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Ankle Instability And Rest Intervals Impact Muscle Activation And Lower Extremity Kinematics During The Sebt: 2606 Board #129 June 3, 11: 00 AM - 12: 30 PM.

Shorter rest intervals between trials during functional tests negatively affects performance. While a 10 or 20 second rest interval is typically used during the Star Excursion Balance Test (SEBT), it is not known whether this is adequate for recovery between trials. If this results in acute fatigue, muscle activation and kinematics may be impacted. It is unknown whether there are differences in response between healthy individuals and those with chronic ankle instability (CAI). PURPOSE: To determine whether different rest intervals during the SEBT and the presence of CAI affect muscle activation and kinematics of the lower extremity during the SEBT. METHODS: 24 healthy (age:22.7±1.6 yrs) and 24 CAI subjects (age:21.9±2.3 yrs) participated. Subjects performed 3 trials in each of 3 directions (anteromedial;AM, medial:M, and posteromedial;PM) in random order. A total of 3 visits were needed to complete the 3 rest intervals (10, 20, 40 seconds). Normalized maximum reach distance, electromyographic activation of tibialis anterior (TA), peroneas longus (PL), and medial gastrocnemius (MG) muscles, and dorsiflexion (DF) and tibial internal rotation (TIR) excursions were calculated and compared between groups in each direction for each rest interval. RESULTS: Normalized maximum reach distance in CAI subjects was significantly greater than healthy subjects in all directions (AM: 89.9±5.9 vs. 74.5±7.4, M: 88.6±5.7 vs. 83.3±8.4, PM: 102.1±6.8 vs. 92.3±9.2). Healthy subjects demonstrated significantly greater mean amplitude (MA) of TA in all direction (AM: 38.3±22.3 vs. 21.5±11, M: 37.7±13.5 vs. 24.2±9.4, PM: 50.6±24 vs. 28.7±12.3), MA of PL in only AM direction (AM: 65.1±37.4 vs. 45.4±25.7), and MG in all directions than CAI (AM: 49.1±40.2 vs. 31.6±19.3, M: 47.1±34.2 vs. 28.8±19.7, PM: 40±33.2 vs. 26.3±17.3). CAI subjects demonstrated significantly greater DF excursion in all direction (AM: 15.9±5.4 vs. 20±5.3, M: 14.6±6.1 vs. 19.7±4.3, PM: 12.8±5.4 vs. 17.5±4.5) and TIR excursion in only anterior direction than healthy subjects (AM: 6.7±2.7 vs. 8.7±2.9). CONCLUSIONS: Rest interval time was not an appropriate fatigue factor for performance of the SEBT in individuals with CAI. However, muscle activation and multiplanar motion of the lower extremity were able to discriminate between individuals with and without CAI.