Stiffness and proprioceptive contributions of ankle braces and the influence of localized muscle fatigue.

Ankle braces are a common treatment to reduce ankle sprain recurrence among individuals with chronic ankle instability (CAI). Bracing provides supplemental external joint stiffness and/or improved proprioceptive acuity. The goals of this study were to assess the effects of two ankle braces on joint position sense (JPS) and ankle stiffness, and determine whether bracing effects are reduced with localized muscle fatigue. Measures of JPS and ankle stiffness were obtained from participants with CAI (n=12) for three conditions (no brace, a neoprene wrap brace, and a semi-rigid brace), before and after inducing localized muscle fatigue at the ankle. Pre-fatigue JPS measures did not differ between brace conditions, but pre-fatigue stiffness was ∼0.8 and 2.5Nm/rad (∼5 and 14%) greater for the semi-rigid brace than the neoprene and no brace conditions, respectively. Fatigue increased absolute JPS errors by 0.3° (∼6 to 12%) across all conditions. Stiffness was unaffected by fatigue among females. Among males, fatigue increased stiffness by 0.75Nm/rad (∼3.3%) with the semi-rigid brace and decreased stiffness by 0.32Nm/rad (1.5%) with no brace. The semi-rigid brace may better protect males from sprains while either brace may be effective for females.