A meta-analysis of frontalis EMG levels with biofeedback and alternative procedures.

The lack of comparative reviews of the efficacy of EMG frontalis biofeedback versus alternative procedures for reduction of muscle tension prompted the present meta-analytic treatment of literature previously concluded to be "equivocal." Twenty studies comparing EMG frontalis biofeedback with other tension-reduction procedures produced a total of 68 separate effect sizes suitable for meta-analysis. Differences between "clinical" and "normal" samples were nonsignificant, and data analyses revealed that EMG frontalis biofeedback was significantly superior to control (p less than .05) but that alternative forms of muscle relaxation, while effective, did not reach statistical significance.