Relative contribution of individual muscles to the isometric contraction of a muscular group.

A technique was developed for calculating the torque generated by two individual muscles (biceps brachii and brachioradialis) that contribute to the isometric flexion of the elbow. The external torque is the sum of individual torques which are unknown. Each individ.ual torque (C, or C,,) can be related to the corresponding integrated rectified surface EMG (Qe or QBR) by means of coefficients @a or pea). A block of several equations C = pB ol, + pax p,, is obtained by exploring several experimental conditions. In these conditions. isometric fiexion efforts of the elbow were associated to isometric efforts of supination or pronation so as to vary integrated rectified EMG by reciprocal inhibition. By means of a least square method it was possible to know the coefficients ps and pBR. With these coefficients, it was possible to calculate the individual torques generated by the biceps brachii and brachioradialis muscles in each experimental condition.