Abstract
The aim of this study was to clarify the relation between the power spectrum of mass EMG and firing rates or motor units by direct measurements and by using an EMG model to produce a simulated power spectrum.We measured mass EMG or the human brachialis and extensor digitorum communis and calculated the power spectrum of the mass EMG by the maximum entropy method. A distinct peak in the power spectrum below 40Hz was related to the observed firing rates or the motor units. Use of the EMG model made it clear that the peak in the power spectrum reflects an average firing rate of the motor units.
