MUSCLE POTENTIALS ACCOMPANYING A SINGLE VOLITIONAL TWITCH

Abstract

Voluntary twitch electromyograms recorded from arm and hand muscles of 6 subjects show grading of response exclusively by the number of motor units responding. It is confirmed that the simplest response is a single discharge of a single motor unit in the effective electrode area. Double discharges of a single unit occur only with slightly prolonged effort and with spike intervals corresponding to those in sustained contractions. Stronger than minimal efforts give 1) overlapping discharges of 2 or more units. 2) serial discharges of 2 or more units, or 3) a combination of 1 and 2. Strong efforts may invplve repetition of some units in a response in which many other units discharge once.