Effects of Ankle Bracing on Postural Sway

Abstract

Ankle bracing can alter postural control strategies during static and dynamic tasks, theoretically through mechanical constraint of the ankle joint and/or sensorimotor reorganization. While a majority of studies have focused on center of pressure (COP) characteristics or clinical tests of balance to explore this theory, fewer studies have investigated sway characteristics of the center of mass (COM). Additionally, the effects of various styles of ankle braces on postural sway remains inconclusive. Assessing the effects of ankle bracing on postural sway could provide additional insight into potential systemic motor adaptations that occur in response to ankle constraint. PURPOSE: Examine effects of lace-up and semi-rigid bracing on postural sway characteristics during a quiet-standing task. METHODS: Thirty-five adults between the ages of 18-30yrs (height: 1.72 ± 0.1m; mass: 75.49 ± 18kg) participated in the study. Participants performed a single one-minute trial of quiet-standing during each of the following conditions: No brace (NB), lace-up brace (LB), and semi-rigid brace (SRB). A ten-camera motion capture system was utilized to capture lower extremity positon. To assess postural sway, mediolateral (ML) and anteroposterior (AP) lower extremity COM trajectories were extracted, and root-mean-square deviation (RMSx, RMSy) and velocity (RMSvx, RMSvy) of the COM were calculated. Repeated-measures ANOVAs were employed to assess differences in postural sway measures across all conditions. RESULTS: Analysis revealed a significant main effect for RMSy (F = 7.061; p < .01). Pairwise comparisons indicated that RMSy was significantly lower in the SRB condition (1.770±1.698mm) compared to C (2.182 ±1.515mm) (p < .01). CONCLUSION: Results from study indicate that subjects exhibited an altered AP postural sway pattern when a semi-rigid brace is applied. These findings align with previous research reporting reduced AP COP excursions with ankle bracing during quiet-standing. Altered sway patterns with ankle bracing appears to support the presence of sensorimotor reorganization, possibly due to altered proprioceptive and/or haptic feedback stemming from greater mechanical constraint of the ankle joint.