Effects of frontalis biofeedback on subjective ratings of relaxation.

Two groups of 20 subjects with elevated muscle tension levels were provided with either contingent (Group 1) or false (Group 2) EMG feedback from the frontalis muscle. Each group received 8 sessions of identical length. Performance of the 2 groups over the final training session was compared. Group 1 showed a marked decrease in frontalis EMG levels over Session 8 whereas Group 2 showed no change in frontalis activity. However, both groups showed a significant increase in reported feelings of relaxation with no difference between groups. To investigate the possibility that subjects attaining very low frontalis levels might show a more marked subjective response, 10 subjects from Group 1 who showed the most marked decrease in EMG activity were compared with the 10 subjects from Group 2 who showed the least decrease. Although both showed an increase in mental relaxation, there was no difference between the groups.