We conducted high intensity electrical stimulation of the quadriceps femoris and hamstring muscle groups daily during a three-week period of lower extremity cast immobilization for an athlete who sustained Grade II medial collateral and anterior cruciate ligament sprains. Thigh muscle hypertrophy of the injured (stimulated) leg was suggested by an increase in girth measurement on the day of cast removal. Three weeks after cast removal, single-leg, vertical-leap height was 92% of that accomplished by the dominant, uninjured leg, and the patient was able to return to athletic competition. This case report documents the usefulness of high intensity electrical stimulation for maintaining limb motor function during cast immobilization. Limb stabilization during stimulation and simultaneous excitation of agonist-antagonist muscle pairs also are discussed.