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图变化。本研究开发的计算机子程序包括用于获得平均工频和表面肌电信号振幅均方根值的快速傅立叶变换算法和模数转换程序。通过输入各种波形对系统进行校准，发现上述肌电参数的测定误差在0.5%以内。根据deVries等人（1981）和Moritani等人（1985）描述的程序，进行了初步研究，以确定刺激频率和肌肉力量输出之间的关系。结果表明，经皮模拟胫骨后神经，以75 ~ 110 V， 500 uV， 50 ~ 80 hz的脉冲宽度刺激，可以达到人体三头肌表面肌群最大自主收缩时的力输出。为了确定肌肉纤维类型（比目鱼肌和腓肠肌）与疲劳特征之间的关系，对5名男性受试者进行了测试。结果发现，与连续高频（50和80赫兹）电刺激所获得的自愿收缩力相比，力输出急剧下降。3 .体表和肌内电极记录的质量动作电位（m波）表明，力的下降伴随着m波振幅的逐渐下降和动作电位传导速度的减慢，表明肌膜兴奋受损的存在。然而，在持续的最大自主收缩时，这些现象没有被观察到，但随着表面肌电谱平均工频的显著降低，运动单元（MU）放电频率衰减和平均峰值幅度下降。与比目鱼肌相比，快速收缩纤维较多的腓肠肌在这些参数上有明显的变化，提示疲劳时肌肉代谢谱可能在调节肌膜兴奋性中起重要作用。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