Relationship between the electromyogram and isometric reflex response in pre-strain conditions in normal humans.

Abstract

DATA have been reported which show a high positive correlation between the impulse of the isometric reflex contraction (area under the myogram) and the impulse of the synchronous muscle action potential (area of the diphasic spikes of the electromyogram) recorded from surface electrodes during a phasic stretch reflex in normal human subjects1. An explanation for this relationship was given in terms of consistency of gamma efferent control of muscle spindle sensitivity because the influence of supra-spinal centres of the central nervous system was reduced by (a) having the subjects well trained in Jacob-son's method of mental and physical relaxation2 and (b) conducting the experiments in a sound-proofed, electrically shielded and thermally insulated room3 to reduce sensory stimulation which can activate reticular neurones and augment gamma discharge.