Modulations of soleus H-reflex excitability during gait initiation: Central versus peripheral influences

Soleus and tibialis anterior electromyogram (EMG) and soleus H-reflexes wer e recorded from the stance limb of an individual who suffered a traumatic p eroneal nerve injury and of four nonimpaired individuals during gait initia tion. The control subjects also initiated walking after swaying forward (sw ay-gait initiation), which eliminated the initial tibialis anterior activat ion. During the initial period of gait initiation, H-reflexes were depresse d to 43% of standing values during normal-gait initiation and 86% during sw ay-gait initiation in the nonimpaired subjects. H-reflexes of the nerve-inj ured subject were depressed to 37%, even though no tibialis anterior EMG wa s observed. The findings support the view that reciprocal inhibition of the soleus during a task, which normally involves tibialis anterior activation , is due to a centrally mediated process. (C) 2001 John Wiley & Sons, Inc.