Increased common corticospinal input during eyes-closed unilateral stance in people with chronic ankle instability

Neuromuscular control deficits and altered spinal and corticospinal mechanisms are central to chronic ankle instability (CAI) and its persistent symptoms, but the role of ankle muscle coordination and common neural inputs during unipedal stance in CAI remains unexplored. This study aimed to compare intermuscular coherence between individuals with CAI and healthy controls during single-leg stance and investigate functionality of intermuscular coherence to postural control. Sixteen CAI and 16 healthy control (HC) participants performed single-leg balance tasks under eyes-open and eyes-closed conditions. The surface electromyograms were recorded from tibialis anterior (TA), peroneus longus (PL), gastrocnemius medial head (GM), and soleus (SOL) muscles. Coherence was analysed for PL-TA, PL-SOL, PL-GM, SOL-TA and SOL-GM muscle pairs in the delta (0.5-5 Hz) and beta (15-35 Hz) frequency bands. The CAI group exhibited greater beta-band intermuscular coherence for PL-SOL, PL-GM and SOL-TA during eyes-closed stance but not in eyes-open conditions, compared to healthy controls, suggesting increased common corticospinal inputs to agonist-antagonist muscle pairs. Higher beta-band coherence in the antagonistic muscle pairs correlated with reduced COP complexity, suggesting that strengthened beta-band indicates reduced postural adaptability. These findings suggest increased common corticospinal inputs to agonist-antagonist muscle pairs in CAI individuals, suggesting reduced postural adaptability during eyes-closed stance. Future research should address methodological considerations and validate protocol for intermuscular coherence analysis during single-leg stance. Future studies should also include CAI copers to determine whether their common corticospinal inputs have returned to healthy levels, supporting the potential effectiveness of targeted neuromodulatory or rehabilitation interventions.