INTERPRETATION OF THE ELECTROMYOGRAM

TLDR

Electromyography interpretation has diverged over time, with early studies linking single‑fiber action potentials to larger motor‑unit rhythms and defining the motor unit as a motor neuron and its innervated fibers. The study aims to critically discuss the fundamental principles of electromyography, which is widely used in clinical settings for diagnostic purposes. The rhythmic pattern of electrical changes (action potentials) is highlighted.

Abstract

IN RENEWING electromyographic investigations of human muscles after an interval, I find that considerable differences of opinion have accumulated in regard to the interpretation of several electromyographic changes encountered in neurologic disorders. Since electromyography is in common use in some clinics and can provide useful diagnostic information, it may be of general interest to discuss critically some of the fundamental principles involved in the method. Early work on the action potentials of muscle has been reviewed by others,¹and Pennybacker and I²previously discussed at length the relation of action potentials of single muscle fibers to those series of much larger rhythmic variations which are associated with the natural discharge of a single motor nerve cell. Physiologically, the "motor unit" is defined as a motor cell, its axon process and the group of muscle fibers which this one cell innervates. The rhythmic pattern of electrical changes (action potentials)