Modulation of H reflex of pretibial and soleus muscles during mastication in humans

A previous study in our laboratory demonstrated that the soleus H reflex was facilitated during mastication in humans. In the present study, we investigated whether there was any modulation of the magnitude of the pretibial H reflex during mastication in five healthy adult volunteers. The pretibial H reflex was significantly facilitated during mastication, and there was no significant difference in the facilitation between jaw‐closing and jaw‐opening phases; that is, the gain of the H reflex was modulated tonically but not in a phase‐dependent manner during mastication. Furthermore, in the same subjects, we confirmed that the soleus H reflex was facilitated during mastication. Based on our findings, we conclude that the H reflexes in both the pretibial and soleus muscles undergo a nonreciprocal facilitation during mastication. It is suggested that mastication contributes to stabilization of postural stance in humans. © 2001 John Wiley & Sons, Inc. Muscle Nerve 24: 1142–1148, 2001