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

OBJECTIVE

To investigate how fatigue impacts the ankle control strategy of athletes with chronic ankle instability (CAI) during stair descent.

DESIGN

Case-control study.

SETTINGS: Sports Biomechanics Laboratory.

PARTICIPANTS

A total of 50 male athletes (N=50) (25 CAI and 25 non-CAI) were recruited.

INTERVENTIONS: Not applicable.

MAIN OUTCOME MEASURES: 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.

RESULTS

Pre-fatigue, athletes with CAI showed larger maximum eversion angle and dorsiflexion torque (PFDR<.05) and lower medial gastrocnemius RMS (PFDR<.05), whereas fatigue caused athletes with CAI to increase maximum inversion and plantarflexion torque (PFDR<.05); maximum eversion torque, tibialis anterior, and peroneus longus RMS decreased (PFDR<.05).

CONCLUSIONS

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.