Power spectral analysis of electromyogram and compound muscle action potential during muscle fatigue and recovery.

Abstract

The power spectral changes of the voluntary electromyogram (EMG) and of the compound muscle action potential (CMAP) evoked by supramaximal nerve stimulation were compared in fatigue and recovery of human voluntary muscle contraction. The mean power frequency (MPF) of the volunatry EMG and that of the CMAP were similar during fatigue. Power spectral shift was largely accounted for by change in shape of muscle action potentials. The recovery rates of force and action potential amplitude were similar, being half complete at 30 s. MPF and relaxation rate recovered more slowly, being half complete at 3 min. The recovery of power spectral changes was apparently dependent on the metabolic state of the muscle.