Junge D, Clark G T
School of Dentistry, University of California, Los Angeles 90024.
Arch Oral Biol. 1993 Jul;38(7):583-8. doi: 10.1016/0003-9969(93)90123-4.
The jaw-closing muscles differ from peripheral limb muscles in that the maximum attainable force does not decline following a sustained isometric contraction. Also, the averaged electromyographic (EMG)/force ratio in these muscles does not change with sustained contraction, whereas it increases in fatiguing limb muscles. The present study analysed EMG records from masseters in healthy male subjects. No statistically significant difference was seen between average rectified EMG signals at the beginning or the end of a sustained isometric contraction at 25-100% of maximum voluntary contraction (MVC). However, when the number of turns, or reversals of direction, was taken at various percentage MVC levels, a significant decrease was seen after 60s or at the end of the contraction. The turns/force ratio decreased monotonically with percentage MVC, but the ratio was not significantly different at the end of a contraction from that at the beginning. This result confirms an earlier suggestion that neuromuscular fatigue does not accompany sustained contractions of these muscles.
闭口肌与外周肢体肌肉不同，其在持续等长收缩后最大可达到的力量不会下降。此外，这些肌肉的平均肌电图（EMG）/力量比值不会随持续收缩而改变，而在疲劳的肢体肌肉中该比值会增加。本研究分析了健康男性受试者咬肌的肌电图记录。在最大自主收缩（MVC）的25%-100%进行持续等长收缩开始或结束时，平均整流肌电图信号之间未观察到统计学上的显著差异。然而，当在不同百分比MVC水平下记录转向次数或方向反转次数时，在60秒后或收缩结束时出现了显著下降。转向/力量比值随MVC百分比单调下降，但收缩结束时该比值与开始时无显著差异。这一结果证实了早期的一个观点，即这些肌肉的持续收缩不会伴随神经肌肉疲劳。
