THE RELATIVE ACTIVATION OF ELBOW-FLEXOR MUSCLES IN ISOMETRIC FLEXION AND IN FLEXION EXTENSION MOVEMENTS/

Coordination studies of multi-joint movements suggest that the central nervous system uses some constraints to reduce the large number of de grees of freedom of the arm. To gain insight into how the net joint to rque is distributed among the muscles, intramuscular EMG recordings we re made to determine the relative activation of five major elbow-flexo r muscles during isometric, shortening, and lengthening contractions a t three elbow joint angles. A regularization procedure was used to eva luate the effect of two different approaches used to calculate the rel ative contribution of elbow-flexor muscles to joint torque from intram uscular EMG recordings. The results demonstrate a significant increase of the relative contribution of the biarticular muscles for more exte nded elbow joint angles and for isotonic tasks relative to isometric t asks. (C) 1997 Elsevier Science Ltd.