Abstract
The purpose of this study was to investigate the influence of voluntary muscle contraction in the lower extremity on excitability of contralateral alpha-motoneuron evoked Hoffman-reflex (H-reflex).
Seven healthy male subjects performed eighteen kinds of isometric contraction of the skeletal muscle that were flexion and extension in hip, knee and ankle joint with three kinds of %MVC (Maximum Voluntary Contraction) to the right lower extremity. We observed the H-reflex amplitude of the left soleus muscle. The amplitude of H-reflex during isometric muscle contraction was compared with that of the rest.
When the right soleus muscle contracted, the H-reflex amplitude of the left soleus muscle increased specifically. No remarkable change was, however, observed while the other muscle contracted.
These results suggest that the excitability level of an alpha-motoneuron is increased by the contraction of contralateral homonymous muscle.
