THE ELECTROMYOGRAPHY OF FATIGUE

Abstract

The changes in the electrical activity of muscle during and following fatigue are discussed. There are changes in size and form of the action potential ; synchronization occurs in the motor unit discharges. In fatigue which follows a short strong contraction, the electrical changes can be shown to depend on peripheral factors, mainly the failure of the contractile mechanism to produce as much tension as in the normal state. Thus, as the contraction proceeds, the integrated electrical activity in a muscle exerting a constant tension increases gradually. When the contraction ceases, the electrical activity falls rapidly to its unfatigued level, as measured by brief test contractions of the same force. An arterial occluding cuff prevents this recovery, if inflated at the end of the contraction. Muscular tremor, as recorded both mechanically and by the grouping of action potentials, is increased during and after muscular fatigue.