胫骨前肌疲劳时比目鱼肌诱发肌电图H波的变化及其机制探讨

为了解主动肌疲劳时拮抗肌脊髓运动神经元兴奋性变化的规律 ,本研究采用踝关节背屈运动形式 ,对胫骨前肌 (主动肌 )疲劳状态下的比目鱼肌 (拮抗肌 )诱发肌电图H波成分进行了观察。并以压迫阻断胫骨前肌Ⅰa类神经纤维传导的方法 ,对比目鱼肌H波变化机制进行了分析探讨。结果发现 :(1)胫骨前肌疲劳后 ,比目鱼肌H波明显受到抑制 ,与安静时比较呈非常显著性差异 ;(2 )胫骨前肌Ⅰa类神经纤维传导被阻断后 ,比目鱼肌H波的抑制现象没有解除。表明 ,胫骨前肌疲劳时比目鱼肌H波被抑制的原因 ,可能是由于主动肌内的代谢产物激活了Ⅲ·Ⅳ类神经纤维的感受器 ,Ⅲ·Ⅳ类神经纤维的传入冲动增加 ,使Ⅰa抑制性中间神经元被激活 ,导致拮抗肌脊髓运动神经元的兴奋性受到了抑制

Changes in H Wave of Evoked EMG in Soleus Muscle during Tibialis Anterior Muscle Fatigue and Its Mechanism

To find out the rules of changes in excitability of antagonist spinal motor neurons when the muscle fatigue of agonist occurs, ankle joint dorsal flexion form was applied to investigate the soleus muscle H wave under the state of tibialis anterior muscle fatigue. We analyzed and explored the mechanism of the changing by using the method of pressing and blocking the conduction of Ia afferent fibers of tibialis anterior muscle. Results were: (1)soleus muscle H wave was inhibited obviously under the state of tibialis anterior muscle fatigue and the difference was significant when compared with the quiet state. (2)after the conduction of Ia afferents tibialis anterior muscle was blocked, the inhibiting phenomenon of H wave of soleus muscle did not disappear. Accordingly, we conclude that under the state of agonist fatigue, the reason for inhibition of antagonist spinal neurons may due to the activation of the receptors of Ⅲ·Ⅳ afferent fibers by metabolic products of agonist, and thus enable the Ⅲ·Ⅳ afferent fibers to increase the afferent impulse, activate the Ia inhibitory interneurones and finally inhibit the excitability of spinal motor neurons of antagonist.