Hill Ethan, Housh Terry, Smith Cory, Schmidt Richard, Johnson Glen
Department of Nutrition and Health Sciences, University of Nebraska-Lincoln, Lincoln, NE 68505, USA.
Sports (Basel). 2016 Sep 30;4(4):47. doi: 10.3390/sports4040047.
Electromyographic (EMG) and mechanomyographic (MMG) studies of fatigue have generally utilized maximal isometric or dynamic muscle actions, but sport- and work-related activities involve predominately submaximal movements. Therefore, the purpose of the present investigation was to examine the torque, EMG, and MMG responses as a result of submaximal, concentric, isokinetic, forearm flexion muscle actions.
Twelve men performed concentric peak torque (PT) and isometric PT trials before (pretest) and after (posttest) performing 50 submaximal (65% of concentric PT), concentric, isokinetic (60°·s), forearm flexion muscle actions. Surface EMG and MMG signals were simultaneously recorded from the biceps brachii and brachioradialis muscles.
The results of the present study indicated similar decreases during both the concentric PT and isometric PT measurements for torque, EMG mean power frequency (MPF), and MMG MPF following the fatiguing workbout, but no changes in EMG amplitude (AMP) or MMG AMP.
These findings suggest that decreases in torque as a result of fatiguing, dynamic muscle actions may have been due to the effects of metabolic byproducts on excitation⁻contraction coupling as indicated by the decreases in EMG MPF and MMG MPF, but lack of changes in EMG AMP and MMG AMP from both the biceps brachii and brachioradialis muscles.
疲劳的肌电图（EMG）和机械肌电图（MMG）研究通常采用最大等长或动态肌肉动作，但与运动和工作相关的活动主要涉及次最大运动。因此，本研究的目的是检查次最大、向心、等速前臂屈曲肌肉动作后的扭矩、EMG和MMG反应。
12名男性在进行50次次最大（向心峰值扭矩的65%）、向心、等速（60°·秒）前臂屈曲肌肉动作之前（预测试）和之后（后测试）进行向心峰值扭矩（PT）和等长PT试验。同时从肱二头肌和肱桡肌记录表面EMG和MMG信号。
本研究结果表明，在疲劳运动后，向心PT和等长PT测量中，扭矩、EMG平均功率频率（MPF）和MMG MPF均有类似程度的下降，但EMG幅度（AMP）或MMG AMP没有变化。
这些发现表明，疲劳性动态肌肉动作导致的扭矩下降可能是由于代谢副产物对兴奋-收缩偶联的影响，如EMG MPF和MMG MPF的下降所示，但肱二头肌和肱桡肌的EMG AMP和MMG AMP均未发生变化。
