A Comparative Study of Muscle Fatigue during Electrically-induced and Voluntary Contractions.

1.我们开发了一个在线计算机分析系统，用于研究与肌肉疲劳相关的肌电变化。本研究开发的计算机子程序包括求取表面肌电幅的平均功率频率和均方根值的快速傅立叶变换算法和模数转换程序。通过馈送各种类型的波形对系统进行了标定，发现上述肌电参数的确定误差在0.5%以内。根据DeVries等人描述的程序，进行了一项初步研究，以确定刺激频率和肌力输出之间的关系。(1981)和Moritani等人。(1985年)。结果表明，对于人的小腿三头肌肌群，以75~110V的电压刺激胫后神经，以50~80 Hz的脉冲宽度500 UV刺激，可以匹配最大自主收缩时的力输出。…为了进一步确定肌肉纤维类型(比目鱼肌和腓肠肌)与疲劳特征之间的关系，对五名男性受试者进行了测试。结果发现，由于持续的高频(50&80赫兹)电刺激，与自主收缩时的力输出相比，力输出急剧下降。记录到的肌表电极和肌内电极的质量动作电位(M波)表明，肌力下降伴随着M波幅度的进行性下降和动作电位传导速度的减慢，表明存在受损的肌膜兴奋。然而，在持续的最大自主收缩过程中没有观察到这些现象，但有进行性运动单位(MU)放电频率的下降和平均峰电位幅度的下降，以及表面EMG频谱的平均功率频率的显著下降。由于快收缩纤维较多的腓肠肌与比目鱼肌相比，这些参数发生了显著的变化，提示肌肉的代谢特征在调节疲劳时肌膜的兴奋性方面可能起着重要的作用。较少

1. We have developed an on-line computer analysis system for studying electromyographic changes associated with muscular fatigue. The computer subroutines developed under the present study consisted of fast Fourier transform algorithm for obtaining mean power frequency and root mean square value of the surface EMG amplitude and analog-to-digital conversion programs. The system was calibrated by feeding various types of waveform and found that the above-decribed EMG parameters could be determined within 0.5% error.2. A preliminary study was undertaken to determine the relationship between stimulation frequency and muscular force output according to the procedures described by deVries et al. (1981) and Moritani et al. (1985). The results indicated that for the human triceps surae muscle group it was possible to match the force output during maximal voluntary contraction by percutaneously simulating the poterior tibial nerve with 75 - 110 V, stimulus pulse width of 500 uV at 50 - 80 Hz.3. … More To determine the relationship between muscle fiber types (Soleus and Gastrocnemius muscles) and fatigue characteristics, five male subjects were tested. It was found that force output was sharply declined in comparison to that obtained during voluntary contraction as a result of continuous high frequency (50 & 80 Hz) electrical stimulations. The recorded mass action potentials (M-wave) from the surface and intramuscular electrodes indicated that the force decline was accompanied by a progressive decline in M-wave amplitude and slowing of action potential conduction velocity, indicating the existence of impaied muscle membrane excitation.4. However, these phenomena could not be observed during sustained maximal voluntary contractions, but there were progressive motor unit (MU) firing frequency decay and mean spike amplitude decline along with significant decreases in mean power frequency of the surface EMG spectra. Since the gastrocnemius muscle with more fast-twitch fibers showed marked changes in these parameters as compared to the soleus muscle, it was suggested that the metabolic profiles of muscle might paly an important role in regulating the muscle membrane excitability during fatigue. Less