An evaluation was carried out of the strength gains after a 19-day training program that consisted of isometric exercise coupled with electromyographic biofeedback to the knee extensor muscles. The subjects were 30 female undergraduate students who were randomly assigned to one of three groups. The experimental group performed isometric exercise and received electromyographic biofeedback, another group performed isometric exercise without receiving biofeedback, and the control group performed no exercises other than the pretest and posttest. The combination of biofeedback and isometric exercise was shown to produce greater gains in peak torque than isometric exercise alone over a 19-day training period. The authors believe that this study may provide a strong rationale for the clinical use of biofeedback.