The purpose of this study was to determine whether different rest intervals affect performance on the Star Excursion Balance Test (SEBT) associated with chronic ankle instability (CAI) and whether foot-tibia coordination can be associated factors that may help discriminate between individuals with and without CAI during the SEBT. Participants included forty-eight individuals with (n = 24) and without CAI (n = 24). Subjects completed 3 trials in each of the 3 reach directions (anteromedial, medial, posteromedial) in random order. A total of three visits were required to complete the 3 rest interval conditions (10, 20, 40 s). Coupling angles (CA) of tibial internal rotation/dorsiflexion (TIR/DF) and tibial internal rotation/eversion (TIR/EV) were calculated and compared between groups in each direction for each rest interval. Individuals with CAI showed greater CAs of TIR/DF in the M direction (p = 0.01) and of TIR/EV in the P direction (p = 0.04) than healthy individuals in 20 s rest interval time. Overall, joint CAs were different between healthy individuals and those with CAI during the SEBT regardless of rest interval. Based on these results, rest interval and a natural result of CAI could alter ankle joint coordination in comparison of healthy individuals when performing the SEBT.
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