[Phenomenon of a quiet period in the myoelectric amplitudes evoked by H-reflex during voluntary muscle contraction].
The purpose of this study was to analyze the occurrence mechanism of quiet period (silent period, QP) in myoelectric signals of the gastrocnemius muscle by the measure of the electric stimulation with H-reflex, during various background levels of voluntary contraction strength. While surface myoelectric signals of the lateral gastrocnemius muscle in six man subjects with normal neuromuscular functions were recorded during isometric contractions, the tibial nerve was stimulated to evoke H-reflex and subsequent QP. QP was observed invariably in trials with background strength levels of less than 45%MVC (maximum voluntary contraction) starting just after H-wave and lasting 3-120msec. QP occurrence depended upon two neuromuscular factors--low initial strength levels and moderate H-wave amplitudes, and QP duration were changed with the logarithmic relationship according to the initial level of %MVC gradually. From these observation, following conclusions were gotten such as that inhibitory function in the spinal cord was generated to alpha motor neuron from the voluntary contraction and then QP occurrence mechanism should be considered to associate with changes in recurrent inhibition during voluntary contractions by an H-reflex.
D000328:Adult; D004558:Electric Stimulation; D004576:Electromyography; D006181:H-Reflex; D006801:Humans; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction; D012023:Reflex, Monosynaptic