Instability of motor unit firing rates during prolonged isometric contractions in human masseter
Instability of motor unit firing rates during prolonged isometric contractions in human masseter
复制标题
人类咬肌长时间等长收缩期间运动单位放电率的不稳定
DOI：
10.1016/0006-8993(91)90467-a
复制
发表时间：
1991
期刊：
影响因子：
2.9
通讯作者：
T. Miles
中科院分区：
文献类型：
--
作者：
M. Nordstrom;T. Miles
在15 min持续时间的连续等长收缩过程中，使用肌内电极研究了多达4个同时活动的咬肌运动单元的放电模式，其中受试者将一个选定单元的平均放电率保持在10 Hz。通过这种范例，肌肉中一个单位的净兴奋（即平均放电率）得到控制。这作为其他活动单位在长时间收缩期间的功能状态的参考。随着平均发射率的一个单位在肌肉固定，58%的其他活动单位表现出缓慢的，在15分钟内的平均发射率显着变化。单位的初始发射率没有影响率的变化。在短期收缩中反映招聘顺序的原始解雇率等级在长期收缩中发生了变化。运动神经元净兴奋的这些差异性变化的解释尚不清楚;它们可能是运动神经元固有的，也可能是由反射通路介导的。选择性促进或抑制某些运动单位的持续激活意味着运动单位的原始大小结构组合可以在长时间收缩期间进行修改。
The firing patterns of up to 4 concurrently active masseter motor units were studied with intramuscular electrodes during a continuous isometric contraction of 15 min duration, in which the subject maintained the mean firing rate of one selected unit at 10 Hz. With this paradigm the net excitation (i.e. mean firing rate) of one unit in the muscle was controlled. This served as the reference for the functional state of other active units during the prolonged contraction. With the mean firing rate of one unit in the muscle fixed, 58% of other active units showed a slow, statistically-significant change in mean firing rate over the 15 min. The initial firing rate of the units did not influence the change in rate. The original firing rate hierarchy, which in short-term contractions reflects the recruitment order, was altered during the prolonged contraction. The explanation for these differential changes in motoneuron net excitation is not clear; they could be intrinsic to the motoneurons or perhaps mediated by reflex pathways. The selective facilitation or suppression of some motor units with continuous activation means that the original size-structured combination of motor units can be modified during a prolonged contraction.