|Abstract or Summary
- Ankle injuries comprise more than 15% of all sports injuries worldwide. The efficacy of the ankle taping for injury prevention has long been under scrutiny as numerous studies have shown that tape rapidly loses its ability to constrain ankle motion with exercise. Consequently, ankle braces (orthoses) are being used with increasing frequency for the prevention and functional management of ankle injuries. However, the motion restraining qualities of ankle orthoses have not been widely evaluated in closed kinetic chain environments under physiologic loads. The primary purpose of this study was to compare the abilities of four ankle orthoses (ankle taping, lace-up brace, semirigid orthosis and hybrid brace) against a control condition (no brace or tape) to control subtalar and talocrural motion during running on a laterally-tilted treadmill at 16.2 km/h before and after exercise. It has been hypothesized that ankle orthoses make a secondary contribution to injury prevention through enhanced proprioception. The secondary purpose of this study was to quantify the effects of the aforementioned ankle orthoses on
postural stability during single-limb stance following a bout of exercise. Fifteen healthy university students (8 men and 7 women) with no history of significant ankle injuries (age, mean ± SD: 22.9 ± 3.9 years) volunteered to participate in this study. Three-dimensional kinematic data were captured with an active infrared digital camera system sampling at 120 Hz. To address the first question, data analyses were performed using 2way univariate (Ankle Orthoses x Pre/Post-Exercise x Subjects) (5 x 2 x 15) repeated measures analysis of variance (ANOVA) to determine the existence of differences among three closed and four open kinematic chain dependent measures before and after exercise. Maximum inversion angles (MAXINV) were similar for all ankle orthoses, with no orthosis limiting inversion during tilted treadmill running significantly more than another, or compared to the control condition, either before or after exercise (p>.05). Pre-exercise MAXINV group means and standard deviations during treadmill running ranged from 6.8 ± 3.4 deg with the Royce Medical Speed Brace to 9.5 ± 4.1 deg in the tape condition; post-exercise MAXINV mean values ranged from 7.6 ± 3.2 deg for the Aircast Sport Stirrup to 9.1 ± 4.6 deg with closed basketweave tape. While not statistically significant (p=0.10), ankle taping provided the least amount of inversion restraint, both before and after the exercise bout. The MAXINV angles measured during treadmill running (8.2 ± 4.0 deg) and open chain inversion AROM measured with a goniometer
(34.5 ± 6.2 deg) were not related (r=-0.0003). The compressive forces present during closed kinetic chain activity are known to increase joint stability and thus may explain why MAXINV under dynamic varus loads was so much less in magnitude than inversion AROM measured under open kinetic chain conditions. The nonlinear relationship of these two variables supports our contention that reports of the motion controlling properties of ankle orthoses measured in open kinetic chain environments should not be used to infer the response characteristics of these same orthoses under dynamic, physiologic loads. To address the second question, data were analyzed using 3-way univariate (Ankle Orthoses x Pre/Post-Exercise x Eyes Open/Closed x Subjects) (5 x 2 x 2 x 15) repeated measures ANOVAs. Subjects' postural stability was assessed using a Biodex Balance System with eyes open and eyes closed conditions, before and after an exercise bout. The ankle orthoses evaluated did not influence postural stability as measured by mediolateral sway index, anteroposterior sway index, and overall sway index. Removal of visual perception via blindfolding resulted in significant decreases in all three measures of postural stability (p=.001). There was poor association among the closed chain postural stability parameters and the open chain AROM measures. These correlations ranged from r=.04 to .17, indicating minimal relationship between the amount of AROM permitted by the orthoses and postural stability as quantified by this method.