INTERACTION OF RECIPROCALLY INDUCED-INHIBITION AND PREMOTOR FACILITATION OF SOLEUS H-REFLEXES IN HUMANS

During contraction of the soleus muscle, H reflex magnitude is facilitated and vibration induced, late reciprocal inhibition of H reflex magnitude is reduced. The current study investigated whether reduction of electrically evoked late reciprocal inhibition also occurs in the period immediately before movement. H reflexes were facilitated immediately prior to unconditioned plantar flexion movements and conditioning stimuli to the common peroneal nerve produced long-lasting inhibition of the H reflex in 5 subjects. Conditioning stimuli applied during premotor facilitation lead to a significant inhibition of the facilitated H reflex (P < 0.05) in 3 of the 5 subjects. The level of this inhibition was not reduced from that seen with conditioning stimuli alone. These observations suggest that peripherally induced, long-lasting inhibition from the antagonist nerve can alter the excitability of the motoneuronal pool immediately before movement in humans.