Tokunaga T
Nihon Hotetsu Shika Gakkai Zasshi. 1989 Aug;33(4):804-17. doi: 10.2186/jjps.33.804.
During sustained isometric contraction of the jaw muscles, muscular fatigue causes a shift towards lower frequencies in the EMG frequency power spectrum. This shift is due to a reduction of myoelectric conduction velocity. The purpose of this study was to investigate the effect of surface electrode location on the estimates of frequency components, and to determine the appropriate frequency parameters of surface EMG which provided the best fit when comparing conduction velocity. Studies were performed in the masseter muscles of 8 healthy subjects. The myoelectric potentials were derived using 12 differential amplifiers from electrode arrays. The frequency parameters calculated were as follows: peak frequency, mean power frequency, cumulative power function (10, 25, 50 and 75%), median frequency ratio, low frequency ratio and measure H. As the results, following findings were obtained: 1. The high frequency content occurred at the region of end-plate zone and tendonous insertion of the muscle. 2. EMG spectra obtained during fatigue were shifted to lower frequencies for all regions except adjacent end-plate zone. 3. The relationships between conduction velocity and frequency parameters during fatiguing contractions were almost linear except peak frequency. 4. It was concluded that the location between distal end-plate and the tendon was "stable" zone for studying muscular fatigue.
在颌肌持续等长收缩过程中，肌肉疲劳会导致肌电图（EMG）频率功率谱向低频方向偏移。这种偏移是由于肌电传导速度降低所致。本研究的目的是探讨表面电极位置对频率成分估计的影响，并确定在比较传导速度时能提供最佳拟合的表面肌电图的合适频率参数。对8名健康受试者的咬肌进行了研究。使用来自电极阵列的12个差分放大器导出肌电电位。计算的频率参数如下：峰值频率、平均功率频率、累积功率函数（10%、25%、50%和75%）、中频比率、低频比率和测量值H。结果得到以下发现：1.高频成分出现在终板区和肌肉肌腱附着区域。2.除相邻终板区外，疲劳期间所有区域获得的肌电图频谱均向低频方向偏移。3.疲劳收缩期间传导速度与频率参数之间的关系除峰值频率外几乎呈线性。4.得出结论，远端终板与肌腱之间的位置是研究肌肉疲劳的“稳定”区域。
