Disruption of Ankle Control Strategies by Exercise-Induced Fatigue during Stair Descent in Athletes with Chronic Ankle Instability.

Abstract

To investigate how fatigue impacts the ankle control strategy of athletes with CAI during stair descent. Case-control study. Sports Biomechanics Laboratory. Fifty male athletes (25 CAI and 25 healthy controls) were recruited. Not applicable. Ankle joint angle and torque in inversion/eversion, internal/external rotation, and dorsiflexion/plantarflexion, and EMG root mean square (RMS) values of the medial gastrocnemius, tibialis anterior, and peroneus longus. Pre-fatigue, athletes with CAI showed larger maximum eversion angle and dorsiflexion torque (p_FDR <0.05) and lower GM RMS (p_FDR <0.05), while fatigue caused athletes with CAI to increase maximum inversion and plantarflexion torque (p_FDR <0.05); maximum eversion torque, TA, and PL RMS decreased (p_FDR <0.05). Pre-fatigue, athletes with CAI may adopt a compensatory protective strategy centered on an "excessive ankle eversion-dorsiflexion". However, fatigue disrupted this protective strategy, as reflected in a shift toward an "inversion-plantarflexion" pattern. These findings reveal that fatigue dismantles a key protective motor strategy in athletes with CAI during a common daily task. This highlights the need for clinicians and trainers to incorporate targeted endurance training for ankle evertor and dorsiflexor muscles to prevent re-injury.