study was to investigate the effect of lower extremity fatigue on landing performance assessed with the Landing Error Scoring System (LESS) in patients after ACLR compared to a CTRL group. The authors’ hypothesis was that

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patients after ACLR would demonstrate a higher LESS score than those in the CTRL group. In addition, the authors expected that fatigue would result in higher LESS scores in the ACLR group compared to CTRL group.

Besides the relationship between physical impairments and RTS, evidence is emerging that psychological responses are strong predictors associated with RTS rate following athletic injury.19,20 The ACLReturn to Sport after Injury (ACL-RSI) scale has been shown to be a valid tool to predict athletes’ emotions, confidence and risk appraisal when returning to sport after ACLR.21 As was reported in a systematic review, ground reaction forces and hip and knee flexion moments were reduced when fatigued,14 which may contribute to an adaptive strategy to ensure a safe landing.22 Therefore, it seems plausible that confidence and risk appraisal in the ACLR group would have an effect on the ACL-RSI when performing a jump-landing task during fatigue and the change in LESS as determined by non-fatigue condition and the fatigue condition. Thus, the secondary purpose of this study was to determine the relationship between ACL-RSI and LESS scores after fatigue. It was hypothesized that a correlation exists between the ACL-RSI and LESS scores after fatigue.

METHODS Participants Twelve patients following ACLR (6 males, 6 females) who were tested at 10 ± 2.4 months after surgery participated in the current pilot study. Patients were

operated by one of two experienced orthopaedic surgeons from the same hospital. Briefly, a transtibial technique was used and in all cases a hamstring tendon graft was used. All patients completed their rehabilitation at the same rehabilitation center and were cleared to return to sports by the orthopaedic surgeons and physical therapists. In addition 10 active healthy subjects (5 males, 5 females) recruited from the local university served as the CTRL group.

These CTRL subjects had no history of previous knee injury or surgery and had no other injuries in the six months prior to participating in the study. The characteristics of both groups are presented Table 1. Sample size estimations were performed a priori using the Statistical Solutions toolkit (http://www.sta tisticalsolutions.net/pss_calc.php). Means and standard deviations from previous reported data were entered for the LESS.9 Clinically meaningful differences of two normalized units of LESS were used.

Based on statistical power to detect clinically meaningful differences, eight subjects were needed per group to compare functional differences between the experimental conditions. The Institutional Review Board approved the study and prior to participating in this study, all subjects read and signed an informed consent form.

Procedure After informed consent was obtained the subject then changed into athletic clothing. One investigator placed 14 mm reflective markers on the following anatomical landmarks of both legs: 1) greater trochanter, 2) lateral epicondyle and 3) tibial tuber-

Table 1. Characteristics of patients after ACL reconstruction (ACLR) and healthy controls (CTRL) ACLR (n=12)

CTRL (n=10)

6/6

5/5

Age (years)

27.4 ± 9.6

21.0 ± 0.8

Time post surgery (months)

10.0 ± 2.4

NA

Height (centimeters)

177.7 ± 7.4

179.1 ± 9.4

Weight (KG)

77.3 ± 12.5

72.6 ± 8.7

Gender (male/female)

All descriptive data are reported as mean +/- standard deviation.

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osity to enhance video analysis for the LESS. Prior to the start of the experiment, each subject performed a standard sub-maximal 15-minute warm-up consisting of running, agility drills and stretching of the quadriceps, hamstrings and calf muscles. The same investigator instructed subjects in performing the LESS and demonstrated its performance. Each subject was allowed to practice the jump-landing task sub-maximally 3 times prior to data collection.

Double-Legged Drop Jump (LESS) The double legged jump-landing task incorporated vertical and horizontal movements as subjects jumped from a 30-centimeter high box to a distance of 50% of subjects’ body-height away from the box, down to the ground, and immediately rebounded for a maximum vertical jump.9 During task instruction, emphasis was placed on subjects jumping as high as they could once they landed from the box. Subjects were not provided any feedback or coaching on their landing technique. A successful jump was characterized by 1) jumping off of both feet from the box; 2) jumping forward, but not vertically, 3) immediately jumping vertically after landing and 4) completing the task in a fluid motion.

Two standard 60 HZ video cameras (Sony; DSRhc62, Tokyo, Japan) captured frontal plane and sagittal plane view as each subject performed the jump landing procedures. Each jump was videotaped and scored at a later date using the pause and rewind functions. The LESS is a count 17 items of landing technique “errors” on a range of readily observable items. A higher LESS (>6) indicates poor technique in landing from the jump; a lower LESS (≤4) indicates better jump-landing technique.9 The authors used the following criteria for evaluating individual LESS items according to DiStefano et al where subjects were scored with an “error” if the subject demonstrated the specific landing characteristic error during two or more of the three trials; otherwise, that individual item was coded as “no error.”23 The LESS of the involved leg of individuals in the ACLR group was compared to the non-dominant leg of individuals in the CTRL group which has been shown to be able to accurately detect differences between groups.24 Leg dominance was defined as the leg with which the subject would kick a ball.

Fatigue Protocol The LESS was used to assess landing movement patterns under two conditions: pre-fatigue and post-fatigue.

The pre-fatigue protocol consisted of the above-mentioned test, and was considered a non-fatigue baseline.

After the baseline condition the fatigue protocol was executed. Subjects first performed a maximum counter movement jump (CMJ), which was marked for jump height. For this study fatigue was operationally defined as the point where jump height fell below 70% of the maximum jump height of that person which is similar to protocols used in previous studies.13,22 The fatigue protocol consisted of ten double-legged squats until 90 degrees of knee flexion followed by two repetitions of the CMJ. This scheme was conducted until subjects were no longer able to reach 70% of their maximum CMJ height for 2 consecutive trials (the operational definition of fatigue).

The subjects were asked to give a rating of perceived exertion (RPE) for the local fatigue in the lower extremities. The RPE is a subjective scale of ranging from 6 to 20, where 6 means “no exertion at all” and 20 means “maximal exertion”. The RPE scale is commonly used to gauge activity intensity, and is designed to estimate a subject’s heart rate based on how the subject feels.25 To ensure that fatigue was indeed present during the post-fatigue assessment, the authors’ ensured this postfatigue assessment started within 30 seconds after the fatigue protocol. After the patients in the ACLR group finished the LESS, they filled out the ACL-RSI questionnaire.26 The ACL-RSI is a 12-item scale designed to measure psychological factors associated with RTS following ACLR. The scale items are created around three specific psychological responses related to sport resumption; emotions, confidence, and risk appraisal.26 Statistical analysis All data were analyzed using SPSS (version 18.0 for Windows, SPSS Inc., Chicago, Illinois), with an a priori alpha level of p<0.05. Due to the limited sample size and skewed distribution of the data, the authors choose to apply non-parametric analyses. Changes in LESS between pre-fatigue and post-fatigue conditions for all participants were analyzed using the Wilcoxon signed ranks test. Differences in changes in LESS between ACLR and CTRL were analyzed using a Mann-Whitney U test. The non-parametric correlation of the association between ACL-RSI score of the

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Table 2. Median and Inter Quartile Range (IQR 25th, 75th Percentiles) of the Landing Error Scoring System (LESS) Scores before (Pre-fatigue) and after the fatigue protocol (Fatigue) in patients after ACL reconstruction (ACLR) and healthy controls (CTRL) ACLR

CTRL

Median

IQR

Median

IQR

Pre-fatigue

6.5

(5.5, 7.5)

2.5

(2.0, 4.0)

Fatigue

7.0

(6.0, 10.0)

6.0

(3.0, 7.0)

1.0

(0.0, 2.0)

2.0

(1.0, 3.0)

a

Change

IQR=Inter Quartile Range a

The median change of the LESS between pre-fatigue and fatigue conditions was not statistically significant different between the groups (p=0.165).

ACLR group and the change in LESS due to fatigue was explored.

RESULTS The mean RPE during the fatigue protocol was 18.7 ± 1.4 in ACLR and 18.7 ± 1.0 in CTRL group. Two of the 12 patients after ACLR only performed the LESS in the pre-fatigued condition. They declined to repeat the LESS after the fatigue protocol due to a lack of confidence in the stability of the knee. Subsequently, the analysis was performed on the remaining 10 patients. The results of the LESS in the two experimental conditions are presented in Table 2.

The LESS score increased significantly after fatigue conditions (Wilcoxon signed rank test p=0.001). The median (interquartile range) LESS scores for all participants increased from 5.0 (2.0; 7.0) for pre–fatigue condition to 7.0 (4.3; 7.8) for post-fatigue condition (p=0.001). The median increase in LESS was larger in the CTRL (2.0) group compared to patients after ACLR (1.0) but the difference was not significant (Mann-Whitney U test , p=0.165, Table 2). Box plots are presented of the LESS scores in pre-fatigue and fatigue conditions for both groups. (Figure 1) The frequency of errors was counted as the number of patients that had a specific error divided by the total group multiplied by 100. In the post-fatigue condition, the most noticeable landing errors were knee flexion at initial contact (ACLR 90%, CTRL 30%), extension on the hips (ACLR 60%, CTRL 20%), knee valgus at initial contact (ACLR 70%, CTRL 90%), lateral trunk flexion (50% ACLR, CTRL 0%), asymmetrical foot contact (ACLR 60%, CTRL 10%), maximal

Figure 1. Box plot of the Landing Error Scoring System (LESS) scores (median) for patients after ACLR and the healthy CTRL group. The box signifies the upper and lower quartiles, and the median is represented by a short black line within the box.

knee valgus (ACLR 90%, CTRL 100%). A representative landing style of a patient after ACLR showing the difference between pre-fatigued and post-fatigued state is depicted in Figures 2 and 3. The mean ACLRSI of the ACLR group was 49.68 ± 3.62 and there was no relationship (r=0.1, p=0.777) between the ACLRSI and the change in LESS as determined between the non-fatigue and the fatigue conditions.

DISCUSSION The most important findings of this study were that the LESS was higher in patients at a mean 10 ± 2.4

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Figure 2. Example of a representative patient after ACLR during the double-legged drop jump analyzed in the frontal view, A) pre-fatigued and B) post-fatigued states. An asymmetrical loading pattern in the post-fatigued state is observed with lateral trunk lean and increased valgus of the left knee. Of particular interest is the fact that the right leg is the ACLR leg, indicating that the patient was unloading her involved leg after fatigue, potentially putting her uninvolved leg at greater risk of sustaining an injury.

Figure 3. Example of a representative patient after ACLR during the double-legged drop jump analyzed in the sagittal view, A) pre-fatigued and B) post-fatigued states. A change in loading pattern is observed during the post-fatigued state demonstrated by decreased trunk, hip, and knee ďŹ&#x201A;exion.

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months after ACLR at baseline as well as after fatigue compared to CTRL. All patients after ACLR had a high LESS (>6) indicating poor landing technique.

In the current study, a series of CMJ were used to induce a generalized fatigue in subjects. These activities were selected to also induce a localized fatigue of the quadriceps, with the assumption that an amount of localized quadriceps fatigue in addition to general fatigue may result in biomechanical changes at the knee during landing.22 It seems that this series of activities was successful in inducing changing landing mechanics as assessed with the LESS. Overall, the results from the current study showed that fatigue induced changes in landing the ACLR group.

However, increased LESS were also noted in the CTRL after fatigue. In fact, the changes in the LESS were more pronounced in the CTRL compared to the ACLR group. This may be attributed to the difference in pre-fatigue LESS scores between groups.

Since the ACLR group had a higher LESS score, they may have decreased room for an increase in their LESS score, thus sort of a ceiling effect. Conversely, the CTRL group with lower pre-fatigue LESS scores had more room for increasing their LESS score.

The LESS items in the ACLR group showed more asymmetrical landing compared with the CTRL group typically with smaller knee flexion angle at initial contact, increased valgus at initial contact, more lateral trunk flexion, smaller hip flexion angle, asymmetrical foot contact and increased valgus displacement. Fatigue led to a substantial increase in LESS in the CTRL group as 90% of the subjects were classified as having a landing error due to an increase in knee valgus both at initial contact and maximal valgus angle. A systematic review of fatigue exercise on single-limb landing biomechanics revealed various biomechanical alterations that may increase the risk of a noncontact ACL injury.14 More specifically, repetitive exercise has also been shown to alter lower extremity biomechanics during doubleleg landing tasks.15,16 Recently, Schmitz et al found sagittal plane lower extremity joint biomechanics from a drop jump were altered toward the end of a 90-minute intermittent exercise protocol designed to simulate a soccer match. Subjects performed landing with less hip flexion and this more erect landing style has been associated with ACL injury mechanisms27 and has been characterized as a reduction

in shock-attenuating ability of the lower extremity.28 In the current study an increase in knee valgus was observed in the fatigued condition and is consistent with other studies.13,16 The mechanism of increased valgus may in part be attributed to a an alteration in hip kinematics. Pollard and co-workers showed that limited hip and knee flexion during landing is associated with increased valgus angles and moments.29 The authors of the current study analyzed the involved leg of the ACLR group, but the asymmetrical landing patterns were also seen in the uninvolved leg. The authors are currently working on a revision of the LESS that includes a comparative analysis of both limbs to assess side-to-side symmetry.

Biomechanical and neuromuscular risk factors for injury to the ipsilateral and contralateral knee have recently been established for both male and female patients after ACLR with high sensitivity and specificity.5 Regression analyses indicated four predictive factors for secondary injury risk with excellent specificity (88%) and sensitivity (92%): uninvolved hip rotation net moment impulse during landing, frontal-plane knee motion during landing, sagittal plane knee moment asymmetries at initial contact, and deficits in postural stability on the reconstructed leg.

The highly predictive model of second injury risk underscores the importance of targeted return-tosport rehabilitation, as all predictors are modifiable in nature.30 Although the authors performed a different jump task analysis and did not examine postural deficits there are similarities with the current findings and those of Paterno et al.5 The asymmetrical LESS items (knee flexion, knee valgus, extension the hips, trunk lean) may indicate similar landing strategies as found by Paterno and co-workers.

Given that the authors of the current study observed a greater frequency of asymmetrical landings in those with ACLR following fatigue, this may indicate greater relative loading on the uninvolved leg of the patients after ACLR as they are trying to compensate by unloading the involved leg. It could be speculated that this pattern of asymmetrical loading where the athlete initially loads their uninvolved leg more frequently post-fatigue may result in the type of loading pattern reported by Paterno et al.5 However, future research is needed to investigate the effects of asymmetrical loading on these specific variables.

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The authors of the current paper emphasize the need to use objective tools that are sensitive to detect limbto-limb deficits. There is a growing body of literature that supports the current study that put forward the assessment of the quality of movement patterns after ACLR.31-34 Subsequently rehabilitation protocols can de developed that are targeted to minimize limb asymmetries to prevent second ACL injury.35 Whilst this study only assessed subjects when they were at maximum fatigue, it is possible that the effects of fatigue are seen at a much earlier time point during a fatigue protocol. Previous studies have, for example, shown significant increases in initial contact hip extension and internal rotation, and in peak knee valgus and internal rotation when participants were only partially fatigued.13,22 Effects of fatigue may also induce task specific effects. Webster and colleagues used a series of squats, bilateral jumps and single leg landings to induce fatigue.22 Only hip flexion at initial contact was significantly larger in the ACLR leg compared to the contralateral or control group values. The greater hip flexion was suggested to be a compensatory strategy for patients to reduce the demand for knee control when landing from a height.22 The greater hip flexion is not in agreement with a previous study that showed that patients after ACLR with a hamstring graft utilized reduced hip flexion at initial contact and had lower peak hip flexion compared to a ACLR group who had a patellar tendon graft and CTRL.36 The differences in outcomes between these studies may be attributed to differences in jump tasks, kinematic analysis, time after surgery, and type of surgery.

The ACL-RSI provides preliminary evidence that the scale may be a relevant screening tool to identify athletes who may be at risk of not returning to their preinjury level of sport by 12 months after surgery.21 A score of less than 56 points on the ACL-RSI for the ACLR group may indicate an increased risk of not returning to the preinjury level and may help clinicians to identify at-risk athletes.21 In the current study the mean ACL-RSI was 49.6 points. Although the authors did not find a relationship between the ACL-RSI and the change in LESS scores in the subjects with ACLR, patients after ACLR had abnormal scores on both the ACL-RSI and LESS which in turn may be used for development of RTS criteria in future studies.

Limitations A number of study limitations must be considered.

The patient population in the current study consisted of young patients recruited from the same hospital, which may reduce generalizability of the results.

Although the current results showed that fatigue influenced landing strategies, a more precise determination of fatigue should be developed. Only the involved leg in the ACLR group was analyzed and a small sample size was studied. Given the high LESS scores in patients after ACLR and the effect fatigue induced asymmetrical landing patterns putting also the uninvolved leg at risk, future researchers should employ bilateral LESS analysis. The effect of fatigue was only examined directly after the fatigue protocol was completed and it is unknown how long the effects last. Very importantly, it is unknown if LESS scores would improve in the course of time after ACLR, and as such a longitudinal study would be valuable.

CONCLUSION This pilot study showed different movement patterns between ACLR and CTRL groups in both fatigue and non-fatigue conditions during jump landing. Significant differences in both groups were found between pre-fatigue vs. post-fatigue LESS scores. The ACLR group showed smaller knee flexion angles at initial contact, increased valgus at initial contact, more lateral trunk flexion, smaller hip flexion angle, asymmetrical foot contact and increased maximal valgus.

Fatigue resulted in an increase of the LESS scores in both groups. The authors of the current paper emphasize the need to use valid and objective tools that are sensitive to detect limb-to-limb deficits and to develop rehabilitation protocols that are targeted to eliminate limb asymmetries. Individualized rehabilitation programs that consider specific neuromuscular characteristics with and without fatigue should be developed in rehabilitation after ACLR. REFERENCES 1. Simoneau GG, Wilk KE. The challenge of return to sports for patients post-ACL reconstruction. J Orthop Sports Phys Ther. 2012;42:300-301.

2. Wilk KE, Macrina LC, Cain EL, Dugas JR, Andrews JR. Recent advances in the rehabilitation of anterior cruciate ligament injuries. J Orthop Sports Phys Ther.

2012;42:153-171.

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3. Barber-Westin SD, Noyes FR. Factors used to determine return to unrestricted sports activities after anterior cruciate ligament reconstruction.

Arthroscopy. 2011;27:1697-1705.

4. Sward P, Kostogiannis I, Roos H. Risk factors for a contralateral anterior cruciate ligament injury.

Knee Surg Sports Traumatol Arthrosc. 2010;18: 277-291.

5. 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;38:1968-1978.

6. Ahlden M, Samuelsson K, Sernert N, Forssblad M, Karlsson J, Kartus J. The Swedish National Anterior Cruciate Ligament Register: a report on baseline variables and outcomes of surgery for almost 18,000 patients. Am J Sports Med. 2012;40:2230-2235.

7. Jang SH, Kim JG, Ha JK, Wang BG, Yang SJ. Functional performance tests as indicators of returning to sports after anterior cruciate ligament reconstruction. Knee. 2014;21:95-101.

8. Logerstedt D, Grindem H, Lynch A, et al. Singlelegged Hop Tests as Predictors of Self-reported Knee Function After Anterior Cruciate Ligament Reconstruction: The Delaware-Oslo ACL Cohort Study. Am J Sports Med. 2012;40:2348-2356.

9. Padua DA, Marshall SW, Boling MC, Thigpen CA, Garrett WE, Beutler AI. The Landing Error Scoring System (LESS) Is a Valid and Reliable Clinical Assessment Tool of Jump-Landing Biomechanics The JUMP-ACL Study. Am J Sports Med. 2009;37:1996-2002.

10. Smith HC, Johnson RJ, Shultz SJ, et al. A Prospective Evaluation of the Landing Error Scoring System (LESS) as a Screening Tool for Anterior Cruciate Ligament Injury Risk. Am J Sports Med. 2012;40:521-526.

11. Theiss JL, Gerber JP, Cameron KL, et al. JumpLanding Differences Between Varsity, Club, and Intramural Athletes: The Jump-ACL Study. J Strength Cond Res. 2014;28:1164-1171.

12. Goerger BM, Marshall SW, Beutler AI, Blackburn JT, Wilckens JH, Padua DA. Anterior cruciate ligament injury alters preinjury lower extremity biomechanics in the injured and uninjured leg: the JUMP-ACL study. Br J Sports Med. 2014 Feb 21. doi: 10.1136/ bjsports-2013-092982. [Epub ahead of print] 13. Borotikar BS, Newcomer R, Koppes R, McLean SG. Combined effects of fatigue and decision making on female lower limb landing postures: central and peripheral contributions to ACL injury risk. Clin Biomech. 2008;23:81-92.

14. Santamaria LJ, Webster KE. The effect of fatigue on lower-limb biomechanics during single-limb landings: a systematic review. J Orthop Sports Phys Ther. 2010;40:464-473.

15. Chappell JD, Herman DC, Knight BS, Kirkendall DT, Garrett WE, Yu B. Effect of fatigue on knee kinetics and kinematics in stop-jump tasks. Am J Sports Med. 2005;33:1022-1029.

16. McLean SG, Fellin RE, Suedekum N, Calabrese G, Passerallo A, Joy S. Impact of fatigue on genderbased high-risk landing strategies. Med Sci Sports Exerc. 2007;39:502-514.

17. Sanna G, O’Connor KM. Fatigue-related changes in stance leg mechanics during sidestep cutting maneuvers. Clin Biomech. 2008;23:946-954.

18. Augustsson J, Thomee R, Karlsson J. Ability of a new hop test to determine functional deficits after anterior cruciate ligament reconstruction. Knee Surg Sports Traumatol Arthrosc. 2004;12:350-356.

19. Ardern CL, Taylor NF, Feller JA, Webster KE. A systematic review of the psychological factors associated with returning to sport following injury.

Br J Sports Med. 2013;47:1120-1126.

20. Ardern CL, Taylor NF, Feller JA, Webster KE. Fear of re-injury in people who have returned to sport following anterior cruciate ligament reconstruction surgery. J Sci Med Sport. 2012;15:488-495.

21. Ardern CL, Taylor NF, Feller JA, Whitehead TS, Webster KE. Psychological Responses Matter in Returning to Preinjury Level of Sport After Anterior Cruciate Ligament Reconstruction Surgery. Am J Sports Med. 2013;41:1549-1558.

22. Webster KE, Santamaria LJ, McClelland JA, Feller JA. Effect of fatigue on landing biomechanics after anterior cruciate ligament reconstruction surgery.

Med Sci Sports Exerc. 2012;44:910-916.

23. DiStefano LJ, Padua DA, DiStefano MJ, Marshall SW. Influence of Age, Sex, Technique, and Exercise Program on Movement Patterns After an Anterior Cruciate Ligament Injury Prevention Program in Youth Soccer Players. Am J Sports Med. 2009;37: 495-505.

24. Myer GD, Schmitt LC, Brent JL, et al. Utilization of Modified NFL Combine Testing to Identify Functional Deficits in Athletes Following ACL Reconstruction. J Orthop Sports Phys Ther.

2011;41:377-387.

25. Brazen DM, Todd MK, Ambegaonkar JP, Wunderlich R, Peterson C. The effect of fatigue on landing biomechanics in single-leg drop landings. Clin J Sport Med. 2010;20:286-292.

26. Webster KE, Feller JA, Lambros C. Development and preliminary validation of a scale to measure the

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27.

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30.

psychological impact of returning to sport following anterior cruciate ligament reconstruction surgery.

Phys Ther Sport. 2008;9:9-15.

Boden BP, Dean GS, Feagin JA, Jr., Garrett WE, Jr. Mechanisms of anterior cruciate ligament injury.

Orthopedics. 2000;23:573-578.

Blackburn JT, Padua DA. Influence of trunk flexion on hip and knee joint kinematics during a controlled drop landing. Clin Biomech. 2008;23:313-319.

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. 2010;25:142-146.

Myer GD, Martin L, Jr., Ford KR, et al. No association of time from surgery with functional deficits in athletes after anterior cruciate ligament reconstruction: evidence for objective return-to-sport criteria. Am J Sports Med. 2012;40:2256-2263.

31. Pairot de Fontenay B, Argaud S, Blache Y, Monteil K. Asymmetries in joint work during multi-joint movement after anterior cruciate ligament reconstruction: A pilot study. Scand J Med Sci Sports.

2014.Mar 20. doi: 10.1111/sms.12207. [Epub ahead of print] 32. Xergia SA, Pappas E, Zampeli F, Georgiou S, Georgoulis AD. Asymmetries in functional hop tests,

33.

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lower extremity kinematics, and isokinetic strength persist 6 to 9 months following anterior cruciate ligament reconstruction. J Orthop Sports Phys Ther.

2013;43:154-162.

Castanharo R, da Luz BS, Bitar AC, D’Elia CO, Castropil W, Duarte M. Males still have limb asymmetries in multijoint movement tasks more than 2 years following anterior cruciate ligament reconstruction. J Orthop Sci. 2011;16:531-535.

Orishimo KF, Kremenic IJ, Mullaney MJ, McHugh MP, Nicholas SJ. Adaptations in single-leg hop biomechanics following anterior cruciate ligament reconstruction. Knee Surg Sports Traumatol Arthrosc.

2010;18:1587-1593.

Gokeler A, Benjaminse A, Hewett TE, et al.

Feedback Techniques to Target Functional Deficits Following Anterior Cruciate Ligament Reconstruction: Implications for Motor Control and Reduction of Second Injury Risk. Sports Med. 2013;43:1065-1074.

Decker M, Torry M, Sterett W. Functional adaptations affect landing performance after ACL reconstruction.

Biomechanics. 2000:29-40.

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IJSPT

ORIGINAL RESEARCH

THE ACTIVITY PATTERN OF THE LUMBOPELVIC MUSCLES DURING PRONE HIP EXTENSION IN ATHLETES WITH AND WITHOUT HAMSTRING STRAIN INJURY Mahnaz Emami, PT, MSc1 Amir Massoud Arab, PT, PhD2 Leila Ghamkhar, PT, MSc1

ABSTRACT Background: Altered muscular activation pattern has been associated with musculoskeletal disorders. Some previous studies have demonstrated muscle weakness or tightness in athletes who have sustained hamstring (HAM) injuries. However, no study has clinically investigated the muscular activity pattern in subjects with HAM strain injuries.

Objective: To investigate the activity pattern of the ipsilateral erector spinae (IES), contralateral erector spinae (CES), gluteus maximus (GM), and medial and lateral HAM muscles during the prone hip extension (PHE) test in athletes with and without history of HAM strain injury.

Design: Cross-sectional non-experimental study design.

Participants: A convenience sample of 20 soccer athletes participated in the study. Subjects were categorized into two groups: those with history of HAM strain injury (n=10, mean age = 22.6 ± 3.74) and without history of HAM strain (n =10, mean age = 22.45 ± 3.77).

Methods: Three repetitions of the PHE were performed by each subject, and the electromyographic (EMG) outputs of the IES, CES, GM, and HAM muscles were recorded, processed and normalized to maximum voluntary electrical activity (MVE). Independent ttests were used for comparing activation means of each muscle between athletes with and without history of HAM strain injury.

Results: There were significant differences in EMG activity of the GM (p= 0.04) and medial HAM (p = 0.01) between two groups.

No significant difference was found in EMG signals of the IES (p= 0.26), CES (= 0.33) and lateral HAM (p= 0.58) between the two groups. Greater although non-significant normalized EMG outputes of IES, CES and lateral HAM were seen in athletes with history of HAM strain compared to those without HAM strain.

Conclusion: The findings of this study demonstrated greater normalized EMG activity of GM and medial HAM tested in athletes with history of HAM strain compared to those without HAM strain (altered activation pattern).

Level Of Evidence: 3a Key Words: Electromyography, hamstring strain, movement pattern, prone hip extension.

1

University of Social Welfare and Rehabilitation Sciences, Evin, Tehran, Iran 2 Department of Physical Therapy, University of Social Welfare and Rehabilitation Sciences, Evin, Tehran, Iran.

Source of Support: Partially supported by the University of Social Welfare and Rehabilitation Sciences Institutional review board: Human subject committee of University of Social Welfare and Rehabilitation Sciences, Tehran, Iran Disclosures: None

CORRESPONDING AUTHOR Amir Massoud Arab, PT, PhD Associate Professor Department of Physical Therapy University of Social Welfare and Rehabilitation Sciences Evin, Koodakyar Ave., Tehran, Iran Zip Code: 1985713831 Tel: (98) 21 22180039 (Office) (98) 21 22358149 (Home) Fax: (98) 21 22180039 E-mail: arabloo_masoud@hotmail.com; Amarab@uswr.ac.ir

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INTRODUCTION Hamstring injuries are frequently identified as a common soft tissue injury occurring in athletes who participate in sports involving rapid acceleration and frequent stopping and starting, like soccer.1-7 Hamstring strain injuries account for 12-16% of soccer injuries and the financial impact of this has been estimated to be 115.86 million dollars.4 A rate of five to six hamstring strain injuries per club per season has been observed, resulting in minimum of three and maximum of 15-21 matches missed per club per season on average.3 Hamstring muscle strain is a frustrating injury with persistent symptoms, often slow healing (at least 2-3 weeks), with a high re-injury rate.3 It has been reported that the re-injury rate of Australian football players who lost the entire season after the first hamstring injury was as high as 12-31%.1,4,5,7 Hamstring muscle dysfunction (weakness or tightness) has been frequently associated with hamstring muscle strain. Authors of previous studies describe hamstring muscle weakness or tightness in athletes with hamstring muscle injury.8,9 During the recent decades, the approach of assessment and treatment of musculoskeletal pain has been changed from exercises targeted at developing strength alone, toward modifying the motor system.10 Balance within the motor system is derived from coordinated activity of synergist and antagonist muscles. According to this point of view, change in muscle length and strength characteristics can lead to altered movement patterns, pain, and movement disorders.10 Increased or decreased muscle activity and delayed muscular activation can also change the normal movement pattern.11,12 Recently, several authors have suggested that the main focus of rehabilitation should be on modification of the altered movement patterns found in patients with musculoskeletal pain and disorders.12-14 Several authors have shown altered activation pattern of the certain lumbo-pelvic muscles such as the gluteal muscles, trunk extensor muscles, trunk flexor muscles, and hip extensors in people who suffer from lumbo-pelvic disorders.15-18 The prone hip extension (PHE) test is a commonly and widely accepted test used to assess muscular

activation patterns in the lumbo-pelvic area. In PHE, subjects lie in prone position and lift the chosen leg off the bed to 10 degrees of hip extension whilst keeping the knee straight.12 PHE is a muscle activity pattern that has been theorized to simulate those muscles used during functional movement patterns such as gait.11,14 It has been theorized that changes in the typical activity pattern can overstress the various structures such as joint, ligament, capsule and etc., resulting in pain during walking.19 Good reliability has been reported for PHE test.20 Both timing (onset time) and amplitude of muscle activity are commonly calculated using electromyography (EMG) to investigate muscular activation patterns in musculoskeletal disorders.21-24 During PHE, the investigator evaluates the activity pattern of the ipsilateral erector spinae (IES), contralateral erector spinae (CES), ipsilateral gluteus maximus (GM) and ipsilateral hamstring (HAM) muscles21.

It is assumed that when a muscle responsible for a specific joint movement (the prime mover) is inhibited or weakened, the amplitude of activation is lowered and the synergistic muscles substitute and become overactive during the movement.17,21,23 When a muscle is tight, the irritability threshold of the muscle is believed to be decreased. With less slack to take up before contraction begins, the muscle is activated earlier than normal in a movement sequence.10 Thus, the patterns of tightness or weakness seen in the muscle imbalance process result in alteration of the normal movement pattern.10 Considering HAM muscle weakness or tightness that has been reported in athletes who have sustained HAM muscle strains,25-27 it is possible that altered muscular activation patterns exist during PHE in these subjects.

According to Sahrmann, abnormal movement pattern during PHE could place unusual mechanical stresses on the structures in lumbo-pelvic area.10 Review of the literature revealed that previous studies have examined HAM muscle strength or tightness in athletes with HAM injuries. However, to the authorsâ&#x20AC;&#x2122; knowledge, no study has clinically investigated the muscular activity pattern of lumbo-pelvic muscles during PHE in athletes with HAM strain injuries. The purpose of this study was to investigate the amplitude of the activation of IES, CES, GM and medial and lateral

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HAM muscles during PHE in male athletes with and without history of HAM strain injury.

METHODS Subjects A cross-sectional non-experimental observational study was used to compare the muscle activity pattern during PHE in two groups of male professional soccer athletes with history of HAM strain (N = 10, average age: 22.6 [SD = 3.74] years old, average height: 180 [SD = 0.04] cm, average weight: 75.8 kg [SD = 7.49] kg) and athletes with no history of HAM strain (N = 10, average age: 104 22.45 [SD = 3.77] years old, average height: 177 [SD = 0.07] cm, average weight: 74.1 [SD = 8.02] kg).

Athletes with history of HAM strain were referred for participation in the study by orthopedic specialists and physiotherapy clinics. The patients were included if they had a history of HAM strain during the year before the time of the study. They could not have sustained a hamstring strain in the month before the study date.3,27 All players with history of HAM strain reported localized posterior thigh pain at the time of injury that resulted in missed training and/or playing time (at least one match). Athletes who sustained contact injuries (direct trauma) were excluded. The healthy players were included if they had no history of HAM strain and were matched for age, height, weight and BMI. The exclusion criteria in both groups were history of hip pain, dislocation or fracture of the lower extremity, history of lumbar spine surgery, history of knee ligament injury or rupture, history of anterior knee pain, history of pain or injury in lumbar area in the prior three months, recent episodes of ankle sprain 3 month prior to the study, leg length difference of more than one centimeter, inability to perform active PHE without pain, shortness of hip flexors (by Thomas Test), or positive neurological symptoms. Each eligible subject was enrolled after signing an informed consent form approved by the human subjects committee at the University of Social Welfare and Rehabilitation Sciences. Ethical approval for this study was granted from the internal ethics committee at the University of Social Welfare and Rehabilitation Sciences.

The injured leg of the injured subjects and dominant leg of healthy subjects were chosen for investigation.

The raw EMG activity pattern of IES, CES, GM and HAM muscles during PHE was collected using the MIE-MT8 Telemetry EMG instrument (MIE-Medical, Leeds, UK). A preamplifier with a gain of (4000Ă&#x2014;), band pass filter (6-500 HZ) and A-D convertor (sampling rate = 1000 HZ) were used to process the EMG signal. The subjects were asked to lie prone with their arms at their side and head in mid line.

The skin was shaved, rubbed, and cleaned with alcohol. To record muscle activity, disposable, bipolar, self-adhesive Ag/Agcl electrodes (In Vivo Metric, Healdsburg, CA, USA) were placed in pairs with distance of 1.5-2 cm from each other and parallel to the muscle fibers.25 Electrode placement to collect EMG signals were as follow: for the ES muscles, bilaterally at least 2 cm lateral to spinous process of L3 parallel to the vertebral column on the muscle belly; for the GM, at the midpoint of a line running from S2 to the greater trochanter; for the lateral HAM, laterally on the mid distance between gluteal and popliteal fold; and for the medial HAM, medially on the mid distance between gluteal and popliteal fold. Figure 1 depicts the electrode placement for EMG assessment of the muscles.

The maximum voluntary electrical activity (MVE) for each muscle was calculated for use during normalization. Testing procedure to calculate MVE were similar to those described for manual muscle testing of the muscles, as described by Kendall et al.28 The pelvis was secured to the bed with a sling to prevent pelvic motion substitution only during MVE testing.

For the ES muscles the subject was asked to bring up their trunk against the maximum resistance applied

Figure 1. Electrode placement for EMG assessment of the muscles.

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below the scapula. For the GM, the hip joint was placed in an extended position with the knee flexed to 90 degrees, and resistance was applied to the distal aspect of posterior portion of thigh. For the HAM muscles, the hip joint was placed in extension position of zero degrees, the knee was flexed to nearly 70 degrees, and resistance was applied to the distal aspect of the posterior portion of the shank during knee flexion with medial rotation for medial HAM and with lateral rotation for lateral HAM. Each contraction was repeated 2 times and held 5 seconds.

One-minute rest was given between contractions.

An average of the two MVC contractions was used for calculations.

Before testing, the subjects were familiarized with the standard position and movement. All subjects were asked to lift the chosen leg off the bed to 10 degrees of hip extension whilst keeping the knee straight, as soon as they heard the command “lift”. An adjustable bar was placed at this level and the subjects were asked to extend their hip until the calcaneus touched the bar. The subjects were instructed only to reach the adjustable bar and were not instructed to press against the bar with the distal segment of the lower extremity. This was repeated three times for each individual. Figure 2 presents an example of the raw EMG signals for tested muscles. The raw data were processed into the root mean square (RMS). The EMG signals collected during hip extension were normalized to MVC expressed as percentage of the calculated mean RMS of MVE (%MVE). The muscle activity pattern was characterized by maximal amplitude of normalized voluntary activity.

Figure 2. Example of data recording from the tested muscles.

Data Analysis Statistical analysis was performed using SPSS Version 17. Multivariate analysis was used to compare the maximal amplitude of normalized voluntary activity of the tested muscles between athletes with and without history of HAM strain. Statistical significance was defined as a p-value less than 0.05.

RESULTS The demographic data for each are displayed in Table 1. There was no statistically significant difference in subjects’ age, height, weight and BMI between the two groups. The maximal amplitude of normalized electrical activity of the IES, CES, GM and medial and lateral HAM muscles during PHE test in athletes with and without history of HAM strain are presented in Table 2. There was significant difference in EMG activity of the GM (F=3.48, p=0.04) and medial HAM (F=5.26, p = 0.01) between the two groups. However, no significant difference was found in EMG activity of the IES (F=1.39, p= 0.26), CES (F=1.14, p= 0.33) and lateral HAM (F=0.54, P= 0.58) among the two groups. The results indicated that normalized electrical activity of the IES, CES, and lateral HAM muscles is greater during PHE, (although not statistically significantly) in athletes with history of HAM injury compared to those without HAM injury.

DISCUSSION The current study compared muscular activation patterns between individuals with and without history of HAM strain. The results of this study showed higher maximal amplitude of normalized electrical activity of the tested muscles in athletes with history of HAM strain compared to those without history of HAM. However, only the difference in EMG activity of medial HAM and GM were statistically significantly different between the two groups. These findings demonstrate that a difference exists in the muscular activity pattern during PHE in athletes with history of HAM strain compared with healthy, uninjured subjects.

Many factors affect absolute EMG amplitudes, such as thickness of tissues overlying the muscle and skin impedance. To obtain an EMG output that is independent of these factors, the EMG amplitude must be normalized to the amplitudes obtained in MVE.

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Table 1. Demographic data of the subjects in each group With Hamstring strain (n=10)

Without Hamstring strain (n=10)

Average (SD)

Mean

Average (SD)

Mean

Variables

Age (years)

(3.74)

22.6

(3.77)

22.45

Weight (kg)

(7.49)

75.8

(8.02)

74.1

Height (cm)

(0.04)

180

(0.07)

177

BMI (kg/m2)

(1.81)

23.23

(1.28)

23.44

SD = Standard Devia on BMI = Body Mass Index

Table 2. Electromyographic activity of the muscles during prone hip extension in subjects with and without Hamstring strain Muscle ac vity

Without Hamstring strain

With Hamstring strain

p-value

IES

28.20(16.59)

41.60 (23.77)

0.26

CES

36.40(14.09)

44.90(17.97)

0.33

GM

18.33(12.08)

27.83(23.84)

0.04

Med HAM

40(16.92)

72(23.81)

0.01

Lat HAM

51.08(23.72)

60.40(19.66)

0.58

(%MVE)

Values are Mean (SD), bold p-values indicate sta s cal signiďŹ cance IES: Ipsilateral erector spinae; CES: Contralateral erector spinae; GM: Gluteus maximus; Med HAM: Medial hamstring; Lat HAM: Lateral hamstring

However, this procedure may not be appropriate for subjects who have sustained injury because they may be unwilling or not able to perform maximum contractions due to pain or fear of re-creating pain.

Normalization to sub maximal contractions is not a good method because the EMG amplitudes during these contractions will be affected similarly during the activities to be studied. In the current study, MVE method was used because subjects had no pain during the test and none of the subjects reported that pain was a limiting factor to perform the PHE test.

Thus the direct effects of pain can be minimized.

Investigators have attributed the HAM strain to various factors, such as muscle weakness, reduced flexibility or tightness, fatigue, and muscle imbalance.

Some investigators have demonstrated HAM muscle

weakness or tightness and muscle imbalance in athletes with HAM muscle strain injury.8,9 The concept of muscle imbalance has been explained by different authors.10-12,28-30 In its simplest form it is defined as the ratio between the strength or flexibility of the agonist and antagonist muscles around a joint.

However, more in-depth descriptions of muscle imbalance define the altered movement pattern in musculoskeletal disorders. When a muscle is weakened or inhibited, the synergistic muscle substitute and become overactive to perform the movement.

Thus, the pattern of tightness or weakness seen in the muscle imbalance process result in alteration of the normal movement pattern.10 Hence, contemporary treatment focus has shifted to modification of the altered movement pattern in patients with musculoskeletal pain and disorders.12-14

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To the authors’ knowledge, this is the first study to investigate the muscular activation pattern in a specified movement pattern (PHE) in athletes with HAM strain injury. The difference in the normalized EMG activity of the muscles between individuals with and without HAM strain found in the current study complements the results of authors which indicated that muscle imbalance is associated with HAM strain injury and could be considered as an important risk factor. The current data revealed a significant difference in activity pattern of medial HAM (p = 0.01) while there was no significant difference in lateral HAM activity (p= 0.58) between athletes with and without history of HAM strain. This discrepancy may be due to the site of injury in the HAM muscles in the participants with hamstring strain. Different parts of the HAM muscles (medial vs. lateral) vary from each other with respect to muscle architecture, e.g. fascicular length, physiological cross-sectional area, length of the proximal and distal free tendons, extent of the intramuscular tendons and flexion moments.31,32 In this study, medial side of hamstring was mostly commonly affected in the subjects with hamstring strain.

Controversy exists regarding the most common site of strain injury (medial vs. lateral) in HAM muscles.

In this study, most of the subjects had strain injury in the medial portion of the HAM muscles. Change in medial-lateral HAM muscle activation ratio has been previously reported in other musculoskeletal disorders including lumbo-pelvic and low back pain.33 The current data showed a significant difference in EMG activity of the GM between the athletes with and without history of HAM strain. GM provides powerful hip extension during sprinting. The hamstrings are thought to act as transducers of power.

HAM muscle dysfunction followed by strain injury may cause the GM to be overactive. Both of these two actions may predispose an athlete to re-injury.

Lumbo-pelvic dysfunction and disorders has been associated with HAM strain.34 Some investigators have shown an altered muscular activation pattern of the erector spinae, gluteal maximus, and hamstring muscles during PHE subjects with and without low back pain.21,24 Considering the association between HAM strain and lumbo-pelvic abnormality or dysfunction, the current findings are in accordance

with other studies showing alteration in muscular activity patterns in patients with low back pain.21,25,35 However, in this study, none of participants had low back pain. Subjects in the current study with HAM strain had non-statistically significant higher EMG activity of the IES, CES, and lateral HAM muscles during PHE compared with those without HAM injury (Table 2). However, the reason that no statistical differences were found between groups may be explained by the relatively small sample size. Therefore, it is essential to continue to investigate using a larger sample size in order to obtain the answers of the research questions more precisely. Additionally, in this study, the severity of strain injuries was mild and moderate and athletes with severe or acute HAM strain were not included in order to lessen the direct effects of pain as an important limiting factor.

Some investigators stated that muscle dysfunction in subjects with musculoskeletal disorders might be related to pain, called “pain interference”.35-37 They believed that ability of voluntary contraction in all muscles during a movement is reduced because of the pain sensation. In this study, none of the subjects reported that pain was a limiting factor when producing hip extension. If a study is performed using athletes with severe injuries, muscular activity patterns may be significantly different between athletes with and without HAM strain injury due to muscle inhibition from pain or inflammation.

The authors acknowledge several limitations. One of the limitations and a weakness of this study was the sample size. Subjects with severe and acute HAM strain were excluded in order to assess the muscle activity pattern in a more homogenous population.

So, the accessible population, that is athletes with mild and moderate HAM strain injury and no other type of strain injury, was limited to a relatively small group of patients that were available during the time frame that this study was conducted. The authors’ suggest that this study could be repeated on subjects with different types and varied acuity of HAM strain to provide more insight regarding the muscular activity pattern in athletes with greater variety of HAM strain injury.

It should also be noted that EMG measurements do not always guarantee the actual magnitude of force production or and objective measure of actual muscle

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strength.. In some cases, an inhibited muscle may work harder than a normal one in order to produce the required force for a particular task. Thus, the timing of the onset of muscle activity in addition to normalized EMG amplitude could provide additional useful information regarding the muscular activation pattern.

CONCLUSION The results of this study indicate that there was statistically significantly greater normalized EMG activity of the medial HAM and GM in athletes with history of HAM strain injury compared to healthy subjects during the PHE test.

REFERENCES 1. Bing Yu RMQ ANA, Yu Liu, Claude T. Moorman, William E. Garrett. Hamstring muscle kinematics and activation during overground sprinting.

J Biomech. 2008;41:3121-3126.

2. Chumanov E TD. Hamstring strain injuries: recommendations for diagnosis, rehabilitation, and injury Prevention. J Orthop Sports Phys Ther.

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3. Engebretsen A MG, Holme I, Engebretsen L, Bahr R. 2010;38(6):1147-1153. Intrinsic risk factors for hamstring injuries among male soccer players. Am J Sports Med. 2010;38(6):1147-1153.

4. Hoskins W PH. The management of hamstring injury--Part 1: Issues in diagnosis. Man Ther.

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5. Hunter D SC. The assessment and management of chronic hamstring/posterior thigh pain Best Pract Res Clin Rheumatol. 2007;21(2):261-277.

6. Page P FC, Lardner R. Assessment and Treatment of muscle Imbalance. Human Kinetics. 2010.

7. Petersen J HP. Evidence based prevention of hamstring injuries in sport. Br J Sports Med. 2005;39(6):319-323.

8. Askling C ST, Thorstensson A. Type of acute hamstring strain affects flexibility, strength, and time to return to pre-injury level. Br J Sports Med. 2006;40(1):40-44.

9. Silder A TD, Heiderscheit BC. Effects of prior hamstring strain injury on strength, flexibility, and running mechanics. Clin Biomech. 2010;25:681-686.

10. Sahrmann. S. Diagnosis and treatment of movement impairment syndrome: 1th ed. St Louis: Mosby. 2002.

11. Sahrmann. S. Posture and muscle imbalance.

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13. O’Sullivan P PD TL, Allison G. Evaluation of specific stabilizing exercise in the treatment of chronic low back pain with radiologic diagnosis of spondylolysis or spondylolisthesis. Spine. 1997;22(24):2959.

14. V. J. Pain in the locomotor system-A broad approach.

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16. Hungerford B GW, Hodges P. Evidence of altered lumbopelvic muscle recruitment in the presence of sacroiliac joint pain. Spine. 2003;28:1593-1600.

17. Leinonen V KM, Airaksinen O, Hanninen O. Back and hip extensor activities during trunk flexion/ extension: Effects of low back pain and rehabilitation. Arch Phys Med Rehabil. 2000;81:32-37.

18. Newcomer K JT, Gabriel D, Larson D, Brey R, An K. Muscle activation patterns in subjects with and without low back pain. Arch Phys Med Rehabil 2002;83:816-821.

19. Vogt L PK, Banzer W. Neuromuscular control of walking with chronic low-back pain. Man Ther.

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20. Murphy D BD, Mccarthy P, Humphreys K, Gregory A, Rochon R. Interexaminer reliability of the hip extension test for suspected impaired motor control of the lumbar spine. J Manipulative Physiol Ther.

2006;29:374-377.

21. Bruno P BJ. An investigation into motor pattern differences used during prone hip extension between subjects with and without low back pain.

Clinical Chiropractic. 2007;10:68-80.

22. Lehman G LD, Tresidder B, Rayfield B, Poschar M. Muscle recruitment patterns during the prone leg extension. BMC Musculoskelet Disord. 2004;5(1):3.

23. Lewis C SS. Muscle activation and movement patterns during prone hip extension exercise in women. J Athl Train. 2009;44(3):238-248.

24. Sakamoto A T-SL, de Paula-Goulart F, de Morais Faria C, Guimarães C. Muscular activation patterns during active prone hip extension exercises. J Electromyogr Kinesiol. 2009;19(1):105-112.

25. Arab AM GL, Emami M, Nourbakhsh MR. Altered muscular activation during prone hip extension in women with and without low back pain. Chiropr Man Therap. 2011;19:18-24.

26. DLC. BJ. Muscle alive: their functions revealed by electromyography. Baltimore: Williams and Wilkins.

1985:Links.432.

27. Franklin BA. Balady GJ BK, Golding LA, Gordon N, Mahler DA Myers JN, and Sheldhal LM, ACSM’s.

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Garrett WE RF, Nickolaou PK, et al. Computed tomography of hamstring muscle strains. Med Sci Sports Exerc. 1989;21:506-514.

Woodley SJ MS. Hamstring muscles: architecture and innervation. Cells Tissues Organs 2005;179:125-141.

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Hennessey L WA. Flexibility and posture assessment in relation to hamstring injury. Br J Sports Med 1993;27:243-246.

Moseley GL HP. Are the changes in postural control associated with low back pain caused by pain interference? Clin J Pain. 2005;21:323-329.

Hodges PW MG, Gabrielsson A. Evidence for a direct effect of pain on postural recruitment of the trunk muscles in pain free humans. Exp Brain Res. 2004.

Zedka M PA, Knight B, et al. Voluntary and reďŹ&#x201A;ex control of human back muscles during induced pain.

J Physiol (Lond). 1999;520:591-604.

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IJSPT

ORIGINAL RESEARCH

ASSOCIATION BETWEEN QUADRICEPS STRENGTH AND SELFREPORTED PHYSICAL ACTIVITY IN PEOPLE WITH KNEE OSTEOARTHRITIS Brian Pietrosimone, PhD, ATC1 Abbey C. Thomas, PhD, ATC2 Susan A. Saliba, PhD, PT, ATC3 Christopher D. Ingersoll, PhD, ATC4

ABSTRACT Purpose/Background: Physical inactivity is common in patients with knee osteoarthritis (OA) and has been linked to serious comorbidities such as cardiovascular disease, obesity, and diabetes. The purpose of this study was to examine the association between quadriceps strength and self-reported physical activity in patients with radiographically confirmed knee OA. Secondarily, the authors’ sought to determine if there were differences in quadriceps strength between knee OA patients with low physical activity (LPA) and knee OA patients with higher physical activity (HPA). A tertiary aim of this study was to examine the effect of gender on physical activity and quadriceps strength in patients with knee OA. Methods: Thirty-six patients with radiographically diagnosed tibiofemoral knee OA participated (15 males, 21 females; age = 59.9±11.6 yrs; height = 171.2±9.2 cm; mass = 84.3±18.9 kg; body mass index (BMI)= 28.9±6.9;Godin Leisure-Time questionnaire =32.5±25.01). Maximal isometric knee extensor strength was assessed with a Isokinetic dynamometer in 70° of knee flexion. Knee extension torque values were normalized to body mass (Nm*kg-1). Physical activity was evaluated using the Godin Leisure-Time questionnaire. A Godin-Leisure time score of 32.5, which was the mean score in the current dataset, was what was used to categorize subjects into LPA and HPA subgroups. Independent t-tests were used to determine differences in strength between HPA and LPA subgroups, as well as differences in strength and physical activity between genders. Pearson Product Moment and Spearman rank correlations were used to analyze associations between normally and non-normally distributed variables.

Results: Quadriceps strength was positively correlated with physical activity (r=0.44, r2=0.18, p=0.01). The HPA subgroup had significantly greater quadriceps strength (n=15, 2.01±0.84) compared to the LPA subgroup (n=21, 1.5±0.59, p=0.04).

Strength was significantly correlated with physical activity in the HPA subgroup (ρ=0.53, p=0.04), but not in the LPA subgroup (ρ=-0.21,p=0.35). Males reported significantly more physical activity (43.0±28.5 vs 25.1±19.64; p=0.03) and greater strength than females in the entire cohort (2.15±0.73 Nm*kg-1 vs 1.40±0.57 Nm*kg-1; p= 0.002), and the HPA subgroup (2.4±0.65 Nm*kg-1 vs 1.4± 0.68 Nm*kg-1; P=0.02). There were no gender differences for strength in the LPA subgroup.

Conclusion: Higher levels of quadriceps strength correlate with higher physical activity in knee OA patients. The association between higher strength and increased physical activity is stronger in the HPA subgroup compared to the entire sample.

Additionally, the HPA subgroup demonstrated greater quadriceps strength compared to the LPA subgroup.

Level of Evidence: 3 Key Words: Inactivity, maximum voluntary isometric contraction, physical function, quadriceps

1

Department of Exercise and Sport Science, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA 2 Department of Kinesiology, University of Toledo, Toledo, Ohio, USA 3 Department of Human Services, University of Virginia, Charlottesville, Virginia, USA 4 Herbert H. and Grace A. Dow College of Health Professions, Central Michigan University, Mount Pleasant, Michigan, USA Funding Sources: American Physical Therapy Association, Orthopedic Section Grant

CORRESPONDING AUTHOR Brian Pietrosimone, PhD, ATC Assistant Professor Department of Exercise and Sport Science University of North Carolina at Chapel Hill CB# 8700, 209 Fetzer Hall Chapel Hill, NC 27599 Phone: 919-962-3617 Fax: 919-962-0489 E-mail: brian@unc.edu

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INTRODUCTION There is currently no cure for knee osteoarthritis (OA), a disease that disables 12.1-16% of adults in the United States.1,2 Patients with knee OA are at greater risk of developing cardiovascular disease, obesity, and diabetes, all of which can be linked to increased body mass index and physical inactivity.3 Furthermore, disability, impaired ambulation, and decreased physical activity may lead to secondary health complications and increased risk of mortality in patients with knee OA.3,4 Interventions that focus on increasing walking have been successful in improving physical activity,5 reducing self-reported workplace limitations,6 as well as decreasing pain and improving fatigue in patients with knee arthritis.7 Identifying factors that may allow for increased physical activity and exercise in patients with knee OA is important for developing clinical methods to improve general health in patients with knee OA. Improving lower extremity strength is a hallmark characteristic of non-surgical knee OA management.8 Specific attention as been paid to the quadriceps musculature, which is important for ambulatory propulsion and energy attenuation at the knee during gait,9 and, quadriceps dysfunction is common in patients with knee OA.10 Quadriceps strength and voluntary muscle activation are associated with physical disability in people with knee osteoarthritis.11 Physical inactivity is associated with quadriceps weakness in patients with chronic diseases12,13,14,15 and even quadriceps muscle wasting in patients with chronic obstructive pulmonary disease.16 Knee OA patients and people at risk of developing knee OA have demonstrated decreased physical activity,17,18 yet the association between quadriceps muscle strength and physical activity remains uncertain.

Associations between quadriceps muscle strength, quadriceps activation, and disability have been evaluated in patients with knee OA;11,19,20 while these associations provide information regarding the consequence of muscle weakness on movement patterns, pain, and physical function, the current literature has not evaluated if an association exists between strength and exercise habits or the amount of physical activity in which people with knee OA engage. Establishing the association between quadriceps muscle strength and the amount of exercise in which knee OA patients par-

ticipate is important for understanding the effects of physical inactivity on the quadriceps, a group of muscles known to predict disability in knee OA patients.11 Additionally, an association between the amount of exercise and quadriceps strength may provide evidence that increasing quadriceps strength may positively affect exercise tolerance in patients with knee OA. The Godin Leisure-Time Exercise questionnaire is a self-reported measure of the frequency and intensity of exercise in which people engage, which demonstrates acceptable test-retest reliability (reliability coefficient 0.74).21 The Godin Leisure-Time Exercise questionnaire asks individuals to quantify the amount of time participating in activities of different intensities (mild, moderate and strenuous). The Godin LeisureTime questionnaire has been found to discriminate between fit and unfit health people (ages 18-65) as well as between those with higher and lower body fat.21 Therefore, the overall goal of the current study was to evaluate the association between quadriceps strength to leisure-time exercise in people with knee OA. The primary purpose of this study was to examine the association between quadriceps strength and self-reported physical activity in patients with radiographically confirmed knee OA. Secondarily, the authorsâ&#x20AC;&#x2122; sought to determine if there were differences in quadriceps strength between knee OA patients with low physical activity (LPA) and knee OA patients with higher physical activity (HPA). A tertiary aim of this study was to examine the effect of gender on physical activity and quadriceps strength in patients with knee OA. METHODS Participants Thirty-six participants were enrolled in this study and demographics are presented in Table 1. Participants with radiographically confirmed (Kellgren-Lawrence score 1-4), symptomatic tibiofemoral OA were recruited for this study from participating orthopedic surgeons. The current study was part of a randomized control trial that included patients with voluntary quadriceps activation failure. Voluntary quadriceps activation is a product of motor unit recruitment and firing frequency of the muscle.22 Because the larger trial was evaluating knee OA patients with lower activation, patients were excluded if the vol-

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Table 1. Demographic and Descriptive data, reported as counts or means and standard deviations

untary quadriceps activation was greater than 90% on the symptomatic limb. Voluntary quadriceps activation was assessed using the burst superimposition technique and calculated with the central activation ratio.23 The CAR was performed in the same position as isometric strength testing, which is described later in the manuscript.23 After warming up for 5 minutes on a stationary bike and practicing maximal voluntary isometric contractions (MVIC) of the quadriceps, patients performed CAR trials. During CAR testing, an exogenous electrical stimulus, used previously by the authors,23-27 was applied to the quadriceps when the test administrator observed that the maximal force plateau had been reached. Two trials, separated by a 60 second rest period, were performed to ensure that two acceptable trials could be averaged at each testing session. CAR was calculated by dividing the force measurements of the maximal voluntary contraction by that of the force produced by the exogenous electrical stimulus.23-27 Participants with a diagnosed heart condition limiting exercise, lower body surgery, or acute knee trauma in the past 6 months were excluded. Participants with a history of a total knee

arthroplasty were included in the study, but the side with the knee replacement was excluded from being classified as the involved knee. The involved knee, used for the study was considered the knee with the greatest radiographic evidence of OA or, in the case that both knees were graded similarly, the knee with the worst patient-reported dysfunction. Participants were asked to discontinue the use of all non-essential pain medication 24-hours prior to all testing sessions.

The Institutional Review Board at the University of Virginia approved this protocol prior to participant enrollment, and written informed consent was obtained prior to participation. The Western Ontario and McMaster University Osteoarthritis Index questionnaire (pain, stiffness and function subsets) was completed by each participant to determine selfreported disability, and the results are reported in the demographics section (Table 1).

Procedures Maximal Voluntary Quadriceps Activation Testing The same investigator collected all data. Quadriceps strength was measured isometrically at 70째 of knee

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flexion using an isokinetic dynamometer (Biodex System 3, Biodex, Shirley, NY). The torque signal was collected from the dynamometer and output via a custom cable to a separate analog to digital converter for digitization and analysis (Biopac MP150, Biopac Systems Inc., Galeta CA). Prior to testing, participants performed a standardized warm up by pedaling a stationary bicycle at a self-selected speed for five minutes.23 Participants were seated on the dynamometer, with straps placed across the chest and waist to stabilize the pelvis and trunk. The hips of each participant were flexed to 85o and knees were positioned in 70o of flexion. Submaximal warm-up trials at 25, 50 and 75% of the participant’s perceived maximal effort was performed on the dynamometer to assure that participants were able to exert maximal effort during the test. Participants performed two to four practice maximal voluntary isometric contractions (MVIC), separated by at least 60 seconds of rest, until peak torque until peak torque no longer continued to increase and the investigator was confident that each participant was able to exert maximal effort. Participants were then instructed to extend their knee with maximal effort into the stationary arm of the dynamometer.

All participants were provided verbal encouragement and were able to visualize torque output on a monitor in real-time as the MVIC was performed. Patients were encouraged to contract the quadriceps until the investigator visualized a plateau in maximal force production. Three trials, separated by a 60 second rest period, were performed and the two trials with the highest MVIC were averaged for analysis.23 Self – Reported Physical Activity Self-reported physical activity was evaluated with the Godin Leisure-Time Questionnaire.21 The investigator explained the questionnaire to each participant and provided a quiet room with a desk for participants to complete the questionnaire. The investigator remained easily accessible to the participant to answer any questions. Participants were instructed to recall the number of sessions that strenuous, moderate and mild physical activity was performed over the previous, typical seven-day period. A single session of physical activity had to last greater than 15 minutes to be recorded on the Godin Leisure-Time Questionnaire. A higher Godin Leisure-Time score was interpreted as more physical activity. A Godin Leisure-Time score of 24

or above has previously been considered to represent active individuals, while individuals scoring 14- 23 are considered to be moderately active, and those scoring less than 14 are considered insufficiently active.28 Data Analysis All raw torque data were low-pass filtered at 15 Hz. The MVIC was calculated from a 0.15 second time epoch of voltage signal that represented the plateau in torque output. All MVICs were normalized to body mass (Nm*kg-1). A self-reported physical activity score was determined by multiplying the frequency of sessions by an assigned value for strenuous (9), moderate (5) and mild (3) activity. The total of all activity grades was summed to calculate the total score.21 Statistical Analyses Means and standard deviations for normalized quadriceps MVIC and Godin Leisure-Time exercise scores were calculated. The mean Godin Leisure-Time exercise score of the entire sample was used as a cut off score to dichotomize patients into high physical activity and low physical activity sub-groups. Three correlation analyses were performed to determine the association between muscle strength and self-reported function in the entire sample as well as the high and low physical activity subgroups. Pearson Product Moment and Spearman rank correlations were used to analyze associations between parametric and non-parametric variables, respectively. Independent t-tests were used to determine if differences in quadriceps strength existed between high and low physical activity sub-groups.

Additionally, independent t-tests were used to determine if there were differences in quadriceps strength and physical activity within the entire group as well as high and low physical activity subgroups between genders. Correlation coefficients were classified in the current study, 0.0-0.4 as weak, 0.41–0.7 as moderate, and 0.7-1.0 as strong. Alpha levels were determined a priori as p< 0.05 and all statistical analyses were conducted with IBM SPSS Version 19.

RESULTS Association Between Strength and Physical Activity in Entire Group Forty-nine people with knee OA were screened prior to the study and 13 people (26%) were excluded as

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they exhibited quadriceps voluntary activation above 90%. Means and standard deviations for outcome measures and demographics are presented in Table 1. Three of the knee OA patients had undergone total knee arthroplasties on the uninvolved limb prior to the study. Quadriceps strength was significantly, positively correlated with physical activity (r=0.44, r2=0.18, p=0.01) with all patients with knee OA included in the correlation analysis. A Godin-Leisure time score of 32.5, which was the mean score in the current dataset, was used to divide subjects into the high and low physical activity subgroups.

The mean cutoff score in the current study (32.5) is higher than a previously suggested Godin LeisureTime questionnaire cutoff score of (24),28 suggesting that the cohort of knee OA patients being studied was slightly more active than previously studied populations.

Differences between Physical Activity Subgroups Physical activity was reported to be significantly lower in the LPA (15.61±10.68) subgroup compared to the HPA group (56.27±19.20; p<0.001). The high physical activity subgroup had significantly greater quadriceps strength (n=15, 2.01±0.84 Nm/*kg-1) compared to the LPA subgroup (n=21, 1.50±0.59 Nm/*kg-1, p=0.04). Quadriceps strength significantly correlated with physical activity in the HPA subgroup (ρ=0.53, p=0.04), but not in the low physical activity subgroup (ρ=-0.21, p=0.35).

Differences between Males and Females Overall, males (43.0±28.5) reported significantly more physical activity than females (25.1±19.64; p=0.03) and demonstrated significantly greater strength (2.15±0.73 Nm*kg-1) compared to females (1.40±0.57 Nm*kg-1; p= 0.002). In the LPA subgroup, (6 male, 15 female) there was no difference in quadriceps strength (1.76±0.65 vs 1.39±.54 Nm*kg-1; p=0.2) or physical activity (16.3±12.88 vs. 15.33±10.0 p=0.85) between males and females, respectively. In the HPA subgroup, men demonstrated significantly greater strength (2.4±0.65 Nm*kg-1) compared to the women (1.4± 0.68 Nm*kg1 ; p=0.02), while there was no difference between physical activity (60.78 ±20.7 vs. 49.5±15.9; p=0.28) between males and females, respectively.

DISCUSSION Quadriceps strength was moderately associated with physical activity and predicted 18% of the variance (r=0 .44, r2=0.18) in physical activity in the total sample of patients with knee OA. Additionally, patients reporting high physical activity (> 32.5 on the Godin leisure-time questionnaire) had stronger quadriceps than the subgroup of patients with low physical activity. A similar association between quadriceps strength and physical activity were found in the HPA subgroup (ρ=0.53); patients with knee OA who were more physically active also demonstrated greater quadriceps strength. A significant correlation between quadriceps strength and physical activity did not exist in the subgroup with low physical activity (ρ=-0.21), which may suggest that there may be other factors that are more influential than quadriceps strength that predict physical activity in patients with low self-reported physical activity. It is possible that motivation to engage in physical activity may influence physical activity more in the LPA subgroup than muscle strength. It is possible that the size of the LPA subgroup sample was too small to detect meaningful correlations, as one limitation to the current study is that these data were acquired from a randomized controlled trial originally powered to detect differences between groups receiving transcutaneous electrical nerve stimulation to increase voluntary quadriceps activation.23 The exact reason that quadriceps strength does not predict the majority of variance in physical activity is unknown but there are likely multiple other factors that influence physical activity in patients with knee OA. Knee OA is a multifactorial condition that includes injury and disease of multiple joint structures. Strength or activation of multiple lower extremity muscles affect contact forces at the knee,29 many of which may uniquely contribute to explaining a portion of the diminished physical activity seen in patients with knee OA. Additionally, the inability to tolerate pain during locomotion may explain additional variance regarding physical activity, as fear of pain during ambulation may decrease physical activity.3,30,31 Non-physiological factors such as socioeconomic status may be associated with lower leisure-time physical activity.32 It is possible that severity of joint damage at the time of testing may

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have contributed to explain a proportion of variance in the amount of physical activity. The distribution of radiographic OA severity between the HPA and LPA groups was slightly different, as there were more people with Kellgren and Lawrence grade 3 and 4 in the LPA subgroup. (Table 1) There is previous evidence33 that radiographic severity is not a suitable predictor of function. In order to determine this in the current sample, the authors performed a post hoc 1 Ă&#x2014; 4 analysis of variance to determine if physical activity was significantly different between the Kellgren and Lawrence scores 1-4. No statistically significant difference was present in between group comparisons (F3,35=0.84, p=0.47), indicating that physical activity was not different between patients with different radiographic severities of knee OA. Quadriceps strength is essential for physical performance during locomotion and energy attenuation around the knee during the stance phase of gait.

Decreased quadriceps strength and voluntary activation predict disability when measured using both physical performance and self-reported assessments in patients with knee OA.11 Additionally, patients with OA demonstrate more extended knees during gait,34 which may decrease energy attenuation capabilities during the stance phase of gait and contribute to joint deterioration.9 Furthermore, quadriceps strength has been found to contribute to a poor quality of life in several other conditions, including coronary artery disease,12 diabetes,15 and chronic obstructive pulmonary disease.35 Patients with knee OA are commonly more sedentary than healthy controls, demonstrating less overall physical activity. Increased inactivity in patients with knee OA may put them at higher risk for developing life-threating, inactivity-related comorbidities.3 In fact, disability related to impaired ambulation and decreased physical activity has been linked to secondary health complications and increased risk of mortality in patients with knee OA.3 Slemenda et al demonstrated that quadriceps weakness preceded the development of pain and muscle atrophy in patients with radiographic knee OA,36 suggesting that quadriceps strength was a primary risk factor for the development of knee deterioration. Women with moderate (50th-25th percentile) and high (top 25th percentile) strength have a 55-65% decreased risk of developing knee OA when studied over a 14-year period.37 As more

evidence emerges, the association between quadriceps strength and knee OA has become less clear. There is evidence that declining quadriceps strength is more closely related to the incidence of knee OA38 than OA progression.39 Furthermore, quadriceps strength in the top tertile of people without knee OA may be may protect against the development of knee OA in patients reporting both clinical symptoms and demonstrating radiographic evidence of OA, but not protective in asymptomatic patients with radiographic evidence of OA.38 Furthermore, gender may play a role in the association between knee OA and quadriceps strength, as quadriceps weakness has been associated with knee OA and joint space narrowing in women but not men.40 There is evidence that minor gender differences are found for torque and power measures in people with knee OA,41 while gender does not seem to affect strength gains following isometric exercise in knee OA patients.42 In the current study men reported higher physical activity and demonstrated greater quadriceps strength overall compared to females. The HPA group demonstrated the same trend, with men displaying greater normalized strength and physical activity, while the LPA group demonstrated no differences in strength and activation between genders. Gender did not seem to influence strength or physical activity in the most sedentary patients with knee OA, yet the disproportionately high number of females compared to the males in the dataset may influence the current findings.

Although the association between OA progression and strength is not clear, quadriceps weakness remains a hallmark physical impairment associated with tibiofemoral OA. There is substantial evidence linking quadriceps weakness to arthrogenic muscle response (AMR) in patients with knee OA.10 AMR is characterized as an altered neural excitability (inhibition or facilitation) of the uninjured musculature surrounding an injured joint.43 The authors of a recent meta-analysis concluded that voluntary quadriceps activation was significantly decreased in knee OA patients compared to healthy, age matched participants. Decreased voluntary quadriceps activation has been found to moderate the association between muscle strength and disability in patients with knee OA, as weak patients with low voluntary activation demonstrate more disability.10 Participants in the current study all demonstrated voluntary quadri-

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ceps activation less than 90%, suggesting that these patients were afflicted with AMR that may have contributed to their strength deficits.

While it remains unclear how quadriceps strength contributes to OA progression, the need to encourage physical activity in patients with knee OA seems to be critical for maintaining or improving general wellness in this population. Furthermore, there is evidence that the level of physical activity does not affect the progression of knee OA,44 suggesting that physical activity does not hasten knee deterioration in patients with knee OA.17 The authors of a previous study reported that increased quadriceps strength was related to increased joint damage measured with radiographs,45 similar findings have not been corroborated by more sophisticated magnetic resonance imaging techniques.46 Data from the current study may suggest that improving quadriceps strength is critical for increasing physical activity, even though past research may not confirm the protective capabilities of quadriceps strength on OA disease progression. Low impact, aerobic exercise interventions have demonstrated improvements in physical activity, functional performance, and strength, as well as reduction in pain for patients with knee OA.5 Physical activity recommendations for patients with knee OA have focused on improving the duration of activity rather than intensity. Increasing the duration of physical activity requires both muscular strength and endurance.5 The authorsâ&#x20AC;&#x2122; have previously demonstrated that improving strength in patients with knee OA may be enhanced by targeting voluntary quadriceps activation deficits in combination with strength training.47 Nearly half (47%) of strength changes in patients with knee OA can be explained by changes in voluntary quadriceps activation following four weeks of strength training.

Transcutaneous electrical nerve stimulation,23 neuromuscular electrical stimulation,48 and focal joint cooling49 have been proposed to specifically target deficits in voluntary quadriceps activation and augment therapeutic exercise in patients with knee OA. Future clinical trials and therapeutic management strategies should evaluate the effectiveness of combining interventions that target enhancement of voluntary quadriceps activation, muscular strength, and duration of physical activity in an effort to improve general wellness in patients with knee OA.

It should be noted that the current study used selfreported measures of physical activity from the Godin Leisure-Time questionnaire and isometric assessments of quadriceps strength. Future study of the association between quadriceps strength and physical activity in the knee OA population could be strengthened by evaluating more objective measures of physical activity, such as daily step count or an activity log. Different modes of strength measurement, such as isokinetic or isotonic strength may provide a more functional assessment of strength. Additionally, clinical therapeutic trials should evaluate the association between the change in quadriceps strength and improvement in physical activity to best examine the influence that quadriceps strength has on physical activity. Clinicians may focus on simultaneously increasing quadriceps strength and encouraging physical activity to in order to improve the translation of clinical therapeutic strengthening outcomes into healthy behavioral adaptations such as increased levels of physical activity.

CONCLUSION In summary, higher levels of physical activity moderately correlate with higher quadriceps strength in the entire current sample of patients with knee OA. However, quadriceps strength predicted only 18% of the variance in physical activity in this sample. The association between higher quadriceps strength and increased physical activity was stronger in the high physical activity subgroup, as compared to the entire sample. Quadriceps strength did not significantly correlate with physical activity in the LPA subgroup but the HPA subgroup demonstrated greater quadriceps strength compared to the subgroup of patients who reported LPA. REFERENCES 1. Dillon C, Rasch E, Gu Q, Hirsch R. Prevalence of knee osteoarthritis in the United States: Arthritis data from the third national health and nutrition examination survey 1991-94. J Rheumatol.

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2. Jordan J, Helmick C, Renner J, Luta G, Dragomir A, Woodard J, Fang F, Schwartz T, Abbate L, Callahan L, Kalsbeek W, Hochberg M. Prevalence of knee symptoms and radiographic and symptomatic knee osteoarthritis in African Americans and Caucasians: the Johnston County Osteoarthritis Project.

J Rheumatol. 2007;34(1):172-180.

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3. Nuesch E, Dieppe P, Reichenbach S, Williams S, Iff S, Juni P. All cause and disease specific mortality in patients with knee or hip osteoarthritis: population based cohort study. BMJ. 2011;342.

4. van Dijk G, Veenhof C, Spreeuwenberg P, Coene N, Burger B, van Schaardenburg D, van den Ende C, Lankhorst G, Dekker J, Group. CS. Prognosis of limitations in activities in osteoarthritis of the hip or knee: a 3-year cohort stud. Arch Phys Med Rehabil.

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5. Talbot L, Gaines J, Huynh T, Metter E. A HomeBased Pedometer-Driven Walking Program to Increase Physical Activity in Older Adults with Osteoarthritis of the Knee: A Preliminary Study.

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6. Nyrop K, Charnock B, Martin K, Lias J, Altpeter M, Callahan L. Effect of a six-week walking program on work place activity limitations among adults with arthritis. Arthritis Care Res (Hoboken).

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7. Callahan L, Mielenz T, Freburger J, Shreffler J, Hootman J, Brady T, Buysse K, Schwartz T. A randomized controlled trial of the people with arthritis can exercise program: symptoms, function, physical activity, and psychosocial outcomes.

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8. Fransen M, McConnell S. Exercise for osteoarthritis of the knee. Cochrane Database Syst Rev. 2008;8: CD004376.

9. Radin E, Yang K, Riegger C, Kish V, O’Connor J. Relationship between lower limb dynamics and knee joint pain. J Orthop Res. 1991;9(3):398-405.

10. Pietrosimone B, Hertel J, Ingersoll C, Hart J, Saliba S. Voluntary quadriceps activation deficits in patients with tibiofemoral osteoarthritis: A metaanalysis. PM&R. 2011;3(2):153-162.

11. Fitzgerald GK, Piva SR, Irrgang JJ, Bouzubar F, Starz TW. Quadriceps activation failure as a moderator of the relationship between quadriceps strength and physical function in individuals with knee osteoarthritis. Arthritis Rheum. 2004;51(1):40-48.

12. Kamiya K, Mezzani A, Hotta K, Shimizu R, Kamekawa D, Noda C, Yamaoka-Tojo M, Matsunaga A, Masuda T. Quadriceps isometric strength as a predictor of exercise capacity in coronary artery disease patients. Eur J Prev Cardiol. May 30 2013.

13. van den Borst B, Slot IG, Hellwig VA, Vosse BA, Kelders MC, Barreiro E, Schols AM, Gosker HR. Loss of quadriceps muscle oxidative phenotype and decreased endurance in patients with mild-tomoderate COPD. J Appl Physiol. May 2013;114(9):1319-1328.

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Shrikrishna D, Patel M, Tanner R, Seymour J, Connolly B, Puthucheary Z, Walsh S, Bloch S, Sidhu P, Hart N, Kemp P, Moxham J, Polkey M, Hopkinson N. Quadriceps wasting and physical inactivity in patients with COPD. Eur Respir J. 2012;40(5):1115-1122.

Felson DT, Niu J, Clancy M, Sack B, Aliabadi P, Zhang Y. Effect of recreational physical activities on the development of knee osteoarthritis in older adults of different weights: the Framingham Study.

Arthritis Rheum. Feb 15 2007;57(1):6-12.

Richmond S, Fukuchi R, Ezzat A, Schneider K, Schneider G, Emery C. Are joint injury, sport activity, physical activity, obesity, or occupational activities predictors for osteoarthritis? A systematic review.

J Orthop Sports Phys Ther. 2013;43(8):515-B519.

Hurley M, Scott D, Rees J, Newham D. Sensorimotor changes and functional performance in patients with knee osteoarthritis. Ann Rheum Dis. 1997;56(11):641648.

Miller M, Rejeski W, Messier S, Loeser R. Modifiers of change in physical functioning in older adults with knee pain: the Observational Arthritis Study in Seniors (OASIS). Arthritis Rheum. 2001;45(4):331-339.

Godin G, Shephard R. A simple method to assess exercise behavior in the community. Can J Appl Sport Sci. 1985;10(3):141-146.

Kent-Braun J, Le Blanc R. Quantitation of central activation failure during maximal voluntary contractions in humans. Muscle Nerve.

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Pietrosimone B, Saliba S, Hart J, Hertel J, Kerrigan D, Ingersoll C. Effects of transcutaneous electrical nerve stimulation and therapeutic exercise on quadriceps activation in people with tibiofemoral osteoarthritis. J Orthop Sports Phys Ther. 2011;41(1): 4-12.

Pietrosimone B, Hart J, Saliba S, Hertel J, Ingersoll C. Immediate effects of transcutaneous electrical nerve stimulation and focal knee joint cooling on quadriceps activation. Med Sci Sports Exerc.

2009;41(6):1175-1181.

Pietrosimone B, Ingersoll C. Focal knee joint cooling increases the quadriceps central activation ratio.

J Sports Sci. 2009;27(8):873-879.

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26. Pietrosimone B, Park C, Gribble P, Pfile K, Tevald M. Inter-limb differences in quadriceps strength and volitional activation. J Sports Sci. 2012;30(5):471-477.

27. Pietrosimone BG, Hammill RR, Saliba EN, Hertel J, Ingersoll CD. Joint angle and contraction mode influence quadriceps motor neuron pool excitability.

Am J Phys Med Rehabil. Feb 2008;87(2):100-108.

28. Godin G. The Godin-Shephard Leisure-Time Physical Activity Questionnaire. Heath & Fitness Journal of Canada. 2011;4(1):18-22.

29. Sasaki K, Neptune R. Individual muscle contributions to the axial knee joint contact force during normal walking. J Biomech. 2010;43(13):2780-2784.

30. Wideman T, Finan P, Edwards R, Quartana P, Buenaver L, Haythornthwaite J, Smith M. Increased sensitivity to physical activity among individuals with knee osteoarthritis: relation to pain outcomes, psychological factors, and responses to quantitative sensory testing. Pain. 2014;155(4):703-711.

31. Pisters M, Veenhof C, van Dijk G, Dekker J, Group CS. Avoidance of activity and limitations in activities in patients with osteoarthritis of the hip or knee: a 5 year follow-up study on the mediating role of reduced muscle strength. Osteoarthritis Cartilage.

2014;22(2):171-177.

32. Beenackers M, Kamphuis C, Giskes K, Brug J, Kunst A, Burdorf A, van Lenthe F. Socioeconomic inequalities in occupational, leisure-time, and transport related physical activity among European adults: a systematic review. Int J Behav Nutr Phys Act. 2012;19(9):1-23.

33. Creamer P, Lethbridge-Cejku M, Hochberg M. Factors associated with functional impairment in symptomatic knee osteoarthritis. Rheumatology (Oxford).39(5):490-496.

34. Rudolph K, Schmitt L, Lewek M. Age-related changes in strength, joint laxity, and walking patterns: are they related to knee osteoarthritis? Phys Ther.

2007;87(11):1422-1432.

35. Mador MJ, Bozkanat E, Kufel TJ. Quadriceps fatigue after cycle exercise in patients with COPD compared with healthy control subjects. Chest. Apr 2003;123(4):1104-1111.

36. Slemenda C, Brandt KD, Heilman DK, Mazzuca S, Braunstein EM, Katz BP, Wolinsky FD. Quadriceps weakness and osteoarthritis of the knee. Ann Intern Med. Jul 15 1997;127(2):97-104.

37. Hootman J, FitzGerald S, Macera C, Blair S. Lower Extremity Muscle Strength and Risk of Self-Reported Hip or Knee Osteoarthritis. J Phys Act Health.

2004;1(4):321-330.

38. Segal N, Torner J, Felson D, Niu J, Sharma L, Lewis C, Nevitt M. Effect of thigh strength on incident

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Segal N, Torner J, Felson D, Niu J, Sharma L, Lewis C, Nevitt M. Knee extensor strength does not protect against incident knee symptoms at 30 months in the multicenter knee osteoarthritis (MOST) cohort.

PM&R. 2009;1(5):459-465.

Segal N, Glass N, Torner J, Yang M, Felson D, Sharma L, Nevitt M, Lewis C. Quadriceps weakness predicts risk for knee joint space narrowing in women in the MOST cohort. Osteoarthritis Cartilage.

2010;18(6):769-775.

Berger M, McKenzie C, Chess D, Goela A, Doherty T. Sex differences in quadriceps strength in OA. Int J Sports Med. 2012;33(11):926-933.

Anwer S, Equebal A, Nezamuddin M, Kumar R, Lenka P. Effect of gender on strength gains after isometric exercise coupled with electromyographic biofeedback in knee osteoarthritis: a preliminary study. Ann Phys Rehabil Med. 2013;56(6):434-442.

Hopkins JT, Ingersoll C. Arthrogenic muscle inhibition: a limiting factor in joint rehabilitation.

J Sport Rehabil. 2000;9(2):135-159.

Hootman J, Macera C, Helmick C, Blair S. Influence of physical activity-related joint stress on the risk of self-reported hip/knee osteoarthritis: a new method to quantify physical activity. Prev Med. 2003;36(5):636-644.

Sharma L, Dunlop DD, Cahue S, Song J, Hayes KW. Quadriceps strength and osteoarthritis progression in malaligned and lax knees. Ann Intern Med. 2003;138(8):613-619.

Amin S, Baker K, Niu J, Clancy M, Goggins J, Guermazi A, Grigoryan M, Hunter DJ, Felson DT. Quadriceps strength and the risk of cartilage loss and symptom progression in knee osteoarthritis.

Arthritis Rheum. Jan 2009;60(1):189-198.

47. Pietrosimone B, Saliba S. Changes in voluntary quadriceps activation predict changes in quadriceps strength after therapeutic exercise in patients with knee osteoarthritis. Knee. 2012;19(6):939-943.

48. Palmieri-Smith R, Thomas A, Karvonen-Gutierrez C, Sowers M. A clinical trial of neuromuscular electrical stimulation in improving quadriceps muscle strength and activation among women with mild and moderate osteoarthritis. Phys Ther. 2010;90(10):1441-1452.

49. Palmieri-Smith R, Thomas A. A neuromuscular mechanism of posttraumatic osteoarthritis associated with ACL injury. Exerc Sport Sci Rev. 2009;37(3):147-153.

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IJSPT

ORIGINAL RESEARCH

ACTIVATION DEFICITS DO NOT LIMIT QUADRICEPS STRENGTH TRAINING GAINS IN PATIENTS AFTER TOTAL KNEE ARTHROPLASTY Adam R. Marmon, PhD1 Lynn Snyder-Mackler, PT, ScD1

ABSTRACT Purpose/Background: Patients after total knee arthroplasty (TKA) are known to exhibit deficits in quadriceps muscle activation. The purpose of this study was to determine if quadriceps activation levels in patients after TKA at the beginning of rehabilitation would influence quadriceps strength after rehabilitation.

Design: A secondary analysis of data from a prospective, randomized, longitudinal clinical trial.

Setting: Institutional clinic and research laboratory.

Participants: Patients who underwent unilateral TKA (Men= 102; Female= 84).

Main Outcome: Voluntary activation of the quadriceps during maximal voluntary isometric contractions (MVIC) was measured using the central activation ratio (CAR). Hierarchical multivariate regression analysis was used to determine if CAR prior to treatment could predict MVIC after the strength training intervention.

Results: After controlling for age, sex, and initial strength levels (R2= 0.548; p<0.001), the predictability of quadriceps strength after the 6-week intervention did not change when pain during MVIC (R2= 0.551; p= 0.317) and pre-rehabilitation activation levels (R2= 0.551; p= 0.818) were introduced into the regression.

Conclusions: Initial quadriceps activation levels, for patients who underwent TKA, did not predict the quadriceps strength following a strength training intervention. Therefore, deficits in voluntarily activation post-operatively should not be considered as a rate-limiting factor in recovering quadriceps strength after TKA. Keywords: Central activation ration, knee extensors, knee replacement Level of Evidence: Retrospective cohort study. Level IIb

1

University of Delaware, Newark DE, USA

Acknowledgement of ďŹ nancial support National Institutes of Health (grant 5P20RR016458 and 5P20RR016458-S1). F32 AR060684-02 (Grants F32 AR060684-02, 5P2ORRO16458, and 5P2)RR)16548-S1) The study was approved by the University of Delaware Human Subjects Review Board.

CORRESPONDING AUTHOR Adam R. Marmon 540 South College Avenue Health Sciences Complex â&#x20AC;&#x201C; STAR Campus University of Delaware Department of Physical Therapy Email: marmon@udel.edu Phone: 302-831-7393

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INTRODUCTION Total knee arthroplasty (TKA) is the surgical procedure of choice for many with end-stage knee osteoarthritis. The 2010 National Statistics for the United States indicate that over 600,000 TKAs were performed,1 with projections of 3.48 million TKA procedures to be performed annually by 2030.2 The projected increases may be attributed in part to the ability of the TKA to relieve pain and lead to improvements in lower extremity function,3,4 but also to the number of younger and more active patients undergoing TKA.5,6 While the recommendations and activity options for mature athletes become clearer, deficits in functional ability for patients who undergo TKA persist for years after surgery and may remain unresolved, especially when compared to age-matched individuals without knee pathology.7â&#x20AC;&#x201C;10 In individuals with knee osteoarthritis, pain is positively correlated with disability and strength is negatively correlated with disability.11â&#x20AC;&#x201C;13 However, following TKA, when the arthritic pain is typically resolved, strength is often substantially reduced.7,14,15 The weakening of the quadriceps following TKA is attributed to muscle atrophy and reduced levels of voluntary activation,14,15 with activation deficits explaining more of the strength deficits than atrophy,14 primarily in the early stages after TKA.16 The factors that typically contribute to reductions in voluntary activation include pain11,17 and swelling.18,19 Joint damage can also lead to alterations in the sensory information from the periphery (e.g. afferent feedback), which influences the excitability of alpha motor neuron pool, in turn reducing the voluntary activation, even in the presence of maximal descending commands.20 In patients with end-stage, unilateral knee osteoarthritis, muscle activation has also been shown to be a better predictor of quadriceps weakness than lean muscle cross-sectional area,21 which further supports the suggestion that quadriceps activation failure is a moderator of the relation between quadriceps strength and physical function.12 Therefore, in individuals with weak quadriceps, the level of voluntary activation influences their functional abilities. Large activation deficits may, in turn, impede the recovery of quadriceps strength if the intensity of the strength training exercises falls below the necessary threshold for inducing strength gains.22 The benefits of high-resistance strength training, as discussed in

the review by Folland and Williams, can be attributed to a combination of both neural and muscular adaptations that are more likely to be achieved at higher resistance intensities, including hypertrophy of type II fibers and improvements in muscle activation.23 Therefore, if activation deficits influence the effectiveness of the strength training intervention because insufficient resistances can be utilized, clinicians need to question the whether the strength training intervention will be an effective treatment for these individuals.

A recent clinical trial incorporated progressive strength training of the lower extremity musculature as a post-surgical treatment regimen that was based-on a model described by Stevens et al.24 The training comprised a 6-weeks regimen designed to reduce pain, improve range of motion, and focused on increasing quadriceps strength through progressive increases in exercise resistances. The findings from this study demonstrated that substantial recovery of quadriceps strength, as well as significantly greater recovery of functional performance, were observed compared to standard of care treatments that focus on range of motion and pain alone.25 However, it is unclear if the quadriceps activation levels of patients after TKA, prior to starting a progressive strength training rehabilitation regimen, can predict the recovery in quadriceps strength in response to rehabilitation. Quadriceps activation is often assessed by the burst superimposition technique, where a train of electrical stimuli are applied to a muscle during a maximal voluntary contraction and the increase in muscle force, in response to the stimulation, is quantified.26 Quadriceps muscle activation is often assessed in patients after TKA.27â&#x20AC;&#x201C;30 The theory is that if the neural drive to a muscle is disrupted, the magnitude of disruption or activation deficit can be quantified and expressed relative to the maximal force output generated with the addition of a peripheral stimulation provided to the muscle. Scopaz and colleagues recently demonstrated that pre-exercise therapy levels of the quadriceps activation, in patients with knee OA, was not predictive of the change in quadriceps strength following therapy.31 However, the surgical procedures involved in TKA lead to substantial changes to the knee joint, especially with respect to joint receptors and reduc-

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tions in pain. Therefore, the objective of this study was to determine if the post-surgical levels of voluntary quadriceps activation assessed prior to the start of out-patient rehabilitation for patients after TKA could predict quadriceps strength in patients that participated in a strength training intervention. The authors’ hypothesized that quadriceps activation levels prior to participating in a progressive strength training rehabilitation protocol would be predictive of quadriceps strength observed following a strength training regimen, such that individuals with lower levels of voluntary activation pre-treatment would demonstrate less strength than those with higher activation levels after treatment.

METHODS Subjects The data from patients at the initial evaluation (IE) for outpatient rehabilitation and at the end of a strength training program (~3mos) were examined as a secondary analysis of a cohort enrolled in a prospective, randomized, longitudinal clinical trial. Subjects underwent unilateral TKA (ages ranged from 48-84 years; mean age 64.8 ± 8.6 years) and participated in a clinical trial investigating two rehabilitation protocols; patients who received conventional treatment and those who received progressive strength training (with an imbedded cohort of patients with [Exercise + NMES] and without neuromuscular electrical stimulation [Exercise Only]). The progressive strength training group (including those in the imbedded cohort) exhibited significantly larger improvements in strength and functional measures compared to the standard of care group.25 The NMES protocol is described in detail elsewhere,25 however, in brief the treatment involved 10 electrically evoked contractions of the quadriceps that lasted 10 seconds each. The intensity of the stimulations was determined based on patient tolerance, with a targeted minimum of 30% of the subjects’ maximum voluntary isometric contraction (MVIC). There were no differences at any time period between the two progressive strength training cohorts (Exercise+NMES and Exercise Only); subjects combined from both groups comprise the study group for this analysis.

Patients scheduled for unilateral TKA were invited to participate in the study by mail; interested participants were screened through a telephone interview.

Individuals were subsequently excluded if they had uncontrolled hypertension, diabetes, body mass index (BMI) ≥40, symptomatic osteoarthritis in the contralateral knee (>4 out of 10 pain on verbal analog scale), other neurologic impairments or lower extremity orthopedic problems that limited function. The surgical procedure was cemented tricompartmental TKA with medial parapatellar approach.

All patients received both inpatient and home physical therapy treatment prior to enrolling. The Human Subject Review Board at the University of Delaware approved the study, with all participants providing informed consent prior to participation.

Progressive Strength Training Intervention The treatment programs were administered at the University of Delaware’s Physical Therapy Clinic.

The progressive strength training programs focused on improving strength in the quadriceps, hamstrings, triceps surae, and the hip flexors, extensors, and abductors.24 The programs were individualized, with the type and intensity of the exercises determined and adjusted by a licensed physical therapist based each individual’s clinical evaluation and follow-up assessments. In general, subjects completed two sets of the prescribed exercises bilaterally with the resistance set to achieve a maximum of 10 repetitions. Training was progressed in all exercises to achieve a similar maximum of 10 repetitions over three sets. All subjects completed two or three sessions each week for six weeks (average of 17 sessions). The participants in the progressive strength training combined with neuromuscular electrical stimulation group also completed a set of electrically stimulated contractions to the quadriceps. The electrical stimulation protocol, which did not result in any additive benefit over the progressive strengthening program, is described in detail elsewhere.25 Strength and Activation Assessments Quadriceps strength of the operated knee was quantified as the peak force generated during a maximal voluntary isometric knee extensor contractions (MVIC).

The MVICs were completed while the subject sat on an electromechanical dynamometer (KinCom; Chattecx, Chattanooga, TN) with the knee flexed to 75°, the axis of rotation of the knee was aligned with the axis of rotation of the dynamometer, and the force

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activation and a CAR of less than 95% indicating incomplete activation. If incomplete activation was observed, the procedure was repeated up to 3 times for each leg, with the subject provided with sufficient rest between trials (~5-minutes). The maximum MVIC and CAR from the two to three trials was retained for analyses. Pain was assessed during the MVIC using a Verbal Analog Scale (PainMVIC; 0= no pain, 10= worst pain). Subjects were also asked about their pain via the Knee Outcomes Survey by identifying to the degree to which pain affects their daily activity. The options are assigned numeric scores ranging from “I do not have pain”, which is assigned a zero, to “pain prevents me from all daily activities” which is assigned a score of five.

Figure 1. Experimental set-up for measuring maximal isometric knee extensor strength (MVIC) and voluntary activation (CAR) levels, as well as treatments using neuromuscular electrical stimulation (NMES).

transducer affixed to the leg approximately 2 cm above the lateral malleolus (Figure 1). Subjects first completed warm-up contractions at 50, 75, and 100% of maximum and were provided visual feedback on a computer screen and received verbal encouragement to maximize effort. Voluntary activation was examined with the burst superimposition test26 while the subject remained seated and fitted to the dynamometer with same set-up as the MVIC. A custom written program (LabVIEW 4.01; National Instruments, Austin, TX) delivered a 100-Hz, 12-pulse, stimulus train at 135 Volts (Grass S8800 stimulator in series with a Grass model stimulus isolation unit; Grass Instruments, West Warwick, RI) during the peak force of a maximal voluntary contraction through two stimulating electrodes (7.2- ⫻ 12.7-cm; CONMED Corp, Utica, NY) positioned proximally over the rectus femoris muscle and distally over the vastus medialis muscle (Figure 1). Any increased force in response to the electrical stimulation was used to quantify the level of activation. The Central Activation Ratio (CAR) was used to quantify voluntary activation by dividing the maximum force output produced voluntarily by the maximum force generated in response to the electrical stimulation.26 The CAR was expressed as a percentage, such that a CAR of 1.0 is equivalent to 100%

Data Analysis All data analyses were performed with SPSS statistical software (IBM Inc., Somers, NY). Descriptive statistics were initially evaluated to identify outliers and to assess data distribution. Bivariate correlation coefficients were then determined as factors that covaried with MVIC and/or CAR, including age, sex, BMI, pain during MVIC (PainMVIC), and group randomization (Exercise Only or Exercise +NMES).

Spearman Rho coefficients were used for categorical variables (sex, group) and continuous variables that were not normally distributed (age, BMI, MVIC, Pain during MVIC, CAR). Hierarchical multivariate regression analysis was then completed to examine the predictability of quadriceps strength (MVIC) at the end of the strength training program (~3mos; dependent variable) from variables associated with voluntary activation (CAR) or strength (MVIC) at initial evaluation (IE), prior to beginning the training program. The initial steps of the analysis controlled for those factors other than strength and activation that were correlated with either MVIC or CAR at IE. The next step of the analysis controlled for MVIC at IE and the final steps of the analysis examined the influence of PainMVIC and CAR at IE on MVIC at 3mos. Statistical significance was set at α= 0.05.

RESULTS The current study examined the associations between data from prior to (IE) and after the strength training program (~3mos)(N=186). Data from 186 of the original 199 subjects enrolled in the clinical

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trial were included in the analyses; the 13 subjects not included were not tested at 3mos. The physical activity levels for this cohort ranged from sedentary to heavy work/ manual labor. Descriptive statistics for the included subjects are presented in Table 1.

Correlation analyses identified age and sex as covariates (Table 2). Sex was significantly correlated with MVIC at both IE (ρ= -0.206, p= 0.006 and 3mos (ρ= -0.490, p<0.001). Age was not correlated with MVIC at either IE (ρ= -0.006, p=0.930) or 3mos (ρ= -0.137, p=0.062), but was correlated with CAR at IE (0.202; p= 0.006). BMI was not correlated with MVIC at IE (ρ= 0.024, p= 0.747) or 3mos (ρ= 0.084; p=0.252) nor was BMI correlated with CAR at IE (-0.015, p= 0.839). Upon completing the correlation analyses,

age and sex, but not BMI, were entered into the regression analyses prior to MVIC at IE to assess the ability of using CAR at IE to predict MVIC at 3mos.

Findings from the linear regression analyses of CAR at IE predicting MVIC at 3mos are presented in Table 3. After controlling for MVIC at IE, age, and sex (R2= 0.548; p=<0.001), the addition of voluntary activation levels prior to treatment (CAR at IE) did not significantly improve the ability to predict MVIC at 3mos (R2= 0.548; p= 0.911).

DISCUSSION The post-surgical impairments in quadriceps activation observed here were not predictive of the improve-

Table 1. Descriptive statistics for the 186 patients tested. (Men= 102, Women= 84, of which Group Exercise= 106; Exercise + NMES 80)

M ea n ± S D

R an g e / M e d ia n

Age (yrs)

64.8 ± 8.6

4 8 - 84 / 64

Height (m)

1 .7 1 ± 0 . 1 0

1 . 47- 1 . 93 / 1 . 73

W ei g h t ( k g )

89 . 2 ± 1 7 .2

4 7 .6 - 16 2 .8 / 8 8 . 4

Pain MVICIE *

2.0 ± 2.9

0 - 10 / 2.9

BMIIE (kg/m2)

30.3 ± 4.8

21.2 - 53.8 / 30.3

MVICIE (N)

2 9 6 . 1 ± 1 18 . 1

3 3 – 69 8 / 2 8 0 .5

MVIC3mos (N)

506.7 ± 189.9

138 – 1195 / 467.5

CARIE (%)

79.6 ± 16.5

20 – 100 / 84

CAR3mos (%; N=181)

88.8 ± 11.2

43 – 100 / 92.6

£PainADL at IE

2.5 ± 1.0

1-5/3

£PainADL at 3mos

1.2 ± 1.0

1-4/1

MVIC=Maximum voluntary isometric contraction; BMI= Body mass index; CAR= Central activation ratio; IE=initial evaluation; 3mos=3 months post-operative Note: *Pain MVICIE was the subjects’ pain during MVIC at initial evaluation and was assessed with a Verbal Analog Scale. (0-10, 0= no pain; 10= worst pain) £PainADL was the degree of pain reported at IE (initial evaluation) and at 3months (3months post TKA) on the Knee Outcome Survey. (0= I do not have pain; 5= Pain prevents me from all daily activities) The International Journal of Sports Physical Therapy | Volume 9, Number 3 | June 2014 | Page 333

Table 2. Spearman Rho correlation coefficients between potential covariates and both voluntary activation (CARIE ) and strength of the quadriceps (MVICIE & MVIC3mos )

CARIE

MVICIE

MVIC3mos

0.115

-0.206

-0.490

0.120

0.005

<0.001

0.216

0.001

-0.107

0.003

0.988

0.146

-0.028

-0.004

0.075

p=

0.708

0.951

0.309

Group

-0.042

0.030

-0.031

p=

0.565

0.681

0.672

-0.329

-0.075

0.099

<0.001

0.310

0.177

-

0.555

0.214

-

<0.001

0.003

Sex p= Age p= BMI

PainMVIC p= CARIE p=

MVIC= Maximal Voluntary Isometric Contraction CAR= Central Activation Ratio PainMVIC was the pain felt during the MVIC at IE.

ments in quadriceps strength achieved through progressive strength training for patients after TKA. In that, the ability to predict patients’ strength after a progressive strength training rehabilitation protocol was not dependent upon pre-treatment voluntary activation. As the goal of the progressive strength training intervention is to more aggressively address muscle weakness after TKA than in standard care, the authors were concerned that activation deficits would have a confounding effect on the ability to strengthen the quadriceps. While the findings in this study do not agree with the stated hypothesis, they are in agreement with previous work by Scopaz and colleagues,31 who found that pretreatment quadriceps activation levels were not predictive of the change in quadriceps strength in response to rehabilitation for individuals with knee OA. The current work extends the findings of Scopaz et al31 by demonstrating that idea that activation deficits are not an impediment to strength gains

for individuals free from arthritic knee pain (after TKA), compared to the patients with knee OA who do have pain.

Reductions in voluntary activation are attributed to arthrogenic muscle inhibition; a process that reduces the excitability of the alpha motor neuron pool responsible for activating a muscle.32 Various mechanisms have been linked to reductions in activation levels including joint swelling, inflammation, joint laxity, and damage to the joint’s sensory receptors, all of which influence the sensory information transmitted to the nervous system.32 While TKA reliably reduces pain,33 activation impairments persist,14,34 whereas individuals with moderate knee OA who complete exercise therapy without undergoing TKA exhibit improvements in both quadriceps strength and voluntary activation31 presumably without any significant changes in pain, which was already low (0.5 ±

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Table 3. Hierarchical regression analysis of quadriceps strength after the strength training intervention

R2

Adj. R2

df

β

F Change

Sign. F Change

Sex

0.237

0.233

1,184

-0.487

57.244

<0.001

Sex +Age

0.276

0.268

1, 183

-0.511 -0.199

9.857

0.002

1, 182

-0.385 -0.180 0.536

109.495

<0.001

1, 181

-0.378 -0.166 0.543 0.052

0.971

0.317

1, 180

-0.382 -0.168 0.543 0.056 0.016

0.053

0.818

Factor

Sex +Age +MVICIE

0.548

Sex +Age +MVICIE +PainMVICIE 0.551 Sex +Age +MVICIE +PainMVICIE +CARIE 0.551

0.541

0.541

0.538

β = standardized coefficients; CAR = central activation ratio; MVIC= maximal voluntary contraction, IE= initial evaluation (post surgery), 3mos= 3 months after surgery 1.4 out of 10). Therefore, while pain may contribute to activation deficits, it is not likely to be the primary mechanism responsible for the deficits after TKA. Conversely, damage to the knee joint sensory apparatus and subsequent joint swelling are to be expected with the surgical procedures involved in TKA, but arthrogenic muscle inhibition is present for patients after TKA and individuals with end-stage knee OA, therefore, the impairments in voluntary activation after TKA cannot be solely attributed to the surgical procedure. The average activation levels observed here (80.0 ± 16.6%), when a medial parapatellar surgical approach was used, were comparable to a previous report on patients 3-months after undergoing bilateral TKA with either a midvastus (76.1 ± 20.0%) or subvastus (76.7 ± 14.5%) approach,35 further suggesting that surgical approach is not likely a factor contributing to the impairments in activation.

Irrespective of the mechanism leading to post-surgical weakness, resolving quadriceps weakness following TKA remains a primary focus for clinicians, as quadriceps strength and functional ability are so strongly related. Moreover, as quadriceps weakness

is more strongly attributed to voluntary activation deficits in the early post-operative period14 compared to muscle atrophy, it seems reasonable that resolving activation deficits, early in the recovery process after surgery, may lead to more substantial improvements in strength.36 Regardless of the etiology, the importance of restoring quadriceps strength after TKA should remain a primary goal for treatment of individuals who undergo TKA. And while the findings here do not suggest that voluntary activation levels before rehabilitation can predict strength gains, activation failure has been shown to contribute more to quadriceps weakness after TKA than muscle atrophy, in the short-term.14 Similar to Scopaz et al.,31 the patients in the current study demonstrated a broad range of changes in quadriceps strength from IE to 3mos (-29.6% to 85.4% MVIC) and pretreatment activation was moderately correlated with pretreatment strength (r= 0.555; p< 0.001). However, in the long-term treatment of individuals after TKA (e.g. more than one year after TKA), muscle volume, as estimated using MRI, contributes more substantially

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to quadriceps strength than activation.16 Therefore, future work should consider evaluating if even earlier resolution of quadriceps activation deficits after TKA can influence the long-term recovery of quadriceps strength and lower extremity functional performance after TKA. Additionally, as pre-surgical (prior to TKA) exercise therapy has been shown to attenuate post-surgical weakness and activation impairments,37 factors other than voluntary activation must be influencing the response to treatment; these factors may include the frequency, type, and duration of the rehabilitation protocol, patient compliance with therapist directed home exercises, or management of other impairment related factors (e.g. effusion).

CONCLUSION Activation deficits of the quadriceps in patients who undergo TKA are not predictive of quadriceps strength three months after surgery. These findings should provide clinicians with confidence that with patients who exhibit poor voluntary activation of the quadriceps after TKA are capable of achieving meaningful gains in quadriceps strength in response to strength training and that the magnitude of recovery of quadriceps strength is not limited by pretreatment activation levels.

REFERENCES 1. 2010 National statistics - principal procedure only Outcomes by 81. 54 Total Knee Replacement. 2013.

2. Kurtz S, Ong K, Lau E, Mowat F, Halpern M. Projections of primary and revision hip and knee arthroplasty in the United States from 2005 to 2030.

J Bone Joint Surg Am. 2007; 89(4): 780–5.

3. König A, Walther M, Kirschner S, Gohlke F. Balance sheets of knee and functional scores 5 years after total knee arthroplasty for osteoarthritis: a source for patient information. J Arthroplasty. 2000; 15(3): 289– 94.

4. Gonzalez Sáenz de Tejada M, Escobar A, Herrera C, et al. Patient expectations and health-related quality of life outcomes following total joint replacement.

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5. Porucznik, M. Total Knee Replacement in the Younger Patient: It’s Happening, but Is It Reasonable? AAOS Now. 2012; at <http://www.aaos. org/news/aaosnow/apr12/clinical17.asp> 6. Kurtz SM, Lau e, Ong K, et al. Future young patient demand for primary and revision joint replacement:

national projections from 2010 to 2030. Clin Orthop Relat Res. 2009; 467(10): 2606–12.

7. Bade MJ, Kohrt WM, Stevens-Lapsley JE. Outcomes before and after total knee arthroplasty compared to healthy adults. J Orthop Sports Phys Ther. 2010; 40(9): 559–67.

8. Mizner RL, Petterson SC, Clements KE, et al.

Measuring Functional Improvement After Total Knee Arthroplasty Requires Both Performance-Based and Patient-Report Assessments A Longitudinal Analysis of Outcomes. J Arthroplasty. 2010; 26(5): 728-37.

9. Rowe PJ, Myles CM, Nutton R. The effect of total knee arthroplasty on joint movement during functional activities and joint range of motion with particular regard to higher flexion users. J Orthop Surg (Hong Kong). 2005; 13(2): 131–8.

10. Walsh M, Woodhouse LJ, Thomas SG, Finch E. Physical impairments and functional limitations: a comparison of individuals 1 year after total knee arthroplasty with control subjects. Phys Ther. 1998; 78(3): 248–58.

11. O’Reilly SC, Jones A, Muir KR, Doherty M. Quadriceps weakness in knee osteoarthritis: the effect on pain and disability. Ann Rheum Dis. 1998; 57(10): 588–94.

12. Fitzgerald GK, Piva SR, Irrgang JJ, Bouzubar F, Starz TW. Quadriceps activation failure as a moderator of the relationship between quadriceps strength and physical function in individuals with knee osteoarthritis. Arthritis Rheum. 2004; 51(1): 40–8.

13. McAlindon TE, Cooper C, Kirwan JR, Dieppe PA. Determinants of disability in osteoarthritis of the knee. Ann Rheum Dis. 1993; 52(4): 258–62.

14. Mizner RL, Petterson SC, Stevens JE, Vandenborne K, Snyder-Mackler L. Early quadriceps strength loss after total knee arthroplasty. The contributions of muscle atrophy and failure of voluntary muscle activation. J Bone Joint Surg Am. 2005; 87(5): 1047–53.

15. Petterson SC, Barrance P, Marmon AR, et al. Time course of quad strength, area, and activation after knee arthroplasty and strength training. Med Sci Sports Exerc. 2011; 43(2): 225–31.

16. Meier WA, Marcus RL, Dibble LE, Foreman KB, et al.

The long-term contribution of muscle activation and muscle size to quadriceps weakness following total knee arthroplasty. J Geriatr Phys Ther. 2009; 32(2): 79–82.

17. Arvidsson, I., Eriksson E, Knutsson E, Arnér S. Reduction of pain inhibition on voluntary muscle activation by epidural analgesia. Orthopedics. 1986; 9(10): 1415–9.

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18. Fahrer H, Rentsch HU, Gerber NJ, et al. Knee effusion and reflex inhibition of the quadriceps. A bar to effective retraining. J Bone Joint Surg. Br. 1988; 70(4): 635–8.

19. Spencer JD, Hayes KC, Alexander IJ. Knee joint effusion and quadriceps reflex inhibition in man.

Arch Phys Med Rehabil. 1984; 65(4): 171–7.

20. Stokes M, Young A. The contribution of reflex inhibition to arthrogenous muscle weakness. Clin Sci (Lond). 1984; 67(1): 7–14.

21. Petterson SC, Barrance P, Buchanan T, BinderMacleod S, Snyder-Mackler L, Mechanisms underlying quadriceps weakness in knee osteoarthritis. Med. Sci. Sports Exerc. 2008; 40(3): 422–7.

22. Jones DA, Rutherford OM, Parker DF. Physiological changes in skeletal muscle as a result of strength training. Q J Exp Physiol. 1989; 74(3): 233–56.

23. Folland JP, Williams AG. The adaptations to strength training: morphological and neurological contributions to increased strength. Sports Med. 2007; 37(2): 145–68.

24. Stevens JE, Mizner RL, Snyder-Mackler L. Neuromuscular electrical stimulation for quadriceps muscle strengthening after bilateral total knee arthroplasty: a case series. J. Orthop. Sports Phys Ther. 2004; 34(1): 21–9.

25. Petterson SC, Mizner RL, Stevens JE, et al. Improved function from progressive strengthening interventions after total knee arthroplasty: a randomized clinical trial with an imbedded prospective cohort. Arthritis Rheum. 2009; 61(2): 174–83.

26. Kent-Braun JA, Le Blanc R. Quantitation of central activation failure during maximal voluntary contractions in humans. Muscle Nerve. 1996; 19(7): 861–9.

27. Berth A, Urbach D, Awiszus F. Improvement of voluntary quadriceps muscle activation after total knee arthroplasty. Arch Phys Med Rehabil. 2002; 83(10): 1432–1436.

28. Stevens JE, Mizner RL, Snyder-Mackler L. Quadriceps strength and volitional activation before and after total knee arthroplasty for osteoarthritis.

J Orthop Res. 2003; 21(5): 775–779.

29. Thomas AC, Stevens-Lapsley JE. Importance of attenuating quadriceps activation deficits after total knee arthroplasty. Exerc Sport Sci Rev. 2012; 40(2): 95–101.

30. Vahtrik, D, Gapeyeva H, Ereline J, Pääsuke M. Relationship between leg extensor muscle strength and knee joint loading during gait before and after total knee arthroplasty. Knee. 2013; at <http://www. sciencedirect.com/science/article/pii/ S0968016013000744> 31. Scopaz KA, Piva SR, Gil AB, et al. Effect of baseline quadriceps activation on changes in quadriceps strength after exercise therapy in subjects with knee osteoarthritis. Arthritis Rheum. 2009; 61(7): 951–7.

32. Rice DA, Mcnair PJ. Quadriceps Arthrogenic Muscle Inhibition: Neural Mechanisms and Treatment Perspectives. Semin Arthritis Rhem. 2010; 40(3): 250– 266.

33. Desmeules F, Dionne CE, Belzile EL, et al.

Determinants of pain, functional limitations and health-related quality of life six months after total knee arthroplasty: results from a prospective cohort study. BMC Sports Sci Med Rehabil. 2013; 5: 2.

34. Stevens-Lapsley JE, Balter JE, Wolfe P, Eckhoff DG, Kohrt WM. Early neuromuscular electrical stimulation to improve quadriceps muscle strength after total knee arthroplasty: a randomized controlled trial. Phys Ther. 2012; 92: 210–26.

35. Berth A, Urbach D, Neumann W, Awiszus F. Strength and voluntary activation of quadriceps femoris muscle in total knee arthroplasty with midvastus and subvastus approaches. J Arthroplasty. 200722: 83–8.

36. Kittelson, A. J., Stackhouse, S. K. & Stevens-Lapsley, J. E. Neuromuscular electrical stimulation after total joint arthroplasty: a critical review of recent controlled studies. Eur. J Phys Rehabil Med. 2013; at <http://www.ncbi.nlm.nih.gov/pubmed/24285026> 37. Swank AM, Kachelman JB, Bibaue W, et al.

Prehabilitation before total knee arthroplasty increases strength and function in older adults with severe osteoarthritis. J Strength Cond Res. 2011; 25: 318–25.

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IJSPT

ORIGINAL RESEARCH

RUNNING MORE THAN THREE KILOMETERS DURING THE FIRST WEEK OF A RUNNING REGIMEN MAY BE ASSOCIATED WITH INCREASED RISK OF INJURY IN OBESE NOVICE RUNNERS Rasmus Oestergaard Nielsen, PT, MHSc1,4 Michael Lejbach Bertelsen, PT1,4 Erik Thorlund Parner, PhD2 Henrik Sørensen, PhD1 Martin Lind, PhD3 Sten Rasmussen, MD4,5

ABSTRACT Background: Training guidelines for novice runners are needed to reduce the risk of injury. The purpose of this study was to investigate whether the risk of injury varied in obese and non-obese individuals initiating a running program at different weekly distances.

Methods: A volunteer sample of 749 of 1532 eligible healthy novice runners was included in a 3-week observational explorative prospective cohort study. Runners were categorized into one of six strata based on their body mass index (BMI) (≤30=low; >30=high) and running distance after 1 week (<3 km = low; 3 to 6 km = medium; >6 km = high).

Data was collected for three weeks for the six strata. The main outcome measure was running-related injury.

Results: Fifty-six runners sustained a running-related injury during the 3-week data collection. A significantly greater number of individuals with BMI>30 sustained injuries if they ran between 3 to 6 km (cumulative risk difference (CRD) = 14.3% [95%CI: 3.3% to 25.3%], p<0.01) or more than 6 km (CRD = 16.2% [95%CI: 4.4% to 28.0%], p<0.01) the first week than individuals in the reference group (low distance and low BMI). The effect-measure modification between high running distance and BMI on additive scale was positive (11.7% [-3.6% to 27.0%], p=0.13). The number of obese individuals needed to change their running distance from high to low to avoid one injury was 8.5 [95%CI: 4.6 to 52].

Conclusions: Obese individuals were at greater risk of injury if they exceeded 3 km during the first week of their running program. Because of a considerable injury risk compared with their non-obese peers, individuals with a BMI>30 may be well advised to begin running training with an initial running distance of less than 3 km (1.9 miles) the first week of their running regime. Large-scale trials are needed to further describe and document this relationship.

Level of Evidence: Level 2b Keywords: Body mass index, distance, injury risk, Running

1

Department of Public Health, Section of Sport Science, Aarhus University, DK-8000 Aarhus 2 Department of Public Health, Section of Biostatistics, Aarhus University, DK-8000 Aarhus 3 Department of Orthopaedics, Aarhus University Hospital, DK-8000 Aarhus.

4 Orthopaedic Surgery Research Unit. Science and Innovation Center, Aalborg University Hospital, DK-9000 Aalborg.

5 Department of Clinical Medicine, Aarhus University, DK-8000 Aarhus Conflicts of interest: None of the authors had any conflicts of interest, including relevant financial interests, activities, relationships, or affiliations.

The study was approved by The Ethics Committee of Central Denmark Region (M-20110114).

CORRESPONDING AUTHOR Nielsen, Rasmus Oestergaard Department of Public Health, Section of Sport Science Faculty of Health Science, Aarhus University, Dalgas Avenue 4, DK-8000 Aarhus C. Denmark Email: roen@sport.au.dk Telephone: +45 87 16 81 79

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INTRODUCTION Running as a leisure-time activity has increased in popularity during the past decades,1 and as a consequence, millions of novice runners around the world begin running each year. They may start their running career by using training schedules found on the Internet; by using advice from a friend, a coach or a clinician; or by simply using a self-structured approach. Unfortunately, none of these approaches relies on evidence-based knowledge on how training schedules should be designed in order to reduce the risk of running-related injuries.2 Running-related injuries are common among novice runners,2 affecting approximately 30 runners per 1000 hours of running.3-5 Because of the high incidence, interventions to reduce the number of injuries are greatly needed.6 Training errors are believed to be the primary risk factor for injury because training, pragmatically, must be a part of the causal chain leading to injury.2,7,8 Randomized controlled trials have been conducted,5,9 but despite adequate designs, these studies fail to identify training-related mechanisms leading to injury in novice runners. In contrast, studies have identified high body mass index (BMI) to be associated with increased risk of injury.10,11 In novice runners enrolled in a prospective study, Buist et al10 found 25% (82 of 334) of the novice runners with BMI above 25 sustained a running-related injury (RRI) during follow-up compared to 15% (76 of 514) in the group of participants with BMI below 25 (p=0.03). Importantly, the mean exposure time (time spent running) was equal in both groups. This may lead to the assumption, that increasing BMI exposes the lower extremity to increased load while running which ultimately increase the injury risk. Still, a BMI > 26 has been suggested to be protective for injury.12 But importantly, this observation did not take into account the running exposure. If the overweight persons ran less, the statement presented that high BMI is protective, may be caused by a reduced training stimulus which reduces the risk of injury. In order to identify the role of BMI in the development of injury, it is important to take into account the exposure to running and to question if an obese individual is able to tolerate the same training load as a non-obese individual.

Since no studies have investigated the association between weekly distance during the first week of

a running regimen and the risk of running-related injuries, the purpose of this study was to investigate whether the risk of injury varied in obese and nonobese individuals initiating a running program at different weekly distances. The risk of injury was hypothesized to be more pronounced in novice runners with a BMI greater than 30.

METHODS Study design An observational 3-week prospective cohort study was designed based on the Danish Novice Running (DANO-RUN) study. The original purpose of the DANO-RUN study is presented elsewhere.13 Because the study was explorative, several other papers have been published from the same dataset. 14-16 The study design, the study procedures, and the informed consent procedure were presented to the Ethics Committee of Central Denmark Region (M-20110114).

The committee waived the request of ethics approval because the study design was observational. According to Danish law, observational studies do not need to be approved by an ethics committee. The Danish data protection agency approved the study.

Participants A sample of 933 healthy novice runners was included in the DANO-RUN study. Informed written consent was obtained from all participants prior to inclusion.

A novice runner was defined as a person who had not run regularly during the preceding year. The cut-off to define regularly was set at 10 km of total running distance the year prior to inclusion. Thus, persons running 4 times 2 km the past year were eligible to participate, whereas persons running a total of 3 times 6 km the past year were excluded. A flow-chart of those excluded prior to or at baseline is presented in another paper.16 Exclusion criteria were: age below 18 or above 65, injury in the lower extremities or back three months preceding a baseline investigation, no e-mail address or access to the internet, participation in other sports for more than four hours per week, use of insoles while running, pregnancy, previous strokes, heart diseases, pain in the chest during training, or unwilling to run in a neutral running shoe or use a global positioning system (GPS) watch to quantify training characteristics.

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Assessment of running distance At baseline, all participants received the same neutral running shoe (Supernova Glide 3 Male/Female, Adidas, Herzogenaurach, Germany) and were instructed to use the shoe in all running sessions.

Participants were then instructed to run as much as they wanted during the 3-week follow-up period.

Their running regime was considered self-structured because no prescriptions or guidelines regarding the training distance, duration, intensity, or frequency were given. Participants were thus allowed to run any distance of their choice (for example, 500 meters, or a greater distance of 15 km) during the first week of the study period.

The running distance was measured in km using a global positioning system (GPS) watch (Forerunner 110 M, Garmin International Inc., Olathe, KS, USA).

The GPS method to objectively measure training distance among runners has previously been proven as valid, with a measurement error of ≤ 6.2% compared with a gold standard.11,17 Participants were instructed to upload training data to a web-based training diary (http://www.vilober.dk/). If a problem with the GPS device occurred during follow-up, participants were instructed to upload the missing training session(s) manually by reporting running distance and time spent running. Participants were also instructed to contact the DANO-RUN study group through their diary to solve any technical problems in particular if the GPS device did not work correctly. During and after follow-up, data quality control was performed.

If suspicious data occurred, the participant was contacted to verify that the data uploaded to the diary was correct. If the participant did not respond to this contact, they were censored at the time the suspicious data was uploaded for the first time. As an example of suspicious data, a person was contacted if he or she ran with an average speed of 50 km per hour.

Definition of exposure The main exposure of interest was the cumulative running distance (measured in km) during the first week (7 days) after the beginning of the running assessment (first time the participant ran after being included in the study). The beginning of the first week (day 1) was defined as the moment the participant completed the first running session, and the end of week 1 was defined as six days after day 1.

Participants were then categorized into exposure strata based on their cumulative running distance the first week. The categorization was performed using two cut offs. By doing so, a more or less equal number of subjects (approximately 33%) were assigned to one of the following strata: less than 3 km (n = 258), 3 to 6 km (n= 225), and finally more than 6 km (n = 266). In addition to the categorization of running distance into three categories, analysis were stratified based on BMI (dichotomized based on BMI≤30 or BMI>30) because a high BMI has been shown to be associated with increased risk of injury among novice runners.10,11 The authors hypothesized that BMI would be related to the association between running distance the first week and risk of injury as an effectmeasure modifier. Because running distance was categorized into three categories and analysis was stratified based on BMI into two groups, a total of six strata were identified (Table 1).

The follow-up of three weeks was chosen because it was hypothesized that injuries occurring after three weeks are related to the weekly change in running distance rather than the absolute distance covered from the beginning of the running program.

Assessment of outcome: Running-related injury At baseline, participants were presented with the injury definition; “An injury is defined as any musculoskeletal complaint of the lower extremity or back causing a restriction of running for at least one week”. This injury definition was a modified version of a definition used by Buist et al.5 If a running-related injury was sustained, participants were instructed to use their personal web– based training diary to contact the medical team.

Table 1. The categorization and number of the participants in the six strata BMI category

BMI≤30

Running distance the first week

Number of par cipants

<3 km 3 to 6 km >6 km

n=200* n=180 n=228

<3 km n=58 3 to 6 km n=45 >6 km n=38 * = the reference strata. BMI = Body mass index. Km = kilometers.

BMI>30

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The injured participant was contacted by telephone and an appointment for a clinical examination was made, preferably no later than 1 week after initial contact. After thorough examination by a physiotherapist with experience in diagnosing runningrelated injuries, a diagnosis was made. In most cases, the diagnosis was made without the use of diagnostic imaging, as suggested by Khan et al,18 but if further examination including diagnostic imaging was needed, the participant was referred to an extensive medical examination at the Division of Sports Traumatology, Aarhus University Hospital.

Importantly, only injuries occurring during the first 3 weeks from the first day in the study were included in the analyses. Of the 933 participants originally included in the DANO-RUN study, 183 sustained injuries. Of these, three were included by mistake because they were injured just before inclusion in the study. The remaining 180 injuries occurred after the end of the study period of three weeks used for the present paper (the total follow-up in the DANORUN study was 1 year). The 183 injured individuals may have influenced the results regarding the risk of injury during the first three weeks and were, therefore, excluded from the analysis in the present study.

In addition, one participant was excluded because data from the first seven running sessions were uploaded manually. Thus, the sub-sample included in the present study comprised 749 individuals.

Assessment of confounders Prior to analyses, the authors hypothesized that the following variables would be the major factors possibly confounding the association between running distance during the first week of a running regime and risk of running-related injury during the following three weeks: distance covered in week two, distance covered in week three, frequency and intensity of training sessions in weeks one to three, and progression in running distance from weeks one to three.2 In addition, more variables than BMI may be considered as effect-measure modifiers on the association between running distance and risk of injury, mainly previous running-related injuries and age.19 Statistical analyses The injury proportion as a function of distance was estimated using the Kaplan-Meier curve. Time to

injury at 10 and 20 km was analyzed using the cumulative running distance as time scale. The cumulated injury risk difference was analyzed across the six exposure groups by performing a generalized linear regression using the pseudo values method.20,21 In all analyses, the reference group was persons with a BMI less than 30 running less than 3 km the first week.

This group was selected as reference because it was hypothesized that these individuals would have the lowest injury risk. When estimating risk differences by the pseudo values method, at least 10 injuries are needed per parameter (number of parameters = number of categories per variable – 1) to avoid violation of the statistical assumptions.22 Participants were categorized into six groups based on their BMI (≤ 30 and > 30) and based on the distance covered after 1 week of running (< 3 km, 3 km to 6 km and > 6 km).

Based on this, at least 50 running-related injuries were needed to perform a valid analysis stratified by BMI. In addition, the remaining injuries above the 50 needed for the crude analysis did only allow for one confounder (distance covered in week 2) to be included in the adjusted analysis. Participants were right-censored in case of pregnancy, disease, lack of motivation, non-running-related injury causing a permanent stop of running, unwillingness to attend clinical examination in case of injury, if a different shoe was used than the neutral shoe, or end of followup after 1-year, whichever came first. The number needed (equal to number needed to treat [NNT]) to convert their running distance from more than 3 km to less than 3 km in order to avoid one RRI was based on the equation: NNT = -1 / cumulative risk difference. The absolute excess risk was used to measure the size of effect-measure modification. Differences were considered statistically significant at p<.05, and estimates are presented with 95% confidence intervals (CI). Results were presented according to the guidelines suggested by Knol and VanderWeele.23 All analyses were performed using STATA/SE version 12 (StataCorp LP, 2011, College Station, Texas, USA).

RESULTS Of the 749 participants (381 males/368 females; mean age 36.7 ± 10.2; mean BMI 26.2 ± 4.4 kg/ m2) included in the analyses, a total of 56 sustained a running-related injury during the three week follow-up, with 15 injuries occurring in week one, 19

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running more than 3 km the first week compared with individuals with a BMI less than 30 and running less than 3 km the first week (p < 0.01). Among the obese individuals, those running more than 6 km during the first week faced a greater, although non-significant risk (risk difference = 10.8% [95% CI: -3.1% to 24.7%], p=0.13) after 20 km of running compared with those running less than 3 km the first week. Based on this, the number of obese individuals needed to change their running distance from more than 6 km to less than 3 km the first week in order to avoid one running-related injury was 8.5 [95% CI: 4.6 to 52]. In addition to this, if the obese individuals running more than 6 km reduced their BMI and started by running less than 3 km the first week, the number needed to treat to avoid one injury was 6.17 [95% CI: 4 to 13]. In addition to the stratified analyses, adjusted analyses were performed. The analyses adjusted for the running distance in week two revealed no significant changes in any of the estimates from the crude analyses presented.

injuries occurring in week two, and finally 22 injuries occurring in week three. The numbers of injured participants, non-injured participants, and censored participants after week one, after week two, and after week three stratified by BMI status are presented in Table 2. In addition, the numbers of injuries per day during the first 21 days of the study are presented in Figure 1. One of the injuries occurred on a traumatic basis while the rest were considered overuse. The most frequent diagnoses were medial tibial stress syndrome n=13; medial meniscus injury n=8; patellofemoral pain n=7; and achilles tendinopathy n=7.

During the first week, the median running distance was 4.46 km, ranging from a minimum of 413 meters to a maximum exceeding 30 km (n = 2).

The novice runners included in the analyses ran a total of 14,767 km until injury, until censoring, or until the end of the 3-week follow-up. The Kaplan-Meier curve for the six exposure groups, visualizing the injury proportion as a function of km, is presented in Figure 2. In Table 3, results from the generalized linear regression model for the cumulative risk of running-related injury at 10 and 20 km are presented.

DISCUSSION This is the first study to provide insight into the initial running distance completed by novice runners and their risk of injury during the first 3 weeks of

Results revealed significant differences in cumulative risk between individuals with a BMI above 30

Table 2. The flow of the included participants. Number (counts) of injured, noninjured, and censored participants are presented after week 1, week 2, and week 3 stratified by BMI status. In addition, the median distances in kilometer (km) the participants covered during each of the 3 weeks are presented.

Subgroup Week 1 Week 2 Week 3 All participants

All

749

715

693

Injured

All BMI ≤ 30 BMI > 30

15 10 5

18 9 10

22 18 4

Non-injured

All BMI ≤ 30 BMI > 30

715 587 128

693 575 118

668 554 114

Censored

All BMI ≤ 30 BMI > 30

19 11 8

3 3 0

3 3 0

Median distance

All BMI ≤ 30 BMI > 30

4.47 4.66 3.58

4.11 4.26 3.77

3.82 3.90 3.33

BMI = body mass index.

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Figure 1. Number of injuries per day during the 3-week (21 days) follow-up.

their running regime. Importantly, individuals with a BMI greater than 30 may be well advised to take-up running but refraining from running more than 3 km during the first week in order to reduce the risk of injury. If they do so, the risk of injury declines from 22.7% to 11.9% after 20 km of running. Although more time-consuming, another approach that may be effective in reducing the risk of injury may be to

Figure 2. Visualizing the injury proportion as a function of km in the six exposure groups. All red lines represent individuals with a BMI > 30, while the blue lines represent individuals with a BMI ≤ 30.

reduce the BMI before initiating a running program: Among those running more than 6 km the first week, obese individuals faced a 17.2% greater risk of injury than those with a BMI less than 30. Thus, a weight-loss intervention targeted individuals with a BMI greater than 30 prior to the start of a running regime may also be an injury-reducing approach.

Table 3. Cumulative risk differences (cRD) for running-related injury*.

Running distance the first week ≤ 3km

> 3 to ≤ 6 km

cRDs [95%CI] for > 3 to ≤ 6 km within strata of BMI

> 6 km

cRDs [95%CI] for > 6 km within strata of BMI

Injury/ no injury

cRD [95%CI]

Injury/ no injury

cRD [95%CI]

Injury/ no injury

cRD [95%CI]

Low BMI [≤30]

4/196

Reference

7/173

1.0% [-3.4%; 5.3%] p=0.67

4/224

-1.6% [-5.8%; 2.5%] p=0.44

1.0% [-3.4%; 5.3%] p=0.67

-1.6% [-5.8%; 2.5%] p=0.44

High BMI [>30]

4/54

5.8% [-0.5%; 12.2%] p=0.07

4/38

7.3% [0.2%; 14.3%] p=0.04

5/33

12.7% [5.2%; 20.2%] p<0.01

1.5% [-7.0%; 9.9%] p=0.74

6.9% [-2.0%; 15.8%] p=0.13

Low BMI [≤30]

5/195

Reference

13/167

2.5% [-4.3%; 9.4%] p=0.47

13/215

-1.0% [-7.4%; 5.5%] p=0.78

2.5% [-4.3%; 9.4%] p=0.47

-1.0% [-7.4%; 5.5%] p=0.78

High BMI [>30]

4/54

5.4% [-4.5%; 15.4%] p=0.28

7/38

14.3% [3.3%; 25.3%] p=0.01

7/31

16.2% [4.4%; 28.0%] p<0.01

8.8% [-4.4%; 22.1] p=0.19

10.8% [-3.1%; 24.7%] p=0.13

After 10km:

After 20km:

CI = confidence interval. Km = kilometer. BMI = body mass index Chi2 tests for difference between all six groups were performed after 10 km and 20 km revealing a significant difference across all six groups (p<0.01). *Two analyses are presented: after 10 km and after 20 km. The reference risks for the runners with a BMI ≤ 30 and running less than 3 km during the first week were 3.1% [0.1% to 6.1%] after 10 km and 6.5% [1.7% to 11.2%] after 20 km. Kilometers at risk for the 749 novice runners were 14,676 km. Measure of effect modification on additive scale (Absolute Excess Risk): 11.7% [-3.6% to 27.0%], p=0.13 (BMI>30 and >6km after 20 km) and 6.3% [-8.6% to 21.2%], p=0.41 (BMI>30 and >3 to ≤ 6 km after 20 km).

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The effect-measure modification on additive scale was positive and close to significant (11.7% [-3.6% to 27.0%], p=0.13). This means that there were some indications that the estimated joint effect on the additive scale of running more than 6 km with a BMI greater than 30 was larger than the estimated effect of BMI and running distance, so there is positive effect modification of increasing running distance the first week across strata of BMI. Based on this, individuals with a BMI greater than 30 should ideally lose weight and take-up running with a distance below 3 kilometers the first week.

One major strength of the present paper was the approach used to categorize participants into six different strata. BMI was considered to be an effectmeasure modifier on the association between running distance the first week and development of injury. As described by Meeuwisse,19 it is very important to distinguish between stratified analysis (using effect-measure modification) and adjusted analysis (using confounders). In a majority of the previous studies on novice runners,3-5,9 other variables have been included as confounders. But the findings in the present paper suggest that BMI should be included as an effect-measure modifier because the effect of the running distance is different across BMI strata. The authors therefore suggest that more work should be devoted to distinguish between confounders and effect-measure modifiers in studies on running-related injuries.

It is very important to stress that the results of the present study should be interpreted with caution.

Owing to the prospective design of the present study, the risk of the results being biased by confounding is noteworthy, and it is, indeed, possible that the estimates presented in the present article are highly biased. One variable (cumulative running distance in week two) was adjusted for and we had the data to undertake further adjustments. But the number of events per parameter included in a pseudo-values approach with cumulative risk difference as measure of association is at least 10. In the present study, 56 runners sustained a running-related injury of whom 28 sustained the injury before completing a total of 10 kilometers of running and 49 before completing a total of 20 kilometers. Then, one categorical variable with three groups (running volume the first week

categorized into three groups) further stratified by BMI as a dichotomous variable (BMIâ&#x2030;¤30 or BMI>30) and one continuous variable (cumulative running distance in week 2) was the upper limit of variables to be included in the adjusted/stratified analysis to avoid violation of the assumptions behind the statistical model. Instead of including more variables, which the model allows for, the authors chose to strictly follow the assumption behind the statistical model. As a consequence, possible confounders like the running frequency, running pace, or how rapidly the runners changed their training distance over time were not adjusted for.2 In addition, it was not possible to further stratify the results based on previous injuries. It may be very likely that individuals with a high BMI who ran more than 3 km the first week may face an even more pronounced risk of injury if they had a previous injury, whereas the risk may have been smaller among the obese individuals who had not had any severe injuries previously.

Unfortunately, at least 200 injuries were needed to perform such detailed analysis. The problem presented highlights the need for further prospective studies that include more individuals than the 933 originally included in the present study. Still, the results from the present study provide a foundation for designing future randomized controlled trials in this field of research.

CONCLUSION Individuals with a BMI greater than 30 had an increased risk of RRI in the first three weeks of training, and may be well advised to begin running with an initial total running distance of less than 3 km during the first week of their running regimen. More large-scale randomized studies are needed to further describe and document this relationship.

REFERENCES 1. Laub TB, Pilgaard M. Sports participation in Denmark 2011. Copenhagen, Denmark: Danish Institute for Sports Studies; 2013.

2. Nielsen RO, Buist I, Sorensen H, Lind M, Rasmussen S. Training errors and running related injuries: A systematic review. Int J Sports Phys Ther.

2012;7(1):58-75.

3. Buist I, Bredeweg SW, Bessem B, van Mechelen W, Lemmink KA, Diercks RL. Incidence and risk factors of running-related injuries during preparation for a

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Buist I, Bredeweg SW, Lemmink KA, van Mechelen W, Diercks RL. Predictors of running-related injuries in novice runners enrolled in a systematic training program: A prospective cohort study. Am J Sports Med. 2010;38(2):273-280.

Buist I, Bredeweg SW, van Mechelen W, Lemmink KA, Pepping GJ, Diercks RL. No effect of a graded training program on the number of running-related injuries in novice runners: A randomized controlled trial. Am J Sports Med. 2008;36(1):33-39.

Finch C. A new framework for research leading to sports injury prevention. J Sci Med Sport. 2006;9(12):3-9.

Meeuwisse WH, Tyreman H, Hagel B, Emery C. A dynamic model of etiology in sport injury: The recursive nature of risk and causation. Clin J Sport Med. 2007;17(3):215-219.

Hreljac A. Etiology, prevention, and early intervention of overuse injuries in runners: A biomechanical perspective. Phys Med Rehabil Clin N Am. 2005;16(3):651-67, vi.

Bredeweg SW, Zijlstra S, Buist I. The GRONORUN 2 study: Effectiveness of a preconditioning program on preventing running related injuries in novice runners. the design of a randomized controlled trial.

BMC Musculoskelet Disord. 2010;11:196.

Buist I, Bredeweg SW. Higher risk of injury in overweight novice runners. Br J Sports Med. 2011;45(4):338.

Nielsen RO, Cederholm P, Buist I, Sorensen H, Lind M, Rasmussen S. Can GPS be used to detect deleterious progression in training volume among runners? J Strength Cond Res. 2013;27(6):1471-1478.

Taunton JE, Ryan MB, Clement DB, McKenzie DC, Lloyd-Smith DR, Zumbo BD. A prospective study of running injuries: The vancouver sun run “in training” clinics. Br J Sports Med. 2003;37(3):239-244.

Nielsen RO, Ramskov D, Sørensen H, Lind M, Rasmussen S, Buist I. Protocol for the dano-run

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study: A 1-year observational follow up study on running related injuries in 1000 novice runners. Br J Sports Med. 2011;45(4):365.

Bertelsen ML, Jensen JF, Nielsen MH, Nielsen RO, Rasmussen S. Footstrike patterns among novice runners wearing a conventional, neutral running shoe. Gait Posture. 2013;38(2):354-356.

Nielsen RO, Buist I, Parner ET, et al. Predictors of running-related injuries among 930 novice runners: A 1-year prospective follow-up study. OJSM. 2013;1(1):1-7.

Nielsen RO, Buist I, Parner ET, et al. Foot pronation is not associated with increased injury risk in novice runners wearing a neutral shoe: A 1-year prospective cohort study. Br J Sports Med. 2014;48(6):440-447.

Townshend AD, Worringham CJ, Stewart IB. Assessment of speed and position during human locomotion using nondifferential GPS. Med Sci Sports Exerc. 2008;40(1):124-132.

Khan KM, Tress BW, Hare WS, Wark JD. Treat the patient, not the x-ray: Advances in diagnostic imaging do not replace the need for clinical interpretation. Clin J Sport Med. 1998;8(1):1-4.

Meeuwisse WH. Athletic injury etiology: Distinguishing between interaction and confounding. Clin J Sport Med. 1994;4(3):171-175.

Parner ET, Andersen PK. Regression analysis of censored data using pseudo-observations. Stata Journal. 2010;10(3):408.

Klein JP, Logan B, Harhoff M, Andersen PK. Analyzing survival curves at a fixed point in time.

Stat Med. 2007;26(24):4505-4519.

Hansen SN, Andersen PK, Parner ET. Events per variable for risk differences and relative risks using pseudo-observations. Lifetime Data Anal. 2014: In press.

Knol MJ, VanderWeele TJ. Recommendations for presenting analyses of effect modification and interaction. Int J Epidemiol. 2012;41(2):514-520.

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IJSPT

ORIGINAL RESEARCH

A SPEED DISTANCEď&#x161;şBASED CLASSIFICATION SYSTEM FOR INJURY PREVENTION AND RESEARCH IN INTERNATIONAL AND DOMESTIC YOUTH BASEBALL PLAYERS Michael J. Axe, MD1,2 Michael Strube, PhD3 David Osinski4 James R. Andrews, MD5,6,7,8 Lynn Snyder-Mackler, PT, ScD1

ABSTRACT Background: An objective classification system for studying youth baseball players in the U.S.A. was published in 1996. Professional baseball is composed of greater than 25% international players a majority of whom come from five countries. Many youth baseball players are injured in early years play, both in the U.S.A. and internationally. There is no international classification system to study youth baseball pitching injuries, biomechanics, or maturation, but one is needed in order to compare and combine pitchers in multi-center studies.

Uniform domestic and international pre-injury normative data is optimum. Ideally, data collection should be practical requiring inexpensive equipment and limited time demands.

Hypothesis: The mathematical model, developed in 1996 on 853 boys and validated on 114 boys in the Mid-Atlantic Region, U.S.A., is internationally applicable, allowing easy classification of youth baseball pitchers and levels throughout the world.

Methods: Seven-hundred-twenty-one international pitchers, ages 8-14, threw five full-speed pitches recorded with a calibrated radar gun and four maximum distance throws on a marked field. Demographics included age, height, weight, and years pitched. Collection sites included foreign national baseball clubs (Dominican Republic, Venezuela, Puerto Rico, Japan and the Philippines), the Mexican national youth tournament, and a multinational tournament (Brazil, Peru and Colombia). The mathematical model developed in 1996 was used to generate predicted distances for this sample for comparison with actual distances. In addition to the overall analysis, adequate sample sizes were available for comparing predicted and actual distances by country for four of the countries.

Results: The correlation between predicted distance using the mathematical model and actual distance was 0.90. The mean of the international players was 1-2 standard deviations above the USA mean for speed and one standard deviation above the mean for distance. There was no systematic over or under prediction indicating that both relative and absolute fit for the model was excellent.

Conclusions: The mathematical model developed in 1996 on U.S.A. baseball players is robustly generalizable to international youth baseball pitchers.

Clinical Relevance: Pre-injury distance/speed data allows for classification of youth baseball player of multiple levels between the ages of 8-14. International and regional comparisons are now possible for multi-center studies in order to better define risk factors, compare studies, and combine data based upon pre-injury maximum long toss data. Data collection requires only a field, a few balls, and a tape measure.

1

University of Delaware, Newark, DE, USA First State Orthopaedics, Newark, DE, USA 3 Washington University, St. Louis, MO, USA 4 American Baseball Foundation, Birmingham, AL, USA 5 American Sports Medicine Institute, Birmingham, AL, USA 6 University of Virginia, School of Medicine, Charlottesville, VA, USA 7 University of Kentucky Medical Center, Lexington, KY, USA 8 University of Alabama at Birmingham, School of Medicine, Birmingham, AL, USA 2

Acknowledgements: The staff of the American Baseball Foundation, graduate student Kevin McGinnis, Coach Bill Thurston and research assistant Ben Joseph.

CORRESPONDING AUTHOR Lynn Snyder-Mackler, PT, ScD, FAPTA Alumni Distinguished Professor, Department of Physical Therapy Faculty Athletics Representative STAR University of Delaware 540 South College Avenue Newark, DE 19713 E-mail: smack@udel.edu

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INTRODUCTION The American Orthopaedic Society for Sports Medicine’s – Sports Trauma and Overuse Prevention (STOP) sports injury program was developed to address the dramatic increase in traumatic and overuse injuries in youth sports.1,2 Youth baseball injuries, particularly in young pitchers, have been growing exponentially.3 Pitching speed, pitching volume, fatigue, and year-round play have all been identified as risk factors for injury in youth baseball pitchers.2,4-9 The ability to throw at high speed increases the forces about the shoulder and elbow.10,11,12 The growth plates of the shoulder and the growth plates and ligaments of the elbow are therefore at risk.4,10,13,14 Little LeagueTM baseball is the best known of the youth baseball organizations and has addressed the rise in youth injuries with strict limits on pitch counts and mandatory rest days. What remains, however, is how to lower the risk to the high velocity youth pitchers.

Little LeagueTM baseball expanded to a worldwide organization in 1954 and each year hosts a tournament with players from 8 regions in the United States and 8 international regions. Japan has 7 Little LeagueTM World Series titles, Mexico 3, Venezuela 2, South Korea 2 and Chinese Taipei (Taiwan) 13.15 Major League Baseball (MLB) has scouts around the world. More than 25% of professional baseball players are from outside the 50 United States (according to the MLB operational definition of “international”).

A majority of international players in MLB are from the Dominican Republic, Puerto Rico, Mexico, Venezuela and Japan. In 2013, there were more than 850 major league players on opening day rosters; 89 were from the Dominican Republic and 63 from Venezuela.16 MLB teams invest upwards of $76 million in the Dominican Republic (DR), of which $15 million is used in the operation of official MLB team baseball academies based in the DR. Most MLB teams own academies in the DR, where new talent can legally qualify for admission to an academy as early as age 14 and this largely unregulated industry has been called “baseball’s puppy mill.”17 International youth pitchers may be at more risk than US players. The lay press has reported for years on the how the careers of young Latin American players often end in injury and failure.18 More recently the Japanese orthopaedic literature has begun to focus on

youth baseball injuries.5,19-21 Risk factors are similar to those identified for the USA. The authors developed a mathematical model that allowed the use of maximal throwing distance as a surrogate for pitch speed, obviating the need for a radar gun. The result was a data-based and validated functional and practical classification system to identify at risk young baseball players requiring only baseballs, a tape measure, and a field, and the data were published in 1996.22 Using a table of normative data from the USA sample where age and means of maximum pitching speed and maximum throwing distance were presented with the standard deviations, a business size card was developed. (Figure 1) Each level, 1-5 reflects the number of standard deviations above the USA mean.

The authors have classified Levels 3-5 as elite and at risk extrapolating from 80-85 mph risk speed for injury in high school age players.2,6 Our perceptions that those who throw faster are more at risk led us to test whether our classification system was robust enough to use in identifying elite and at risk youth pitchers around the world.

Identifying elite pitchers early and advising them and their families about pitching excessively is the most sensible way to protect them.23 If the U.S.A. classification system is applicable to the international youth baseball player, true epidemiologic comparisons can be made.

Injury risk, biomechanics and pitching maturation studies can also use the classification system to define their populations. The purpose of this study therefore was to determine if the classification system developed on young USA baseball players is generalizable to an

Figure 1. Front and back of business size card that summarizes normative data for throwing speeds and distance by age of the original US sample.

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international sample of youth players from countries that regularly contribute players to the Little LeagueTM World Series and MLB. METHODS Seven-hundred-twenty-one international pitchers, ages 8-14, (8 years, 32; 9 years, 46; 10 years, 73; 11 years, 148; 12 years, 171; 13 years, 128; 14 years, 123) were studied in conjunction with coaching clinics conducted by the staff of the American Baseball Foundation at local youth baseball clubs in the DR, Venezuela, Puerto Rico, Japan, and the Philippines, as well as a national tournament in Mexico and at a multinational tournament in Brazil (Brazil, Peru and Colombia) between May of 2007 and September of 2009. The proposal to use de-identified data in this study was evaluated by The University of Delaware IRB and they determined this project is exempt from IRB review according to federal regulations.

Speed Players threw five maximal-effort throws from a pitcher’s mound to a catcher at the mound-to-home plate distance that they normally used in their local competitions. Speed was recorded in miles per hour for each pitch using a recently calibrated radar gun (JUGS Sports, Tualatin, OR).

Distance A field was laid out using a tape measure to 300 feet from the ball release line. A starting point was designated at the beginning of the tape. The athletes were required to use three-step footwork (i.e. crow’s hop) to ball release point. Boys threw four times at maximal effort. Ball release and landing sites were monitored by the testing staff. The length of the throw was then measured to the nearest foot. The longest distance was used for analysis.

Weight and Height Weight in kilograms and height in centimeters were recorded for each of the boys and converted to pounds and inches to be tested in the mathematical model.

Data Analysis Maximum speed and maximum distance for each boy were used in the analysis. Predicted maximum throwing distance was calculated for each boy from his maximum pitch speed using a mathematical model previously developed from a sample of 853 baseball players (8 years, 46; 9 years, 144; 10 years, 175; 11 years, 187; 12 years, 116; 13 years, 105; 14 years, 80) who were studied at summer baseball camps in the early 90s in the Mid-Atlantic States and validated on 114 additional players.22 (Figure 2) These data were

Age is represented as an effects coded variable: Age 8 9 10 11 12 13 14

E1 1 0 0 0 0 0 -1

E2 0 1 0 0 0 0 -1

E3 0 0 1 0 0 0 -1

E4 0 0 0 1 0 0 -1

E5 0 0 0 0 1 0 -1

E6 0 0 0 0 0 1 -1

Let V = Speed Predicted Distance = -20.9553 + (E1 x 325.8318) + (E2 x 9.3640) + (E3 x 52.2417) + (E4 x 43.7000) + (E5 x 1.9804) + (E6 x 2.5019) + (V x 1.7308) + (V x V x 0.0296) – (E1 x V x 15.1524) + (E2 x V x 0.0638) – (E3 x V x 1.0536) – (E4 x V x 0.9153) + (E5 x V x 0.3249) + (E6 x V x 1.0413) + (E1 x V x V x 0.1728) – (E2 x V x V x 0.0085) – (E3 x V x V x 0.0012) + (E4 x V x V x 0.0014) – (E5 x V x V x 0.0075) – (E6 x V x V x 0.0174) The quality of predic ons depends on similarity of predic on sample to the sample on which the model was developed and to similarity of condi ons under which speeds are measured (e.g., weather, field condi ons).

Figure 2. The mathematical model to predict maximum throwing distance from age and pitch speed.

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Table 1. Maximum Speed and Distance by Age. SD in parentheses.

Age (years) 8 9 10 11 12 13 14

USA Interna onal USA Interna onal USA Interna onal USA Interna onal USA Interna onal USA Interna onal USA Interna onal

Maximum Distance ( ) 95.5 (13.7) 114.5 (18.3) 104.5 (17.6) 117.9 (29.5) 123.2 (17.3) 136.6 (20.5) 134.5 (19.6) 149.1 (24.6) 141.3 (25.1) 172.9 (31.0) 163.6 (23.6) 202.4 (37.9) 195.6 (29.2) 220.0 (39.8)

Maximum Speed (mph) 40.3 (3.5) 44.8 (4.8) 42.8 (3.8) 46.2 (6.1) 46.1 (3.8) 51.8 (6.0) 48.2 (4.2) 54.6 (5.6) 50.4 (4.8) 59.1 (6.8) 54.3 (4.9) 66.3 (8.4) 60.4 (5.7) 69.1 (8.1)

plotted against the actual maximal distance for each subject. The relation between predicted and actual distances was examined using a Pearson Product Moment Correlation. The average actual and predicted distances were also compared using a t-test to detect systematic over- or underprediction. A best-fit model for the international data was also created de novo using multiple regression analysis and compared to the predictive capability of the model developed on the USA sample.

RESULTS Mean maximum pitch speed of the international sample was between one and two standard deviations above the mean of the U.S.A. sample. Maximum throwing distance was approximately one standard deviation above the mean of the U.S.A. sample (Table 1). There were no significant differences between the heights and weights of the international sample and the USA sample at any age.

The Pearson correlation was .90 (p<0.001; Figure 3).

For the four countries for which sufficient sample size across age groups was present, individual correlational analyses (DR, Japan, Puerto Rico and Venezuela) were performed, and the r2 values ranged from .85 to .92 (p<0.001; Figure 4). Means and standard deviations for pitch speed and maximum throwing distance by age for these four countries are summarized in Table 2.

As an additional way to establish the quality of the original prediction model, the authors developed a new model for the current data for comparison. The

Figure 3. Graph of predicted distance from the original model versus actual maximum throwing distance for the entire sample.

best-fitting new model using age, height, country, maximum velocity, and the square of maximum velocity produced predicted distances that correlated with actual maximum distances at r = .93 (p < .001).

This small increase in prediction compared to the original model is to be expected. That the increase is so small suggests the original model is quite robust.

The new model did reveal one interesting additional finding; there were significant country differences by country in maximum distance that remained after controlling for country differences in age, height, and velocity. In the international sample, the Japanese and Venezuelan pitchers threw further even when accounting for age and height. For example, compared to the reference country (Dominican

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Figure 4. Scatterplot of predicted distances (ft) from the original US model versus actual maximum throwing distances (ft). All correlations (Pearson Product Moment) are significant (p<0.001).

Table 2. Maximum Speed and Distance by Age and Country.

Dominican Republic Japan Puerto Rico Venezuela

Max Distance ( ) 123.9 (21.0) 130.4 (14.6) 119.0 (17.5) 135.3 (21.2)

11-12 Max Speed (mph) 46.8 (3.9) 49.4 (3.8) 46.2 (4.3) 51.4 (5.0)

Republic) and after controlling for differences in age, height, and velocity (Figure 5), Japan and Venezuela had distances that were on average 14.68 and 10.02 feet greater (p < .001). Puerto Rico, on the other hand, did not differ significantly from the DR (3.07 greater, p = .18). These are unique country-based difference because the differences in age, height, and velocity had been statistically controlled. Their origin is uncertain (e.g., differences in weather, field conditions, training and development).

The final analysis examined the difference between the predicted and actual distances for the sample. This analysis addresses the absolute, rather than relative, accuracy of the mathematical model. For those subjects who had an available data for actual and predicted distances, the average difference between actual and predicted was an over-estimate of 5.18 feet (maxi-

13-14

Max Distance ( ) 156.6 (18.9) 196.4 (22.4) 163.4 (23.3) 182.0 (34.8)

Max Speed (mph) 55.7 (4.8) 63.7 (4.9) 56.5 (5.5) 59.0 (5.9)

Max Distance ( ) 198.6 (36.7) 232.0 (25.6) 211.2 (38.3) 224.3 (26.4)

Max Speed (mph) 64.8 (7.1) 69.1 (5.6) 69.2 (7.9) 69.2 (4.4)

Country Differences Adjusting for Age and Height

300.00000 Japan Puerto Rico

250.00000

Venezuela Dominican Republic

Maximum Distance

Age <10

200.00000 150.00000 100.00000 50.00000 0.00000 30

40

50

60 70 Maximum Velocity

80

90

Figure 5. In this figure, the maximum velocity ranges from -2 SD below the country average to +2 SD above the country average. The lines are displaced horizontally because the countries varied in their averages and SDs. The vertical separation of the lines reflects the country differences that remain after adjusting for differences in age and height.

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mal actual throwing distance = 170.86 feet; average predicted distance = 176.03 feet). This difference is statistically significant, p<0.001, but represents only 3% of the actual average distance. Importantly, the difference between actual and predicted distances did not vary meaningfully by country or age group. For the four countries for which sufficient overall sample sizes and age group samples sizes were available to perform meaningful analyses (DR, Japan, Puerto Rico and Venezuela) the predicted distance overestimated actual distance by 6.93 feet for the Dominican Republic sample, by 4.05 feet for the Puerto Rican sample, and by .88 feet for the Venezuelan sample.

The predicted distance underestimated the actual distance for the Japanese sample by 3.95 feet. For the age groups, predicted distances were overestimates for ages 8 (1.99 feet), 10 (4.48 feet), 11 (6.80 feet), 12 (3.55 feet), and 13 (4.58 feet) but underestimates for ages 9 (3.66 feet) and 14 (3.06 feet).

DISCUSSION The mathematical model originally developed by the authors on a large sample of youth baseball players from the Middle Atlantic region of the USA was generalizable to an international sample of youth players. Both relative (regression) and absolute prediction was strong. The classification system has construct and face validity as well; the International sample as a whole had more baseball experience and had a higher proportion of pitchers in the samples.

As expected, they pitched with higher speeds and threw further than the USA sample, but there was no systematic over or underprediction, absolute differences were small and the performance of each sample was related to the level of play of the subjects in each country. The classification can be used to identify at risk players or to allow for comparison of results by aptitude across studies.

The DR was the largest group (126) and the athletes were tested at various baseball clubs on the island.

They were mostly pitchers with varying years of pitching experience. 28.5% (36/126) were two or more standard deviation above the mean of the USA sample and 8% (10/126) 3 or more standard deviations above. In the Dominican Republic, because of the popularity of baseball, the authors expected the sample to be skewed toward more talented pitchers since 89 of 856 major league players on opening day

rosters in 2013 were from the DR. The Dominican Republic sample, however, was more like the USA sample with a large range of abilities from 2 standard deviations below to 3 standard deviations above the USA mean. The correlation was .86 and the predicted versus actual distance was excellent (less than 1 foot) across all levels from -2 to +3 standard deviations in all ages from 8-14. The DR was therefore used as the reference country for comparison of country differences in throwing as a surrogate for the USA. The Japanese athletes were predominantly pitchers from baseball clubs in the Tokyo region and ranged in age from 9-14. They were on average 2 standard deviations above the mean for the USA athletes (range 1-5). The correlation coefficient was .85, again reflecting the strength of the classification system and the predicted distance only under-estimated by 3.95 feet, less than 2% of the actual average distance. As the Japanese players were all pitchers and experienced players, the authors expected them to throw faster and farther and they did. The Japanese research scientists are adding to youth baseball literature contributing their expertise and demonstrating that cultural differences do exist.24 In a 2010 study by Harada et al, 79/296 (27%) of players from youth baseball teams in Yamagata, Japan, threw every day. Pitchers in this study were 4.5 times more likely to have elbow injuries than non-pitchers and 42/63 (67%) of pitchers had elbow injuries.

Twenty-six of these 12 year olds had four or more years of throwing experience with 15/26 (58%) having elbow injuries. In Japan only those leagues associated with Little LeagueTM are forced to adhere to game pitch counts and mandatory rest days. Only a small minority of players in Japan, however, belong to Little LeagueTM. For most Japanese youth leagues, there are no practice or game restrictions. Unfortunately, neither speed nor maximum throwing distances were published for any of the cited studies of injury in Japanese youth baseball, therefore the level of thrower cannot be determined.

Venezuela provided 76 players for the study from baseball clubs around the country. While the majority had more than two years of pitching experience, all positions were represented. There were 57% Level 2 or greater and the 29% Level 3 or greater.

There were 33% (25/76) at Level 1 or lower. While

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this group mirrored the U.S.A. Mid-Atlantic sample of all positions, all ages and abilities, they were more experienced and better players and therefore the correlation of .91 was higher than expected. Venezuela had 63 major leaguers opening day 2013 (856 major leaguers). The Venezuelan Maracaibo team won the Little LeagueTM World Series in 2000. While political considerations led of MLB to largely abandon Venezuela for investment in academies, new rules to limit steroid use and age fraud in the Dominican Republic have revitalized the youth baseball recruitment in Venezuela, where these rules (drug tests and age verification) have not yet been implemented.16,25 Venezuelan youth, like the Dominicans, are at great risk for injury as a consequence of the largely unregulated academy systems in their countries. No systematic study in the peer-reviewed literature has examined risk and injuries in these countries. A simple classification system like the one presented here may allow for some risk assessment and testing of simple interventions in the Dominican Republic and Venezuela.

Puerto Rico provided 116 athletes that ranged from -1 to 5 standard deviations from the USA mean.

Their correlation coefficient was the highest at .92, very similar to the Venezuelanâ&#x20AC;&#x2122;s .91. Twenty-seven percent were Level 2 and only 12% Level 3 to 5. The mathematical model overestimated the Puerto Rican sample by just 6.4 feet. There were 13 Puerto Rican players on Major League rosters on opening day 2013.

Puerto Rico was also one of the eight international teams in the 2010 Little LeagueTM World Series. The Mexican data were collected at their 2007 national tournament. All subjects were pitchers. 78 pitchers ages 10-14 threw for speed but only 32 threw for maximum distance, because they were in competition at the time and thus the sample range and size was too small to be analyzed in our by country analysis.

Nevertheless, discussion of the sample contributes to the face validity of the international classification.

This was the only country where representative pitchers selected for their respective regional teams (in a country that in 1997 won the Little LeagueTM World Series and in 2010 were semifinalists) comprised our sample. The authors expected, therefore, that they would pitch faster and throw further than our USA sample and they did. Ninety percent of the Mexican pitchers in the current sample were Level 2 or greater with 57% Level 3 or greater. Only 10%

of the pitchers sampled from their national youth tournament were within one standard deviation of the U.S.A. youth player mean.

The international sample was very diverse. The between country differences in maximal throwing distance underscore this diversity and breadth.

Beyond the contribution of age and height, there were significant country differences. Once the fact that there are country differences in age and height were controlled, there were still differences in the maximum throwing distances present in boys from different countries. The players from Japan and Venezuela were the best players in the subsample; the Japanese players were mostly pitchers. The country difference in distance may reflect ability, more practice, or the type and quality of instruction that is given to children in different countries, but at this time, the actual reason for the differences remains unknown. The original model had an excellent ability to predict the distances. The difference between the original model and the best fit model of r=.03 is trivial compared to the importance of being able to use the same classification around the baseball playing world.

The mathematical model to predict distance from age and speed is a complicated multiple regression equation using polynomial fittings and includes interactions (Figure 2). Its construction was necessary when standard physical equations systematically overpredicted distance by approximately 80% because youth baseball players are not cannons. If they had an excellent 3-step crow hop, were able to transfer all the power that they generated from the lower extremities 100% through their core, and released the ball at their maximum height on a 45-degree trajectory, the predicted and actual distances from the standard physical equations would be much closer. The mathematical model is based on data from all players, not solely pitchers, from the Mid-Atlantic region of U.S.A. It assumes that any new sample would have similar age, speed, and distance characteristics, an assumption that was verified in our international sample. In the 1996 study, height and weight data did not add to the accuracy of the predicted distance. This can be explained by age and speed capturing most differences. Older athletes who throw with the same speed as a younger pitcher will throw nearly 8 feet further, 9 year olds

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versus 11 year olds, perhaps as a result of improvement in biomechanics and coordination.26 In a world interested in reducing youth baseball injuries, education and protection are two key concepts in injury prevention.22,27 Young athletes who can throw further and faster than age norms have increased elbow forces and moments and therefore place their growth plates and ligaments at greater risk of injury.23,28 Pitchers with better mechanics threw faster but have increased medial elbow stresses.10 Risk factors for injury have been identified. While those who have complained of shoulder pain versus elbow pain may have some differences, pitching with fatigue often associated with increased pitch counts, both in a single game and cumulative for the year, and poor self perceived performance parameters are common to both.6 The Japanese have also identified risk factors for elbow injuries among youth baseball players. In their study of 294 baseball players, ages 9-12, 60 had elbow injuries.5 While both Lynam et al7,8 and Harada et al5 studied youth baseball players who participated in organized teams, comparison of these studies without a classification system is difficult. When studying pitching biomechanics in youth baseball pitchers and looking at pitching faults as risk for injury, the lack of speed or distance data to classify the talent level limits the ability to aggregate the results of studies and assess their generalizability. Either pitch speed or distance can be used and allow us to compare and contrast across studies of risk and/or biomechanics.29 How fast or how far is elite? Few would argue that the pitchers in the Little LeagueTM World Series are elite, but where does elite begin? Of the 20 pitchers from the countries studied (USA, Japan, Puerto Rico and Mexico) who appeared in the televised final games of the 2010 Little LeagueTM World Series in Williamsport, Pennsylvania, all were Level 4 or 5 (mostly 12 year olds with pitch speeds of 70 mph or above). In developing our classification of elite and at risk players, the authors extrapolated from the literature that suggested higher risk of injury in high school age players who have pitch speeds in above 80 mph, which in 14 year olds is Level 3. Therefore the authors propose that Level 3 be the threshold for classifying a pitcher as elite and potentially at risk. A 12 y. o. who is Level 3 would throw 65 mph or 216 feet, well below

the 2010 Little LeagueTM World Series pitchersâ&#x20AC;&#x2122; mean pitch speed of 72.5 mph. The categorization of the 2010 Little LeagueTM World Series pitchers as at risk has face validity. Only three pitchers have pitched in both the Little LeagueTM World Series and in the major leagues. It is reasonable to assume that injury may have played some role in this.

In some youth baseball pitching studies with reported velocity, their athletes, described as all-stars or members of travel teams, are near the mean for our USA or Level 1.29-31 However, all-star and travel team pitchers are not necessarily elite. Nakamizo et al in their study of glenohumeral anterior rotation in youth pitchers did record pitch speed in the 25 10-12 year old pitchers in their study.30 Sabick et al studied 14 youth pitchers with a mean age of 12 and speed of 21.6 m/s (48.2 mph), Level 0 or at the mean of the 1996 USA sample.32 Based on the authorsâ&#x20AC;&#x2122; developed classification system, these pitchers are at or slower than 1 standard deviation above the USA mean (23.7 m/s; 53 mph). So, these studies did not examine elite pitchers, nor did they study at risk pitchers, according to the authors of the current study. Fleisig et al studied a range of ages (10-15) and abilities (Level 0-4) with a mean speed of 28 m/s (63 mph).28,33 The classification system developed by the authors would allow for comparison across all of these studies and ultimately aggregate analysis for methods such as meta-analysis that can lead to more powerful prediction of injury risk.

Maximum long-toss can be used as a surrogate for speed. Long toss distance can be recorded each year following preseason and before the first game as a team or league competition single event, or as part of a performance battery of running, hitting and throwing and can be used for classification as well as a long toss target in rehabilitation, training and conditioning programs. While the radar gun may be helpful in comparing fast ball speed with the speeds of other pitches, to compare the pitchers average speed at different times in the game and different times in the year from preseason to playoffs and may be used in tryouts for All-Star teams, the radar gunâ&#x20AC;&#x2122;s place in youth baseball is difficult to define. Little LeagueTM baseball frowns upon the use of a radar gun, as do most other youth baseball organizations because of the potential for abuse of the quest for speed at any

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cost Here we have demonstrated that a radar gun is not necessary to classify players as elite or at risk.

Limitations of the study include unequal sample sizes and ranges of ages across the countries studied.

Collecting data internationally is culturally challenging. A planned trip to Cuba to study youth baseball players already has been postponed three times due to bureaucratic issues. The problems with the Mexican pitchers not throwing long toss during the tournament was detailed above. Nevertheless, the result demonstrates a robust and generalizable model.

CONCLUSIONS The authors tested a mathematical model published in 1996 on a sample of US baseball players on a varied sample of international youth players. The strong correlation between actual and predicted distance demonstrates that the model is robust and generalizes to the entire international sample. These data suggest that the classification system is valid and can be used prospectively and retrospectively to categorize pitchers in order to allow for studies of youth baseball injury epidemiologically and to allow for classification for biomechanical or interventional studies in youth baseball internationally. The implementation of this system can ultimately allow for important questions about risk and performance to be answered across in the U.S.A. and around the world.

REFERENCES 1. Parks ED, Ray TR. Prevention of Overuse Injuries in Young Baseball Pitchers. Sports Health: A Multidisciplinary Approach. 1(6):514 -517.

2. Pasternack JS, Veenema KR, Callahan CM. Baseball injuries: a Little League survey. Pediatrics.

1996;98(3):445.

3. STOP Sports Injuries | Sports Injury Prevention.

2010. Available at: http://www.stopsportsinjuries. org/ [Accessed October 27, 2010].

4. Albright JA, Jokl P, Shaw R, Albright JP. Clinical study of baseball pitchers: correlation of injury to the throwing arm with method of delivery. Am J Sports Med. 1978; 6(1):15-21.

5. Harada M, Takahara M, Mura N, et al. Risk factors for elbow injuries among young baseball players.

J Shoulder Elbow Surg. 2010;19(4):502-507.

6. Kerut EK, Kerut DG, Fleisig GS, Andrews JR. Prevention of arm injury in youth baseball pitchers.

J La State Med Soc. 2008;160:95â&#x20AC;&#x201C;8.

7. Lyman S, Fleisig GS, WATERBOR JW, et al.

Longitudinal study of elbow and shoulder pain in youth baseball pitchers. Medicine & Science in Sports & Exercise. 2001;33(11):1803.

8. Lyman S, Fleisig GS, Andrews JR, Osinski ED. Effect of pitch type, pitch count, and pitching mechanics on risk of elbow and shoulder pain in youth baseball pitchers. The American Journal of Sports Medicine.

2002;30(4):463.

9. Olsen SJ, Fleisig GS, Dun S, Loftice J, Andrews JR. Risk factors for shoulder and elbow injuries in adolescent baseball pitchers. The American journal of sports medicine. 2006;34(6):905.

10. Bushnell BD, Anz AW, Noonan TJ, Torry MR, Hawkins RJ. Association of maximum pitch velocity and elbow injury in professional baseball pitchers.

Am J Sports Med. 2010;38(4):728-732.

11. Hurd WJ, Jazayeri R, Mohr K, Limpisvasti O, Elattrache NS, Kaufman KR. Pitch velocity is a predictor of medial elbow distraction forces in the uninjured high school-aged baseball pitcher. Sports Health. 2012 Sep;4(5):415-8. PubMed PMID:023016114; PubMed Central PMCID: PMC3435942.

12. Ramappa AJ, Chen P, Hawkins RJ, et al. Anterior shoulder forces in professional and Little League pitchers. J Pediatr Orthop. 2010;30(1):1-7.

13. Osbahr DC, Kim HJ, Dugas JR. Little league shoulder. Curr. Opin. Pediatr. 2010;22(1):35-40.

14. Petty DH, Andrews JR, Fleisig GS, Cain EL. Ulnar collateral ligament reconstruction in high school baseball players. The American Journal of Sports Medicine. 2004;32(5):1158.

15. Welcome to the 2010 Little League Baseball World Series! Available at: http://www.littleleague.org/ worldseries/index.html [Accessed October 28, 2010].

16. Opening Day rosters feature 241 players born outside the U.S. http://mlb.mlb.com/news/article.jsp?ymd= 20130401&content_id=43618468&vkey=pr_mlb&c_ id=mlb [Accessed April 30, 2014.]

17. Gregory S. Baseball Dreams: Striking Out in the Dominican Republic. Time. 2010. Available at: http://www.time.com/time/magazine/article/ 0,9171,2004099,00.html [Accessed October 27, 2010].

18. EchevarrĂ­a RG. American Dream, Dominican Nightmare. The New York Times. 2003. Available at: http://www.nytimes.com/2003/08/12/opinion/ american-dream-dominican-nightmare.html?scp=1& sq=american%20dream%20dominican&st=cse [Accessed October 27, 2010].

19. Harada M, Takahara M, Sasaki J, et al. Using sonography for the early detection of elbow injuries

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Ultrasonographic assessment of the ulnar collateral ligament and medial elbow laxity in college baseball players. J Bone Joint Surg Am. 2002;84-A(4):525-531.

Takahara M, Shundo M, Kondo M, et al. Early detection of osteochondritis dissecans of the capitellum in young baseball players. Report of three cases. J Bone Joint Surg Am. 1998;80(6):892-897.

Axe MJ, Snyder-Mackler L, Konin JG, Strube MJ. Development of a distance-based interval throwing program for Little League-aged athletes. Am J Sports Med. 1996;24(5):594.

Axe MJ. Recommendations for protecting youth baseball pitchers. Sports Medicine and Arthroscopy Review. 2001;9(2):147.

Grondin S, Koren S. The relative age effect in professional baseball: a look at the history of Major League Baseball and at current status in Japan.

AVANTE-ONTARIO-. 2000;6(2):64â&#x20AC;&#x201C;74.

Schmidt MS. Scrutiny of Dominican Baseball Prospects Is Having an Effect. The New York Times.

2010. Available at: http://www.nytimes. com/2010/10/10/sports/baseball/10dominican. html?_r=1&scp=1&sq=dominican%20baseball&st =cse [Accessed October 27, 2010].

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Axe MJ, Wickham R, Snyder-Mackler L. Data-based interval throwing programs for little league, high school, college, and professional baseball pitchers.

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Carson WG, Gasser SI. Little Leaguerâ&#x20AC;&#x2122;s shoulder.

A report of 23 cases. Am J Sports Med. 1998;26(4): 575-580.

Davis JT, Limpisvasti O, Fluhme D, et al. The effect of pitching biomechanics on the upper extremity in youth and adolescent baseball pitchers. Am J Sports Med. 2009;37(8):1484-1491.

Nakamizo H, Nakamura Y, Nobuhara K, Yamamoto T. Loss of glenohumeral internal rotation in little league pitchers: a biomechanical study. J Shoulder Elbow Surg. 2008;17(5):795-801.

Keeley DW, Hackett T, Keirns M, Sabick MB, Torry MR. A biomechanical analysis of youth pitching mechanics. J Pediatr Orthop. 2008;28(4):452-459.

Sabick MB, Kim Y, Torry MR, Keirns MA, Hawkins RJ. Biomechanics of the shoulder in youth baseball pitchers: implications for the development of proximal humeral epiphysiolysis and humeral retrotorsion. Am J Sports Med. 2005;33(11):1716-1722.

Fleisig GS, Barrentine SW, Zheng N, Escamilla RF, Andrews JR. Kinematic and kinetic comparison of baseball pitching among various levels of development. J Biomech. 1999: 32(12):1371-5.

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IJSPT

ORIGINAL RESEARCH

LOWER EXTREMITY BALANCE IS IMPROVED AT TIME OF RETURN TO THROWING IN BASEBALL PLAYERS AFTER AN ULNAR COLLATERAL LIGAMENT RECONSTRUCTION WHEN COMPARED TO PREOPERATIVE MEASUREMENTS Joseph Hannon, PT, DPT, CSCS1 J. Craig Garrison, PhD, PT, SCS, ATC1 John Conway, MD2

ABSTRACT Background/Purpose: Lower extremity balance deficits have been shown to lead to altered kinematics and increased injury risk in lower extremity athletes. The purpose of this study was to compare lower extremity balance in baseball players with an ulnar collateral ligament (UCL) tear pre-operatively and postoperatively at the beginning of the pre-return to throwing program stage of rehabilitation (3 months).

Methods: Thirty-three competitive high school and collegiate male baseball players (18.5 ± 3.2) with a diagnosed UCL tear volunteered for the study. Of the 33 baseball players 29 were pitchers, 1 was a catcher, and 3 were infielders. Participants were seen pre-operatively and at 3 months post operatively. This 3 month point was associated with a follow-up visit to the orthopedic surgeon and subsequent release to begin the pre-return to throwing mark for baseball players following their surgery. Following surgery, each participant followed a standard UCL protocol which included focused lower extremity balance and neuromuscular control exercises. Participants were tested for single leg balance using the Y-Balance Test™ – Lower Quadrant (YBT-LQ) on both their lead and stance limbs. YBT-LQ composite scores were calculated for the stance and lead limbs pre- and post-operatively and compared over time. Paired t-tests were used to calculate differences between time 1 and time 2 (p < 0.05).

Results: Baseball players with diagnosed UCL tears demonstrated significant balance deficits on their stance (p < .001) and lead (p = .009) limbs prior to surgery compared to balance measures at the 3-month follow up (Stance Pre-Op = 89.4 ± 7.5%; Stance 3 Month = 94.9 ± 9.5%) (Lead Pre-Op = 90.2 ± 6.7%; Lead 3 Month = 93.6 ± 7.2%).

Conclusion: Based on the results of this study, lower extremity balance is altered in baseball players with UCL tears prior to surgery. Statistically significant improvements were seen and balance measures improved at the time of return to throwing.

Level of Evidence: Level 2b Keywords: Balance, baseball, ulnar collateral ligament

1 2

Texas Health Ben Hogan Sports Medicine, Fort Worth, TX, USA Texas Health Physicians Group, Fort Worth, TX, USA

CORRESPONDING AUTHOR Joseph Hannon 800 5th Avenue, Suite 150 Fort Worth, TX 76104 Phone: 817-250-7500 Email: JosephHannon@texashealth.org

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INTRODUCTION Ulnar collateral ligament (UCL) injuries and reconstructions have become increasingly common in the overhead athlete. The reported incidence of UCL injuries in high school baseball players has risen significantly, with the year round nature of the sport being suggested as a contributing factor.1 Additionally, 5% of youth pitchers sustained serious upper extremity injury (requiring shoulder or elbow surgery or ended career) over a 10-year span with pitching greater than 100 innings per year significantly increasing the risk.2 As the number of athletes playing baseball and the number of innings played per year increases, the need to better understand these injuries also increases.

Post-operative rehabilitation of UCL reconstruction often includes elbow and shoulder range of motion (ROM), strengthening of the rotator cuff and posterior shoulder musculature, and correction of faulty scapular mechanics.3-6 The athletes are progressed from the ROM phase (early) to the strengthening phase (middle) and eventually to the return to throwing phase (late). In our center, the phase just prior to returning to throwing is referred to as the “pre-return to throwing” phase. In this phase, plyometric activities are begun to prepare the athlete to accept the high forces at the shoulder and elbow that accompany throwing. With most post-operative UCL protocols, this phase typically begins around 3 months post-surgery, with the anticipation of beginning a throwing program at four months post surgically.5,6 Because throwing is a whole body movement that requires balance, coordination, and efficient energy transfer, high valgus forces at the elbow are likely not the sole contributor to UCL injuries. The true etiology is likely mulitfactorial and may be related to a break down along the kinetic chain.7,8 Balance has previously been defined as the dynamics of body posture to prevent falling and is affected by the internal forces acting on the body.9 This may involve movement around an established base of support while performing tasks, such as standing on one limb while reaching with another segment, without disrupting the established base of support.7,10 Alterations in trunk and lower extremity control during the throwing motion have been hypothesized to alter the location of the shoulder and elbow,

potentially resulting in increased stress across both joints. Recently published data suggests that lower extremity balance may be associated with UCL tears in the overhead athlete.11 High school and college baseball players with a diagnosed UCL tear scored significantly lower on the Y-Balance Test™ – Lower Quadrant (YBT-LQ) on their stance (p = 0.001) and lead (p < 0.001) limbs when measured pre-operatively as compared to their non-injured cohort.11 Although this recently published data does not explain a direct cause and effect for these injuries, the results suggest a relationship between UCL tears and deficits in lower extremity balance. While the importance of balance has been studied extensively in lower extremity rehabilitation,12-14 there is limited evidence to support this in upper extremity injuries, specifically in baseball players.11 Therefore, the purpose of this study is to examine the pre-surgical and 3 month post-operative measurements of lower extremity balance in baseball players who have undergone a UCL reconstruction.

METHODS Participants Thirty-three male competitive high school and collegiate baseball players from across the United States (average age = 18.6 ± 2.9) volunteered to participate in this study. Of the 33 participants, 29 were pitchers, 1 was a catcher, and 3 were infielders. Participants had an average of 13.2 ± 2.2 years of playing experience. All subjects gave informed consent to participate and the rights of each person were protected. The Institutional Review Board of Texas Health Resources approved the research procedures. Table 1 summarizes the demographic characteristics of the participants.

Table 1. Characteristics of baseball players with UCL tears (n=33) Age Throwing arm

18.5 ± 3.2 (range= 15-25) years Right Le

Years of Experience Posi on

28 5 13.2 ± 2.2 (range= 7-17) years

Pitcher Catcher Infielder

29 1 3

College High school

20 13

Level of play

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The diagnosis of UCL injury was made based upon clinical examination by a fellowship-trained, boardcertified orthopedic surgeon (JEC) and was confirmed via results of magnetic resonance imaging (MRI).

Subjects were considered for study participation if they were a baseball player between the ages of 15 and 25. Inclusion criteria for the study included 1) the individual’s ability to throw was affected by the injury, 2) the individual was unable to continue to participate in baseball at the level prior to UCL tear, 3) clinical exam results were positive for UCL tear, 4) confirmation of UCL tear was made via MRI, and 5) the individual was attempting to return to their sport at a competitive level.

Exclusion criteria included 1) a previous UCL reconstruction that failed, 2) previous shoulder injury or surgery (to include labral tear or rotator cuff involvement), and 3) if the patient did not plan to return to baseball at a competitive level following treatment.

Patients were enrolled into the study by an investigator in the outpatient sports physical therapy facility once screened for the inclusion and exclusion criteria. Once the patient offered consent, objective measurements of YBT-LQ were taken. Patients were seen at initial evaluation prior to surgery, which occurred at an average of 5 weeks from injury onset. Patients were seen again for follow up measurements at 3 months post-surgery.

Testing The YBT-LQ was utilized as a measure of trunk and lower extremity function. The YBT-LQ assesses ROM, strength, and neuromuscular control of the lower extremity and was chosen to assess the participants’ lower limb balance as numerous prior studies have demonstrated its utility as a clinical test to assess for lower limb balance deficits in the athletic population.12,13,15,16 Previous authors have described deficits in balance scores as they relate to lower extremity injury risk.12 Additionally, the YBT-LQ has been used previously to assess balance deficits in the UCL injured athlete.11 Measurements were taken in 3 distinct directions of anterior (ANT), posteromedial (PM) and posterolateral (PL) on both the stance and lead limbs. The stance limb was determined as the limb on which a thrower begins the throwing motion (same side as the dominant arm) thus identifying the opposite limb as the lead limb. The participants

were instructed in the YBT-LQ protocol using a combination of verbal cues and demonstration.15 The Y Balance Test Kit™ was utilized throughout the study.

All participants wore shoes during testing and began on their stance limbs. The participants were asked to perform single limb stance on the extremity while reaching outside their base of support to push a reach indicator box along the measurement pipe.15 Elevation of the heel, toe or loss of balance resulting in a stepping strategy was recorded as a trial error indicating the trial should then be repeated. Subjects were allowed at least 4 practice trials in the ANT, PM and PL directions prior to recording the best of 3 formal trials in each plane. Three trials were completed on the stance limb in the ANT (Figure 1) direction followed by 3 trials completed on the lead limb.15 This protocol was then replicated in the PM (Figure 2) and PL (Figure 3) directions. The maximal reach distance was recorded at the place where the most distal part of the foot reached based on the measurement pipe.

Figure 1. Y Balance Test™ Anterior Reach.

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length was determined using the distance between the most prominent portion of the greater trochanter and the floor while the individual was in a standing position. Composite YBT-LQ scores of the stance and lead limbs were computed for each of the athletes in this study.

Inter-rater reliability was determined prior to the initiation of this study using an Intraclass correlation coefficient (ICC). Reliability of the measurements for the anterior (ICC3,1 = 0.86; SEM, 3.3 cm), posteromedial (ICC3,1 = 0.99; SEM, 1.7 cm), and posterolateral (ICC3,1 = 0.95; SEM, 2.7 cm) directions for the testers participating in the study was considered to be acceptable. These values are similar to previously published data on intrarater (ICC3,1 = 0.91) and interrater (ICC2,1 = 0.99) reliability of composite scores for this test.15,17 Validity of the test has been previously shown in relation to hip kinematics and gluteal muscle activation.17

Figure 2. Y Balance Testâ&#x201E;˘ Posterior Medial Reach.

Figure 3. Y Balance Testâ&#x201E;˘ Posterior Lateral Reach.

The composite scores were calculated by adding the reach distances of ANT, PM, and PL, dividing by three times the participantâ&#x20AC;&#x2122;s leg length, and then multiplying by 100 to obtain a percentage.12,15 The leg

Treatment Treatment of each subject was guided by a standard UCL post-operative protocol (Appendix A) developed in conjunction with the orthopedic surgeon (JEC).

The protocol includes an early emphasis on ROM recovery, progressing to integrated strengthening of the shoulder and elbow musculature, and finally to upper body plyometrics and throwing. Included within this protocol are instructions to incorporate lower extremity strengthening, neuromuscular control, and balance exercises, beginning as early as 4-6 weeks post operatively. Balance exercises typically included in this phase of rehabilitation were designed to challenge the stability of the athlete while requiring them to demonstrate adequate trunk control throughout the given motion. The single leg stride (Figure 4 A, B) is an exercise used during this phase. During this exercise the athlete stands on their stance limb and maximally reaches into the frontal plane with their lead limb. They are instructed to reach as far as possible and return to the starting position without placing the lead limb onto the ground or without losing balance. A second exercise that is implemented during this phase includes single limb transverse plane core reaches (Figure 5 A, B). During this exercise the athlete stands in a single limb stance with their back to a wall. They are instructed to move into a combination of hip

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Figure 4. Single leg stride exercise, important to the motion of pitching. A= starting position, B= ďŹ nish position. The athlete starts in a single limb stance. They are then instructed to reach out with their lead limb while maintaining their balance on their stance limb.

and trunk extension with rotation until their shoulder contacts the wall. Participants are cued to perform this exercise in a slow and controlled manner and to increase the distance from the wall as control improves. Additional exercises that can be incorporated include the single limb lawnmower and body blade exercises (Figure 6 A, B), and the single limb wall ball exercise (Figure 7).

Figure 5. Single leg core reaches, A=starting position, B= ďŹ nish position. The athlete stands with their back to the wall on a single limb. The athlete is then instructed to move into trunk extension and rotation while maintaining single limb control and attempt to tap their shoulder to the wall. The athlete is instructed to tap their right and left shoulders to the wall in an alternating fashion.

DATA ANALYSIS Paired T-Tests were used to determine significant mean differences between the pre- and post-test results of YBT-LQ composite scores for stance and lead limbs at both points in time with significance set at p < 0.05.

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Figure 7. Single Limb Wall Ball exercise: The athlete stands with their involved UE nearest the wall. Their arm is placed in the 90/90 position to mimic the athletes arm slot during throwing. The athlete is then instructed to stand on their stance limb and perform repeated ball bounces on the wall while maintaining their balance.

reconstruction demonstrated a significant improvement in lower extremity balance on both their stance (94.9 ± 9.5%) and lead (93.6 ± 7.2%) limbs compared to their pre-operative measurements. Table 2 outlines the lower limb balance findings at time 1 (pre-operative) and time 2 (three months post operative). Baseball players with diagnosed UCL tears demonstrated significant balance improvements on their stance (p = .001) and lead (p = .009) limbs after surgery compared to balance measures taken preoperatively.

Figure 6. Single limb UE exercises, A= “lawnmower” motion, B= Body Blade™ throwing motion. These exercises are designed to mimic the throwing motion with the UE while maintaining single limb control throughout the motion.

RESULTS Baseball players with a diagnosed UCL tear demonstrated diminished stance (89.4 ± 7.5%;) and lead (90.2 ± 6.7%) limb balance, as measured by the YBTLQ at time of injury. The YBT-LQ composite balance scores on both the stance and lead limbs fall below previously published normative data for lower extremity injury risk (≤94%)12 and are in line with earlier YBT-LQ composite scores in baseball players with a UCL tear (stance = 88.2 ± 7.9%, lead = 89.1 ± 6.7%).11 At 3 month post-operative follow up, baseball players with a diagnosed UCL tear and a subsequent

DISCUSSION Improvements were found in lower extremity balance on both the stance and lead limbs of baseball players at the three month mark following UCL reconstruction. These individuals demonstrated significant improvements in lower extremity balance Table 2. Y Balance Test-Lower Quarter™ composite scores, normalized by leg length.

Pre-surgical 3- month follow up

P value

Y Balance Test™ – 89.4±7.5% composite score normalized for stance leg

94.9±9.5%

.001*

Y Balance Test™ – composite lead leg

93.6±7.2%

.009*

*Denotes

90.2±6.7%

significant difference, p < 0.05

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on their stance and lead limbs at the three-month follow up compared to their pre-operative measurements. These results are consistent with recently published data examining lower extremity balance deficits in baseball players with UCL tears.11 High school and college baseball players with a diagnosed UCL tear were compared to age- and position-matched controls and were found to have significant balance deficits in both their stance (7.2%) and lead (6.7%) lower extremities at the time of initial diagnosis. Although both studies found balance deficits at the time of UCL injury and prior to surgical reconstruction, it is difficult to determine whether this deficit played a role in predisposing the athlete to injury or was a result of the injury. Both studies are observational, and as such no cause and effect relationship can be stated. Previous research does indicate that a deficiency in balance can predict lower extremity injury in basketball players.12 However, to the authorsâ&#x20AC;&#x2122; knowledge, there are no other studies that directly examine lower extremity balance deficits as they relate to upper extremity injury risk.

While lower extremity balance deficits were present prior to surgery, significant improvements were made in both the stance and lead limbs by the time the athletes began their pre-return to throwing phase (3 months). This finding could have significant implications for rehabilitation and safe progression for return to throwing. Because this study is observational in nature and did not involve a controlled intervention or control group, it is not possible to attribute the lower extremity balance improvements in the current study to a specific treatment effect. However, there are numerous studies examining balance deficits and treatment in lower extremity athletes.16,18 Previous research in female soccer players demonstrated improvements in the Star Excursion Balance Test (SEBT) following a neuromuscular training program.18 The authors of that previous study concluded that neuromuscular training that focused on core stability and lower extremity strength significantly improved balance scores. Improvements in neuromuscular control measured by the SEBT have also been shown in individuals with chronic ankle sprains following neuromuscular training.14,19 While the previous studies all demonstrate the positive effect of neuromuscular training on balance measures, none of the studies examined the effects of neuromuscular training in the overhead athletic

population. In the aforementioned studies female soccer18 and basketball12 athletes underwent lower extremity neuromuscular training for 6 and 8 weeks respectively. In both cases a significant improvement in performance was reported. In the present study, initial and follow-up measurements were taken 12 weeks apart, allowing a significantly longer training period than reported in past studies. While the observational design of the current study limits the ability to show a cause and effect relationship, it is possible that waiting 12 weeks between measurements allowed adequate training to take place. A systematic review by Zech et al20 reported that balance training on stable or unstable platforms with or without recurrent destabilization of 6 to 12 weeks, improved neuromuscular control better than training of only 4 weeks, indicating that the longer training duration in the present study may have contributed to the improvements in balance. Similarly, both Zech et al20 and a second systematic review by Thacker et al21 reported that individuals who participate in a neuromuscular training program demonstrate significantly decreased injury risk compared to controls.

The summary of these findings suggests that participation in a neuromuscular training program, such as the one implemented in the current study may help to improve balance measures in overhead athletes.

What these balance deficits mean at this point is yet to be determined. This can be attributed to a lack of research on balance deficits in throwers, in addition to an incomplete understanding of the kinetic chain effects on the upper extremity during throwing. The effects of lower extremity biomechanics and ground reaction forces (GRF) on pitching have previously been studied in relation to injury prevention and performance.22-25 Additionally, authors of clinical commentaries have attempted to address this void in the literature. Kibler and Chandler26 described how a 20% decrease in kinetic energy delivered from the hip and trunk to the arm required a 34% increase in the rotational velocity of the shoulder to impart the same amount of force to the hand in tennis players.

Likewise, the pitching motion has been defined as an integrated motion of the entire body that culminates with rapid motion of the upper extremity.27 While the above explanations are only hypotheses and have yet to be supported by research, the role of the

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kinetic chain in the throwing motion and the impact that it could potentially have on injury and injury prevention is beginning to be recognized. This role is evident in a clinical commentary in which the authors hypothesized that distant physiological and biomechanical factors play an important role in generating forces, motions and loads experienced at the elbow.7 The current hypothesis seems to suggest that lower extremity force generation may play a significant role in attenuating stress across the upper extremity.

At this time, these are simply hypotheses and more research is needed to further understand how the role of lower extremity balance, neuromuscular control and the kinetic chain affects the throwing motion.

A major limitation of this study is the lack of control of the treatment during the 3-month time period. Protocols were supplied and encouraged to be followed, but tracking compliance by the patient and treating therapist was not performed. Although each patient was given a standardized protocol and instructed in the gradual progression based upon both criteria and time for healing, the authors were unable to specifically control what occurred with treatment progression as each patient returned to his home and underwent physical therapy there. Despite this limitation, significant findings were noted. More research is warranted to examine the role of lower extremity balance and the kinetic chain on the throwing motion to help better understand the rehabilitation considerations following UCL reconstruction in baseball players.

CONCLUSION The results of this study point to improvements in lower extremity neuromuscular control on both the stance and lead limbs of baseball players at the 3 month mark following UCL reconstruction.

No direct correlation can be made in regards to decreased lower extremity neuromuscular control and UCL tears; however, improvements in balance were noted on the stance and lead lower extremities at the time of the pre-return to throwing phase.

REFERENCES 1. Petty DH, Andrews JR, Fleisig GS, Cain EL: Ulnar Collateral Ligament Reconstruction in High School Baseball Players Clinical Results and Injury Risk Factors. Am J Sports Med. 2004; 32(5): 1158-1164.

2. Fleisig GS, Andrews JR, Cutter GR, et al.: Risk of Serious Injury for Young Baseball Pitchers. Am J Sports Med. 2011; 39(2): 253-257.

3. Fleisig GS, Bolt B, FortenBaugh D, Wilk KE, Andrews JR: Biomechanical Comparison of Baseball Pitching and Long-Toss: Implications for Training and Rehabilitation. J Ortho Sports Phys Ther 2011; 41(5): 296-303.

4. Seto JL, Brewster CE, Randall CC, FW J: Rehabilitation Following Ulnar Collateral Ligament Reconstruction of Athletes. J Orthop Sports Phys Ther 1991; 14(3): 100105.

5. Wilk KE, Macrina LC, Cain EL, Dugas JR, JR A: Rehabilitation of the Overhead Athleteâ&#x20AC;&#x2122;s Elbow.

Sports Health 2012; 4(5): 404-414.

6. Wilk KE, Arrigo CA, JR A: Rehabilitation of the Elbow in the Throwing Athlete. J Ortho Sports Phys Ther 1993; 17(6): 305-317.

7. Kibler WB, Sciascia A: Kinetic chain contributions to elbow function and dysfunction in sports. Clin Sports Med 2004; 23(4): 545-552.

8. Burkhart SS, Morgan CD, Kibler WB: The disabled throwing shoulder: spectrum of pathology Part III: The SICK scapula, scapular dyskinesis, the kinetic chain, and rehabilitation. Arthroscopy 2003; 19(6): 641-661.

9. Winter DA: Human balance and posture control during standing and walking. Gait & Posture 1995; 3: 193-214.

10. Gribble PA, Hertel J, PJ. P: Using the Star Excursion Balance Test to assess dynamic postural-control deďŹ cits and outcomes in lower extremity injury: a literature and systematic review. J Athl Train 2012; 47(3): 339-357.

11. Garrison JC, Arnold A, Macko MJ, Conway JE: Baseball players diagnosed with ulnar collateral ligament (UCL) injuries demonstrate decreased balance compared to healthy controls. J Ortho Sports Phys Ther 2013; 43(10): 752-758.

12. Plisky P, Rauh M, Kaminski T, Underwood F: Star Excursion Balance Test as a Predictor of Lower Extremity Injury in Highschool Basketball Players.

J Ortho Sports Phys Ther 2006; 36(12): 911-919.

13. Sefton JM, Yarar C, Hicks-Little C, Berry JW, Cordova ML: Six Weeks of Balance Training Improves Sensorimotor Function in Individuals With Chronic Ankle Instability. J Ortho Sports Phys Ther 2011; 41(2): 81-89.

14. Hale SA, Hertel J, Olmsted-Kramer LC: The Effect of a 4-Week Comprehensive Rehabilitation Program on Postural Control and Lower Extremity Function in Individuals With Chronic Ankle Instability. J Ortho Sports Phys Ther 2007; 37(6): 303-311.

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15. Plisky P, Gorman PP, Butler RK, Kiesel KB, Underwood FB, Elkins B: The reliability of an instrumented device for measuring components of the star excursion. N Amer J Sports Phys Ther 2009; 4(2): 92-99.

16. Paterno MV, Myer GD, Ford KR, Hewett TE: Neuromuscular training improves single-limb stability in young female athletes. J Ortho Sports Phys Ther 2004; 34(6): 305-316.

17. Kivlan BR, Martin RL: Functional Performance Testing Of The Hip In Athletes: A Systematic Review For Reliability And Validity. I J Sports Phys Ther 2012; 7(4): 402-412.

18. Filipa A, Byrnes R, Paterno MV, Myer GD, Hewett TE: Neuromuscular Training Improves Performance on the Star Excursion Balance Test in Young Female Athletes. J Ortho Sports Phys Ther 2010; 40(9): 551558.

19. Mckeon P, Ingersoll C, Kerrigan DC, Saliba E, B B, Hertel J: Balance training improves function and postural control in those with chronic ankle instability. Med Sci Sports Exerc 2008; 40(10): 18101819.

20. Zech A, Hubscher M, Vogt L, Banzer W, Hansel F, Pfeifer K: Balance Training for Neuromuscular Control and Performance Enhancement: A systematic Review. J Athl Train 2010; 45(4): 392-403.

21. Thacker SB, Stroup DF, Branche CM, Gilchrist J, Goodman RA, Kelling E: Prevention of Knee injuries

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Davis JT, Limpisvasti O, Fluhme D, et al.: The Effect of Pitching Biomechanics on the Upper Extremity in Youth and Adolescent Baseball Pitchers. Am J Sports Med. 2009; 37(8): 1484-1491.

Fortenbaugh D, Flesig GS, Andrews JR: Baseball Pitching Biomechanics in Relation to Injury Risk and Performance. Sports Health 2009; 1(4): 314-320.

Guido JA, Werner SL: Lower-Extremity Ground Reaction Forces in Collegiate Baseball Pitchers.

J. Strength Cond. Res. 2012; 26(7): 1782-1785.

MacWilliam BA, Tony C, Perezous MK, Chao EY, McFarland EG: Characteristic Ground-Reaction Forces in Baseball Pitching. Am J Sports Med. 1998; 26(1): 66-71.

Kibler WB, Chandler J: Baseball and Tennis. In: LY IG, ed. Rehabilitation of the Injured Knee. St. Louis: Mosby, 1995; 219-226.

Seroyer ST, Nho SJ, Bach BR, Bush-Joseph CA, Nicholson GP, Romeo AA: The Kinetic Chain in Overhand Pitching: Its Potential Role for Performance Enhancement and Injury prevention.

Sports Health 2010; 2(2): 135-146.

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IJSPT

ORIGINAL RESEARCH

CLINICAL OUTCOMES OF THE ADDITION OF ECCENTRICS FOR REHABILITATION OF PREVIOUSLY FAILED TREATMENTS OF GOLFERS ELBOW Timothy F. Tyler, MS, PT, ATC1,2 Stephen J. Nicholas, MD2 Brandon M. Schmitt, DPT, ATC2 Michael Mullaney, DPT1 Daniel E. Hogan, MS1

ABSTRACT Introduction and Purpose: Eccentric training of the wrist extensors has been shown to be effective in treating chronic lateral epicondylosis. However, its efficacy in the treatment of medial epicondylosis has yet to be demonstrated. The objective of this study was to assess the effectiveness of a novel eccentric wrist flexor exercise added to standard treatment for chronic medial epicondylosis in patients who did not respond to previous therapeutic interventions for this disorder.

Number of Subjects: 20 Materials/Methods: Patients (13 men, 7 women; age 49±12 yr) with chronic medial epicondylosis who had failed previous treatment for this disorder (physical therapy 7, cortisone injection 7, PRP 1, NSAIDS 15) were prescribed isolated eccentrics in addition to wrist stretching, ultrasound, cross-friction massage, heat and ice. The specific isolated eccentric wrist flexor strengthening exercise performed by the patients involved twisting a rubber bar (Flexbar, Hygenic Corportation, Akron OH) with concentric wrist flexion of the noninvolved arm and releasing the twist by eccentrically contracting the wrist flexors of the involved arm (3 × 15 twice daily). A DASH questionnaire was recorded at baseline and again after the treatment period. Treating clinicians were blinded to baseline DASH scores. Treatment effect was assessed using paired t-test. Based on previous work it was estimated that with a sample of 20 patients there would be 80% power to detect a 13 point improvement in DASH scores (p<.05).

Results: The pathology was in the dominant arm of 18 patients and recurrent in 10. Primary symptomatic activities were golf (14), tennis (2), basketball (1), weight lifting (1), and general activities of daily living (2). There was a significant improvement in outcomes following the addition of isolated eccentrics (Pre DASH 34.7±16.2 vs. Post DASH 7.9±11.1, p<.001). For the 18 patients involved in sports, the sports module of the DASH score improved from 73.9±28.9 to 13.2±25.0, p<.001).

Physical therapy visits ranged from 1-22 with an average of 12±6 and, average treatment duration of 6.1±2.5 wks (range 110). Home exercise program compliance was recorded for each subject (15 full, 3 mostly, 1 occasionally, 1 none).

Conclusions: The outcome measure for chronic medial epicondylosis was markedly improved with the addition of an eccentric wrist flexor exercise to standard physical therapy. Given the inconsistent outcomes for patients previously treated with chronic medial epicondylosis the addition of isolated eccentrics seems warranted based on the results of this study.

Clinical Relevance: This novel exercise, using an inexpensive rubber bar, provides a practical means of adding isolated eccentric training to the treatment of chronic medial epicondylosis.

Level of Evidence: 2b Keywords: Eccentric exercise, failed treatment, medial epicondylosis

1

The Nicholas Institute of Sports Medicine and Athletic Trauma New York, NY USA 2 Pro Sports Physical Therapy of Westchester Scarsdale, NY USA The North Shore/Long Island Jewish Health System Institutional Review Board approved of this study protocol.

CORRESPONDING AUTHOR Timothy F. Tyler, MS, PT, ATC The Nicholas Institute of Sports Medicine Athletic Trauma @ Lenox Hill Hospital Phone: (914) 723-6987 Fax: (914) 723-7546 E-mail: shoulderpt@yahoo.com

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INTRODUCTION Golfers elbow, or medial epicondylosis, is a common condition that is characterized by pain at the medial epicondyle, aggravated by resisted muscle contraction of the wrist flexors and supinator. The estimated annual incidence in the military population for medial epicondylosis is 1% versus 3% for the same condition occurring on the lateral side.1,2 A variety of specific treatment strategies have been described over the years, including electrophysical modalities,3 corticosteroid injections,4 exercise therapy and mobilization,5 low level laser therapy6 repetitive low-energy shockwave treatment,7 autologous blood injection,8 and isolated eccentric training.9 Typically, physical therapy interventions include wrist flexor stretching, isotonic wrist flexor strengthening, ultrasound, cross-friction massage, heat and ice. Isolated eccentric strength training has been shown to be effective for treating achilles,10,11 patella,12 shoulder tendonopathies13 and lateral epicondylosis.14,15 A common factor in the eccentric exercise programs utilized in these studies was that the exercises could be performed at home without the need for expensive equipment or regular physical therapy visits. Recently, isolated eccentric training was also shown to be effective in treating chronic lateral epicondylosis using an inexpensive rubber bar called a flexbar to perform a exercise named the Tyler Twist in a recent currents concepts article.15,16 The purpose of this study was to assess the efficacy of a novel eccentric wrist flexor strengthening exercise called the Reverse Tyler Twist15 added to standard physical therapy interventions for chronic medial epicondylosis cases that were unresponsive to previous therapeutic interventions.

Materials and Methods Twenty patients with chronic medial epicondylosis participated in the study (n=20, 13 men, 7 women; age 49 + 12 yr). Eighteen of these patients participated in competitive athletics. Patients were included and classified as having chronic medial epicondylosis if they were diagnosed with medial epicondylosis symptoms for greater than 6 weeks. Medial epicondylosis was diagnosed using the following tests: (1) pain on palpation at the medial epicondyle, (2) pain on resisted wrist flexion, and (3) pain on medial side of forearm. Subjects needed to test positive on all 3 tests to be included in the study.

Patients with a history of fracture, dislocation, surgery, medial epicondylar avulsion, osteochondritis dissecans or steochondrosis of capitellum or radial head, olecranon apophysitis, cubital tunnel syndrome, flexor pronator strain, ulnar collateral ligament strain, and ulnar neuritis were excluded.1 All patients had failed various previous treatments for this pathology. Seven patients had prior physical therapy, seven patients had a corticosteroid injection one patient had a platelet-rich plasma injection, and 15 patients had taken non-steroidal anti-inflammatory medications. Two patients developed medial epicondylosis from playing tennis, 14 from golf, one during weight training, 1 from basketball, and two were attributable to activities of daily living. All subjects gave written informed consent and the protocol was approved by an North Shore/Long Island Jewish Health System Institutional Review Board.

Physical Therapy Treatment All patients received self wrist flexor stretching five times for 30 seconds, ultrasound 3.3 Mhz, 1.2 W/cm2 50% duty cycle for five minutes, cross friction massage over most painful area for five minutes, 15 minutes of heat prior to the treatment and 15 minutes of ice following their physical therapy visits.15 Additionally, all patients performed the isolated eccentric contractions of the wrist flexors, as described below.

The isolated eccentric strengthening exercise was performed using a rubber bar (Thera-Band 速 FlexBar, The Hygenic Corporation, Akron OH) that was twisted using wrist flexion of the uninvolved limb and slowly allowed to untwist with eccentric wrist flexion by the involved limb (Figs. 1A-E (Supplemental File 1)). Each eccentric wrist flexor contraction lasted approximately 5 seconds (i.e. slow release). Both upper extremities were reset for the subsequent repetitions. A 60 second rest period was timed between each set of 15 repetitions. Three sets of 15 repetitions were performed daily.

Intensity was increased by giving the patient a thicker (greater resistance) rubber bar if the patient reported that they no longer experienced discomfort during the exercise. The eccentric strengthening and stretching exercises were also prescribed as a home exercise program. The home exercise program consisted of three sets of isolated eccentric exercises. Self-stretching consisted of three 30-second wrist flexor stretches.

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Figure 1. A: Rubber bar held in involved (right) hand in maximum wrist flexion.

B: Other end of rubber bar grasped by noninvolved (left) hand.

C: Rubber bar twisted by flexing the noninvolved wrist while holding the involved wrist in flexion.

D: Arms brought in front of body with elbows in extension while maintaining twist in rubber bar by holding with noninvolved wrist in full flexion and the involved wrist in full flexion.

E: Rubber bar slowly untwisted by allowing involved wrist to move into extension, slowly, approximately a five second release, i.e. eccentric contraction of the involved wrist extensors.

Note: Supplemental File 1 on the IJSPT website is a Video that demonstrates this exercise.

Isolated eccentric exercises were performed until discomfort was achieved twice a day every day in which the subject did not receive physical therapy and compliance was recorded. Treatments were continued until patients had resolution of symptoms or were referred back to their physician with continued symptoms.

Outcome Measures The Disability of Arm, Shoulder, and Hand Questionnaire (DASH) was used to determine the degree

of patient reported disability caused by the medial epicondylosis. In addition, athletes were asked to fill out the Sports module of the DASH. The DASH questionnaire and Sports module of the DASH were completed prior to and after the treatment period.

Pre- and post-treatment outcome measures included the DASH and a compliance log which were recorded by the same physical therapist, who was blinded to the patient’s pre treatment scores. The compliance log was self-reported by the patient indicating the

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days per week they completed their home exercise program and categorized as either full (everyday), mostly (5-7 days), occasionally (1-4 days), or not compliant (0 days).

Statistics Paired t-tests were used to examine the effect of eccentric training on all dependent variables.

Results are reported as mean±SD. Based on previous work8,15 it was estimated that 20 patients would be sufficient to detect a 40% improvement in DASH score at P<0.05 with 80% power.

RESULTS Overall, DASH scores improved from 34.7±16.2 to 7.9±11.1, p<.001. For the 18 athletes Sport DASH scores improved from 73.9±28.9 to 13.2±25.0, p<.001.

Home exercise program compliance was recorded for each subject 15 full, 3 mostly, 1 occasionally, 1 none.

Follow-up DASH scores were 22 and 39 for the two non-compliant patients. The number of physical therapy visits averaged 12±6 or duration of treatment 6.1±2.5 wks.

DISCUSSION The eccentric exercise program introduced in this study appears to be an effective method of treating chronic medial epicondylosis. DASH scores and Sports module of the DASH were markedly improved with the addition of an eccentric wrist flexor exercise to standard physical therapy interventions. This novel exercise, using an inexpensive rubber bar, provides a practical means of adding isolated eccentric training to the treatment of chronic medial epicondylosis. A prescription of 3 sets of 15 repetitions daily for approximately 6 weeks appeared to be an effective treatment in the majority of patients who had already failed a previous intervention for this disorder.

There are many different approaches to the treatment of chronic medial epicondylosis, such as electrophysical modalities,3 corticosteroid injections,4 exercise therapy and mobilization,5 low level laser therapy,6 repetitive low-energy shockwave treatment,7 autologous blood injection.8 These are commonly provided independently from or as part of standard physical therapy care. Compared to isolated eccentric strength training, treatments such as low-

level laser therapy, shockwave therapy, corticosteroid injections or autologous blood injection, require direct medical supervision and in some cases have significant side effects. While the efficacy of isolated eccentric training for the treatment of tendinopathies in various joints has been clearly established10 -15 the additional benefit of this treatment for medial epicondylopathy is that it can be performed as part of a home program and it does not involve continued medical supervision. Not only does this provide a cost benefit, but treatment dosage is not limited by the patient having to come to a clinic or needing direct supervision.

With respect to eccentric training for chronic medial epicondylosis, The authors’ of the current study are unaware of a single study examining the effect of eccentric training for medial epicondylosis. However, for lateral epicondylosis, Croisier et al14 and Tyler et al15 were able to show significant improvements using isokinetic eccentric wrist extensor training and a home eccentric flexbar program, respectively.

The subjects in these studies were not ones that had failed previous treatments, unlike those enrolled in the current study. Due to the lack of incidence and prevalence of this pathology the authors’ chose not to design a prospective randomized trial as has been utilized in lateral epicondylosis studies. A limitation of the current study is that the effectiveness of the treatment cannot be attributed directly to the use of eccentric strengthening because there was no control group and other treatment techniques were being used simultaneously. Other limitations include the patient population included various mechanisms of injury; and that the failed treatments were from many different clinicians using multiple treatment methods.

The use of patients who have failed a previous treatment intervention represents what is often encountered in clinical practice and may even be considered a “quasi control”. A limitation of the present study may be the small sample size. However, based on previous work8,15 it was estimated that 20 patients would be sufficient to detect a 40% improvement in DASH score at p<0.05 with 80% power and this number of enrolled patients was achieved.

The average duration of treatment was approximately six weeks with the average number of physical ther-

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apy visits being 12. It remains to seen if isolated eccentrics alone without the addition of supervised physical therapy has the same clinical effects. Additionally, given that the follow-up period was only six weeks after the initiation of treatment and that medial epicondylosis has a high recurrence rate, the current results should be viewed as evidence for short-term efficacy of the addition of eccentric strengthening to a traditional physical therapy intervention. It remains to be determined if this treatment approach provides similar efficacy in the long term.

A search of the literature revealed a paucity of quality studies examining the efficacy of treatments for medial epicondyle tendinopathy. In two published systematic reviews attempting to examine treatment effectiveness of interventions for medial epipcondylosis their authors found no studies meeting their inclusion criteria.3,5 A combination of dry needling and ultrasound guided autologous blood injection has been shown to decrease pain measured by visual analog scale (VAS) and modified Nirshl scores, but had a small a sample size of 20 similar to the current study.8 There is some evidence to suggest the use of low level laser therapy in the treatment of medial epicodylitis.6 Low level energy shock wave therapy for the treatment of chronic medial tendinopathy was found to offer poor results7 and there were long term benefits reported from a local injection of methylprednisolone.4 Given the inconsistent outcomes for patients previously treated with chronic medial epicondylosis the addition of isolated eccentrics seems promising based on the results of the current study.

CONCLUSION In conclusion, these data provide further evidence for the efficacy of eccentric training for tendinopathies. The outcome measure for chronic medial epicondylosis was markedly improved with the addition of an eccentric wrist flexor exercise to standard physical therapy interventions. Given the inconsistent outcomes for patients previously treated with chronic medial epicondylosis the addition of isolated eccentrics seems warranted based on the results of this study. This novel exercise, using an inexpensive rubber bar, provides a practical means of adding iso-

lated eccentric training to the treatment interventions for chronic medial epicondylosis.

REFERENCES 1. Shiri R, Viikari-Juntura E. Lateral and medial epicondylitis: role of occupational factors. Best Pract Res Clin Rheumatol. 2011;25(1):43-57.

2. Wolf JM, Mountcastle S, Burks R, Sturdivant RX, Owens BD. Epidemiology of lateral and medial epicondylitis in a military population. Mil Med. 2010;175(5):336-9.

3. Dingemanse R, Randsdorp M, Koes BW et al.

Evidence for the effectiveness of electrophysical modalities for treatment of medial and lateral epicondylitis: a systematic review. Br J Sports Med 2013; 0;1-10.

4. Stahl S, Kaufman T. The efficacy of an injection of steroids for medial epicondylitis. A prospective study of sixty elbows. J Bone Joint Surg Am. 1997;79(11):1648-52.

5. Hoogvliet P, Ransdorp MS, Dingemanse R et al. Does effectiveness of exercise therapy and mobilisation techniques offer guidance for treatment of lateral and medial epicondylitis? A systematic review.

Br J Sports Med. 2013 47: 1112-1119.

6. Simunovic Z, Trobonjaca T, Trobonjaca Z. Treatment of medial and lateral epicondylitis--tennis and golfer’s elbow--with low level laser therapy: a multicenter double blind, placebo-controlled clinical study on 324 patients. J Clin Laser Med Surg.

1998;16(3):145-51.

7. Krischek O, Hopf C, Nafe B, Rompe JD. Shock-wave therapy for tennis and golfer’s elbow--1 year follow-up. Arch Orthop Trauma Surg. 1999; 119(1-2):62-6.

8. Suresh SP, Ali KE, Jones H, et al. Medial epicondylitis: is ultrasound guided autologous blood injection an effective treatment? Br J Sports Med. 2006;40(11):935-9 9. Woodley BL, Newsham-West RJ Baxter GD. Chronic Tendinopathy: Effectiveness of Eccentric Exercise.

Br J Sports Med. 2007;41(4):188-98.

10. Alfredson, H., Pietila, T., Jonsson, P., and Lorentzon, R. Heavy-Load Eccentric Calf Muscle Training for the Treatment of Chronic Achilles Tendinosis. Am J Sports Med. 1998;26(3):360-6.

11. Jonsson, P., Alfredson, H., Sunding, K., Fahlstrom, M., and Cook, J. New Regimen for Eccentric CalfMuscle Training in Patients With Chronic Insertional Achilles Tendinopathy: Results of a Pilot Study. Br J Sports Med. 2008;42(9):746-9.

12. Purdam, C. R., Jonsson, P., Alfredson, H., Lorentzon, R., Cook, J. L., and Khan, K. M. A Pilot Study of the

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Eccentric Decline Squat in the Management of Painful Chronic Patellar Tendinopathy. Br J Sports Med. 2004;38(4):395-7.

13. Jonsson, P., Wahlstrom, P., Ohberg, L., and Alfredson, H. Eccentric Training in Chronic Painful Impingement Syndrome of the Shoulder: Results of a Pilot Study. Knee Surg.Sports Traumatol.Arthrosc 2006;14(1):76-81.

14. Croisier, J. L., Foidart-Dessalle, M., Tinant, F., Crielaard, J. M., and Forthomme, B. An Isokinetic

Eccentric Programme for the Management of Chronic Lateral Epicondylar Tendinopathy. Br J Sports Med. 2007;41(4):269-75.

15. Tyler TF, Thomas GC, Nicholas SJ, McHugh MP. Addition of isolated wrist extensor eccentric exercise to standard treatment for chronic lateral epicondylosis: A prospective randomized trial. J Shoulder Elbow Surg. 2010;19(6):917-22.

16. Ellenbecker TS, Nirschl R, Renstrom P. Current concepts in examination and treatment of elbow tendon injury. Sports Health. 2013;5(2):186-94.

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IJSPT

CASE REPORT

DIAGNOSIS AND EXPEDITED SURGICAL INTERVENTION OF A COMPLETE HAMSTRING AVULSION IN A MILITARY COMBATIVES ATHLETE: A CASE REPORT Shaun J. O’Laughlin, PT, DPT, OCS1,2 Timothy W. Flynn, PT, PhD3 Richard B. Westrick, PT, DSc4 Michael D. Ross, PT, DHSc5

ABSTRACT Background and Purpose: Hamstring injuries are frequent injuries in athletes, with the most common being strains at the musculotendinous junction or within the muscle belly. Conversely, hamstring avulsions are rare and often misdiagnosed leading to delay in appropriate surgical interventions. The purpose of this case report is to describe the history and physical examination findings that led to appropriate diagnostic imaging and the subsequent diagnosis and expedited surgical intervention of a complete avulsion of the hamstring muscle group from the ischium in a military combatives athlete.

Case Description: The patient was a 25 year-old male who sustained a hyperflexion injury to his right hip with knee extension while participating in military combatives, presenting with acute posterior thigh and buttock pain. History and physical examination findings from a physical therapy evaluation prompted an urgent magnetic resonance imaging (MRI) study, which led to the diagnosis of a complete avulsion of the hamstring muscle group off the ischium.

Outcome: Expedited surgical intervention occurred within 13 days of the injury potentially limiting comorbidities associated with delayed diagnosis.

Conclusion: Recognition of the avulsion led to prompt surgical evaluation and intervention. Literature has shown that diagnosis of hamstring avulsions are frequently missed or delayed, which results in a myriad of complications.

Keywords: Differential diagnosis, imaging, hamstring avulsion Level of Evidence: Level 4

1

Munson Army Health Center, Fort Leavenworth, KS, USA Graduate Program in Orthopedic and Sports Science, Rocky Mountain University of Health Professions, Provo, UT, USA 3 Rocky Mountain University of Health Professions, Provo, UT, USA 4 United States Military – Baylor University Sports Physical Therapy Doctoral Program, West Point, NY, USA 5 Department of Physical Therapy, University of Scranton, Scranton, PA, USA 2

The opinions expressed herein are those of the authors and do not necessarily reflect the opinions of Rocky Mountain University of Health Professions, Baylor University, University of Scranton, the Department of Defense, the United States Army, or other Federal Agencies.

CORRESPONDING AUTHOR Dr. Shaun J. O’Laughlin Munson Army Health Center 550 Pope Avenue, ATTN: Physical Therapy Fort Leavenworth, KS 66027 Phone (913) 684-6338 E-mail: shaun.j.olaughlin.mil@mail.mil

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INTRODUCTION AND PURPOSE Hamstring injuries are a common injury in athletes, frequently occurring in sprinting sports such as track and field,1-3 soccer,4 and football.5 Most hamstring injuries consist of muscle strains of the long head of the biceps femoris at the musculotendinous junction,6,7 which can be managed with physical therapy.8,9 Complete avulsion of the hamstring muscle group from the ischium is rare10 and requires careful evaluation to be recognized in a time efficient manner, as surgical management may be necessary.11 Hamstring avulsions from the ischium have been reported in skiing sports,10,12,13 judo,14 bull riding,10 running or sprinting, soccer, football, ice hockey, in-line skating, dancing, tennis, and wrestling.15 The mechanism of injury for a complete avulsion of the hamstring muscle group from the ischium typically occurs with sudden hip flexion with knee extension along with a strong eccentric hamstring contraction.16,17 Hamstring avulsions can be difficult to diagnose acutely due to swelling and patient guarding, which may mask a visibly palpable defect and lead to delays in diagnosis.10,13 Hamstring avulsions do not always require surgical repair but surgical intervention is indicated when a complete avulsion of the hamstring muscle group occurs or when two tendons are involved with retraction greater than two centimeters.17 Beneficial outcomes have been noted for both acute and chronic surgical repair of complete proximal hamstring avulsions when compared to nonoperative management.11 However, acute surgical repair has been documented to provide higher functional scores and strength measures with fewer surgical complications compared to chronic surgical repair at long-term follow-ups of a year or more.11,18 The purpose of this case report is to describe the history and physical examination findings that warranted obtaining early diagnostic imaging in order to accurately diagnose and expedite surgical intervention for a complete avulsion of the hamstring muscle group from the ischium in a military combatives athlete.

CASE DESCRIPTION The subject was a 25 year-old male soldier athlete participating in the “modern army combatives program” (a Brazilian Jiu Jitsu based mixed martial arts program). His primary care physician evaluated

Figure 1. Anterior to posterior view radiograph of the pelvis and bilateral hips, which was interpreted as normal.

Figure 2. Frog leg lateral view radiograph of the right hip, which was interpreted as normal.

him one-day following his injury and right hip radiographs were ordered (Figures 1 and 2). Radiographs demonstrated no bony abnormalities; the patient was diagnosed with a hamstring muscle strain, placed on work restrictions, and referred to a physical therapist. The patient presented to the physical therapist with a one-week history of right posterior thigh and buttock pain.

CLINICAL IMPRESSION The physical therapist reviewed the patient’s radiology report, radiographs, and the primary care provider’s documentation on the military electronic medical record system prior to the initial physical therapy evaluation. Prior to meeting the patient the

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Table 1. Differential diagnosis for patients with acute hamstring pain Hamstring muscle strain Hamstring muscle avulsion (≤2 muscles) Complete hamstring avulsion (3 muscles) Referred pain from the lumbar spine (i.e., lumbar disc pathology) Referred pain from gluteal muscles Sacroiliac dysfunction Hip extensor or rotator muscle strain Adductor muscle strain (adductor magnus) Piriformis syndrome Femoral vein thrombosis Bursitis (i.e., ischiogluteal) Ligament sprain (i.e., sacrotuberous, sacrospinous) Vascular claudication Femoral neck stress fracture Posterior compartment syndrome

physical therapist’s initial working diagnosis was a hamstring strain. However, there are many sports injuries and pathologies that cause posterior hip pain, which should be further explored during the history and physical examination (Table 1).

INITIAL PHYSICAL THERAPY EVALUATION At the initial physical therapy examination, the patient described a rapid hip flexion motion combined with knee extension as the mechanism of injury. He reported feeling a “pop” when his opponent landed on his anterior thigh while he was in a splits position in the sagittal plane (contralateral extremity in hip and knee extension). The patient reported no prior history of hamstring injury and reported a resting pain level of six out of ten on the numeric pain rating scale (NPRS) and eight out of ten when sitting or with any active movement of the hip or knee (all planes of motion). The patient described the quality of pain as sharp, with mid posterior thigh pain that referred proximally into the posterior hip but he denied paresthesia. The patient completed a Lower Extremity Functional Scale (LEFS) to assess his level of function with 80 indicating the highest level of function, while lower numbers indicate lower levels of function.19 The patient’s LEFS resulted in a score of 7 out of 80 indicating a very low personal assessment of lower extremity function, and accordingly, he was unable to return to sporting activity.

The patient presented non-weight bearing on the right lower extremity with axillary crutches, but was able to ambulate during the examination with his knee in full extension. His gait was antalgic when full weight

bearing, with a decreased stance phase on the right side using a stiff-legged gait pattern characterized by decreased knee flexion. With the patient lying prone, visual examination revealed moderate ecchymosis 6 cm distal to the ischial tuberosity with a palpable defect approximately 2.5 cm wide by 5 cm long, 8 cm distal to the ischial tuberosity on the medial aspect of the posterior thigh. Palpation of the posterior medial thigh elicited pain at the site of the defect. Knee flexor strength was assessed with the patient positioned in prone with the knee passively positioned at 90 degrees of flexion.

The patient was unable to actively resist manual force and was unable to lower his leg through the full range of motion to the table utilizing an eccentric contraction due to pain and guarding demonstrating a manual muscle testing grade of 2+/5. The proximal hamstring tendon insertion appeared to be absent with palpation during a hamstring contraction.

The patient’s reported mechanism of injury, level of function, and clinical exam findings were consistent with a complete hamstring avulsion. Additional key findings that would be associated with a hamstring avulsion included a “pop” at the time of injury, palpable defect,20 swelling,16 ecchymosis,17,20,21 stiff legged gait pattern,17 and an inability to palpate the proximal tendon attachment at the ischial tuberosity.

INTERVENTION Due to high suspicion of a proximal hamstring avulsion the physical therapist ordered a magnetic resonance image (MRI) study and consulted with a musculoskeletal radiologist to facilitate a same day study. The physical therapist also consulted with the on call orthopaedic physician assistant and an orthopaedic surgeon who agreed to see the patient within two days. MRI (Figures 3-5) revealed a complete proximal hamstring avulsion off the ischial tuberosity with 5 cm tendon retraction of the semimembranosus and semitendinosus muscles and 6.5 cm retraction of the biceps femoris. After evaluation by the orthopedic surgeon, the patient was scheduled for surgical intervention five days later (13 days following his injury).

OUTCOME Surgical intervention was performed by debriding the ischial tuberosity followed by placement of two helix sutures, which were then woven into the hamstring tendon with one suture serving as a gliding stitch. The

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Figure 3. Axial proton density fat saturation magnetic resonance image of the right thigh with noted edema (circle) posteriorly.

Figure 5. Sagittal proton density magnetic resonance image demonstrating a 6.5 cm retraction of the biceps femoris (arrow).

pain, until the patientâ&#x20AC;&#x2122;s run progression was halted at approximately four months post-operative after he sustained an anterior cruciate ligament (ACL) injury on the contralateral lower extremity, unrelated to the hamstring injury. Despite the ACL injury, after 22 months, the patient reported no associated pain or re-injury of the hamstring.

Figure 4. Coronal STIR magnetic resonance image demonstrating proximal hamstring tendon retraction (arrow).

tendon was approximated to the ischial tuberosity by the gliding stitch, followed by fixation of the proximal hamstring tendons, restoring the anatomy. One day following surgery, the patient began physical therapy (14 days after initial injury). Post-operative limitations included: (1) weight-bearing status starting with toe touch weight-bearing for 2 weeks, followed by 25% weight-bearing weeks 2-4, 50% weight-bearing weeks 4-6 with gradual progression to full weightbearing and (2) no active hamstring contractions for the first 6 weeks. Bracing and post-operative rehabilitation was based upon previously publisheded protocols17,22 but will not be covered in this case report, due to itsâ&#x20AC;&#x2122; focus on diagnosis and expedited surgical management. The patient progressed to light jogging three months post-operatively with no associated

DISCUSSION This case report illustrates the clinical evaluation and decision-making process, including the use of MRI, resulting in expedited surgical intervention for a complete proximal hamstring avulsion. A common mechanism of injury for a proximal hamstring avulsion is combined hip flexion and knee extension.23 Although common with hamstring avulsions, this mechanism of injury is also described in patients with hamstring strains, particularly dancers and those participating in kicking activities.9 Clinical presentation of a hamstring avulsion will typically consist of ecchymosis in the posterior thigh, localized tenderness, and a palpable defect, which can also be consistent with hamstring strains. Additional findings that can assist in differentiating hamstring avulsions from hamstring stains include: proximal tenderness with palpation and an inability to palpate the proximal tendon.

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Common patient reported complaints include loss of leg control when walking, painful cramping in the muscle belly, difficulty sitting, and weakness ascending stairs.23 On physical examination, patients with complete hamstring avulsions may have tenderness to palpation of the ischial tuberosity. Birmingham et al15 described an absence of palpable tension in the distal hamstring tendons with the knee actively flexed at 90 degrees while the patient is in a prone position referred to as a positive bowstring sign. A detailed neurological examination is warranted as damage to the sciatic nerve can occur with hamstring retraction.17,21 Diagnostic imaging is essential for confirmation of a suspected proximal hamstring avulsion.17 Radiographs are commonly performed, but typically yield negative results in the adult population due to skeletal maturity.17 Despite the rarity of bony avulsions in a skeletally mature population, they are important to exclude with radiographs. In contrast, it should be noted that adolescents often sustain an apophyseal avulsion, commonly identified on basic radiographs.13 MRI should be used to confirm the diagnosis of a complete hamstring avulsion. Koulouris and Connell24 reported on the accuracy of MRI and sonography on 16 surgically confirmed proximal hamstring avulsions. All 16 patients received MRI, which accurately diagnosed 16 out of the 16 (100%) proximal hamstring avulsions, while sonography was performed on 12 of the patients and accurately identified only 7 out of 12 (58%) demonstrating lower sensitivity.24 Some of the pitfalls of using sonography is the difficulty detecting the injury due to the presence of extensive hematoma combined with the depth of the injured tissue with large gluteal muscles covering the proximal hamstrings.25 Additionally, MRI provides an accurate assessment of the extent of the tendon retraction, if present, as well as tendon morphologic features making it ideal for surgical planning and decision making.25 Nonoperative treatment is indicated in patients with a one tendon avulsion or a two tendon avulsion with a tendon retraction of less than two centimeters.17 Nonoperative management typically consists of rest, ice, modalities, gentle stretching, and gradual return to sport specific training. Patients utilizing nonoperative management should be able to return to sport within six weeks.17

Surgical repair criteria for proximal hamstring avulsions include: (1) involvement of two tendons with greater than two cm of retraction; or (2) three tendon (complete) avulsion regardless of the length of retraction.17 Successful surgical repair has been documented in both acute and chronic injuries;10,11,15,18,26 however, patient outcomes are improved with acute repair within four weeks of injury.15 Harris and colleagues performed a systematic review of 18 studies, reporting that surgical intervention performed within four weeks led to improved patient satisfaction, subjective clinical outcomes, strength and endurance, pain relief, return to prior level of function and reduced re-rupture rate compared to chronic repairs.11 There is limited evidence on clinical outcomes in chronic repairs of complete distal hamstring avulsions. Cross and colleagues10 reported nine cases of chronic surgical repairs of complete hamstring avulsions with an average of 36 months from injury to surgical repair. All subjects complained of weakness and six complained of inability to run pre-operatively. At the average 48 month long term follow up, subjects demonstrated 60.2% in hamstring strength and 57.1% in hamstring endurance when compared to the contralateral side with seven subjects returning to their recreational sports.10 In chronic repairs of hamstring avulsions, neurolysis of the sciatic nerve is required due to scar tissue and onset of sciatic nerve symptoms.23 Additional concerns arise with increased time from injury to surgical intervention including: decreased ability to restore anatomy,27 increased postoperative bracing, reduced postoperative outcomes,21 and a more technically challenging surgery.26 CONCLUSION In summary, proximal hamstring avulsions are often delayed or misdiagnosed. As medical professionals working with athletes, it is important to understand the clinical presentation of hamstring avulsions and the use of, or referral for, appropriate diagnostic imaging. Despite successful surgical outcomes in both acute and chronic cases, expedited surgical care occurring within four weeks leads to improved patient satisfaction and pain relief while mitigating complications in surgery and decreasing the probability of sciatic nerve involvement.

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REFERENCES 1. Bennell KL, Crossley K. Musculoskeletal injuries in track and field: incidence, distribution and risk factors. Aust J Sci Med Sport. Sep 1996;28(3):69-75.

2. Malliaropoulos N, Isinkaye T, Tsitas K, Maffulli N. Reinjury after acute posterior thigh muscle injuries in elite track and field athletes. Am J Sports Med. Feb 2011;39(2):304-310.

3. Malliaropoulos N, Mendiguchia J, Pehlivanidis H, et al. Hamstring exercises for track and field athletes: injury and exercise biomechanics, and possible implications for exercise selection and primary prevention. Br J Sports Med. Sep 2012;46(12):846-851.

4. Henderson G, Barnes CA, Portas MD. Factors associated with increased propensity for hamstring injury in English Premier League soccer players.

J Sci Med Sport. Jul 2010;13(4):397-402.

5. Elliott MC, Zarins B, Powell JW, Kenyon CD. Hamstring muscle strains in professional football players: a 10-year review. Am J Sports Med. Apr 2011;39(4):843-850.

6. Connell DA, Schneider-Kolsky ME, Hoving JL, et al.

Longitudinal study comparing sonographic and MRI assessments of acute and healing hamstring injuries.

AJR Am J Roentgenol. Oct 2004;183(4):975-984.

7. Slavotinek JP, Verrall GM, Fon GT. Hamstring injury in athletes: using MR imaging measurements to compare extent of muscle injury with amount of time lost from competition. AJR Am J Roentgenol.

Dec 2002;179(6):1621-1628.

8. Sherry MA, Best TM. A comparison of 2 rehabilitation programs in the treatment of acute hamstring strains. J Orthop Sports Phys Ther. Mar 2004;34(3):116-125.

9. Heiderscheit BC, Sherry MA, Silder A, Chumanov ES, Thelen DG. Hamstring strain injuries: recommendations for diagnosis, rehabilitation, and injury prevention. J Orthop Sports Phys Ther. Feb 2010;40(2):67-81.

10. Cross MJ, Vandersluis R, Wood D, Banff M. Surgical repair of chronic complete hamstring tendon rupture in the adult patient. Am J Sports Med. NovDec 1998;26(6):785-788.

11. Harris JD, Griesser MJ, Best TM, Ellis TJ. Treatment of proximal hamstring ruptures - a systematic review. Int J Sports Med. Jul 2011;32(7):490-495.

12. Blasier RB, Morawa LG. Complete rupture of the hamstring origin from a water skiing injury. Am J Sports Med. Jul-Aug 1990;18(4):435-437.

13. Sarimo J, Lempainen L, Mattila K, Orava S. Complete proximal hamstring avulsions: a series of 41 patients with operative treatment. Am J Sports Med. Jun 2008;36(6):1110-1115.

14. Kurosawa H, Nakasita K, Nakasita H, Sasaki S, Takeda S. Complete avulsion of the hamstring tendons from the ischial tuberosity. A report of two cases sustained in judo. Br J Sports Med. Mar 1996;30(1):72-74.

15. Birmingham P, Muller M, Wickiewicz T, Cavanaugh J, Rodeo S, Warren R. Functional outcome after repair of proximal hamstring avulsions. J Bone Joint Surg Am. Oct 5 2011;93(19):1819-1826.

16. Orava S, Kujala UM. Rupture of the ischial origin of the hamstring muscles. Am J Sports Med. Nov-Dec 1995;23(6):702-705.

17. Cohen S, Bradley J. Acute proximal hamstring rupture.

J Am Acad Orthop Surg. Jun 2007;15(6):350-355.

18. Cohen SB, Rangavajjula A, Vyas D, Bradley JP. Functional results and outcomes after repair of proximal hamstring avulsions. Am J Sports Med. Sep 2012;40(9):2092-2098.

19. Binkley JM, Stratford PW, Lott SA, Riddle DL. The Lower Extremity Functional Scale (LEFS): scale development, measurement properties, and clinical application. North American Orthopaedic Rehabilitation Research Network. Phys Ther. Apr 1999;79(4):371-383.

20. Chakravarthy J, Ramisetty N, Pimpalnerkar A, Mohtadi N. Surgical repair of complete proximal hamstring tendon ruptures in water skiers and bull riders: a report of four cases and review of the literature. Br J Sports Med. Aug 2005;39(8):569-572.

21. Carmichael J, Packham I, Trikha SP, Wood DG. Avulsion of the proximal hamstring origin. Surgical technique. J Bone Joint Surg Am. Oct 1 2009;91 Suppl 2:249-256.

22. Ali K, Leland JM. Hamstring strains and tears in the athlete. Clin Sports Med. Apr 2012;31(2):263-272.

23. Sallay PI, Ballard G, Hamersly S, Schrader M. Subjective and functional outcomes following surgical repair of complete ruptures of the proximal hamstring complex. Orthopedics. Nov 2008;31(11):1092.

24. Koulouris G, Connell D. Evaluation of the hamstring muscle complex following acute injury. Skeletal Radiol. Oct 2003;32(10):582-589.

25. Koulouris G, Connell D. Hamstring muscle complex: an imaging review. Radiographics. May-Jun 2005;25(3):571-586.

26. Wood DG, Packham I, Trikha SP, Linklater J. Avulsion of the proximal hamstring origin. J Bone Joint Surg Am. Nov 2008;90(11):2365-2374.

27. Klingele KE, Sallay PI. Surgical repair of complete proximal hamstring tendon rupture. Am J Sports Med. Sep-Oct 2002;30(5):742-747.

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IJSPT

CASE REPORT

UPPER EXTREMITY DEEP VENOUS THROMBOEMBOLISM FOLLOWING ARTHROSCOPIC LABRAL REPAIR OF THE SHOULDER AND BICEPS TENODESIS: A CASE REPORT Thomas J.S. Durant, MPT1 Brian T. Swanson, PT, DSc1 Mark P. Cote, PT, DPT1 Donald A. Allen, BS1 Robert A. Arciero, MD1 Augustus D. Mazzocca, MS, MD1

ABSTRACT Study Design: Case Report Background: Upper extremity deep vein thrombosis (UEDVT) is a rare complication following arthroscopic shoulder surgery. However, it is possible that a patient with an UEDVT will present to physical therapy as the first service to interact with the patient following surgery. As a result, proper screening in the physical therapy setting is essential.

Case Description: The purpose of this report is to present the case of a 37 year-old male who developed an upper extremity deep vein thrombosis (UEDVT) following arthroscopic glenohumeral labral repair and arthroscopically assisted biceps tenodesis. This patient presented with disproportionate pain and swelling of his involved upper extremity at his initial evaluation in physical therapy (8 days post-operatively), which raised the index of suspicion for an UEDVT. Outcome: The patient was referred to the emergency department for immediate diagnostic testing and treatment. A Doppler scan provided a definitive diagnosis of UEDVT. Following successful medical treatment with anti-coagulant therapy, the patient went on to complete an otherwise uneventful course of rehabilitation.

Discussion: UEDVT events following arthroscopy are rare, and are often attributed to a systemic secondary stimulus.

UEDVT following shoulder arthroscopy is a complication that occurs in the orthopaedic setting, but may present primarily to the physical therapist, and as such requires awareness of its clinical presentation and treatment. Care of UEDVT requires a systems-based approach when considering clinical manifestation, best treatment, and future research Keywords: Arthroscopy, Shoulder, SLAP Tear, Upper Extremity Deep Venous Thrombosis

1

UCONN Health Center, Department of Orthopaedic Surgery, Farmington, CT, USA

Disclaimer: None of these authors received financial remuneration, or any of their family members related to this study. This report did not require IRB or Ethics Committee approval.

The University of Connecticut Health Center / New England Musculoskeletal Institute receives direct funding and material support from Arthrex Inc. (Naples, FL). The company had no influence on study design, data collection or interpretation of the results or the final manuscript.

CORRESPONDING AUTHOR Augustus D. Mazzocca, MS, MD University of Connecticut Department of Orthopaedic Surgery Farmington, CT 06034 Tel: 860-679-6709 Fax: 860-679-6633 Email: mazzocca@uchc.edu

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INTRODUCTION AND BACKGROUND Upper extremity deep venous thrombosis (UEDVT) is a rare but serious complication of arthroscopic shoulder surgery.1 UEDVTs are of principal concern as they carry the potential to migrate to the lung resulting in a pulmonary embolism (PE).2

including a course of physical therapy. The patient reported no history of steroid, illicit drug or tobacco use. The patient reported no significant past medical history, which of note was unremarkable for clotting disorders. Family history was negative for clotting disorders.

It has been reported that 1–10% of all DVTs occur in the UE, and 9–14% of these cases are complicated

by PE.3-5 In addition, long term comorbidities associated with UEDVT such as post-thrombotic syndrome (PTS) has been reported to have a 7–44% frequency of occurrence status-post UEDVT depending on the criteria used for diagnosis.6 The 3-month UEDVT associated mortality rate without comorbidities, such as cancer or central venous catheter placement, has been reported to be 2.6%.4

Preoperative diagnosis was a massive labral tear with evidence of a labral cyst. Conservative and operative treatment options were discussed at length with the patient and the patient chose operative treatment.

Signs and symptoms of UEDVT are extremely variable, just as they are for lower extremity DVTs.4 However, the generally accepted clinical picture of a patient with an UEDVT includes: +1 pitting edema, ipsilateral pain to palpation, erythema, and warmth with palpation of ipsilateral extremity.7 As the popularity of orthopaedic surgical procedures is on the rise, post-operative complications such as DVTs may become more prevalent in the PT clinic, requiring rigorous screening and a higher index of suspicion.8 As noted by Hannon et al. who recently described a lower extremity DVT (LEDVT) in an otherwise healthy young man, after undergoing ulnar collateral ligament reconstruction.9 The risk of mortality, morbidity, and resulting decreased quality of life are a direct result of this potential post-operative complication, and warrants vigilance in clinical practice for early detection and appropriate management. The purpose of this paper is to (1) present a case report of a patient who presented in physical therapy with an UEDVT following an arthroscopic glenohumeral labral repair and (2) discuss the incidence of UEDVT associated with arthroscopic shoulder surgery.

CASE DESCRIPTION A 37 year-old Caucasian male presented to the primary orthopaedic surgeon (ADM) complaining of significant right shoulder pain sustained during a bench-press injury. The patient reported that this pain had persisted for five months since the injury, and he had already failed conservative treatment

The patient subsequently underwent an arthroscopic labral repair, excision of labral cyst, and an arthroscopic assisted open subpectoral biceps tenodesis. The patient was operated on in the lateral position with a bean bag and an axillary roll, with seven pounds of abduction and five pounds of longitudinal traction applied to the operative upper extremity. From incision to closure, the elapsed time was 119 minutes, and time under anesthesia was a total of 125 minutes. There were no obvious complications during the procedure, and there was minimal blood loss. The patient was placed in an external rotation sling and issued a cryo-cuff to reduce swelling and inflammation post-operatively.

Eight days post-operatively the patient presented to physical therapy with the primary therapist (TJSD).

During the initial history, the patient reportedly kept his affected UE completely immobilized in the external rotation sling from 0-8 days post-op, as per instructions given to him by a post-operative care nurse. Patient reports not removing the sling, except for showering, and only used the exercise stress ball included with the sling.

During the initial interview, the patient complained of pain at rest, which was increased in the dependent position, and was without relief with post-operative medication. The patient also complained of increased swelling, and a sensation of pins and needles in the affected UE distal to the elbow while at rest. The patient denied fever or chills.

Clinical Impression #1 Due to the post-operative nature of this case the differential was focused on pathologies which are congruent with this etiology. Clinical decision-making was required to determine if proceeding with post-operative rehabilitation was appropriate for this patient, or if

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a referral to the medical team may be needed to ensure patient safety before progressing. The differential at this point included three main considerations, which were UEDVT, post-operative infection of joint or wound site, or normal variant of post-operative edema. Given that the patient was 8 days from surgery, all three of these diagnoses were equally probable with regards to time course, and due to the non-specific symptoms, a focused physical examination was required.

Examination On physical exam the right UE was warm, erythematous, edematous, and very painful to palpation (Figure 1 and Figure 2). The erythema was described with non-demarcated borders, extending distally along the medial side of the affected UE, without extension laterally, or proximally. There were no foul smelling odors noted from the wound site. Initial passive range of motion (PROM) revealed 10 degrees of external rotation (ER) and 90 degrees of forward flexion (FF). There were no palpable cords indicating superficial thrombophlebitis.10 +1 pitting edema was noted to extend from the axilla to approximately 15 cm distal to the elbow on the affected UE (Table 1). Passive extension of the elbow on the affected UE reproduced pain over the medial aspect of the subaxillary region. Pain to palpation was also noted

Figure 2.

over the medial aspect of the ipsilateral UE proximal to the elbow, extending to the axilla.

Clinical Impression #2 Following physical exam, the aforementioned differential was considered. Due to the erythematous nature of the UE, pain to palpation away from surgical site and edema distal to the elbow, normal variant post-operative edema was considered unlikely. Due to the patientâ&#x20AC;&#x2122;s afebrile status, post-operative infection was also considered unlikely. Due to pain to localized to palpation along the course of the brachial vein, and unilateral pitting edema distal to the elbow, this combination of signs and symptoms raised suspicion of UEDVT over infection.

Figure 1.

Intervention Due to suspected UEDVT the patientâ&#x20AC;&#x2122;s surgeon was notified, and the patient was sent to the emergency department (ED) for immediate assessment of his condition. A Doppler ultrasound study performed in the ED revealed the presence of a DVT in both the axillary and brachial veins of the ipsilateral UE. The International Journal of Sports Physical Therapy | Volume 9, Number 3 | June 2014 | Page 379

Table 1. Circumferential measurements of the upper extremities 8 days s/p surgery

The patient was immediately started on Coumadin and Lovenoux to induce a therapeutic International Normalized Ratio (INR) above 2.0. Once the patientâ&#x20AC;&#x2122;s INR of 2.0 was established, the Lovenoux was discontinued, and the patient was continued on longterm Coumadin therapy for six months under the supervision of his primary care physician (PCP).

and past literature indicates that UEDVT carries the potential for serious complications and morbidity, and the awareness of this complication in the clinic during post-operative visits, regardless of provider discipline or the apparently benign nature of the operative procedure, is important to consider for patient safety.11

CASE OUTCOME The patient was successfully treated with Coumadin therapy for an UEDVT. The patient did not experience any short or long-term comorbidities from this thrombotic event. The overall rehabilitation protocol for this patient was unaltered due to this adverse event of his surgery. The patient resumed physical therapy 1 week after starting anticoagulant therapy, and progressed appropriately through expected stages of recovery, without restrictions on PT due to Coumadin therapy.

When patient resumed physical therapy after achieving a stable therapeutic INR, PROM measurements included 100 degrees FF and 20 degrees ER. Final clinical outcome was appropriate for this patient, including full ROM and 5/5 strength throughout all planes of glenohumeral motion at 6 months status-post surgery. Patient reported return to recreational activities including bench press at the 12-month follow up.

The clinical decision to send this patient to the ED was based on an 8 day history of immobilization, recent surgical procedure to affected UE, and physical examination revealing +1 pitting edema throughout the UE, erythema and warmth, and ipsilateral tenderness to superficial palpation. Infection was still considered a possibility, but was considered less likely at the time due to a lack of fever.

The patient experienced no complications following treatment for the UEDVT. Following a 6 month course of Coumadin, the patient underwent extensive hypercoagulability testing through his PCP. These tests, including thorough screening for occult cancer all returned negative.

DISCUSSION The purpose of this paper was to report a case of UEDVT following arthroscopic shoulder surgery, and discuss the perceived incidence rate of this rare but potentially serious complication. Current

The UEDVT prediction rule for clinical diagnosis, as developed by Constans et al,12 identified four key points for consideration, scoring one point for venous access to the jugular or subclavian veins/ pace maker placement, unilateral pitting edema, localized pain, and -1 for the presence of a diagnosis at least equally plausible. Subjects presenting with > 2 positive findings had a 70% probability of having an UEDVT. These criteria were considered for this patient in our clinical decision to refer the patient to the ED, however, and it should be noted that this patient presented to the physical therapy clinic with 2 (localized pain and unilateral pitting edema) of these parameters.

It is important to note that the clinical presentation of DVT is known to be variable in nature, and while the criteria set by Constans et al7 may be useful in supplementing a clinicians findings on history and physical examination, they should not be used alone to rule in or rule out the likelihood of DVT as their validity have not been reported.6

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The medical records belonging to the affected patient were ordered and reviewed by a single investigator.

Pre, intra, and postoperative information was obtained and reviewed for intraoperative complications and risk factors as defined by current literature. Medical history and subsequent screening for thrombophillic risk factors on an outpatient basis revealed no conditions associated with increased risk for a vascular thromboembolic event () in this patient. Therefore, it seems that the most plausible etiology of this VTE event is the complete disuse of the affected UE status-post surgery. Due to a lack of muscular assistance promoting venous drainage, the resulting increase in venous stasis is believed to occur in the patientâ&#x20AC;&#x2122;s affected UE. Ultimately, this mimicked the immobilization associated with casting of the lower extremity, which is a known risk factor for ipsilateral limb VTE.13 While there are multiple reports in the literature suggesting that lateral positioning, duration of surgery, use of UE traction, and axillary rolls may play a role in UEDVT formation, the data is speculative, inconclusive and limited to level IV evidence.2,6,11 The arthroscopically assisted mini-open biceps tenodesis, as described by Wiley et al14, was performed on this patient. Currently, there is no literature that demonstrates any causality between this technique and venous endothelial damage and subsequent UEDVT development.15-17 To the authorsâ&#x20AC;&#x2122; knowledge, UEDVT is not a complication that is more highly associated with this type of procedure.

Current literature provides inconsistent estimates of UEDVT incidence rate following shoulder arthroscopy, as it is limited to case reports and chart reviews.18-20 Bongiovanni et al18 performed a retrospective chart review of 1,082 arthroscopic shoulder surgeries performed over the course of three years.

Three cases of VTE events were identified with an incidence rate of 0.3%. Randelli et al11 performed a multicenter study investigating the incidence of DVT events following shoulder arthroscopy. Of 9385 surgeries, 6 DVTs were identified for an incidence of 0.06%. Linneman et al21 recently reported on a cohort of 75 patients with UEDVT events unrelated to central venous catheter placement, 39.2% had at least one thrombophilic disorder. Additionally, Blom et al22 reported an 18-fold increased risk for UEDVT in patients with active malignancy. Accordingly, an

idiopathic UEDVT incident may warrant additional screening for genetic hypercoaguability disorder, occult malignancy, and appropriate follow-up for the risk of developing post-thrombotic syndrome.11,21,22 In an effort to determine the frequency of UEDVT following shoulder arthroscopy, the number of arthroscopic labral tears repaired by the primary orthopaedic surgeon was queried in the institutional database via the CPT code 29807. The total numbers of labral repairs were calculated between the year 2005 and 2010 to determine a 5-year incidence rate.

The number of DVTs presenting in clinic were queried from the ICD-9 code 453.82 in the same database, within the same time frame.

The primary orthopaedic surgeon in this case has performed 139 arthroscopic labral repairs and 1653 arthroscopic shoulder procedures in the last 5 years, with incidence rates of UEDVT at 0.7% and 0.06% respectively attributable to this case of UEDVT alone.

In the last 5 years (ADM) has performed 207 biceps tenodesis procedures with an UEDVT incidence rate of 0.4%, also attributable to this case alone.

It is important to note that these values represent the known incidence. This value is in line with the published literature, which ranges from 0.06% to 0.3%.11,18 True incidence values are unobtainable due to a lack of a screening policy for this complication. UEDVT commonly presents in a subclinical fashion, and therefore there is a high likelihood that the majority of VTE events go undetected in clinical practice. In this regard, retrospective chart reviews yield a crude estimation however prospective data with rigorous screening may help to elicit true incidence values of this potentially fatal post-surgical complication.

CONCLUSION UEDVT following arthroscopic shoulder surgery is an exceedingly rare complication, potentially underdiagnosed, that carries potentially lethal or devastating effects.4 In the physical therapy setting, the index of suspicion for this complication should be raised during the evaluation of post-operative arthroscopic shoulder patients, as this complication may be underdiagnosed and under reported. Should an UEDVT occur, attention should be directed toward immediate treatment due to the inherent risk of the development of PE.4

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REFERENCES 1. Spencer FA, Emery C, Lessard D, Goldberg RJ. Upper extremity deep vein thrombosis: a community-based perspective. Am J Med. Aug 2007;120(8):678-684.

2. Monreal M, Raventos A, Lerma R, et al. Pulmonary embolism in patients with upper extremity DVT associated to venous central lines--a prospective study. Thromb Haemost. Oct 1994;72(4):548-550.

3. Bernardi E, Pesavento R, Prandoni P. Upper extremity deep venous thrombosis. Semin Thromb Hemost. Oct 2006;32(7):729-736.

4. Munoz FJ, Mismetti P, Poggio R, et al. Clinical outcome of patients with upper-extremity deep vein thrombosis: results from the RIETE Registry. Chest.

Jan 2008;133(1):143-148.

5. Sawyer GA, Hayda R. Upper-extremity deep venous thrombosis following humeral shaft fracture.

Orthopedics. Feb 2011;34(2):141.

6. Elman EE, Kahn SR. The post-thrombotic syndrome after upper extremity deep venous thrombosis in adults: a systematic review. Thromb Res. 2006;117(6):609-614.

7. Constans J, Salmi LR, Sevestre-Pietri MA, et al.

A clinical prediction score for upper extremity deep venous thrombosis. Thromb Haemost. Jan 2008;99(1):202-207.

8. Arciero RA, Spang JT. Complications in arthroscopic anterior shoulder stabilization: pearls and pitfalls.

Instr Course Lect. 2008;57:113-124.

9. Hannon J, Garrison C, Conway J. Residents case report: deep vein thrombosis in a high school baseball pitcher following ulnar collateral ligament (ucl) reconstruction. Int J Sports Phys Ther. Aug 2013;8(4):472-481.

10. Chengelis DL, Bendick PJ, Glover JL, Brown OW, Ranval TJ. Progression of superďŹ cial venous thrombosis to deep vein thrombosis. J Vasc Surg. Nov 1996;24(5):745-749.

11. Randelli P, Castagna A, Cabitza F, Cabitza P, Arrigoni P, Denti M. Infectious and thromboembolic complications of arthroscopic shoulder surgery.

J Shoulder Elbow Surg. Jan 2010;19(1):97-101.

12. Constans J SL, Sevestre-Pietri MA, Perusa S, Nguon M, Degeilh M, et al. A clinical prediction score for

13.

14.

15.

16.

17.

18.

19.

20.

21.

22.

upper extremity deep venous thrombosis. Thromb Haemost. 2008;99(202-207).

Healy B, Beasley R, Weatherall M. Venous thromboembolism following prolonged cast immobilisation for injury to the tendo Achillis. J Bone Joint Surg Br. May 2010;92(5):646-650.

Wiley WB, Meyers JF, Weber SC, Pearson SE. Arthroscopic assisted mini-open biceps tenodesis: surgical technique. Arthroscopy. Apr 2004;20(4):444446.

Becker DA, CoďŹ eld RH. Tenodesis of the long head of the biceps brachii for chronic bicipital tendinitis.

Long-term results. J Bone Joint Surg Am. Mar 1989;71(3):376-381.

Boileau P, Baque F, Valerio L, Ahrens P, Chuinard C, Trojani C. Isolated arthroscopic biceps tenotomy or tenodesis improves symptoms in patients with massive irreparable rotator cuff tears. J Bone Joint Surg Am. Apr 2007;89(4):747-757.

Ma H, Van Heest A, Glisson C, Patel S. Musculocutaneous nerve entrapment: an unusual complication after biceps tenodesis. Am J Sports Med. Dec 2009;37(12):2467-2469.

Bongiovanni SL, Ranalletta M, Guala A, Maignon GD. Case reports: heritable thrombophilia associated with deep venous thrombosis after shoulder arthroscopy. Clin Orthop Relat Res. Aug 2009;467(8):2196-2199.

Burkhart SS. Deep venous thrombosis after shoulder arthroscopy. Arthroscopy. 1990;6(1):61-63.

Creighton RA, Cole BJ. Upper extremity deep venous thrombosis after shoulder arthroscopy: a case report. J Shoulder Elbow Surg. Jan-Feb 2007;16(1):e20-22.

Linnemann B, Meister F, Schwonberg J, Schindewolf M, Zgouras D, Lindhoff-Last E. Hereditary and acquired thrombophilia in patients with upper extremity deep-vein thrombosis. Results from the MAISTHRO registry. Thromb Haemost. Sep 2008;100(3):440-446.

Blom JW, Doggen CJ, Osanto S, Rosendaal FR. Old and new risk factors for upper extremity deep venous thrombosis. J Thromb Haemost. Nov 2005;3(11):2471-2478.

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IJSPT

DIAGNOSTICS CORNER

MANAGEMENT OF ACUTE SHOULDER PAIN IN AN ADOLESCENT LACROSSE ATHLETE: A CASE REPORT Terry Malone, PT, EdD, ATC, FAPTA1 Scot Mair, MD1

ABSTRACT Acute onset of shoulder pain in adolescent athletes typically is related to trauma. The subject of this case report, a 13 year-old male, was injured when he collided with another athlete while his right arm was extended. He experienced immediate onset of significant right shoulder pain. Manual assessment in the emergency department revealed anterior tenderness and loss of function due to pain â&#x20AC;&#x201C; most notably limitations in both active internal rotation and abduction. A plain film showed a radiographic density anterior to the humeral head but a donation site (where a bony avulsion may have occurred) was not delineated. Magnetic resonance imaging clearly identified a lesser tuberosity avulsion (thus the site of origin of the bony material) encompassing the insertion of the subscapularis muscle with retraction of approximately one centimeter. Open surgical repair (reduction and fixation) was performed with excellent results.

Level of Evidence: 5 (Single Case report) Key Words: Acute shoulder trauma, adolescent, avulsion fracture, subscapularis

1

University of Kentucky, Lexington, KY, USA

CORRESPONDING AUTHOR Terry Malone, PT, EdD, ATC, FAPTA Division of Physical Therapy, University of Kentucky Suite 204, Wethington Building 900 South Limestone Street Lexington, KY 40536-0200 E-mail: Trmalo1@uky.edu

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INTRODUCTION A significant percentage of young Americans are participating in organized sporting activities and thus being exposed to the potential for sustaining athletic trauma. Clinicians see an increasing number of these young athletes for triage, diagnostics, and care. Importantly, while the majority of shoulder injuries are minor (contusions, abrasions, or minor sprains/strains), there are some injuries that require additional imaging in order to delineate their nature and to plan required conservative or operative interventions in order to provide optimal care.

CLINICAL PRESENTATION A right hand dominant 13 year-old lacrosse player was participating in a summer camp. He collided with a larger “athlete” (in this case, a coach) while he was running with his right arm extended. He fell to the ground and noted immediate onset of pain in the right “front of his shoulder.” The subject reported that he felt the shoulder was injured during the collision and not from his fall to the turf. Approximately two hours after injury, he was evaluated in an emergency department where plain films were obtained and used in an attempt to delineate whether there was possible bony involvement. Figures 1 and 2 show the anterior to posterior and axillary/lateral views. These show a “somewhat” radiographically dense material or area present anteriorly but there was no defined location from which the object that accounted for the density was either avulsed or fractured. The emergency department attending MD

Figure 1. A-P plain film of the right shoulder with very limited definitive findings – a possible slight cloudy area is identifiable medial to the humeral head.

discussed the case with an orthopaedist in order to discern the best follow-up measure and magnetic resonance imaging (MRI) was scheduled.

The MRI obtained (Figures 3,4,5,6) clearly delineates a bony avulsion site at the lesser tuberosity of the humerus. This was consistent with an avulsion of the subscapularis insertion, which was considered to represent a relatively significant retraction of more than a centimeter, and thus surgery was scheduled for the next day. The MRI also was read to exhibit minimal change to the anterior inferior capsule/labrum – consistent with possible previous injury associated instability.

Because the MRI indicated possible labral involvement, arthroscopic assessment was completed prior to the open reduction/fixation. The intra-arthroscopic pictures (Figures 7,8,9) demonstrate subscapularis detachment and medialization due to the inherent tone or tension present in the neurologically intact subscapularis muscle. Interestingly, the remainder of the joint was normal and attention was thus directed to fixation. Figure 10 shows the open joint (incision was made just lateral to the coracoid – in-line with the deltopectoral interval) showing the well- defined location of the detachment. The detachment site was approximately 1.5 × 2.0 centimeters in size. The fixation was accomplished via direct compression using a TwinFix 4.5 mm suture anchor. (Figure 11) The two

Figure 2. Axillary/Lateral plain film of the right shoulder which again could indicate a cloudy area but nothing definitive.

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Figure 3 4, & 5. These consecutive MRI slices nicely delineate the avulsed subscapularis tendon from the lesser tuberosity, outlining the displacement of the avulsed fragment as well.

arthroscopic view (Figures 12 and 13) confirmed anatomic fixation and proper repositioning of the subscapularis. The joint and wound were copiously irrigated and the deltopectoral interval loosely reapproximated while the skin was closed in layers with a running Prolene pullout suture in the most superficial layer. Steri strips and a sterile dressing were applied and the subject was placed into a sling and was issued a Polar Care cryotherapy system to be used post-operatively.

Figure 6. This sagittal MRI delineates the avulsed piece of the lesser tuberosity.

“sets” of sutures were tied with a superior and inferior pattern enabling complete fixation. There was a small capsular rent (tear) near the rotator interval which was then closed via #1 Vicryl suture. The final

The post-operative sequence was divided into four phases. Phase 1 was the initial and can be described as protection and primary healing. He wore his sling at all times other than to shower. He was instructed to use pain medications for the first few days. He was allowed to maintain active motion at the elbow, forearm, and hand and used his Polar Care system for several 30-minute sequences daily. After three weeks, Phase 2 began with active range of motion (limited extension, elevation {not to exceed 90 degrees – progressing slowly to full range over the next month}) and external rotation {ER –not to

Figure 7, 8, & 9. These intra-arthroscopic photograph show the medialization of the subscapularis and detachment from the lesser tuberosity.

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Figure 10. This is an intra-operative view clearly showing the avulsion site from the lesser tuberosity.

Figure 12 & 13. These intra-arthroscopic photographs show the proper orientation and thus reattachment of the subscapularis (taken after completed ďŹ xation).

Figure 11. Examples of the TwinďŹ x suture anchor (Smith & Nephew, Andover, MA, USA).

exceed neutral initially with slow progression to 30 degrees allowed over the next month}. He wore his sling when out and about but was allowed out of the sling when watching television or in a controlled environment. The sling use was gradually discontinued during phase two. Phase 3 consisted of strengthening, return to readiness for his functional sporting activities and encompassed the next four to six weeks as he redeveloped full range of motion, strength, and daily function. He was allowed to return to aquatic activities using only the lower extremities and a belly board at 8 weeks and added

the arms at 12 weeks. The initial strokes were breast stroke and freestyle to limit overall shoulder stress.

He was allowed to begin the lacrosse specific training at 12 weeks. This can then be described as Phase 4 - return to function. During this time he increased his work load and functional training to enhance strength and prepare for his return to the sport of lacrosse. He was cleared for this return at 16 weeks and has done well.

CONCLUSIONS The treatment of subscapularis avulsion fractures may be somewhat controversial in adolescents but the majority of reports in the recent literature are supportive of operative management particularly when significant displacement is present.1,2,3,4 A rather complete review of the literature was accomplished

by Goeminne and Debeer with uniformly positive outcomes in adolescents when surgical intervention was performed.5 These authors found 33 cases of lesser tuberosity avulsion fracture reported in the literature as of 2012. Interestingly, earlier reports were focused on when the injury was not initially

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diagnosed properly, quite likely due to reliance on plain film imaging.

In the present case, the plain film images did not adequately define the avulsion from the lesser tuberosity. (Figures 1 and 2) A clinician could possibly talk themselves into there being a bit of cloudinesspossibly a sliver off the lesser tuberosity but this assumption or explanation becomes clearly focused when the MR images were reviewed. (Figures 3,4,5,6) The MRI did clearly delineate the avulsion of the subscapularis and that retraction/medialization (displacement) of the fragment had occurred from the lesser tuberosity. This led to the selection of surgical fixation, as described previously, as the ideal management approach for this subject. The post- operative management was phased, with initial restrictions of external rotation beyond neutral for the initial three to four weeks and elevation restricted to below 90 degrees during this timeframe as well. He smoothly progressed through motion and strengthening and finally functional return. Lacrosse was not allowed until approximately 4 months post-operatively.

REFERENCES 1. Sewick A, Kelly JD, Leggin B. Subscapularis tears: diagnosis and treatment. Univ PA Orthop Journ 2011;21:25-30.

2. Gruson KI, Ruchelsman DE,Tejwani NC. Isolated tuberosity fractures of the proximal humerus: current concepts. Int J Care Injured 2008;39:284-98.

3. Levine B, Pereira D, Rosen J. Avulsion fractures of the lesser tuberosity of the humerus in adolescents: review of the literature and case report. J orthop trauma 2005;19 (5): 349-52.

4. Provance AJ, Polousky JD. Isolated avulsion fracture of the subscapularis tendon with medial dislocation and tear of the biceps tendon in an skeletally immature athlete: a case report. Curr Opin Pediatr 2010;22(3):366-8.

5. Goeminne S, Debeer P. The natural evolution of neglected lesser tuberosity fractures in skeletally immature patients. J Shoulder Elbow Surg 2012 (21) e6-e11.

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IJSPT

CLINICAL COMMENTARY

CONSIDERATIONS AND RETURN TO SWIM PROTOCOL FOR THE PEDIATRIC SWIMMER AFTER NONď&#x161;şOPERATIVE INJURY Shane Hamman, PT, DPT

ABSTRACT Pediatric swimmers perform repetitive motions over prolonged distance that predisposes them to injury.

There is evidence highlighting biomechanics, evaluation, and treatment of swimmers; however, there is minimal research related to return to swimming following non-operative injury other than some suggestion of restricted distance guidelines. The purpose of this clinical commentary is to discuss considerations related to the training of pediatric swimmers, as well as to provide clinicians with an example return to swim protocol that is sensitive to the multidimensional components of the pediatric swimmerâ&#x20AC;&#x2122;s training and competition.

Keywords: Pediatric, return to sport, swimming Level of Evidence: Level V

1

XX

Acknowledgements: Meghan Converse MPT; Dan Lorenz DPT, PT, LAT, CSCS; Nemours-Alfred I. duPont Hospital for Children: Center for Sports Medicine

CORRESPONDING AUTHOR Shane Hamman 610-306-6002 E-mail: shamman1@gmail.com

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INTRODUCTION In the United States there are approximately 266,000 registered pediatric swimmers as part of 2,800 club teams. The number of participants can increase to 2.5 million swimmers, when non-USA Swimming summer league swimmers are included. Of those youth athletes registered with USA Swimming, 57% are between ages 6 and 12 years of age, while 37% are between 13 and 17 years of age, with an average age of 11.5 years old.1 This population is exposed to potential injury secondary to repetitive motions performed over periods of swimming repetitive distances (for example over a 90 minute practice) at high exertion. Pediatric swimmers, similar to other athletes, require gradual progression to return to their sport following injury. Clinicians should be aware of a pediatric swimmer’s preferred events, of the potential variability with each individual swimmers’ practices, and event differences between age groups. The purpose of this clinical commentary is to introduce the clinician to pediatric swimming training details and provide a proposed return to swim protocol for gradual progression to full participation following non-operative injury.

There is minimal research in regards to pediatric swimming injuries. However, at a Division I swimming program, injury rates were reported to be 4.0 injuries per 1000 exposures in men and 3.78 injuries per 1000 exposures in women with 37% of those injuries resulting in lost time. “Exposure” for these athletes was defined as participation in practices, meets, and land based conditioning or strength training. Shoulder and upper extremity injuries were most commonly reported and consisted of 31% and 36% of injuries in men and women respectively.

While age was not defined in the study, the highest percentage of injury occurred in freshmen for both men and women.2 Overall, pediatric swimmers are potentially predisposed to injuries due to high distance and exertion training demands, training specificity, and year round participation. In a 2006 survey conducted by the American Swim Coaches Association, where 15 different club team representatives replied (out of 75 surveyed), one club’s 10 and younger swimmers midseason average was 25,000 yards per week. A second club’s 11 and 12 year olds averaged 40,000

yards per week during the midseason, and a third club’s 13 and 14 year olds averaged 70,000 yards per week mid season.3 From a stroke count perspective or one completed single arm cycle; a 13 year old swimmer performing freestyle training in a 25 yard pool at 70,000 yards in a week, averaging 12 strokes per lap, could potentially perform 33,600 strokes in a single week.

Competitive swimmers do not train with the same distance at all times throughout a season. For example, a 28-week club team season for six different youth swimmers from November 2010 to April 2011 was comprised of three phases of training. The first 14 weeks distance ranged from approximately 9,000 meters to 14,000 meters per week. Weeks 15 through 22 emphasized increased speed work with distance ranging from approximately 12,000 meters to over 16,000 meters per week. Finally, between weeks 23 and 28 distance ranged from 6,000 meters to 14,000 meters per week.4 A clinician working with pediatric swimmers should be sensitive to what phase of their season a swimmer is in to be prepared for potential distance variations in practices while the athlete is returning to swim.

A clinician should consider the events, both in terms of stroke and distance, related to a pediatric swimmer’s practices and competitions. Events and training are performed in either short course (25 yards or meters for a single length) or long course (50 meters for a single length, also known as Olympic distance).

Generally, freestyle or front crawl competition events range from 50 to 1650 yards or meters and non-freestyle events (butterfly, breaststroke, and backstroke) range from 50 to 200 yards or meters.

In addition, the individual medleys (performance of each of the four strokes for one quarter of the distance) range from 100 to 400 yards or meters. It is critical for the treating clinician to be sensitive to which events each swimmer performs in order to recognize their rehabilitative needs.

An additional consideration is variability between the four strokes, butterfly, backstroke, breaststroke, and freestyle, during total swim training. In a study surveying 72 swimmers ranging from 13 to 25 years of age there was variability reported between what strokes were performed during training. Overall,

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time spent with each particular stroke was 53% freestyle, 21% backstroke, and 13% for both butterfly and breaststroke in the surveyed swimmers. Ninety percent of the swimmers surveyed reported more than half of their training consisted of freestyle even though only 35% reported specializing in freestyle.5 Swimmers may not specialize in a particular stroke; therefore, clinicians must be aware of the stroke distribution each individual swimmer performs during their practices and competition.

RETURN TO SWIM PROTOCOL AFTER NON-OPERATIVE INJURY Currently, there is little evidence on how swimmers should be returned to competition following any injury. Current protocols available through general internet searches and literature review primarily highlight distance restrictions and subsequent progression.6-9 Distance should be progressively increased throughout the return to swimming; however, in this author’s opinion the swimmer’s exertion level should also carefully monitored and progressed in order to minimize overloading. Current available protocols also suggest progressive speed increases; however, they do not detail specifically how swimmers should be limited or progressed. Lastly, limited return to swim protocols exist, specifically those designed for the pediatric population.

A return to swim progression of both distance and effort, measured by assessing time required to complete a workout (thus quantifying a swimmer’s pace) can be more sensitive to a swimmer’s individual needs. The reason for this is that fatigue often affects swim technique, and these alterations potentially yield compensatory maneuvers.10 In addition; these compensatory movements and/or fatigue may overload already compromised structures resulting in recurring or new injury. The variability in a swimmer’s skill, stroke specialization, and sprint versus endurance event specialization is not commonly addressed in return to swim protocols; therefore, it is the author’s perspective that the individual swimmer’s specific pace should also be addressed and included in their rehabilitation.

It is recommended a swimmer should be able to satisfy the following criteria before returning to sport: perform sufficient cardiovascular activity on land

(physical education class, recess, running, elliptical, upper body ergometer, stationary bicycle, etc; future research needed for specific activity amount for optimal return to swim), pain-free activities of daily living, pain-free and normalized ROM (including total glenohumeral motion), strength within at least 90% compared to contralateral side (for upper or lower extremity injury), and normalized scapular kinematics such as appropriate glenohumeral rhythm and non-excessive scapular elevation with glenohumeral elevation.10 In addition, functional testing should be included. Some examples of functional tests appropriate for pediatric swimmers include: functional movement screening, hop testing, the seated shot put test, the closed kinetic chain upper extremity stability test, and the upper extremity Y-balance test. However, it is this author’s opinion that additional research is needed to determine functional testing guidelines for return to swimming and which tests are most applicable to pediatric swimmers. The rationale for potential use of closed chain functional tests is that swimming is not considered to be entirely open or closed chain. The extremities move through a range of motion while propelling the body over their arm.10 Therefore, individual or functional test combinations for the pediatric swimmer should be explored for their ability to promote optimal return to swim.

PROPOSED RETURN TO SWIM PROTOCOL FOR THE PEDIATRIC SWIMMER FOLLOWING NON-OPERATIVE INJURY There are three phases for this proposed protocol with each phase divided into progressive stages related to distance and exertion. Pediatric swimmers should continue to perform dry land activities and their home exercise program as instructed by the clinician regardless of whether they begin at Phase I or II of the protocol. In addition, throughout the protocol, the swimmer and clinician should be mindful of pain. The presence of pain or lack thereof during any phase of the protocol will dictate progression through each phase.

Phase I (Appendix A) reintroduces the pediatric swimmer to the water if they have been removed from swimming for 6 weeks or greater in order to “feel” the water again and regain tolerance to the sport. The goals of this phase are to return the pediatric swimmer to non-organized practices in order

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to minimize competition, focus on stroke technique, and restore normal stroke mechanics. Phase I consists of only freestyle stroke due to the high volume of freestyle performed during all swimming practices compared to backstroke, breaststroke, and butterfly as noted previously.5 In addition, during Phase I the swimmer will use the streamline position (Figure 1 and 2) on the back, and kick (if neck, arm, or shoulder are involved) or use the pull buoy (Figure 3) (if low back or lower extremity is injured) during their progression to introduce the swimmer back into the water while actively resting the affected body part. There are time restrictions for each practice in order to emphasize technique as compared to speed. When a swimmer has completed each stage of Phase I they may transition to Phase II. Phase II (Appendix B) is for swimmers who have completed Phase I or if they have been deactivated from swimming for less than six weeks. This phase also emphasizes technique restoration; however, signifies a return to organized practices with the swimmerâ&#x20AC;&#x2122;s respective team at the practice frequency

Figure 2.

Figure 3.

Figure 1.

prior to injury (example: prior to injury swimmer performed five days per week of practices; therefore, may return to practicing five days per week).

The stages of Phase II specify a practice distance percentage to allow the swimmerâ&#x20AC;&#x2122;s coach to develop The International Journal of Sports Physical Therapy | Volume 9, Number 3 | June 2014 | Page 391

practices within common weekly cycles and allow for daily variability. The percentages include the swimmer’s full warm up and cool down. Therefore, with Stage I of Phase II, for example, full warm up and cool down distance plus the remainder of practice must total 60% of that specific practice’s prescribed distance. For example, for a 10,000 yard practice with a 2,000 yard warm up and 2,000 yard cool down, the remainder of the practice may not exceed 2,000 yards for a total of 6,000 yards or 60% of 10,000 yards. These restrictions allow for gradual progression towards full participation.

In addition to yardage restriction, Phase II introduces pacing restrictions individual to the swimmer regardless of whether the athlete is a sprint or endurance specialist. The swimmer should use their personal record for their 100 yard or meter freestyle (or additional strokes as needed beginning in stage II), divide it to the single length (25 yards/meters for short course or 50 meters for long course), add 2 seconds (for short course) or 4 seconds (for long course), and then return it to a 100 yard/meter distance (short course multiply by 4 or long course multiply by 2) in order to create their “cap” time (Table 1). This “cap” time establishes a maximum speed the swimmer is not permitted to exceed. As the swimmer progresses through the protocol, their distance participation and time “cap” will progress towards their full level prior to injury. An example of a Phase II Stage I time cap is highlighted below.

performs two practices in a single day; however, their secondary practice must progress through Phase II once again to be sensitive to distance and speed progressions. Lastly, no pull buoys or paddles (Figures 4-6) (for upper extremity and neck injuries) or no kickboard or fins (for low back or lower extremity injuries) should be used until Stage III to allow the swimmer to maximize technique without increased extremity loading of the affected extremity.

Figure 4.

Other considerations during Phase II consist of reintroduction of swimmer-preferred strokes (other than freestyle) during Stage II. The swimmer may return to all strokes as long as they adhere to both their respective “cap” times for each stroke and staged distance restrictions. Phase III is applicable if a swimmer commonly Table 1. Example of Phase II-Stage I practice cap time for a swimmer completing 100 meter or yards at 1 minute, 20 seconds.

Figure 5.

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2.

3.

4.

5.

Figure 6.

CONCLUSION A return to swim protocol should be sensitive to the complexity of training and variability of the needs of each pediatric swimmer. The proposed return to swim protocol presented in this clinical commentary attempts to address those multidimensional needs.

This protocol is offered to provide a resource for the clinician as well as to provide an opportunity to individualize the protocol for each individual pediatric swimmerâ&#x20AC;&#x2122;s needs. It continues to be the clinicianâ&#x20AC;&#x2122;s responsibility to monitor each swimmer throughout their progression in order assesses their status, ensure compliance, and monitor any fatigue or soreness that may occur throughout each phase. Further research should explore the value of this or similar return to swim protocols as well as applications to the post-surgical and adult swimming populations.

http://www.usaswimming.org/_Rainbow/Documents/ 2153a918-55db-4d76-a57e-3a7d40803645/USAS%20 General%20Membership%20info.pdf. Accessed December 12, 2013.

Wolf BR, Ebinger AE, Lawler MP, Britton CL. Injury Patterns in Division I Collegiate Swimming. Am J Sport Med. 2009; 37(10): 2037-2042.

Leonard J. Age Group Training Volumes in the USA 2006. American Swimming Coaches Association Newsletter. 2006; 4: 1-2.

Dias P, Marques MC, Marinho DA. Performance evaluation in young swimmers during 28 weeks of training. Journal of Physical Education and Sport.

2012; 12(1): 30-38.

Sein ML, Walton J, Linklater J, et al. Shoulder pain in elite swimmers: primarily due to swim-volumeinduced supraspinatus tendinopathy. Br J Sports Med. 2010; 44: 105-113.

6. Pink MM, Edelman GT, Mark R, Rodeo SA. Applied Mechanics of Swimming. In: Manske RC, Magee DJ, Quillen WS, Zachazewski JE, eds. Athletic and Sport Issues in Musculoskeletal Rehabilitation. 1st Ed. Saint Louis, MI. Saunders; 2011: 331-349.

7. Interval Swimming Program. Massachusetts General Hospital Sports Physical Therapy Website. http:// www.massgeneral.org/ortho/services/sports/ conditioning/MGH%20Interval%20Swimming%20 Program.pdf. Accessed December 19, 2013.

8. Beagan T. Return to Swim Protocol. Richard Bader Physical Therapy Website. http://www.rbpt.com/ return-to-swim-protocol/. Accessed December 19, 2013.

9. Robertson, WJ. Interval Swimming Program. William J Robertson MD UT Southwestern Orthopedics Website. http://www.billrobertsonmd.com/pdf/ interval-swimming-program.pdf. Accessed December 19, 2013.

10. Pink MM, Tibone JE. The Painful Shoulder in the Swimming Athlete. Orthop Clin N Am. 2000; 31 (2): 247-61.

REFERENCES 1. USA Swimming General Membership Information.

United States Swimming Association Website.

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APPENDIX A

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APPENDIX B

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IJSPT

INVITED CLINICAL COMMENTARY

FUNCTIONAL MOVEMENT SCREENING: THE USE OF FUNDAMENTAL MOVEMENTS AS AN ASSESSMENT OF FUNCTION  PART 1 Gray Cook, PT, OCS1 Lee Burton, MS, ATC2 Barbara J. Hoogenboom, PT, EdD, SCS, ATC3 Michael Voight, PT, DHsc, OCS, SCS, ATC, FAPTA4

ABSTRACT To prepare an athlete for the wide variety of activities needed to participate in or return to their sport, the analysis of fundamental movements should be incorporated into screening in order to determine who possesses, or lacks, the ability to perform certain essential movements. In a series of two articles, the background and rationale for the analysis of fundamental movement will be provided. The Functional Movement Screen (FMS™) will be described, and any evidence related to its use will be presented. Three of the seven fundamental movement patterns that comprise the FMS™ are described in detail in Part I: the Deep Squat, Hurdle Step, and In-Line Lunge. Part II of this series which will be provided in the August issue of IJSPT, will provide a detailed description of the four additional patterns that complement those presented in Part I (to complete the seven total fundamental movements): Shoulder Mobility, the Active Straight Leg Raise, the Trunk Stability Push-up, and Rotary Stability, as well as a discussion about the utility of functional movement screening, and the future of functional movement.

The intent of this two part series is to present the concepts associated with screening of fundamental movements, whether it is the FMS™ system or a different system devised by another clinician. Such a functional assessment should be incorporated into pre-participation screening and return to sport testing in order to determine whether the athlete has the essential movements needed to participate in sports activities at a level of minimum competency.

Key Words: Function, movement screening, performance testing Level of Evidence: 5

1

Orthopedic and Sports Physical Therapy, Danville, VA, USA Averett University, Danville, VA, USA 3 Grand Valley State University, Grand Rapids, MI, USA 4 Belmont University, Nashville, TN, USA 2

The Functional Movement ScreenTM (superscripted) is the registered trademark of Functionalmovement.com with profits from the sale of functional movement products going to Gray Cook and Lee Burton and others associated with Functionalmovement.com.

The Editors of IJSPT emphasize (and the authors concur) that the use of fundamental movement screening as an assessment of function is the important concept to be taken from Part I and Part II of this series and such screening can be performed without the use of any trademarked equipment.

CORRESPONDING AUTHOR Barbara Hoogenboom Department of Physical Therapy, Grand Valley State University 301 Michigan St. NE, Rm. 266 Grand Rapids, MI 49506 616-331-2695 E-mail: hoogenbb@gvsu.edu

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INTRODUCTION Over the last 20 years the profession of sports rehabilitation has undergone a trend away from traditional, isolated assessment and strengthening toward an integrated, functional, movement-based approach, incorporating the principles of proprioceptive neuromuscular facilitation (PNF), muscle synergy, and motor learning.1,2 In fact, the American Physical Therapy Association House of Delegates adopted the following vision statement for the profession of physical therapy in 2013: “Transforming society by optimizing movement to improve the human experience”.3, p.18 Attention to optimal movement in patients and clients is important for all physical therapists, and especially for those who treat athletes.

Function is a common term in current physical therapist practice, and what is defined as functional varies greatly between patients and clients. Being functional is of utmost importance to excellent and comprehensive rehabilitation. However, it is difficult to develop and refer to protocols or movement approaches as “functional” when a functional evaluation standard does not exist. Often, rehabilitation professionals in sports settings are far too anxious to perform specific isolated, objective testing for joints and muscles.

Likewise, these clinicians often perform sports performance and specific skill assessments without first examining functional movement. It is important to inspect and understand common fundamental aspects of human movement realizing that similar movements occur throughout many athletic activities. The rehabilitation professional must realize that in order to prepare individuals for a wide variety of activities, screening of fundamental movements is imperative.

Today’s individuals are working harder to become stronger and healthier, by working to improve their flexibility, strength, endurance, and power. It is the belief of the authors that many athletes and individuals are performing high-level activities despite being inefficient in their fundamental movements; thus, without knowing it, these individuals are attempting to add fitness to dysfunction. Many individuals train around a pre-existing problem or simply do not train their weaknesses during strength and conditioning (fitness) programs. In today’s evolving training and rehabilitation market, athletes and medical professionals have access to a huge arsenal of equipment and workout programs;

however, the best equipment and programs cannot improve fitness and health if fundamental weaknesses are not exposed. The goal is to individualize each workout program based on the person’s weak link.

This weak link is a physical or functional limitation. In order to isolate the weak link, the body’s fundamental movement patterns should be considered. Most people do not begin strength and conditioning or rehabilitative programs by determining if they have adequate movement patterns. Thus, the authors suggest that screening an individual’s fundamental movements prior to beginning a rehabilitative or strength and conditioning program is important. By looking at the movement patterns and not just one area, a weak link can be identified. This will enable the medical professional to focus on that area. If this weak link is not identified, the body will compensate, causing inefficient movements. It is this type of inefficiency that can cause a decrease in performance and an increase in injuries.

Prescribed strength and conditioning programs often work to improve agility, power, speed, and strength without consideration of movement competency or efficiency of underlying functional movement.

An example would be a person who has an above average score on the number of sit-ups performed during a test but is performing very inefficiently by compensating and initiating the movement with the upper body and cervical spine as compared to the trunk. Compare this person to an individual who scores above average on the number of sit-ups, but is performing very efficiently and does not utilize compensatory movements to achieve the sit-up. These two individuals would each be deemed “above average” without noting their individual movement inefficiencies. The question arises: If major deficiencies are noted in their functional movement patterns, then should their performance be judged as equal?

These two individuals would likely have significant differences in functional mobility and stability; however, without assessing their functional mobility and stability, it is inappropriate to assume differences.

In an additional example, at the conclusion of “formal rehabilitation”, performance and sport-specific tests are conducted to attempt to determine the readiness of the athlete to return to sport. This systematic process does not seem to provide enough baseline information when assessing an individual’s

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preparedness for participation in sporting activities. Commonly, the pre-return to sport rehabilitation examination includes only information that will exclude an individual from participating in certain activities. The perception of many past researchers is that no set standards exist for determining who is physically prepared to participate in activities.4-8

who possesses, or lacks, the ability to perform certain essential movements. Therefore, the purpose of this clinical commentary (the first of a two-part series) is to describe the first three tests of the FMS™ and offer suggestions on the utility and reliability of functional movement screening as a part of pre-participation and return to sport testing.

Commonly recommended performance tests could include sit-ups, push-ups, endurance runs, sprints, jumps, hops, and other power and agility activities.9 In many athletic and occupational settings, these performance activities are selected and refined for the individual and are specific to the tasks needed for their areas of performance. Most would agree: the main goals in performing pre-participation, performance, or return to sport screening are to decrease the potential for injury, prevent re-injury, enhance performance, and ultimately improve quality of life.6,8,10 Currently the research is inconsistent on whether the pre-participation or performance screenings and standardized fitness measures have the ability to achieve this main goal.6,7 A reason for the lack of predictive value of screenings is that the standardized screenings do not provide individualized, fundamental analysis of an individual’s movements.

THE FUNCTIONAL MOVEMENT SCREEN™ The Functional Movement Screen (FMS)™ is a screening system that attempts allow the professional to assess the fundamental movement patterns of an individual.2,11,12,13 This screening system fills the void between the pre-participation/pre-placement screenings and performance tests by evaluating individuals in a dynamic and functional capacity. Such a screening system may also provide a crucial tool to assist in determining readiness to return to sport at the completion of rehabilitation after injury or surgery. A screening tool such as this may offer a different approach to injury prevention and performance predictability.

When used as a part of a comprehensive assessment, the FMS™ can lead to individualized, specific, functional recommendations for physical fitness protocols in athletic and active population groups.

The intended purpose of movement screening opens the doors for many improvements in the way individuals train and rehabilitate in several ways, including but not limited to: • Identifying individuals at risk, who are attempting to maintain or increase activity level.

• Assisting in program design by systematically using corrective exercise to normalize or improve fundamental movement patterns.

• Providing a systematic tool to monitor progress and movement pattern development in the presence of changing injury status or fitness levels.

• Creating a functional movement baseline, which will allow rating and ranking movement for statistical observation.

The authors of this clinical commentary suggest that screening and analysis of fundamental movement should be incorporated into pre-season screening and return to sport testing in order to determine

The FMS™ is comprised of seven fundamental movement patterns (tests) that require a balance of mobility and stability (including neuromuscular/motor control). These fundamental movement patterns are designed to provide observable performance of basic locomotor, manipulative, and stabilizing movements.

The tests place the individual in extreme positions where weaknesses and imbalance become noticeable if appropriate stability and mobility is not utilized. It has been observed that may individuals who perform at very high levels during activities may be unable to perform these simple movements2 and that these individuals should be considered to be utilizing compensatory movement patterns during their activities; sacrificing efficient movements for inefficient ones in order to perform at high levels. When poor or inefficient movement patterns are reinforced, this could lead to poor biomechanics and ultimately increase the potential for micro- or macro-traumatic injury.

The FMS™ test movements were created for use in screening fundamental movements, based on proprioceptive and kinesthetic awareness principles. Each

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test is a specific movement, which requires appropriate function of the body’s kinetic linking system. The kinetic link model, used to analyze movement, depicts the body as a linked system of interdependent segments. Body segments often work in a proximal-to-distal sequence, in order to impart a desired action at the distal segment.14 An important aspect of this system is the body’s proprioceptive abilities. Proprioception can be defined as a specialized variation of the sensory modality of touch that encompasses the sensation of joint movement and joint position sense.15 Proprioceptors in each segment of the kinetic chain must function properly in order for efficient movement patterns to occur. Proproioceptive input provides the basis for all motor control (motor output) and human movement.

The term “regional interdependence” is used to describe the relationship between regions of the body and how dysfunction in one region may contribute to dysfunction in another region.16,17 In fact, it is becoming accepted that what may appear to be an isolated injury or dysfunction may have far reaching effects in regions away from the injury site.18-23 Nadler et al22 demonstrated that rehabilitation after injury should not be isolated to the injured region, rather, it should address the athlete as a whole in order to return the athlete to the highest level of function.24 During growth and development, and individual’s proprioceptors are developed through predictable reflexive movements in order to perform basic motor tasks. This development occurs from proximal to distal, the infant learning to first stabilize the proximal joints in the spine and torso and eventually the distal joints of the extremities. This progression occurs due to maturation and learning. The infant learns fundamental movements by responding to a variety of stimuli, through the process of developmental motor learning. As growth and development progresses, the proximal to distal process becomes operational and has a tendency to reverse itself. The process of movement regression slowly evolves in a distal to proximal direction.25 This regression occurs as individuals gravitate toward specific skills and movements thorough habit, lifestyle, and training.

Application Examples Firefighters initially train and learn the skills associated with their trade through controlled, voluntary

movements. Then, through repetition, their movements become stored centrally as motor programs, using the complex process of motor learning. It is very important to note that motor learning is not about specific body parts, joints, or the use of isolated muscles. Rather, it is about synergy, balance, symmetry, and skill during WHOLE movement patterns.2 Over time, each motor program requires fewer cognitive commands leading to improved subconscious performance of the task. This subconscious performance involves the highest levels of central nervous system function, known as cognitive programming.15 In this example, problems would arise when the movements and training being “learned” are performed incorrectly, inefficiently, or asymmetrically.

A sport-specific example is a football lineman entering preseason practice who does not have the requisite balance of mobility or stability to perform a specific skill such as blocking. The athlete may perform the skill utilizing compensatory movement patterns in order to overcome the stability or mobility inefficiencies. The compensatory movement pattern will then be reinforced throughout the training process. In such an example, the individual creates a poor movement pattern that will be subconsciously utilized whenever the task is performed.

Programmed altered movement patterns have the potential to lead to further mobility and stability imbalances, which have previously been identified as risk factors for injury.26-28 An alternative explanation for development of poor movement patterns is the presence of previous injuries. Individuals who have suffered an injury may have a decrease in proprioceptive input, if untreated or treated inappropriately.15,29 A disruption in proprioceptive performance will have a negative effect on the kinetic linking system. The result will be altered mobility, stability, and asymmetric influences, eventually leading to compensatory movement patterns. This may be a reason why prior injuries have been determined to be one of the more significant risk factors in predisposing individuals to repeat injuries.29-31 Determining which risk factor has a larger influence on injury, previous injuries or stability/mobility

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imbalances, is difficult. In either case, both can lead to deficiencies in functional performance. Cholewicki et al32 demonstrated that limitation in stability of the spine led to muscular compensation, fatigue, and pain. Gardner-Morse et al33 determined that spinal instabilities result in degenerative changes due to the muscle activation strategies, which may be disrupted due to previous injury, stiffness, or fatigue.

In addition, Battie et al34 demonstrated that individuals with previous low back pain performed timed shuttle runs at a significantly lower pace than individuals who did not have previous low back pain.

Therefore, an important factor in prevention of injuries and improving performance is to quickly identify deficits in symmetry, mobility, and stability because of their influences on creating altered motor programs throughout the kinetic chain. The complexity of the kinetic linking system makes the evaluation of weaknesses using conventional, static methods difficult. For that reason, utilizing functional screening tests that incorporate the entire kinetic linking system is important to identify and describe deficiencies in the system.5,28,34 The FMS™ was designed to identify individuals who have developed compensatory movement patterns within the kinetic chain.2 This identification is accomplished by screening for right and left side imbalances as well as observing mobility and stability dysfunction. The seven movements in the FMS™ attempt to challenge the body’s ability to facilitate movement through the proximal-distal sequence. This course of movement in the kinetic chain allows movement efficiently, much like the correct movement patterns that were initially formed during growth and development. However, due to a weakness or dysfunction in the kinetic linking system, a poor movement pattern may have resulted.

Once an inefficient movement pattern has been isolated by the FMS™, functional strategies can be instituted in order to attempt to avoid problems associated with imbalances and movement compensations.2 Scoring the Functional Movement Screen™ The scoring for the FMS™ consists of four discrete possibilities.12,13 The scores range from zero to three, three being the best possible score. The four basic scores are quite simple in philosophy. An individual is given a score of zero if at any time during the testing he/she has pain anywhere in the body. If pain

occurs, a score of zero is given and the painful area is noted. This score necessitates further assessment by the professional, and an alternate functional movement assessment system developed for patients with known disability, injury, or pain is called the Selective Functional Movement Assessment (SFMA). Although beyond the scope of this clinical commentary, the SFMA is a clinical assessment that is designed to systematically identify causes of movement dysfunction while taking pain into consideration, using an algorithmic approach.2 If the patient does not score a zero, a score of one is given if the person is unable to complete the movement pattern or is unable to assume the position to perform the movement. A score of two is given if the person is able to complete the movement but must compensate in some way to perform the fundamental movement. A score of three is given if the person performs the movement correctly without any compensation, complying with standard movement expectations associated with each test. Specific comments should be noted describing why a score of three was not obtained.

The majority of the tests in the FMS™ examine both the right and left sides, and it is important that both sides are scored. The lower score of the two sides is recorded and is counted toward the total; however it is important to note imbalances that are present between right and left sides.

Three FMS™ tests have additional clearing screens that are graded as positive or negative. These clearing movements only consider pain, thus, if a person has pain during the screening movement, then that portion of the test is scored positive and if there is no pain then it is scored negative. The clearing tests affect the total score for the particular tests with which they are associated. If a person has a positive clearing test then the score will be zero for the associated test.

All scores for the right and left sides, and those for the tests that are associated with the clearing screens, should be recorded. (Appendix A) By documenting all the scores, even if they are zeros, the sports rehabilitation professional will have a better understanding of the impairments identified when performing an evaluation. It is important to note that only the lowest score is recorded and considered when tallying the total

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score. The best total score that can be attained on the FMS™ is twenty-one. It should be noted that movement screening is not about determining whether someone is moving “perfectly”, it is about whether a person can move above an established minimal standard. Scores serve to tell the professional when a person needs more investigation or assessment. Movement screening is about observing a series of sample movements and creating a “movement profile” of what a person can and cannot do. It is crucial that rehab professionals profile movement before attempting sport specific testing or prescribing exercises.2 DESCRIPTION OF THE FMS™ TESTS The following are descriptions of three of the seven specific tests used in the FMS™ and their scoring systems. Each test is followed by tips for testing developed by the authors as well as clinical implications related to the findings of the test.

The Deep Squat Purpose: The squat is a movement needed in most athletic events. It is the ready position and is required for most power movements involving the lower extremities. The deep squat is a test that challenges total body mechanics when performed properly. The deep squat is used to assess bilateral, symmetrical, functional mobility of the hips, knees, and ankles. The dowel held overhead assesses bilateral, symmetrical mobility of the shoulders and the

thoracic spine, as well as stability and motor control of the core musculature.

Description: The individual assumes the starting position by placing his/her feet approximately shoulder width apart and the feet aligned in the sagittal plane.

The individual then adjusts their hands on the dowel to assume a 90-degree angle of the elbows with the dowel overhead. Next, the dowel is pressed overhead with the shoulders flexed and abducted, and the elbows extended, so that the dowel is directly overhead. The individual is then instructed to descend as far as they can into a squat position while maintaining an upright torso, keeping the heels and the dowel in position. Hold the descended position for a count of one, and then return to the starting position. As many as three repetitions may be performed. If the criteria for a score of “3” is not achieved, the athlete is then asked to perform the test with a 2x6 block under the heels. (Figures 1-3) Tips for Testing • When in doubt, score the subject low.

• Try not to interpret the score while testing.

• Make sure if you have a question, to view the individual from the side.

Clinical Implications for the Deep Squat The ability to perform the deep squat requires closed kinetic chain dorsiflexion of the ankles, flexion of the

Figure 1. Performance of the Deep Squat test, scored as a “3”, viewed from the front (a), and from the side (b). Note: The upper torso is parallel with the tibia or toward vertical, the femur is below horizontal, the knees are aligned over the feet, and the dowel is also aligned over the feet.

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Figure 2. Performance of the Deep Squat test, scored as a “2”, viewed from the front (a), and from the side (b). Note: The upper torso is parallel with the tibia or toward vertical, the femur is below horizontal, the knees are over the feet, the dowel is also aligned with the feet, however the heels are elevated on a 2” board.

Figure 3. Performance of the Deep Squat test, scored as a “1”, viewed from the front (a), and from the side (b). Note: the tibia and the upper torso are not parallel, the femur is not below horizontal, the knees are not aligned over the feet, or lumbar flexion is noted. Heels are elevated on a 2” board.

knees and hips, extension of the thoracic spine, and flexion and abduction of the shoulders. The test also challenges the ability to control the body in space using the core musculature.

Poor performance of this test can be the result of several factors. Limited mobility in the upper torso can be attributed to poor glenohumeral and thoracic spine mobility. Limited moblitity in the lower extremity including poor closed kinetic chain dorsiflexion of the ankles or poor flexion of the hips may also cause poor test performance. Limited sta-

bility/motor control of the core can also affect test performance.

When an athlete achieves a score less than “3”, the limiting factor must be identified. Clinical documentation of these limitations may be obtained by using standard goniometric measurements. Previous testing has identified that when an athlete achieves a score of “2”, minor limitations most commonly exist either with closed kinetic chain dorsiflexion of the ankle or extension of the thoracic spine. When an athlete achieves a score of “1” or less, gross limita-

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tions may exist with the motions just mentioned as well as flexion of the hip.

Hurdle Step Purpose: The hurdle step is designed to challenge the body’s proper stride mechanics during a stepping motion. The movement requires proper coordination and stability between the hips and torso during the stepping motion, as well as single leg stance ability. The hurdle step assesses bilateral functional mobility and stability of the hips, knees, and ankles.

Description: The individual assumes the starting position by first placing the feet together and aligning the toes touching the base of the hurdle. The hurdle is then adjusted to the height of the athlete’s tibial tuberosity. The dowel is grasped with both hands and positioned behind the neck and across the shoulders. The individual is then asked to maintain an upright posture and step over the hurdle, raising the foot toward the shin, and maintaining alignment between the foot, knee, and hip, and touch their heel to the floor (without accepting weight) while maintaining the stance leg in an extended position. The moving leg is then returned to the starting position.

The hurdle step should be performed slowly and as many as three times bilaterally. If one repetition is completed bilaterally meeting the criteria provide, a “3”is given. (Figures 4-6)

Tips for Testing: • Score the leg that is stepping over the hurdle • Make sure the individual maintains a stable torso • Tell the individual not to lock the knees of the stance limb during the test • Maintain proper alignment with the string and the tibial tuberosity • When in doubt score low • Do not try to interpret the score when testing Clinical Implications for the Hurdle Step Performing the hurdle step test requires stance leg stability of the ankle, knee, and hip as well as maximal closed kinetic chain extension of the hip. The hurdle step also requires step leg open kinetic chain dorsiflexion of the ankle and flexion of the knee and hip. In addition, the athlete must also display adequate balance because the test imposes a need for dynamic stability.

Poor performance during this test can be the result of several factors. It may simply be due to poor stability of the stance leg or poor mobility of the step leg. Imposing maximal hip flexion of one leg while maintain hip extension of the opposite leg requires the athlete to demonstrate relative bilateral, asymmetric hip mobility.

Figure 4. Performance of the Hurdle Step, scored as a “3”, viewed from the front (a), and from the side (b). Note: hips, knees and ankles remain aligned in the sagittal plane. Minimal to no movement is noted in the lumbar spine, and the dowel and hurdle remain parallel.

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Figure 5. Performance of the Hurdle Step, scored as a “2”, viewed from the front (a), and from the side (b). Note: Alignment is lost between the hips, knees, and ankles. Movement is noted in the lumbar spine, or the dowel and hurdle do not remain parallel.

Figure 6. Performance of the Hurdle Step, scored as a “1”, viewed from the front (a), and from the side (b). Note: An athlete must be scored as a “1” if contact with the hurdle occurs during the test, or a loss of balance is noted.

When an athlete achieves a score less than “3”, the limiting factor must be identified. Clinical documentation of these limitations can be obtained by using standard goniometric measurements of the joints as well as muscular flexibility tests such as the Thomas Test or Kendall’s test for hip flexor tightness.24 Previous testing has identified that when an athlete achieves a score of “2”, minor limitations most often exist with ankle dorsiflexion and hip flexion with the step leg. When an athlete scores a “1” or less, relative asymmetric hip immobility may exist, secondary to an anterior tilted pelvis and poor trunk stability.

In-Line Lunge Purpose: The in-line lunge attempts to place the body in a position that will focus on the stresses simulated during rotational, decelerating, and lateral type movements. The in-line lunge is a test that places the lower extremities in a scissor style position, imposing a narrow base of support that challenges the trunk and extremities to resist rotation and maintain proper alignment. This test also assesses hip and ankle mobility and stability, quadriceps flexibility, and knee stability.

Description: The tester attains the individual’s tibia length, by either measuring it from the floor to the

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tibial tuberosity or acquiring it from the height of the string during the hurdle step test. The individual is then asked to place the end of their heel on the end of the board or a tape measure taped to the floor.

The previous tibial measurement is then applied from the end of the toes of the foot on the board and a mark is made. The dowel is placed behind the back touching the head, thoracic spine, and middle of the buttocks. The hand opposite to the front foot should be the hand grasping the dowel at the cervical spine.

The other hand grasps the dowel at the lumbar spine.

The individual then steps out on the board or tape measure on the floor placing the heel of the opposite foot at the indicated mark. Both toes must point forward, and feet must begin flat. The individual then lowers the back knee enough to touch the surface behind the heel of the front foot, while maintaining an upright posture, and then returns to the starting position. The lunge is performed up to three times bilaterally in a slow controlled fashion. If one repetition is completed successfully then a three is given for that extremity (right or left). (Figures 7-9)

Figure 7. Performance of the In Line Lunge, scored as a “3”, viewed from the front (a), and from the side (b). Note: the dowel remains vertical, and in contact with the spine, there is no torso movement noted, the dowel and feet remain in the sagittal plane, and the knee touches the board behind the heel of the front foot.

Figure 8. Performance of the In Line Lunge, scored as a “2”, viewed from the front (a), and from the side (b). Note: Dowel contacts are not maintained, the dowel does not remain vertical, movement is noted in the torso, the dowel and feet do not remain in the sagittal plane, or the knee does not touch behind the heel of the front foot.

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Figure 9. Performance of the In Line Lunge, scored as a “1”, viewed from the front (a), and from the side (b). Note: A score of “1” is awarded if the athlete loses balance.

Tips for Testing: • The front leg identifies the side being scored • Dowel remains in contact with the head, thoracic, spine, and sacrum during the lunge • The front heel remains in contact with the surface and back heel touches surface when returning to starting position • When in doubt score the subject low • Watch for loss of balance • Remain close to the individual in case he/she has a loss of balance Clinical Implications for the In-Line Lunge The ability to perform the in-line lunge test requires stance leg stability of the ankle, knee, and hip as well as controlled closed kinetic chain hip abduction. The in-line lunge also requires step leg mobility of hip abduction, ankle dorsiflexion, and rectus femoris flexibility. The athlete must also display adequate balance due to the lateral stress imposed.

Poor performance during this test can be the result of several factors. First, hip mobility may be inadequate in either the stance leg or the step leg. Second, the stance leg knee or ankle may not have the required stability as the athlete performs the lunge.

Finally, an imbalance between relative adductor weakness and abductor tightness OR abductor weak-

ness and adductor tightness in one or both hips may cause poor test performance. Limitations may also exist in the thoracic spine region, which may inhibit the athlete from performing the test properly.

When an athlete achieves a score less than a “3”, the limiting factor must be identified. Clinical documentation of these limitations can be obtained by using standard goniometric measurements of the joints as well as muscular flexibility tests such as the Thomas test or Kendall’s test for hip flexor tightness.24 Previous testing has identified that when an athlete achieves a score of “2”, minor limitations often exist with mobility of one or both hips. When an athlete scores a “1” or less, a relative asymmetry between stability and mobility may occur around one or both hips.

SUMMARY Since the publication of the first set of FMS™ papers in the North American Journal of Sports Physical Therapy, several authors have investigated the reliability of the scoring of the FMS™ screening tests both individually and as a complete test battery.35-40 When scored either in real time or using video analysis, the FMS™ has fair to excellent inter-rater reliability for total scores (ICC’s 0.37-0.98), and fair to good reliability for scoring of individual test movements (ICC’s 0.30-0.89).

Gribble et al37 suggested that those with more training had stronger intra-rater reliability (ICC= 0.95) as

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compared to those with less experience (ICC= 0.37).

Overall, these authors have described good to excellent or substantial agreement between trained raters on the majority of the tests, and suggest that the FMS™ group of tests can be reliably used to assess movement patterns of athletes and recognize which individuals display an acceptable movement profile.

According to Battie et al34 the ultimate test of any preemployment or pre-placement screening technique is its effectiveness in identifying individual at the highest risk of injury. Preliminary investigations by Kiesel et al41 and Chorba et al42 described the use of the FMS™ for screening athletes and attempted to determine the predictive value of the FMS™ related to injury. Kiesel et al41 determined that athletes who scored 14 or less on the FMS™ possessed dysfunctional movement patterns that may correlate with greater risk of injury. Chorba et al42 examined female collegiate athletes and found that those who scored less than 14 on the FMS™ had an approximate four-fold increase in risk (odds ratio 3.854.58) of lower extremity injury throughout the course of a season. There was a significant correlation between low-scoring athletes and injury (p = 0.021, r = 0.76) suggesting that the FMS™ may be able to successfully predict which female athletes, without a history of previous musculoskeletal injury, would be injured over the course of a season.14 However, Okada et al43 found no significant correlation between isometric/endurance measures of core stability and FMS™ scores and they concluded that low scores in core stability tests or the FMS™ likely do not influence or predict performance.

If the FMS™ or any similarly developed test battery can identify at risk individuals, then prevention strategies can be instituted based upon their scores. A proactive, functional training approach that decreases injury through improved performance efficiency will enhance overall wellness and productivity in many active populations. The concepts of movement screening are not without controversy. The authors maintain that screening should be used for specific, discrete purposes only, and not be substituted for indepth additional movement analysis when appropriate. The next issue: Volume 9; Number 4, August 2014 of IJSPT will provide the final four fundamental tests incorporated into the Functional Movement Screen (FMS)™ and a further discussion of the relevance and limitations of functional movement screening.

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Fields KB, Delaney M. Focusing on the preparticipation sports examination. J Fam Pract.

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Kibler WB, Chandler TJ, Uhl T, Maddux RE. A musculoskeletal approach to the preparticipation physical examination: Preventing injury and improving performance. Am J Sports Med. 1989;17:525-527.

Meeuwisse WH, Fowler PJ. Frequency and predictability of sports injuries in intercollegiate athletes. Can J Sport Sci. 1988;13:35-42.

Metzl JD. The adolescent pre-participation physical examination: Is it helpful? Clin Sports Med. 2000; 19:577-592.

Physician and Sportsmedicine. The Preparticipation Physical Evaluation. 3rd ed. New York: McGraw-Hill; 2005.

American College of Sports Medicine. ACSM’s Guidelines for Exercise Testing and Prescription. 6th ed. Lippincott Williams and Wilkins; 2000.

Meeuwisse WH. Predictability of sports injuries: What is the epidemiological evidence? Sports Med. 1991;12:8-15.

Cook EG. Athletic body in Balance: Optimal movement skills and conditioning for performance. Champaign, IL: Human Kinetics, 2004.

Cook EG, Burton L, Hoogenboom BJ. The use of fundamental movements as an assessment of function-Part 1. N Am J Sports Phys Ther. 2006;1(2): 62-72.

Cook EG, Burton L, Hoogenboom BJ. The use of fundamental movements as an assessment of function-Part 2. N Am J Sports Phys Ther.

2006;1(3):132-139.

McMullen J, Uhl T. A kinetic chain approach for shoulder rehabilitation. Athletic Training.

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Lephart SM, Pincivero DM, Giraldo JL, Fu FH. The role of proprioception in the management and rehabilitation of athletic injuries. Am J Sports Med. 1997;25:130-138.

Vaughn DW. Isolated knee pain: A case report highlighting regional interdependence. J Orthop Sports Phys Ther. 2008;38(10):616-623.

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17. Wainner RS, Whitman JM, Cleland JA, Flynn TW. Regional interdependence: A musculoskeletal examination model whose time has come. J Orthop Sports Phys Ther. 2007; 37:658-660.

18. Bullock-Saxton JE. Local sensation changes and altered hip muscle function following severe ankle sprain. Phys Ther. 1994;74:17-28.

19. Bullock-Saxton JE, Janda, V, Bullock, MI. The influence of ankle sprain injury on muscle activation during hip extension. Int J Sports Med. 1994;15:330334.

20. Cholewicki J, Green HS, Polzhofer GK, Galloway MT, Shah RA, Radebold A. Neuromuscular function in athletes following recovery from a recent acute low back injury. J Orthop Sports Phys Ther.

2002;32:568-575.

21. Leetun DR, Ireland ML, Willson JD, Ballantyne BT, Davis IM. Core stability measures as risk factors for lower extremity injury in athletes. Med Sci Sports Exerc. 2004;36(6): 926-934.

22. Nadler SF, Malanga GA, Bartoli LA, Feinberg JH, Prybicien M, Deprince M. Hip muscle imbalance and low back pain in athletes: Influence of core strengthening. Med Sci Sports Exerc. 2002;34: 9-16.

23. Zazulak, BT, Hewett TE, Reeves NP, Goldberg B, Cholewicki J. Deficits in neuromuscular control of the trunk predict knee injury risk. Am J Sports Med. 2007;35(7): 1123-1130.

24. Nadler SF, Malanga GA, DePrince M, Stitik TP, Feinberg JH. The relationship between lower extremity injury, low back pain, and hip muscle strength in male and female collegiate athletes. Clin J Sports Med. 2000;10(2):89-97.

25. Gallahue DL, Ozmun JC. Understanding Motor Development. 3rd ed. Madison, WI: Brown and Benchmark; 1995.

26. Baumhauer JF, Alosa DM, Renstrom PA, et al. A prospective study of ankle injury risk factors. Am J Sports Med. 1995;23:564-570.

27. Knapik JJ, Bauman CL, Jones BH, et al. Preseason strength and flexibility imbalances associated with athletic injuries in female collegiate athletes. Am J Sports Med. 1991;19:76-81.

28. Nadler SF, Malanga GA, Feinberg JH, et al.

Relationship between hip muscle imbalance and occurrence of low back pain in collegiate athletes: a prospective study. Am J Phys Med Rehabil.

2001;80:572-577.

29. Nadler SF, Moley P, Malanga GA, et al. Functional deficits in athletes with a history of low back pain: A pilot study. Arch Phys Med Rehabil. 2002;88:17531758.

30. Neely FG. Intrinsic risk factors for exercise-related lower limb injuries. Sports Med. 1998;26:253-263.

31. Paterno MV, Schmitt LC, Ford KR, Rauh MJ, Myer GD, Huang B, Hewett TE. Biomechanical measures during landing and postural stability predict second anterior cruciate ligament injury after anterior cruciate ligament reconstruction and return to sport.

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32. Cholewicki J, Panjabi MM, Khachatryn A. Stabilizing function of trunk flexor-extensor muscles around a neutral spine posture. Spine. 1997;22:2207-2212.

33. Gardner-Morse M, Stokes I, Laible JP. Role of muscles in lumbar spine stability in maximum extension efforts. J Orthop Res. 1995;13:802-808.

34. Battie MC, Bigos SJ, Fisher LD, et al. Isometric lifting strength as a predictor of industrial back pain reports. Spine. 1989;14:851-856.

35. Minick KI, Kiesel KB, Burton L, Taylor A, Plisky P, Butler RJ. Inter-rater reliability of the functional movement screen. J Strength Cond Res. 2010;24(2):479-486.

36. Schneiders AG, Davidsson A, Horman E, Sullivan SJ. Functional Movement Screen™ normative values in a young, active population. Int J Sports Phys Ther.

2011;6(2):75-82.

37. Gribble PA, Brigle J, Pietrosimone BG, Pfile KR, Webster KA. Intrarater reliability of the Functional Movement Screen. J Strength Condit Res. 2012;26(2):408-415.

38. Smith CA, Chimera NJ, Wright NJ, Warren M. Interrater and intrarater reliability of the Functional Movement Screen. J Strength Condit Res. 2013;27(4):982-987.

39. Onate JA, Dewey T, Kollock RO, Thomas KS, Van Lunen BL, DeMaio M, Ringleb SI. Real-time intersession and interrater reliability of the functional movement screen. J Strength Condit Res. 2013;27(4):978-981.

40. Gulgin H, Hoogenboom B. The Functional Movement Screening (FMS)™: An inter-rater reliability study between raters of varied experience.

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41. Kiesel K, Plisky PJ, Voight ML. Can serious injury in professional football be predicted by a preseason functional movement screen? N Am J Sports Phys Ther. 2007;2(3):147-152.

42. Chorba RS, Chorba DJ, Bouillon LE, Overmyer CA, Landis JA. Use of a functional movement screening tool to determine injury risk in female collegiate athletes. N Am J Sports Phys Ther. 2010;5(2):47-54.

43. Okada T, Huxel KC, Nesser TW. Relationship between core stability, functional movement, and performance. J Strength Cond Res. 2011;25(1):252-261.

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APPENDIX A

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IJSPT

CLINICAL SUGGESTION

VARIABLE RESISTANCE TRAINING USING ELASTIC BANDS TO ENHANCE LOWER EXTREMITY STRENGTHENING Daniel S. Lorenz, DPT, PT, ATC/L, CSCS1

ABSTRACT Strengthening of the quadriceps is a central tenet of lower extremity rehabilitation, particularly after knee surgery. Quadriceps deficits after various knee procedures are well-documented. One method common to strength and conditioning circles is variable resistance training (VRT). VRT involves the use of heavy chains and elastic bands to facilitate gains in strength and power. Most of the application in strength training however has been on healthy, trained athletes. Sports physical therapists may use elastic bands for VRT to augment strength gains for the recovering athlete. The purpose of this manuscript is to provide a clinical suggestion for the use of VRT in athletic rehabilitation.

Keywords: Eccentric training, power, strength training, variable resistance training Level of Evidence: 5

1

Specialists in Sports and Orthopedic Rehabilitation, Overland Park, KS, USA

CORRESPONDING AUTHOR Daniel Lorenz E-mail: danielslorenz@gmail.com

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PROBLEM Maximizing strength of the quadriceps is one of the main goals following knee surgery and general knee rehabilitation for the athletic population. For purposes of this manuscript, the athletic population will include not only competitive and recreational athletes but also those characterized as “weekend warriors.” Quadriceps deficits that occur following anterior cruciate ligament (ACL) reconstruction,1-4 knee arthroscopies,5 patellofemoral pain syndrome,6,7 and total knee arthroplasty8,9 are well documented.

Appropriate strength is required for proper progression through a functional testing algorithm following a lower extremity injury.10 There are numerous ways to strengthen the quadriceps in both open and closed kinetic chain and one method that may be used is Variable Resistance Training (VRT), which involves the use of heavy chains or elastic bands in addition to weight on a lifting bar. VRT has been used in the strength and conditioning literature in both strongman competition training11 an eclectic sport where feats of strength are performed by competitors who lift rocks, refrigerators, pull trucks, and lift items overhead for example, as well as to increase strength and power in athletes.12-15 However, to the author’s knowledge, it hasn’t been described as a tool to be used in sports rehabilitation. Because of the benefits in strength and power that may be realized from this method of training, it should be considered as a potential method to facilitate strength gains in the lower extremity. Potentially, it can be used earlier in the rehabilitative process as well, prior to submaximal or maximal strength activities instead of just in the terminal phases of rehabilitation.

For athletes recovering from ACL reconstruction, this may be a particularly advantageous modification to two common exercises because of the added eccentric component to the load. Eccentric strengthening has been shown by several authors to enhance strength and cross-sectional area of the quadriceps and gluteals following ACL reconstruction.16-18

SOLUTION The concept of VRT using elastic resistance can be used to augment an exercise like the leg press or assisted squats to enhance eccentric loading. Figures 1 and 2 show how an athlete may use bands or tubing while performing squats on the Total Gym® (Total Gym, San Diego, CA). The band should be on max tension at full extension of the hip and knee. The athlete should be instructed to lower themselves and the weight slowly and then push back to the start position. This exercise can be done with one or two legs.

In Figures 3 and 4, the athlete uses bands or tubing to increase eccentric loading on the leg press machine.

When enhancement of strength is the training objective, the athlete should perform 5-10 repetitions for 3-4 sets of the exercise. The author suggests using bands or tubing at the highest tension because lowerlevel resistance will not provide the overload that greater resistances provide, however, band tension should be based on the athlete’s ability to control the weight. Unfortunately, it has been shown that there is up to a 5% difference in resting tension and up to 19% in maximum tension of the same color band.19 Therefore, the sports physical therapist should use discretion when not only adding VRT, but also the movement quality when the athlete or patient performs the exercise.

Figure 1. Start position in full hip and knee extension with maximum tension on the band on the Total Gym® (Total Gym, San Diego, CA), single leg example. Any body weight type leg press model would work.

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Figure 2. End of the eccentric/lowering phase using the band on the Total Gym®.

DISCUSSION VRT has been described in the literature as an attempt to combine the range of motion and acceleration benefits of ballistic training while allowing higher loads than are normally used in typical resistance training.15 The advantage of VRT is that typical ballistic type training may be difficult to apply safely for an athlete after knee surgery. VRT allows the sports physical therapist to utilize its benefits of eccentric-emphasized training with minimal risk.

In addition, VRT has been shown to be superior in increasing strength and power, as well as increasing force, lean body mass and overall EMG activity when compared to typical resistance training.15 Some of these gains may be attributed to the human body having to match the loading pattern of the additional resistance, which may yield a greater overload on the muscular system. Overload is achieved by the weight on the bar plus the stretch offered by the elastic bands that serves to increase resistance. In an attempt to return to initial length the bands pull the bar downward with greater force than with free weights alone, thereby increasing the eccentric load

Figure 3. Start position in full hip and knee extension with maximum tension on the band using the Magnum Fitness leg press (Magnum Fitness Systems, Milwaukee, WI), single leg example. Any leg press model would work.

substantially when the bands are at full tension. In the same light, a concentric repetition with the elastic resistance may help athletes break their “sticking point.”20,21 This strategy focuses on the top half of the repetition or the “lockout” portion since the weight exponentially increases as the bar is pushed closer to full extension, which often leads to a point where an athlete gets “stuck” and cannot lockout.

In addition, when free weights are used in conjunction with elastic bands, there may be breakthroughs of strength plateaus that are present due to neural adaptations. Shoepe and colleagues compared a group who participated with free weight training and elastic bands and a group who solely trained with free weights.22 The group who trained with both the free weights and elastic bands had significantly greater strength gains as measured by 1RM in the bench press, back squat, and in lean body mass when compared to the other groups. Interestingly, GarciaLopez et al analyzed the amount of reps their subjects could get during a 70% 1RM bicep curl on both

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with limited resources to maximize strength gains, VRT is a “budget friendly” method to augment strength gains without having to purchase expensive equipment or increase space to accommodate new equipment. In addition, VRT may be an alternative modality of training to help alleviate boredom or to help during times of plateau.

REFERENCES

Figure 4. End of the eccentric/lowering phase using the band on the assisted squat machine, single leg example on Shuttle.

the pulley cable, with its normal open-chain setup, and with elastic resistance attached to the cable.23 The group who participated with the elastic resistance attached had a reduced maximum number of repetitions, yet a similar perception of effort. This study shows the potential efficacy of elastic resistance by bringing a muscle group to failure quicker and with equal perceived exertion as a traditional approach.

CONCLUSION While VRT has been used in the training of healthy athletes to maximize strength and power, it has not been studied in the recovering athlete. This clinical suggestion provides a first step in how VRT using elastic resistance might be used during the process of lower extremity rehabilitation. The concept of VRT may be extrapolated to sport rehabilitation in earlier phases of rehabilitation in order to help facilitate gains in strength and power. VRT can be particularly important for the clinician who lacks resources to train their athletes appropriately in maximizing their quadriceps strength and power. In a facility

1. Lentz TA, Tillman SM, Indelicato PA, et al. Factors associated with function after anterior cruciate ligament reconstruction. Sports Health. 2009; 1(1): 47-53.

2. Moisala AS, Jarvela T, Kannus P, Jarvinen M. Muscle strength evaluations after ACL reconstruction. Int J Sports Med. 2007; 28(10): 868-72.

3. Tourville TW, Jarrell KM, Naud S, et al. Relationship between isokinetic strength and tibiofemoral joint space width changes after anterior cruciate ligament reconstruction. Am J Sports Med. 2014; 42(2): 302-11.

4. Thomas AC, Villwock M, Wojtys EM, Palmieri-Smith R. Lower extremity muscle strength after anterior cruciate ligament injury and reconstruction. J Ath Train. 2013; 48(5): 610-20.

5. McLeod MM, Gribble P, Pfile KR, Pietrosimone BG. Effects of partial meniscectomy on quadriceps strength: a systematic review. J Sport Rehabil. 2012; 21(3): 285-95.

6. Pappas E, Wong-Tom WM. Prospective predictors of patellofemoral pain syndrome: a systematic review with meta-analysis. Sports Health. 2012; 4(2): 115-20.

7. Pattyn E, Mahieu N, Selfe J, et al. What predicts functional outcome after treatment for patellofemoral pain? Med Sci Sports Exerc. 2012; 44(10): 1827-33.

8. Schache MB, McClelland JA, Webster KE. Lower limb strength following total knee arthroplasty: a systematic review. Knee. 2014; 21(1): 12-20.

9. Judd DL, Eckhoff DG, Stevens-Lapsley JE. Muscle strength loss in the lower limb after total knee arthroplasty. Am J Phys Med Rehabil. 2012; 91(3): 220-6.

10. Davies GJ, Zillmer DA. Functional progression of a patient through a rehabilitation program. Orthopedic Physical Therapy Clinics of North America. 2000; 9(2):103-118.

11. Winwood PW, Keogh JW, Harris NK. The strength and conditioning practices of strongman competitors.

J Strength Cond Res. 2011; 25(11): 3118-28.

12. Burnham TR, Ruud JD, McGowan R. Bench press training program with attached chains for female volleyball and basketball athletes. Percept Mot Skills.

2010; 110(1): 61-8.

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13. Ghigiarelli JJ, Nagle EF, Gross FL, et al. The effects of a 7-week heavy elastic band and weight chain program on upper-body strength and upper-body power in a sample of division I-AA football players.

J Strength Cond Res. 2009; 23(3): 756-64.

14. Stevenson MW, Warpeha JM, Dietz CC, et al. Acute effects of elastic bands during free-weight barbell back squat exercise on velocity, power, and force production. J Strength Cond Res. 2010; 24(11): 2944-54.

15. Wallace BJ, Winchester JB, McGuigan MR. Effects of elastic bands on force and power characteristics during the back squat exercise. J Strength Cond Res. 2006; 20(2): 268-72.

16. Gerber JP, Marcus RL, Dibble LE, et al. Effects of early progressive eccentric exercise on muscle size and function after anterior cruciate ligament reconstruction: a 1-year follow up study of a randomized clinical trial. Phys Ther. 2009; 89(1): 51-9.

17. Gerber JP, Marcus RL, Dibble LE, et al. Safety, feasibility, and efficacy of negative work exercise via eccentric muscle activity following anterior cruciate ligament reconstruction. J Orthop Sports Phys Ther.

2007; 37(1): 10-18.

18. Gerber JP, Marcus RL, Dibble LE, et al. Early application of negative work via eccentric ergometry

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McMaster DT, Cronin J, McGuigan MR. Quantification of rubber and chain-based resistance modes. J Strength Cond Res. 2010; 24(8): 2056-64.

Drinkwater EJ, Gaina B, McKenna MJ, et al.

Validation of an optical encoder during free weight resistance movements and analysis of bench press sticking point power during fatigue. J Strength Cond Res. 2007; 21(2): 510-17.

Krol H, Golas A, Sobota G. Complex analysis of movement in evaluation of flat bench press performance. Acta Bioeng Biomech. 2010; 12(2): 93-8.

Shoepe TC, Ramirez DA, Rovetti RJ, et al. The Effects of 24 weeks of Resistance Training with Simultaneous Elastic and Free Weight Loading on Muscular Performance of Novice Lifters. Am J Hum Kinet. 2011; 29:93-106.

Garcia-Lopez D, Herrero AJ, Gonzalez-Calvo G, et al.

Influence of In Series Elastic Resistance on Muscular Performance During a Biceps-Curl Set on the Cable Machine. J Strength Cond Res. 2010; 24(9): 2449-55.

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