An electromyographic study of reciprocal activity of muscles.

Abstract

AbstractAn electromyographic study of elbow flexors and extensors was conducted using 20 adult human subjects to determine if cocontraction occurred during voluntary movement. The interplay of proprioceptive reflex influences arising in the primary and secondary endings of the muscle spindle and in the Golgi tendon organ provide the neurophysiological basis for cocontraction. Whether or not cocontraction occurs during a movement is dependent on the degree to which one proprioceptive influence predominates over the others. This in turn appears to be dependent on factors such as those described below.Incidence and degree of cocontraction was greater during extension than during flexion movements. This may be attributed to the influence of muscle spindle secondary endings.Cocontraction increased with increasing load. Proprioceptive reflexes arising in tendon organs may be involved in this phenomenon.No evidence was found to indicate that the incidence of cocontraction increased with increasing precision of movement. In general, cocontraction was less in skilled and strong subjects than in average subjects during all types of movements.Under the special circumstances of voluntarily attempted cocontraction, evidence of reciprocal inhibition of the antagonist appeared. Proprioceptive reflex activity from tendon organs and from muscle spindle secondary endings are implicated as primarily responsible for this inhibition.