Ankle bracing's effect on lower extremity biomechanics during athletic performance measures: an exploratory study

Introduction: Ankle braces are commonly worn in athletic populations to prevent ankle injuries. Restriction of ankle range of motion (ROM) is considered the main mechanism by which ankle braces prevent ankle injuries. The effects of restricting normal ankle ROM on lower extremity injury, biomechanics, and athletic performance, however, remains unclear. Although the research is conflicting, increases in non-ankle lower extremity injuries when wearing ankle braces has been observed, in addition to changes in lower extremity kinematics, kinetics, vertical jump height, and agility. Decreases in vertical jump height when wearing ankle braces have previously been attributed to restriction of ankle ROM and altered lower extremity kinematics. No studies, however, have considered the effect that ankle braces may have on muscular activation of the lower extremity, specifically proximal musculature of the knee and hip joint, on athletic performance. As such, the purpose of this study was to examine the effects of softshell and semirigid ankle braces on muscle electromyography (EMG), kinetics, and performance during a vertical jump test and cutting task. Methods: 42 physically active individuals (23 male, 19 female) were recruited into the study. Participants completed a Vertical Jump Test and cutting task on two separate days under three bilateral conditions: wearing no ankle braces, ASO® EVO® (AE) softshell ankle braces, or Active Ankle T1TM (T1) semi-rigid ankle braces. Vertical jump height, and mean EMG activity of the peroneus longus (PL), lateral gastrocnemius (LG), biceps femoris (BF), rectus femoris (RF), and gluteus medius (GM) muscles was collected during the landing and takeoff phase of the Vertical Jump Test. Similarly, time to compete the cutting task, as well as mean EMG activity of the peroneus longus (PL), lateral gastrocnemius (LG), biceps femoris (BF), rectus femoris (RF), and gluteus medius (GM) muscles was collected during the deceleration and propulsive phase of the cutting task. Ground reaction forces and impulse were also collected during each task and phase. Due to missing data, repeated measures one-way ANOVAs were conducted to compare the independent variable (brace condition) on each dependent variable. The alpha level was set at p < . 05 for the performance measures. After a Bonferroni adjustment, the alpha level was set at p < . 01, p < . 01, and p < . 017 for EMG, GRF, and impulse variables, respectively. Results: There was a significant decrease in vertical jump height when wearing ankle braces, F(2, 80) = 15.796, p < . 001, ηp2 = . 283. Bonferroni pairwise comparisons analysis revealed a significant decrease in vertical jump height when wearing the AE (2.09 (95% CI, 0.9 to 3.28) cm, p < . 001) and T1 (2.12 (95% CI, 1.058 to 3.193) cm, p < . 001) ankle braces, compared to no braces. There was a significant decrease in LG mean EMG activity during takeoff when wearing ankle braces, F(2, 68) = 5.597, p < . 001, ηp2 = . 141. Bonferroni pairwise comparisons analysis revealed a significant decrease in LG mean EMG activity when wearing the T1 ankle braces (7.34 (95% CI, -13.307 to -1.376) %MVC, p = . 012), compared to no braces. There was a significant increase in peak lateral GRF during takeoff, F(1.118, 43.585) = 39.80, p < . 001, ηp2= . 505. Bonferroni pairwise comparisons analysis revealed a significant increase in peak lateral GRF when wearing the AE (6.64 (95% CI, 4.066 to 9.233) %BW, p < . 001) and T1 (6.76 (95% CI, 4.131 to 9.404) %BW, p < . 001) ankle braces, compared to no braces. There was a significant decrease in peak lateral GRF, F(2, 74) = 5.746, p < . 001, ηp2 = . 134. Bonferroni pairwise comparisons analysis revealed a significant decrease in peak lateral BIOMECHANICS OF ANKLE BRACING iii GRF during landing when wearing the T1 ankle braces (-2.59 (95% CI, -4.432 to -0.764) %BW, p < . 001), compared to no braces. There was a significant increase in time to complete the cutting task, F(2, 76) = 17.242, p < . 001, partial η2 = 0.312. Bonferroni pairwise comparisons analysis revealed a significant increase in time to complete the cutting task when wearing the AE (0.16 (95% CI, .062 to .265) sec, p < . 001) and T1 (0.2(95% CI, .113 to .286) sec, p < . 001) ankle braces, compared to no braces. Conclusion: Based on the results of this study, both softshell and semi-rigid ankle braces significantly decreased vertical jump and cutting task performance. Furthermore, ankle braces decreased EMG activity of ankle musculature and altered GRFs during vertical jumping. Further research is needed to determine how changes in EMG activity and kinetics may affect injury, as well as performance during vertical jumping and cutting. Clinicians, athletes, trainers, and any users or prescribers of ankle braces should weigh the pros and cons of prophylactically bracing the ankle, especially from a performance perspective. BIOMECHANICS OF ANKLE BRACING iv