THE ELECTROMYOGRAM OF VOLUNTARY MOVEMENTS IN MAN

Abstract

A short account has been given of the previously recorded electromyograms of normal voluntary movements in man. These have been compared in respect of the amplitude, form and frequency of their individual deflections. An attempt has been made to outline the principles governing the interpretation of such records in terms of muscle activity and expressed in terms of the electrical and mechanical components of such activity. The principles underlying the known distribution of the electric field about active, simple muscle strips surrounded by a conducting medium have been applied to the case of skeletal muscle voluntarily made active in the intact limb. The inferences permissible with regard to the motor discharge from the central nervous system during voluntary movements have been stated and the factors governing this discharge examined. A suggested explanation for the so frequently observed dominant 50-per-second rhythm has been advanced. The influence of fatigue upon the action currents of voluntary movements has been detailed. The effects of such fatigue have been correlated under the term “effort syndrome” and the other conditions and modes of occurrence of this effort syndrome stated. An attempt has been made to determine the site of the mechanism responsible for the phenomena of the effort syndrome. As a result of the inquiry the existence of a mechanism having certain properties and located in a certain part of the reflex system has been postulated. Short summaries have been made of the recorded characteristics of the voluntary electromyograms obtained from patients suffering from different pathological conditions.