QUADRICEPS FEMORIS MUSCLE RESISTANCE TO FATIGUE USING AN ELECTRICALLYELICITED FATIGUE TEST FOLLOWING INTENSE ENDURANCE EXERCISE TRAINING

Background and Purpose. Electrical stimulation has been used to assess skeletal muscle resistance to fatigue. The purpose of this study was to test the hypothesis that 12 weeks of intense endurance exercise tra ining on a bicycle ergometer would reduce the percentage of decline in quadriceps femoris muscle torque during an electrically elicited fati gue test. Subjects and Methods. Emery nondisabled subjects performed 1 2 weeks of high-intensity endurance exercise training, a 6 subjects se rved as controls and did not exercise. Two electrically elicited fatig ue tests, one with and one without prior voluntary fatiguing exercise, were administered to each subject before and after the 12-week traini ng period. Results. The percentage of decline in peak torque of the qu adriceps femoris muscle over 50 electrically elicited muscle contracti ons did not change as a result of endurance exercise training, despite significant improvements in maximal oxygen consumption and quadriceps femoris muscle endurance. The recovery of maximal isometric torque im mediately after exhausting voluntary exercise followed by electrical s timulation was significantly greater after 12 weeks of intense exercis e training. Conclusion and Discussion. The percentage of decline in pe ak torque during an electrically elicited fatigue test does not detect improvements in quadriceps femoris muscle endurance induced by endura nce exercise training. The percentage of initial torque recovered imme diately after fatiguing exercise, however, is improved by endurance tr aining.