INCREASE IN THE CONTRACTION OF THE STANCE SOLEUS IN MAN DOES NOT DELAY THE SWING PHASE IN STEPS ELICITED BY FORWARD FALL

In this study it was examined in man whether tension increase in the e xtensor muscles of the stance foot delays the stance to swing transiti on, as suggested by some observations made in cats. Steps reproducibly elicited by forward fall were studied. Increase in muscle tension was obtained by electrical stimulation of the tibial nerve during the las t third of the first step stance phase with trains of five rectangular pulses, 1 ms in duration, at 20 Hz, whose intensity was sufficient fo r eliciting maximal responses in the stance Soleus muscle (e.m.g. M re sponses). Trials with and without electrical stimulation were randomly carried out in five healthy subjects who had consented to take part i n the experimentation. The stance to swing transition was characterize d by the time of activation of the Tibialis anterior muscle of the sta nce foot and by the time of clearance of this foot from the ground. It was found that maximal contractions of the stance Soleus muscle did n ot change these times. Thus, in contradiction to some observations mad e in spinal and decerebrated cats, tension increase in the stance Sole us in man during steps elicited by a forward fall does not delay the t ransition to the swing phase.