Coherence Analysis between EEG and EMG in Low-level Isometric Elbow Flexor Muscle Fatigue Contraction

Objective:The aim of this study was to examine coherence between EEG and EMG in elbow flexor muscle fatigue duration induced by low-level isometric contraction and thus to explore the coupling of muscle and cortex during low-level isometric elbow flexor contraction induced muscle fatigue.Methods:Fifteen healthy male volunteers sustained isometric elbow flexion at 20% maximal level until exhaustion while their brain (EEG) and biceps brachii muscle (sEMG) activities were recorded.The initial and final 4.096second data were chosen and coherence was observed between sEMG of biceps brachii muscle and EEG recorded from Fz, C5, Cz, C6, Pz electrodes in alpha (8¹2 Hz) , beta (15³0 Hz) and gamma (30⁶0 Hz) bands.Results:The power of both EEG and EMG increased significantly in alpha, beta, gamma frequency bands while coherence in beta band between sEMG and EEG of C5and coherence in alpha band between sEMG and EEG of Pz increased significantly in final stage compared with initial stage.Conclusions:The coupling between contralateral sensorimotor cortex and muscle activities was enhanced as a result of constant low-level isometric fatiguing contraction.This may be related to changes of cortical regulation activities relevant to exercise-induced muscle fatigue.