Fatigue related electromyographic coherence analysis between agonistic elbow flexion muscles

Objective The aim of this study was to examine coherence between antagonistic elbow muscles and thus to explore the characteristics of common neural inputs to co-contracting agonistic elbow muscles during sustained isometric fatiguing contraction. Method Ten healthy male subjects participated in this study. With elbow flexion muscle at 50% maximum voluntary contraction (MVC) to induce muscle fatigue, surface electromyographic signals (sEMG) was collected from biceps brachii (BB) and brachioradialis (BR). sEMG was divided into two segments and coherence analysis was conducted between BB and BR electromyographic signals in both segments. Result A significant increase in EMG-EMG coherence in the beta frequency bands was observed in the second half of the fatiguing contraction compared to the first half of the fatiguing contraction. No significant difference was observed in the tremor and gamma band coherence between the first and the second half of the fatiguing contraction. Conclusion During the sustained isometric fatiguing contraction following the target force level at 50% MVC, a significant difference was found between the first and second half of the fatiguing contraction in Beta Band, which indicates the increased coupling between synchronized cortical neurons and the motoneuron pool. This suggests an increase in common neural input across these muscles, which may be cortical in origin.