Relationship between motoneuron pool excitability and parameters of timing and force in an isometric ankle-extension movement.

The changes in peak facilitation and slope of facilitation of the H-reflex were compared to the parameters of an isometric plantarflexion task. The amplitude of the reflex was significantly greater for reflexes elicited within 50 msec. of the onset of soleus muscle activity. Neither peak amplitude of the reflex nor slope correlated with rate of rise of isometric force; however, they did show a modest relationship between premotor time and reaction time.