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目的:探讨肌疲劳发生过程中主动肌及其拮抗肌脊髓运动神经元兴奋性的变化规律。方法:以10名健康男子为研究对象,采用50%随意性最大肌肉收缩的踝关节等长收缩形式,观察踝关节跖屈和背屈运动前后比目鱼肌诱发肌电图H波和M波的变化。结果:(1)跖屈运动引起比目鱼肌疲劳后,H/Mmax(最大H波与最大M波振幅比值)下降至运动前的63.07±16.57%(P<0.01),且运动终止后较长时间仍未恢复到运动前水平。(2)背屈运动引起胫骨前肌疲劳后,其拮抗肌比目鱼肌H/Mmax下降至运动前的85.33±10.25%(P<0.01),而后逐渐恢复至运动前水平。(3)背屈运动引起胫骨前肌疲劳后,其拮抗肌比目鱼肌H波阈值与安静时比较明显升高。结论:肌疲劳时,不但主动肌脊髓运动神经元兴奋性受到抑制,拮抗肌脊髓运动神经元兴奋性也受到类似影响。
Objective: To investigate the changes of excitability of motor neurons in aortic muscle and antagonistic muscle during spinal cord injury. Methods: The changes of H wave and M wave of EMG induced by soleus muscle before and after plantar flexion and dorsiflexion were observed in 10 healthy male volunteers with isometric contraction of the ankle at 50% random maximum muscle contraction. . Results: (1) H / Mmax (ratio of maximum H wave to maximum M wave amplitude) decreased to 63.07 ± 16.57% (P <0.01) before exercise due to plantar flexion-induced fatigue, Has not returned to pre-exercise level. (2) After the tibialis anterior muscle fatigue caused by dorsiflexion, the H / Mmax of the antagonist muscle decreased to 85.33 ± 10.25% (P <0.01) before exercise, and then gradually recovered to the pre-exercise level. (3) After dorsiflexion caused the tibialis anterior muscle fatigue, the H wave threshold of the antagonistic muscle soleus muscle was significantly higher than that of the ankle muscle. Conclusion: In the case of muscle fatigue, not only the excitability of the motor neurons in the aortic muscle is inhibited, but also the excitability of antagonizing the motor neurons in the myelinated spinal cord is similarly affected.