Some electrophysiological methods for the study of human muscle.
This article is a review of some of the electrophysiological methods available for studying human muscle. With intracellular recordings, muscle membrane parameters and motor end-plate physiology can be studied. Extracellular recordings with small electrodes, so called Single Fibre EMG, provide information about the individual muscle fibre, its impulse propagation velocity, neuromuscular transmission in individual motor end-plates and the anatomical arrangement of muscle fibres within the motor unit. With a slightly larger recording surface, as used in conventional needle EMG, temporal and spatial summation of activity from about 10 muscle fibres is obtained. The recorded signal is altered in a characteristic way by nerve-muscle disorders. So called Macro EMG studies summate activity from all fibres in a motor unit. Recording with surface electrodes gives information about the gross activity of the whole muscle. Various pathological processes as well as physiological fatigue can be quantified. Certain technical aspects concerning recording and analysis are discussed for each of the described methods.