Camic Clayton L, Housh Terry J, Zuniga Jorge M, Bergstrom Haley C, Schmidt Richard J, Johnson Glen O
Exercise and Sport Science, University of Wisconsin-La Crosse, La Crosse, WI.
J Appl Biomech. 2014 Apr;30(2):255-61. doi: 10.1123/jab.2013-0178. Epub 2013 Oct 15.
The purpose of the current study was to examine the patterns of responses for torque, mechanomyographic (MMG) amplitude, MMG frequency, electromyographic (EMG) amplitude, and EMG frequency across 30 repeated maximal eccentric muscle actions of the leg extensors. Eleven moderately trained females performed an eccentric fatigue protocol at 30°/s with MMG and EMG signals recorded from the vastus lateralis. The results indicated there were significant (P<.05) decreases in MMG frequency (linear, r2=.395), EMG frequency (linear, r2=.177), and torque (linear, r2=.570; % decline=9.8±13.3%); increases in MMG amplitude (linear, r2=.783); and no change in EMG amplitude (r2=.003). These findings suggested that the neural strategies used to modulate torque during fatiguing eccentric muscle actions involved de-recruitment of motor units, reduced firing rates, and synchronization. In addition, the decreases in eccentric torque were more closely associated with changes in MMG frequency than EMG frequency. Thus, these findings indicated that MMG frequency, compared with EMG frequency, more accurately tracks fatigue during repeated maximal eccentric muscle actions.
本研究的目的是检测在腿部伸肌30次重复的最大离心肌肉动作过程中，扭矩、肌机械图（MMG）幅度、MMG频率、肌电图（EMG）幅度和EMG频率的反应模式。11名训练程度中等的女性以30°/s的速度进行离心疲劳实验，同时记录股外侧肌的MMG和EMG信号。结果表明，MMG频率（线性，r2 = 0.395）、EMG频率（线性，r2 = 0.177）和扭矩（线性，r2 = 0.570；下降百分比 = 9.8±13.3%）显著（P<0.05）下降；MMG幅度增加（线性，r2 = 0.783）；EMG幅度无变化（r2 = 0.003）。这些发现表明，在疲劳性离心肌肉动作过程中用于调节扭矩的神经策略包括运动单位的去募集、 firing率降低和同步化。此外，离心扭矩的下降与MMG频率的变化比与EMG频率的变化更密切相关。因此，这些发现表明，与EMG频率相比，MMG频率在重复的最大离心肌肉动作过程中能更准确地跟踪疲劳。
