Hwang Ing-Shiou, Huang Cheng-Ya, Wu Pei-Shan, Chen Yi-Ching, Wang Chun-Hou
School of Physical Therapy, National Cheng Kung University, Tainan, Taiwan.
Int J Neurosci. 2008 Sep;118(9):1317-30. doi: 10.1080/00207450802055606.
The objective of this study was to examine the changes in H reflex sensitivity after neuromuscular fatigue associated with fluctuations of the M wave. In the maximal and submaximal voluntary contraction (MVC and SMVC) paradigms, subjects performed voluntary plantarflexion at 100% MVC and 40% MVC respectively until the limit of torque maintenance was reached. In the submaximal electrical stimulation (SMES) paradigm, the tricep surae was exhausted with sustained electrical stimulation of 40% of the maximal tolerable intensity at a 40-Hz stimulus rate. The H reflexes and maximal M waves (M(max)) of the soleus were recorded before and after the three fatigue paradigms, and the H reflex was standardized with M(max) to minimize possible bias due to fatigue-induced M wave fluctuation. The results showed a significant increase in the standardized H reflex due to the SMES paradigm in spite of M(max) potentiation. The SMVC paradigm led to a reduction in size of the standardized H reflex without modification of M(max), whereas the standardized H reflex was not mediated by the MVC paradigm, which contributed to a noticeable M(max) potentiation. The present study underscored the fact that the H reflex sensitivity and M wave amplitude were not necessarily suppressed consequent to neuromuscular fatigue, but varied with the activation history of a muscle for size-dependent efficacy of the Ia transmission pathways and postactivation potentiation.
本研究的目的是检测与M波波动相关的神经肌肉疲劳后H反射敏感性的变化。在最大和次最大自主收缩（MVC和SMVC）范式中，受试者分别以100%MVC和40%MVC进行自主跖屈，直至达到扭矩维持极限。在次最大电刺激（SMES）范式中，以40Hz的刺激频率对腓肠肌进行持续电刺激，刺激强度为最大耐受强度的40%，直至肌肉疲劳。在三种疲劳范式前后记录比目鱼肌的H反射和最大M波（M(max)），并将H反射用M(max)进行标准化，以尽量减少因疲劳引起的M波波动可能造成的偏差。结果显示，尽管M(max)增强，但由于SMES范式，标准化H反射显著增加。SMVC范式导致标准化H反射大小减小，而M(max)未改变，而标准化H反射不受MVC范式介导，MVC范式导致明显的M(max)增强。本研究强调了这样一个事实，即神经肌肉疲劳后，H反射敏感性和M波振幅不一定会受到抑制，而是会随着肌肉的激活历史而变化，以实现Ia传递通路和激活后增强的大小依赖性效应。
