High-Density Surface Electromyography Feedback Enhances Fibularis Longus Recruitment in Chronic Ankle Instability

Purpose: This study aimed to determine whether individuals with chronic ankle instability (CAI) can activate the fibularis longus compartments with high-density surface electromyography (HD-EMG) biofeedback to the same extent as those without CAI; and to analyze the effect of ankle position on compartment activation in individuals with CAI using HD-sEMG feedback.

Methods: Sixteen volunteers per group (CAI and No-CAI). The sEMG amplitude at each compartment (anterior and posterior) and the barycenter of the spatial sEMG amplitude distribution of the fibularis longus were recorded during eversion in neutral and plantarflexion positions at 30% and 70% of maximum voluntary contraction (MVC) force, both with and without visual feedback on the spatial sEMG amplitude distribution.

Results: sEMG amplitude of the posterior compartment of the fibularis longus in the CAI group trained with HD-sEMG feedback during eversion at 70% MVC (in plantarflexion) was significantly higher than without HD-sEMG feedback (95% CI = 3.75 to 34.50% root mean square, RMS) and was similar to the activation of the No-CAI group (95% CI = -14.34 to 34.20% RMS). Furthermore, individuals with CAI who underwent training with HD-sEMG feedback in plantarflexion exhibited a posterior displacement of the barycenter (95% CI = 0.56 to 2.84 mm).

Conclusions: Utilizing HD-sEMG feedback during eversion in plantarflexion position increases activation of the fibularis longus posterior compartment in individuals with CAI to the same extent as healthy people. HD-sEMG-based topographic maps can serve as effective feedback training to restore motor control of the ankle. Long-term efficacy for improving motor function requires investigation through longitudinal studies.