筋収縮力の違いが主動筋促通及び拮抗筋抑制に与える影響

抄録

Phasic changes in the agonist facilitation and the antagonist inhibition involved in the initiation of the varying force of active ankle dorsiflexion were investigated in man. H-reflex and reaction time methods were combined. The main findings of this study are summarized as follows: 1) Soleus H-reflexes were very weakly inhibited just before the tibialis anterior muscle (TA) EMG onset. These results were similar to the previous reports of Gottlieb et al. (1970) and Pierrot-Deseilligny and Lacert (1973). 2) Since inhibition of soleus H-reflexes appeared just after the TA EMG onset, this inhibition was closely related to the amount of contraction force of the dorsiflexion movement. These results support the previous report of Kagamihara and Tanaka (1985). 3) The onset of the agonist facilitation (TA) was not modified by the different contraction forces. However, the extent of the facilitation just after the TA EMG onset was closely related to the amount of contraction forces of the dorsiflexion movement, similar to that seen in the inhibition of soleus H-reflexes. 4) The onset of the agonist facilitation shifted to the TA EMG onset when the subjects contracted the soleus muscle (plantarflexion) before dorsiflexion. Those results suggest that the initiation of the inhibition on soleus H-reflexes and of the facilitation on TA H-reflexes in active ankle dorsiflexion might start before the TA EMG onset, but these timings were not affected by the varying force. Differences in the extent of the facilitation and the inhibition for different contraction forces after the TA EMG onset indicate the varying strength of the descending motor commands to the TA α-motoneurons and the Ia inhibitory interneurons from the brain. In sequential ankle extension and flexion, changes in the onset of the TA H-reflex facilitation are interpreted as the effects of the reciprocal inhibition from the soleus muslce on the TA motoneurons.