| Sumario: | To investigate how fatigue impacts the ankle control strategy of athletes with chronic ankle instability (CAI) during stair descent. Case-control study. Sports Biomechanics Laboratory. A total of 50 male athletes (N=50) (25 CAI and 25 non-CAI) 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 <.05) and lower medial gastrocnemius RMS (P FDR <.05), whereas fatigue caused athletes with CAI to increase maximum inversion and plantarflexion torque (P FDR <.05); maximum eversion torque, tibialis anterior, and peroneus longus RMS decreased (P FDR <.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 reinjury.
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