Voluntary motor drive is an important central command that descends via the corticospinal tract to initiate muscle contraction. When electrical stimulation (ES) is applied to an antagonist or agonist muscle, it changes the agonist muscle's representative motor cortex and thus its voluntary motor drive. In this study, we used a reaction time task to compare the effects of weak and strong ES of the antagonist or agonist muscle during the premotor period of a wrist extension. We recorded motor evoked potentials (MEPs) induced by transcranial magnetic stimulation (TMS) that was applied to the extensor carpi radialis (ECR; agonist) and flexor carpi radialis (FCR; antagonist). When stronger ES intensities were applied to the antagonist, the MEP control ratio in the ECR significantly increased during the premotor time. Furthermore, the MEP control ratio with stronger antagonist ES intensity was significantly larger than that in the agonist for the same ES intensity. In the FCR, the MEP control ratio was also significantly greater at the strong ES intensity than at the weak ES intensity. Furthermore, the MEP control ratio in the antagonist with a strong ES intensity was significantly larger than that in the agonist with the same ES intensity. These results suggest that agonist corticomotor excitability might be enhanced by ES of the antagonist, which in turn strongly activates the descending motor system in the preparation of agonist contraction.

中文翻译：

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电刺激拮抗性肌肉对自愿运动的影响。

自愿运动驱动是重要的中央命令，其通过皮质脊髓束下降以启动肌肉收缩。当将电刺激（ES）应用于拮抗剂或激动剂肌肉时，它将改变激动剂肌肉的代表运动皮层，从而改变其自愿运动驱动力。在这项研究中，我们使用了一个反应时间任务来比较手腕伸展运动前期拮抗剂或激动剂肌肉的弱和强ES的影响。我们记录了经颅磁刺激（TMS）诱导的运动诱发电位（MEPs），该经颅磁刺激被应用于radial侧腕腕（ECR;激动剂）和flex侧腕腕（FCR;拮抗剂）。当将更强的ES强度应用于拮抗剂时，ECR中的MEP控制比在运动前时间显着增加。此外，在相同的ES强度下，拮抗剂ES强度更高的MEP控制比率显着大于激动剂。在FCR中，强ES强度下的MEP控制率也显着大于弱ES强度下的MEP控制率。此外，具有强ES强度的拮抗剂的MEP控制比显着大于具有相同ES强度的激动剂的MEP控制比。这些结果表明，拮抗剂的ES可以增强激动剂的皮质运动兴奋性，从而在激动剂收缩的制备中强烈地激活下降的运动系统。在强ES强度下，MEP控制率也显着大于弱ES强度。此外，具有强ES强度的拮抗剂的MEP控制比显着大于具有相同ES强度的激动剂的MEP控制比。这些结果表明，拮抗剂的ES可以增强激动剂的皮质运动兴奋性，从而在激动剂收缩的制备中强烈地激活下降的运动系统。在强ES强度下，MEP控制率也显着大于弱ES强度。此外，具有强ES强度的拮抗剂的MEP控制比显着大于具有相同ES强度的激动剂的MEP控制比。这些结果表明，拮抗剂的ES可以增强激动剂的皮质运动兴奋性，从而在激动剂收缩的制备中强烈地激活下降的运动系统。