双关节运动的局部肌肉疲劳与肌电变化

目的：以腕-肘关节为例，探讨不同水平运动负荷诱发尺侧腕屈肌（FCU）和肱二头肌（BB）疲劳过程中sEMG信号与各关节最大屈肌肌力的关系。方法：采集10名青年男性受试者在不同负荷水平（30％、55％、80％MVC）下疲劳过程中尺侧腕屈肌（FCU）和肱二头肌（BB）的表面肌电信号和各关节在疲劳前后的MVC。结果：不同运动负荷强度分别诱发前臂和上臂肌肉疲劳过程中，腕、肘关节最大屈肌肌力明显下降且具有明显负荷强度效应：BB和FCU的MPF与MF单调递减且下降率具有明显的负荷强度效应；不同负荷强度下BB和FCU的MPF和MF下降斜率与肘、腕关节最大屈肌肌力的下降比值之间有明显相关。结论：局部肌肉疲劳过程中MPF和MF下降率变化能够对相应关节最大肌力变化作出比较准确预测。

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.