Lower Extremity Muscle Activation during the Star Excursion Balance Test in Patients with Chronic Ankle Instability and Copers.

: The aim of this study was to assess the impact of ankle muscles on performance of the Star Excursion Balance Test (SEBT) among individuals with stable ankles, a history of ankle sprain, and chronic ankle instability (CAI). : Sixty subjects (twenty per group) performed the SEBT in each of the anterior (A), posteromedial (PM), and posterolateral (PL) directions. Normalized maximum reach distance (NMRD) and normalized mean amplitude of the tibialis anterior (NMA_TA), fibularis longus (NMA_FL), and medial gastrocnemius (NMA_MG) were measured during performance of the SEBT. : Copers have greater NMRD than subjects with stable ankles and those with CAI, and subjects with stable ankles also have greater NMRD than those with CAI in only the PL direction. Subjects with stable ankles and those with CAI showed greater NMA_TA than copers. The A direction showed greater NMA_TA than the PM and PL directions. Copers showed greater NMA_FL than subjects with stable ankles. Subjects with CAI showed greater NMA_MG than copers and subjects with stable ankles. The A and PL directions showed greater NMA_MG than the PM direction. : Overall, copers and/or subjects with CAI demonstrated altered neuromuscular function by compensating for their ankle muscles when compared to subjects with stable ankles due to a history of ankle sprain.