A critical review of electrical stimulation of the quadriceps muscles.

Electrical stimulation (ES) has played an important role in the rehabilitation of muscle for many years. Recently, regimes and stimulators have become more sophisticated in an attempt to minimize loss of, or improve, muscle strength, atrophy, and function. Research into the quadriceps femoris group is divided into that performed on healthy muscle and that on atrophied or weak muscle as a result of knee disease, trauma, or immobilization. This review has found that there are conflicting results concerning the efficacy of ES on the healthy quadriceps. This is, in part, due to problems with outcome measures and differences with methodology, stimulation parameters, and delivery. Similarly, work on atrophied quadriceps has revealed some agreement in the effects of ES on function of the quadriceps and its cross-sectional area, but contradictory results in measures of strength, thigh girth, and biochemical markers. Although research into healthy quadriceps is an important indicator for patients with atrophied muscle, care should be taken when extrapolating results from the healthy volunteers to the patient population. Consequently, although ES is still a frequently used method of rehabilitation, there is considerable debate and some difficulty in obtaining a consensus of opinion on its efficacy in rehabilitation of the quadriceps.