Influence of rest interval on foot-tibia coordination with chronic ankle instability during the Star Excursion Balance Test

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.