An Application of Signal Processing Techniques to the Study of Myoelectric Signals

Abstract

This paper describes the use of power spectral density and cumulative power functions in the examination of the electromyogram (EMG). The EMG signals were obtained with surface electrodes from two muscles, the flexor pollicis brevis and the extensor digitorum, in four subjects. Each muscle was studied at two levels of contraction, both before and during fatigue. The power spectral density functions are compared, using a cumulative power difference function and the mean frequency of the spectrum, to determine differences between loading conditions in an individual muscle, before and during fatigue, between different muscles, between individuals (same muscle), and combinations of these conditions. The difference in cumulative power of the EMG signals produced under various experimental conditions is shown to illustrate clearly the emphasis of particular frequency bands as the experimental conditions change. Muscular fatigue is shown to shift most of the energy in the signal to a lower frequency band. The effect of fatigue on the average power (rms value) of the myoelectric signal is also discussed. Copyright © 1970 by The Institute of Electrical and Electronics Engineers, Inc.