Dimitrova N A, Dimitrov G V
Bulgarian Academy of Sciences, Centre of Biomedical Engineering, Acad. G.Bonchev Str., BL.105, 1113, Sofia, Bulgaria.
J Electromyogr Kinesiol. 2002 Oct;12(5):339-49. doi: 10.1016/s1050-6411(02)00046-9.
To realize possible reasons for changes in EMG amplitude characteristics with fatigue, we analyzed motor unit potentials (MUPs) and M-waves under simultaneous variations of the intracellular action potential (IAP) amplitude, duration, and shape as well as of the muscle fiber propagation velocity and desynchronization in activation of individual muscle fibers. Analysis was performed through computer simulation of MUPs and M-waves detected at different distances from active fibers in infinite anisotropic volume conductor. Changes in the IAP spike and negative after-potential were taken from in vitro experiments reported in the literature. It was shown that the amplitudes of MUP and M-wave detected simultaneously at different distances could decrease close to the active fibers, be almost unchanged at middle distances, and increase far from the fibers even under IAP amplitude decreasing. This reflected the distance-dependent effects of changes in the IAP profile along the fiber. Electrode position affected sensitivity of MUP and M-wave durations to changes in the IAP duration and propagation velocity. Thus, the signal area and RMS depended on electrode position and could change with fatigue in a way different from that of signal amplitude. The results can help to avoid misleading interpretation of EMG changes.
为了探究肌电图（EMG）幅度特征随疲劳变化的可能原因，我们分析了运动单位电位（MUPs）和M波，同时考虑了细胞内动作电位（IAP）的幅度、持续时间和形状变化，以及肌肉纤维的传播速度和单个肌肉纤维激活时的去同步化情况。通过计算机模拟在无限各向异性容积导体中距活动纤维不同距离处检测到的MUPs和M波来进行分析。IAP尖峰和负后电位的变化取自文献报道的体外实验。结果表明，即使在IAP幅度降低的情况下，在不同距离同时检测到的MUP和M波的幅度在靠近活动纤维处可能会降低，在中间距离处几乎不变，而在远离纤维处会增加。这反映了IAP沿纤维轮廓变化的距离依赖性效应。电极位置影响MUP和M波持续时间对IAP持续时间和传播速度变化的敏感性。因此，信号面积和均方根（RMS）取决于电极位置，并且可能随疲劳以不同于信号幅度的方式变化。这些结果有助于避免对EMG变化的误导性解释。
