In conclusion, MRS is a noninvasive method of measuring high energy compounds in resting and exercising human muscle. We found that high levels of work were required to detect significant differences in muscle metabolism. Large variations were seen between control subjects. Endurance athletes had muscles with better oxidative metabolism than the control subjects. By looking carefully at resting metabolism we were able to detect and monitor the level of exercise-induced muscle injury. Finally we were able monitor in a temporal manner changes in muscle metabolism which occur with endurance training and detraining in control subjects.