[Increase of the contraction of the stance soleus muscle in human does not delay the swing phase in step elicited by forward fall].
In this study it was examined in man whether tension increase in the extensor muscles of the stance foot delays the stance to swing transition, 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 last third of the first step stance phase with trains of five rectangular pulses, 1 ms in duration, at 20 Hz, whose intensity was sufficient for eliciting maximal responses in the stance Soleus muscle (e.m.g. M responses). Trials with and without electrical simulation were randomly carried out in five healthy subjects who had consented to take part in the experimentation. The stance to swing transition was characterized by the time of activation of the Tibialis anterior muscle of the stance 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 not change these times. Thus, in contradiction to some observations made in spinal and decerebrated cats, tension increase in the stance Soleus in man during steps elicited by a forward fall does not delay the transition to the swing phase.
Schneider
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Laboratoire de physiologie du mouvement, ER-CNRS 124, université de Paris-Sud, Orsay, France.
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Bussel
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D000058:Accidental Falls; D000818:Animals; D002415:Cats; D004195:Disease Models, Animal; D004558:Electric Stimulation; D004576:Electromyography; D006801:Humans; D009068:Movement; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000502:physiology*