Generalization of conditioned muscle tension: a closer look.

Abstract

ABSTRACTIn EMG biofeedback it has been suggested that covariation in tension levels between a trained and untrained muscle increases with continued training of the target muscle. Predictions of this sort are in contrast to the notion of response generalization which would predict decreased covariation between trained and untrained muscles with continued training. This study examined covariation between facial and forearm EMG levels during facial EMG biofeedback, and evaluated changes in such covariation which occurred with continued facial EMG training. Two groups of individuals were trained either to increase or to decrease facial muscle tension in 3 laboratory sessions during which simultaneous measures of facial and forearm EMG were obtained at 1‐min intervals. Comparison of facial EMG measures for these groups with those for a third, noncontingent control group revealed bidirectional conditioned effects for each training session. Some covariation between forearm and facial EMG was apparent for all groups. However, examination of change in covariation across sessions revealed that covariation decreased for groups receiving facial muscle training, whereas covariation levels exhibited by the noncontingent feedback group remained stable. This finding was consistent with the concept of response generalization but not with the notion of muscle tension generalization as employed in EMG biofeedback.