Physical Therapy in Sport

Physical Therapy in Sport 11 (2010) 3–7

Contents lists available at ScienceDirect

Physical Therapy in Sport journal homepage: www.elsevier.com/ptsp

Original research

Bracing does not improve dynamic stability in chronic ankle instability subjects Phillip A. Gribble*, Brittany L. Taylor, Junji Shinohara University of Toledo, 2801 W. Bancroft St, Toledo, OH 43606, United States

a r t i c l e i n f o

a b s t r a c t

Article history: Received 16 October 2009 Received in revised form 16 November 2009 Accepted 18 November 2009

Objectives: To investigate the effects of an ankle brace on dynamic postural stability, measured with Time to Stabilization (TTS), in subjects with chronic ankle instability (CAI).

Design: Two-within (Condition, Side) repeated measures.

Setting: Research laboratory.

Participants: Fifteen subjects with unilateral CAI. Main outcome measures: Subjects participated in two testing sessions during which a single-limb jumplanding task was performed with one of two conditions: lace-up ankle brace or no ankle brace. Ground reaction forces were used to calculate Resultant Vector TTS (RVTTS).

Results: For RVTTS, there were no statistically significant main effects for Side (F1,14 ¼ 1.005; p ¼ 0.33) or Condition (F1,14 ¼ 2.48; p ¼ 0.14), as well as no significant interaction effect (F1,14 ¼ 1.67; p ¼ 0.22).

Conclusion: While TTS is a useful outcome tool for identifying deficits in subjects with CAI and improvements related to ankle rehabilitation, this measure of dynamic stability does not appear to be sensitive in detecting the influence of the application of an ankle brace in this pathological group.

Researchers need to establish what other testing methods will be the best for determining the outcome of the application of an ankle brace in the laboratory setting to coincide with the epidemiology data that support the use of these devices. Ó 2009 Elsevier Ltd. All rights reserved.

Keywords: Time to stabilization Prophylactic ankle support Jump-landing Ground reaction force

1. Introduction Instability and injury to the ankle is responsible for 25% of all time lost from physical and recreational activity (Ashton-Miller, Ottaviani, Hutchinson, & Wojtys, 1996). Recurrent instability at the ankle, at a rate to be reported as high as 80% following initial insult, (Yeung, Chan, & So, 1994) is commonly referred to as chronic ankle instability (CAI) (Hertel, 2002). One successful method for reducing initial and recurrent ankle injury is through the use of external prophylactic ankle support (PAS) (Gross & Liu, 2003; Mickel, Bottoni, Tsuji, Chang, Baum, & Tokushige, 2006; Olmsted, Vela, Denegar, & Hertel, 2004; Pedowitz, Reddy, Parekh, Huffman, & Sennett, 2008; Rovere, Clarke, Yates, & Burley, 1988; Schmidt, Sulsky, & Amoroso, 2005; Sharpe, Knapik, & Jones, 1997; Sitler et al., 1994; Stasinopoulos, 2004; Surve, Schwellnus, Noakes, & Lombard, 1994; Thacker, Stroup, Branche, Gilchrist, Goodman, & Weitman, 1999).

Previous research has demonstrated the ability of these devices to provide passive restraint to ankle motion (Cordova, Ingersoll, & LeBlanc, 2000; Eils, Demming, Kollmeier, Thorwesten, Vo¨lker, & Rosenbaum, 2002; Eils, Imberge, Vo¨lker, & Rosenbaum, 2007;

* Corresponding author. Tel.: þ1 419 530 2691; fax: þ1 419 530 2477.

E-mail address: phillip.gribble@utoledo.edu (P.A. Gribble).

1466-853X/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.ptsp.2009.11.003

Greene & Hillman, 1990; Gross, Bradshaw, Ventry, & Weller, 1987), but very little examination of the restraint capabilities provided during active movement has been conducted (Delahunt, O’Driscoll, & Moran, 2009; Gribble, Radel, & Armstrong, 2006; Gudibanda & Wang, 2005; Kimura, Nawoczenski, Epler, & Owen, 1987). Surprisingly, of these laboratory studies examining contributions to ankle stability, only two have utilized a pathological group of subjects (Delahunt et al., 2009; Eils et al., 2002). Eils et al. (Eils et al., 2002) examined the passive restraints of ankle bracing in an open chain testing position and Delahunt et al. (Delahunt et al., 2009) utilized ankle taping as the selected PAS. Therefore, information on the ability of ankle bracing to provide ankle restraint during dynamic movement in subjects with injured ankles is lacking.

CAI is associated with deficits in dynamic postural control and stability. Specifically, subjects with CAI present with deficits in dynamic postural control as measured with Time to Stabilization (TTS) during a jump-landing task compared with subjects with no history of ankle pathology (Brown & Mynark, 2007; Brown, Ross, Mynark, & Guskiewickz, 2004; Gribble & Robinson, 2009; Ross & Guskiewickz, 2004; Ross, Guskiewickz, & Yu, 2005; Ross, Guskiewickz, Gross, & Yu, 2008; Wikstrom, Tillman, & PA, 2005; Wikstrom, Tillman, Chmielewski, Cauraugh, & PA, 2007). As stated above, PAS can provide mechanical restraint to the ankle both passively and actively in isolated laboratory testing using a fixed

4

P.A. Gribble et al. / Physical Therapy in Sport 11 (2010) 3–7

leg; however, the contributions of these devices to performance and stability during dynamic, functional testing is somewhat unknown, especially among pathological subjects. Specifically, the ability of PAS to improve dynamic postural control measured through TTS has not been studied extensively among CAI subjects (Wikstrom, Arrigenna, Tillman, & Borsa, 2006); however, there is evidence to suggest that ankle braces may be able to influence this measure of dynamic stability among healthy individuals (Shaw, Frye, & Gribble, 2008).

Shaw et al. (Shaw et al., 2008) compared dynamic stability, using TTS, among Division I volleyball players wearing a lace-up brace and a semi-rigid brace before and after induced fatigue. After fatigue was induced, dynamic stability was better when wearing the lace-up brace. This suggests some ankle bracing may have positive influences on dynamic stability when fatigue is introduced to simulate a high level of physical activity. The limited amount of information that pertains to ankle bracing capabilities on pathological subjects comes from Wikstrom et al. (Wikstrom et al., 2006) who examined the anterior/posterior, medial/lateral and vertical components of dynamic stability during a jump-landing among subjects with functional ankle instability with and without an ankle brace applied. Only the vertical component was significantly influenced with the application of a brace, indicating that perhaps the braces did not contribute positively to dynamic stability, but are able to dissipate vertical ground reaction forces.

Landing from a jump is often implicated as an injurious mechanism for the ankle and PAS are commonly utilized by jumping sport athletes to prevent ankle injury. While epidemiological data mentioned above support the use of braces, because the information from controlled laboratory testing is limited and somewhat conflicting, it is clear that more investigation is needed to determine if PAS can be effective at improving the dynamic stability capabilities among subjects with a history of recurrent ankle instability. Therefore, the purpose of this study was to compare TTS values between braced and non-braced conditions using a lace-up style brace among subjects with unilateral CAI.

2. Methods 2.1. Subjects Fifteen subjects (8 females, 7 males; age: 18.88 1.20 yrs; height: 170.77 10.17 cm; mass: 66.89 6.85 kg) with unilateral CAI volunteered to participate in this study. In a similar investigation using a variation of the dynamic stability measure we have selected, Wikstrom et al. (Wikstrom et al., 2006) used a sample size of twenty-eight subjects with assessments repeated on the same injured limb with and without a brace. However, based on previous work in our laboratory (Shaw et al., 2008) using the same brace and dependant variables we utilized in this current study, our a priori power analysis suggested that eleven subjects would be needed to achieve a power level of 0.85 for our study. Fifteen subjects were selected to bolster this projection.

All subjects participated in at least 30 min of exercise three times per week. Criteria for CAI included having a history of at least 1 acute ankle sprain that resulted in swelling, pain, and temporary loss of function (but none in the previous 3 months); and a history of multiple episodes of the ankle ‘‘giving way’’ in the past 6 months (Gribble & Robinson, 2009). Additionally, subjects had to score <90% on the Foot and Ankle Disability Index (FADI) and <80% on the FADI Sport Scale (Hale & Hertel, 2005). Subjects were excluded if they had a history of any other lower extremity injury besides to the ankle, a balance disorder, or had in the previous 6 months participated in formalized ankle rehabilitation. Prior to participating, subjects read

and sign an informed consent form that was approved by the university’s institutional review board.

2.2. Instrumentation A Bertec 4060NC forceplate (Bertec, Inc., Columbus, OH) integrated with MotionMonitor software (Innovative Sports Technologies Inc., Chicago, IL) was used to collect ground reaction forces during the jump-landing task. A Vertec vertical jump tester (Sports Imports, Columbus, OH) was used to measure the subjects’ standing and jumping height.

2.3. Procedures Subjects were pre-screened to verify inclusion criteria and then reported to the research laboratory for one session. First, an assessment of vertical jump height was performed to determine the target for the jump-landing trials. Standing-reach height was measured as the subjects stood next to a Vertec vertical jump tester, reached up and touched the highest point possible while both feet remained flat on the ground. Subjects then performed three trials of maximal double-limb vertical jump and touched the highest point possible. Maximum vertical height (Vertmax) was determined as the difference between the maximum height reached during the three jumps and the standing-reach height and was used to designate a target for the subjects to reach during the jump-landing trials (Ross & Guskiewickz, 2003).

During the testing session, the dynamic stability of both legs (Injured and Non-Injured) were assessed during the single-limb landing task. When performing the jump-landing task, there were two different bracing conditions, one with the Swede-O UniversalÒ (Swede-O, Inc.; North Branch, MN) applied (Brace) and a control/no brace condition (No Brace). In a previous investigation, this brace was associated with better TTS measures after fatigue when compared to another commonly used brace and a control condition (Shaw et al., 2008).

The order of Side and Condition was counter-balanced. The jumplanding task began with the subject standing 70 cm away from the middle of the forceplate. They began the jump-landing task with both feet on the ground, jumping towards the forceplate, reaching up and touching the indicated marker (50% of each subjects Vertmax) on the Vertec (Fig. 1a) and landing on the test leg on the forceplate (Fig. 1b).

The subjects were instructed to stabilize on the single testing leg and put both hands on their hips as quickly as possible while facing forward, holding the position until 5 s after ground contact.

The subjects were allowed at least 4 practice trials to practice the jump-landing task and familiarize themselves with the procedures on the first designated testing leg (VanMeter & Gribble, 2008). The first bracing condition was revealed for this leg and the practice trials performed using that designated condition. Subjects were allowed as many practices as needed to feel comfortable with the task. After the practice trials and a 5 min rest period, subjects performed five test trials with 1 min rest between trials. After the test trials, a 10 min rest period was provided and the procedures were repeated on the same leg with the second bracing condition.

After both bracing conditions were completed for the first testing limb, a 10 min rest period was provided and then the practice and testing procedures repeated for the second testing limb. If the subject had to hop or touch down the non-testing limb during a trial, then the trial was discarded and repeated.

2.3.1. Data processing The TTS variable was calculated using methods previously described (Ross et al., 2008) and a custom LabView (National Instruments, Inc.; Austin, TX) file. The time point for data selection

P.A. Gribble et al. / Physical Therapy in Sport 11 (2010) 3–7

5

Table 1 RVTTS means and standard deviations (s) and effect sizes (d) with 95% CI.

Brace No-brace Effect size (brace comparison)

Fig. 1. Jump-landing task. (a) – Subject jumping to touch the target set at 50% of the maximum vertical jumping height. (b) – Subject landed on the force plate on test limb with brace applied.

was designated from initial ground impact with the forceplate, designated when the threshold voltage of the force plate registered more than 10 v, until the 5 s trial was completed. First, TTS values in the anterior/posterior (APTTS) and medial/lateral (MLTTS) planes were calculated from A/P and M/L ground reaction force data, respectively, during the five successful landing trials for each leg and bracing condition. Ground reaction force data were collected at 200 Hz and filtered with a 4th order Butterworth filter with a cutoff frequency of 14 Hz (Ross & Guskiewickz, 2004). After APTTS and MLTTS values were calculated, the Resultant Vector of TTS was calculated using the following formula:

RVTTS ¼

qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi APTTS2 þ MLTTS2

While APTTS and MLTTS are commonly reported separately, the RVTTS variable has been developed recently and recommended to provide a single stability assessment of both planes of movement (Ross et al., 2008).

2.3.2. Statistical analysis The means and standard deviations from the testing trials were used for the statistical analyses. For the dependant variable (RVTSS), a within-subjects two-way (Side, Condition) repeated measures ANOVA was performed. Statistical significance was determined a priori at p < 0.05. Effect sizes were calculated using Cohen’s d (Cohen, 1988).

3. Results For the RVTTS, there were no statistically significant main effects for Side (F1,14 ¼ 1.005; p ¼ 0.33) or Condition (F1,14 ¼ 2.48; p ¼ 0.14).

Additionally, there was not a statistically significant interaction effect (F1,14 ¼ 1.67; p ¼ 0.22). Means and standard deviations along with effect size and 95% confidence intervals are provided in Table 1.

4. Discussion There were no statistically significant influences of the application of the selected ankle brace on the RVTTS measures among

Injured side

Non-injured side

Effect size (side comparison)

1.602 0.067 s 1.589 0.055 s 0.21 (0.18, 0.24)

1.601 0.080 s 1.579 0.060 s 0.05 ( 0.35, 0.08)

0.00 ( 0.03, 0.41) 0.17 (0.15, 0.20)

this group of subjects with unilateral CAI. The low effect size values confirm that the ankle brace did not improve dynamic postural stability during landing from a jump in these pathological subjects.

This finding is surprising from a clinical perspective as prophylactic ankle supports are utilized to prevent injurious mechanisms during jumping and landing activities. Previous reports support the concept that ankle braces can prevent ankle injuries (Gross & Liu, 2003; Mickel et al., 2006; Olmsted et al., 2004; Pedowitz et al., 2008; Rovere et al., 1988; Schmidt et al., 2005; Sharpe et al., 1997; Sitler et al., 1994; Stasinopoulos, 2004; Surve et al., 1994; Thacker et al., 1999) and do not hinder physical performance in uninjured populations (Cordova, Scott, Ingersoll, & LeBlanc, 2005). Additionally, previous investigation indicated that the same selected ankle brace was effective in improving dynamic stability during the same jump-landing task in healthy volleyball players after fatigue was induced (Shaw et al., 2008). However, there has been limited investigation into the effect that ankle braces have during landing on populations that have CAI (Wikstrom et al., 2006).

Our findings are similar to what Wikstrom et al. (Wikstrom et al., 2006) reported when testing a semi-rigid and soft brace using a similar jump-landing protocol, but with a variation on the calculation of stabilization of ground reaction forces when landing from a jump (Dynamic Postural Stability Index [DPSI]). They observed no significant difference between braced and no-braced conditions for any of their measures of dynamic stabilization in the anterior/posterior and medial/lateral directions in subjects with functionally unstable ankles. The A/P and M/L aspects of dynamic stability indices (i.e. TTS, DPSI) consistently display deficits in populations with recurrent ankle pathology (Brown et al., 2004; Gribble & Robinson, 2009; Ross & Guskiewickz, 2004; Ross et al., 2005; Ross et al., 2008; Wikstrom et al., 2005; Wikstrom et al., 2007). In both our results and those of Wikstrom et al. (Wikstrom et al., 2006), the A/P and M/L components of dynamic stability do not appear to be improved with the application of the ankle support.

However, Wikstrom et al. (Wikstrom et al., 2006) did report that bracing helped attenuate vertical forces during landing as indicated by a vertical component of the DPSI measures. While they have suggested that the control of the vertical component of the GRF during landing may be important to examine, this was not included in our investigation as it is not a component of the RVTTS variable.

While the attenuation of the vertical component of the ground reaction force may be an important component while landing from a jump, the previous papers utilizing TTS variables have not reported on the vertical component of dynamic stability, instead focusing on the A/P and M/L components (Brown et al., 2004; Gribble & Robinson, 2009; Ross & Guskiewickz, 2004; Ross et al., 2005; Ross et al., 2008; Ross, Guskiewickz, Gross, & Yu, 2009).

These A/P and M/L components of dynamic stability may elucidate more important information about the sagittal and frontal plane injurious mechanisms of interest to the ankle complex. Combining these two measures into the RVTTS has been associated with sensitivity and specificity measures of 0.67 and 0.73, respectively, when differentiating subjects with and without CAI (Ross et al., 2008). However, previous authors have reported increased vertical GRF in addition to increased sagittal and frontal plane GRF among

6

P.A. Gribble et al. / Physical Therapy in Sport 11 (2010) 3–7

subjects with ankle instability (Caulfield & Garrett, 2004; Delahunt, Monaghan, & Caulfield, 2006). Therefore, it may be interesting in future studies to investigate the influence of bracing and CAI on the vertical component of dynamic stability in addition to the A/P and M/L components to make additional comparisons to the previous work in this area (Wikstrom et al., 2006).

Surprisingly, it appears that bracing an unstable ankle during the selected jump-landing task may not improve dynamic stabilizing capabilities. While our current study and the results of Wikstrom et al. (Wikstrom et al., 2006) did use slightly different subject inclusion criteria, the results in both studies seem to agree.

As mentioned previously in the beginning of this manuscript, landing from a jump is an injurious mechanism implicated in ankle sprain pathology, and the application of an ankle prophylactic support has been shown to reduce initial ankle sprain injury rates in sports. One conclusion could be that the application of a brace does not have as great of an influence on ankles that have lingering instability. However, a numbers needed to treat analysis of existing literature concluded that ankle bracing may be more effective at protecting the ankles of individuals with a history of ankle instability compared to the prevention of the first time ankle sprain (Olmsted et al., 2004). Perhaps this contradiction is related to the assessment technique selected in this study. The measurement technique utilized in this investigation is sensitive at detecting deficits in dynamic stability of those with recurrent ankle instability (Brown et al., 2004; Gribble & Robinson, 2009; Ross & Guskiewickz, 2004; Ross et al., 2005; Ross et al., 2008; Wikstrom et al., 2005; Wikstrom et al., 2007). However, another possible explanation for the lack of influence of the brace is that the examination of the time to stabilize the ground reaction forces following a jumplanding may not be a sensitive enough measure to detect the influence of the application of a brace. Additional investigation is needed to determine what forms of functional testing may be able to distinguish the effect of the ankle brace, or if it simply does not exist.

Previous investigations have suggested there are alterations in ankle positioning in those with ankle instability prior to making ground contact (Delahunt et al., 2006; Delahunt, Monaghan, & Caulfield, 2007; Wright, Neptune, van den Bogert, & Nigg, 2000).

While the information related to bracing is limited, a recent paper

by Delahunt et al. (Delahunt et al., 2009) have demonstrated that ankle taping is effective at limiting ankle motion prior to ground impact during landing in subjects with CAI, supporting the need for similar investigations using bracing interventions. Perhaps it will be more telling to focus on the pre-landing changes that bracing may elicit in motion control and neuromuscular control changes in future studies (Eils & Rosenbaum, 2003). However, if the brace successfully limited or controlled ankle motion prior to landing, it does not appear that this had a large influence on the task goal because dynamic stability did not change with the brace. Because it is established that the ankle braces can reduce injury, it is important to determine what testing methods besides TTS can provide transparency to this relationship in the laboratory setting.

Gribble et al. (Gribble et al., 2006), examining the effects of laceup braces on the activation of the peroneal muscles during lateral shuffling, found no significant differences between braced conditions. The conclusions were that the use of ankle braces did not produce immediate changes in muscle activation or changes in activation following short-term brace use. This is related to the findings in this current study as each subject only wore the brace for a short amount of time, but did not experience any significant changes, positively or negatively, during this dynamic task.

A final point for consideration may be in the methodological design. In the previous studies utilizing dynamic stability measures during landing (Brown et al., 2004; Gribble & Robinson, 2009; Ross

& Guskiewickz, 2004; Ross et al., 2005; Ross et al., 2008), comparisons are made between a group of subjects with lingering ankle pathology and a group of matched controls, with the control subjects demonstrating better dynamic postural stability consistently. In the previous paper by Wikstrom et al. (Wikstrom et al., 2006), only the injured sides of FA subjects were included with the control comparison being the no brace condition. In our study design, we attempted to build on this previous paper by also comparing the effects of bracing between the injured and noninjured limbs of CAI subjects. There is some evidence of bilateral changes in static postural control related to ankle injury (Evans, Hertel, & Sebastianelli, 2004). However, in one measure of dynamic postural control, the Star Excursion Balance Test, unilateral deficits have been reported in CAI populations (Gribble, Hertel, Denegar, & Buckley, 2004; Hertel, Braham, Hale, & Olmsted-Kramer, 2006; Olmsted, Carcia, Hertel, & Shultz, 2002). Most of the studies that have used the jump-landing procedure with a dynamic postural control measure similar to this present study have only compared the injured limb with a limb of a control group and have reported a group effect for the CAI group, making conclusions about bilateral deficits difficult to make (Brown & Mynark, 2007; Brown et al., 2004; Ross & Guskiewickz, 2004; Ross et al., 2005; Ross et al., 2009; Wikstrom et al., 2005; Wikstrom et al., 2007). However, one study has made group and side comparisons between and within CAI and healthy groups using TTS, reporting a deficit in the dynamic postural control in the affected ankle compared to the non-affected ankle in the CAI group (Gribble & Robinson, 2009). While our current study as well as that of Wikstrom et al. (Wikstrom et al., 2006) report no differences in dynamic postural control in the A/P and M/L planes during jump-landing related to the brace when only utilizing injured populations, there is a need in future studies to compare the effect of the brace between injured and non-injured groups. The limited information suggests that bilateral differences exist in this measurement (Gribble & Robinson, 2009), justifying our study design. However, additional investigation in this area should include a healthy control group for further comparison.

A limitation to the jump-landing procedures we used is that the horizontal jumping distance of 70 cm, while used consistently in the literature (Gribble & Robinson, 2009; Ross & Guskiewickz, 2003, 2004; Ross et al., 2005; Shaw et al., 2008), may not be as ideal as using a distance normalized to each subject’s height or leg length.

Future investigation is needed to determine what, if any, improvement in the technique may be gained by utilizing a normalized horizontal jumping distance.

5. Conclusion This study was designed to lend support for the use of an ankle brace in subjects with CAI during jumping and landing tasks.

Although the results of this study do not support these conclusions, it may provide an important direction in examining the connection between TTS, ankle bracing, and those with CAI. While TTS is a useful outcome tool for identifying deficits in subjects with CAI and improvements related to ankle rehabilitation, this measure of dynamic stability does not appear to be sensitive in detecting the influence of the application of an ankle brace in this pathological group. Researchers need to establish what other testing methods will be the best for determining the outcome of the application of an ankle brace in the laboratory setting to coincide with the epidemiology data that support the use of these devices.

Conflict of interest statement None.

P.A. Gribble et al. / Physical Therapy in Sport 11 (2010) 3–7

Ethical statement The university Institutional Review Board of the institution employing the authors provided approval for this study.

References Ashton-Miller, J., Ottaviani, R., Hutchinson, C., & Wojtys, E. (1996). What best protects the inverted weightbearing ankle against further inversion? Evertor muscle strength compares favorably with shoe height, athletic tape, and three orthoses. American Journal of Sports Medicine, 24(6), 800–809.

Brown, C., & Mynark, R. (2007). Balance deficits in recreational athletes with chronic ankle instability. Journal of Athletic Training, 42(3), 367–373.

Brown, C., Ross, S., Mynark, R., & Guskiewickz, K. (2004). Assessing functional ankle instability with joint position sense, time to stabilization, and electromyography. Journal of Sport Rehabilitation, 13(2), 122–134.

Caulfield, B., & Garrett, M. (2004). Changes in ground reaction force during jump landing in subjects with functional instability of the ankle joint. Clinical Biomechanics, 19(6), 617–621.

Cohen, J. (1988). Statistical power analysis for behavioral sciences (2nd ed.). Hillsdale (NJ): Lawrence Erlbaum Associates.

Cordova, M., Ingersoll, C., & LeBlanc, M. (2000). Influence of ankle support on joint range of motion before and after exercise: a meta-analysis. Journal of Orthopaedic and Sports Physical Therapy, 30(4), 170–177.

Cordova, M., Scott, B., Ingersoll, C., & LeBlanc, M. (2005). Effects of ankle support on lower-extremity functional performance: a meta-analysis. Medicine and Science in Sports and Exercise, 37(4), 635–641.

Delahunt, E., Monaghan, K., & Caulfield, B. (2006). Changes in lower limb kinematics, kinetics, and muscle activity in subjects with functional instability of the ankle joint during a single leg drop jump. Journal of Orthopaedic Research, 24(10), 1991–2000.

Delahunt, E., Monaghan, K., & Caulfield, B. (2007). Ankle function during hopping in subjects with functional instability of the ankle joint. Scandinavian Journal Medicine and Science in Sports, 17(6), 641–648.

Delahunt, E., O’Driscoll, J., & Moran, K. (2009). Effects of taping and exercise on ankle joint movement in subjects with chronic ankle instability: a preliminary investigation. Archives of Physical Medicine and Rehabilitation, 90(8), 1418.

Eils, E., & Rosenbaum, D. (2003). The main function of ankle braces is to control the joint position before landing. Foot and Ankle International, 24(3), 263–268.

Eils, E., Demming, C., Kollmeier, G., Thorwesten, L., Vo¨lker, K., & Rosenbaum, D. (2002). Comprehensive testing of 10 different ankle braces. Evaluation of passive and rapidly induced stability in subjects with chronic ankle instability.

Clinical Biomechanics, 17(7), 526–535.

Eils, E., Imberge, S., Vo¨lker, K., & Rosenbaum, D. (2007). Passive stability characteristics of ankle braces and tape in simulated barefoot and shoe conditions.

American Journal of Sports Medicine, 35(2), 282–287.

Evans, T., Hertel, J., & Sebastianelli, W. (2004). Bilateral deficits in postural control following lateral ankle sprain. Foot and Ankle International, 25(11), 833–839.

Greene, T. A., & Hillman, S. K. (1990). Comparison of support provided by a semirigid orthosis and adhesive ankle taping before, during, and after exercise. The American Journal of Sports Medicine, 18(5), 498–506.

Gribble, P., & Robinson, R. (2009). Alterations in knee kinematics and dynamic stability associated with chronic ankle instability. Journal of Athletic Training, 44(4), 350–355.

Gribble, P., Hertel, J., Denegar, C., & Buckley, W. (2004). The effects of fatigue and chronic ankle instability on dynamic postural control. Journal of Athletic Training, 39(4), 321–329.

Gribble, P., Radel, S., & Armstrong, C. (2006). The effects of ankle bracing on the activation of the peroneal muscles during a lateral shuffling movement. Physical Therapy in Sport, 7(1), 14–21.

Gross, M., Bradshaw, M., Ventry, L., & Weller, K. (1987). Comparison of support provided by ankle taping and semirigid orthosis. Journal of Orthopaedic and Sports Physical Therapy, 9(1), 33–39.

Gross, M., & Liu, H. (2003). The role of ankle bracing for prevention of ankle sprain injuries. Journal of Orthopaedic and Sports Physical Therapy, 33(10), 572–577.

Gudibanda, A., & Wang, Y. (2005). Effect of the ankle stabilizing orthosis on foot and ankle kinematics during cutting maneuvers. Research in Sports Medicine, 13(2), 111–126.

Hale, S., & Hertel, J. (2005). Reliability and sensitivity of the foot and ankle disability index in subjects with chronic ankle instability. Journal of Athletic Training, 40(1), 35–40.

Hertel, J. (2002). Functional anatomy, pathomechanics, and pathophysiology of lateral ankle instability. Journal of Athletic Training, 37(4), 364–375.

7

Hertel, J., Braham, R., Hale, S., & Olmsted-Kramer, L. (2006). Simplifying the star excursion balance test: analyses of subjects with and without chronic ankle instability. Journal of Orthopaedic and Sports Physical Therapy, 36(3), 131–137.

Kimura, I., Nawoczenski, D., Epler, M., & Owen, M. (1987). Effect of the AirStirrup in controlling ankle inversion stress. Journal of Orthopaedic and Sports Physical Therapy, 9(5), 190–193.

Mickel, T., Bottoni, C., Tsuji, G., Chang, K., Baum, L., & Tokushige, K. (2006).

Prophylactic bracing versus taping for the prevention of ankle sprains in high school athletes: a prospective, randomized trial. Journal of Foot and Ankle Surgery, 45(6), 360–365.

Olmsted, L. C., Carcia, C. R., Hertel, J., & Shultz, S. J. (2002). Efficacy of the star excursion balance tests in detecting reach deficits in subjects with chronic ankle instability. Journal of Athletic Training, 37(4), 501–506.

Olmsted, L., Vela, L., Denegar, C., & Hertel, J. (2004). Prophylactic ankle taping and bracing: a numbers-needed-to-treat and cost-benefit analysis. Journal of Athletic Training, 39(1), 95–100.

Pedowitz, D., Reddy, S., Parekh, S., Huffman, G., & Sennett, B. (2008). Prophylactic bracing decreases ankle injuries in collegiate female volleyball players. American Journal of Sports Medicine, 36(2), 324–327.

Ross, S., & Guskiewickz, K. (2003). Time to stabilization: a method for analyzing dynamic postural stability. Athletic Therapy Today, 8(3), 37–39.

Ross, S., & Guskiewickz, K. (2004). Examination of static and dynamic postural stability in individuals with functionally stable and unstable ankles. Clinical Journal of Sports Medicine, 14(6), 332–338.

Ross, S., Guskiewickz, K., & Yu, B. (2005). Single-leg jump-landing stabilization times in subjects with functionally unstable ankles. Journal of Athletic Training, 40(4), 298–304.

Ross, S., Guskiewickz, K., Gross, M., & Yu, B. (2008). Assessment tools for identifying functional limitations associated with functional ankle instability. Journal of Athletic Training, 43(1), 44–50.

Ross, S., Guskiewickz, K., Gross, M., & Yu, B. (2009). Balance measures for discriminating between functionally unstable and stable ankles. Medicine and Science in Sport and Exercise, 41(2), 399–407.

Rovere, G. D., Clarke, T. J., Yates, C. S., & Burley, K. (1988). Retrospective comparison of taping and ankle stabilizers in preventing ankle injuries. The American Journal of Sports Medicine, 16(3), 228–233.

Schmidt, M., Sulsky, S., & Amoroso, P. (2005). Effectiveness of an outside-the-boot ankle brace in reducing parachuting related ankle injuries. Injury Prevention, 11(3), 163–168.

Sharpe, S., Knapik, J., & Jones, B. (1997). Ankle braces effectively reduce recurrence of ankle sprains in female soccer players. Journal of Athletic Training, 32(1), 21–24.

Shaw, M., Frye, J., & Gribble, P. (2008). Effects of ankle bracing and fatigue on time to stabilization among collegiate volleyball athletes. Journal of Athletic Training, 43(2), 164–171.

Sitler, M., Ryan, J., Wheeler, B., McBride, J., Arciero, R., Anderson, J., et al. (1994). The efficacy of a semirigid ankle stabilizer to reduce acute ankle injuries in basketball. A randomized clinical study at west point. American Journal of Sports Medicine, 22(4), 454–461.

Stasinopoulos, D. (2004). Comparison of three preventive methods in order to reduce the incidence of ankle inversion sprains among female volleyball players. British Journal of Sports Medicine, 38(2), 182–185.

Surve, I., Schwellnus, M., Noakes, T., & Lombard, C. (1994). A fivefold reduction in the incidence of recurrent ankle sprains in soccer players using the sportstirrup orthosis. American Journal of Sports Medicine, 22(5), 601–606.

Thacker, S., Stroup, D., Branche, C., Gilchrist, J., Goodman, R., & Weitman, E. (1999).

The prevention of ankle sprains in sports: a systematic review of the literature.

American Journal of Sports Medicine, 27(6), 753–760.

VanMeter, A., & Gribble, P. (2008). Time to stabilization: number of practice and test trials needed and the influence of limb dominance. Journal of Athletic Training, 43(2-S), 15.

Wikstrom, E., Arrigenna, M., Tillman, M., & Borsa, P. (2006). Dynamic postural stability in subjects with braced, functionally unstable ankles. Journal of Athletic Training, 41(3), 245–250.

Wikstrom, E., Tillman, M., & PA, B. (2005). Detection of dynamic stability deficits in subjects with functional ankle instability. Medicine and Science in Sports and Exercise, 37(2), 169–175.

Wikstrom, E., Tillman, M., Chmielewski, T., Cauraugh, J., & PA, B. (2007). Dynamic postural stability deficits in subjects with self-reported ankle instability.

Medicine and Science in Sport and Exercise, 39(3), 397–402.

Wright, I. C., Neptune, R. R., van den Bogert, A. J., & Nigg, B. M. (2000). The influence of foot positioning on ankle sprains. Journal of Biomechanics, 33(5), 513.

Yeung, M., Chan, K., & So, C. (1994). An epidemiological survey on ankle sprain.

British Journal of Sports Medicine, 28, 112–116.