Electromyograph Biofeedback: Generalization and the Relative Effects of Feedback, Instructions, and Adaptation

The present research describes two experiments. The first experiment examined training conditions designed to enhance generalization during electromyograph (EMG) biofeedback. Twelve female and 12 male subjects were randomly assigned to one of four conditions: frontalis EMG biofeedback; frontalis, forearm extensor and masseter biofeedback; frontalis, forearm extensor and semispinalis/splenius biofeedback; and a no-feedback (instructions only) condition. EMG and heart rate were monitored during 3 training sessions. Although reliable decreases in EMG and heart rate were obtained, no differential effect of single- versus multiple-muscle biofeedback was observed; nor, indeed, were differences between biofeedback and no-feedback apparent. A second experiment was conducted to determine whether EMG and heart rate reductions reflected a general relaxation response or were simply due to the effects of adaptation. Twenty-four female subjects were randomly assigned to either a frontalis EMG biofeedback, a no-feedback or an adaptation control condition. Results indicated that decreases in frontalis EMG levels were due to the instructions to relax whereas heart rate decreases were attributable to adaptation. Equivalence between biofeedback and no-feedback conditions was again apparent. It was concluded that this finding raises serious questions about the presumed critical role of the feedback signal in EMG biofeedback.