Reduced voluntary electromyographic activity after fatiguing stimulation of human muscle.

1. After ischaemic ankle dorsiflexor muscles had been fatigued by repetitive stimulation of the peroneal nerve at 15 Hz, there was a reduction in voluntary EMG activity which persisted as long as the arterial cuff remained inflated. 2. The reduction in voluntary EMG activity could not have been due to loss of excitability at the neuromuscular junctions or muscle fibre membranes since the M-waves (muscle compound action potentials) evoked by peroneal nerve stimulation were well maintained. 3. The preceding observations were consistent with the view that the reduction in EMG activity was due to reflex inhibition of motoneurones by afferents from the fatigued muscle. 4. The absence of responses to stimuli interpolated among the voluntary activity indicated that any motor units which could not be recruited in the fatigued muscle were no longer capable of generating tension.