Local muscle fatigue and sEMG change in two-joint isometric flexion

Objective:To investigate the relationship between sEMG signal and force during fatiguing contractions in flexor carpi ulnaris muscle(FCU) and biceps brachii muscle(BB) respectively based on wrist and elbow flexions. Method:Ten young subjects performed isometric contractions at different load levels(30%,55%,80%MVC) and sEMG signal of FCU, BB and each joint MVCs before and after fatiguing contractions were recorded.Result:The MVCs of wrist flexion and elbow flexion decreased significantly after muscle fatigue progress in forearm and upper arm induced by different load level, and displayed marked load level effect. The mean power frequency(MPF) and median frequency(MF) of BB and FCU showed same varying pattern. There was significant correlation between MPF slope, MF slope and the force drop of BB, FCU at any level.Conclusion:The slope of MPF and MF during local muscle fatigue progress can be used to predict the corresponding joint muscle force changes.