疲劳引起肌电图功率谱右移—前一练习对后一练习的影响

SHIFTING TO RIGHT OF ELECTROMYOGRAPHIC POWER SPECTRUM CAUSED BY FATIGUE-THE INFLUENCE OF THE FIRST EXERCISE TO THE SECOND EXERCISE

本文采用肌电图定量分析技术研究并比较前、后两次虚步(武术中的一种基本步型)练习至疲劳的过程中,股直肌、股外肌表面肌电图功率谱及平均功率频率(MPF)的变化。实验发现前次及后次虚步练习的发展过程中,上述两块肌肉均出现功率谱逐渐左移,及MPF线性减少的现象。当比较两块肌肉前、后两次练习各时程(开始及持续时间的25%、50%、75%、100%)的肌电图功率谱,皆发现后次较前次右移,即高频成分增加,低频成分减少的现象,同时MPF也增加。这一现象在过去文献中尚未见过报导,推测可能由于前一练习所引起的疲劳尚未完全消除,为保持固定的姿势后次练习就需使用更大的力量,所以增加了快运动单位的募集,或有其它尚待研究的原因。

In this study the EMG quantitative analysis was used to research the changes of the power spectrum and mean power frequency (MPF) of the surface EMG recorded from the m. rectus femoris and m. vastus lateralis during the primary and following exercise of sustaining Xu-Bu ′a movement of Wu-Shu) posture fatigue. It was observed that the power spectrum shifted to left gradually and the MPF reduced nearially in both of the muscles during the first and the second exercise. Comparing the power spectrum recorded from these two muscles of two exercises in same time courses (onset, 25%, 50%, 75%, or 100% of the whole duration), we found that the power spectrum in the second exercise shifted to right from that of the first exercise, and the MPF increased. This phenomenon had never been reported. It was infered that it mignt be caused by the increased recruitment of the fast motor units, or by other causes need to be further investigated.