The changes of mitochondria Ca 2+ ATPase and H + ATPase activities of skeletal muscles were observed in rats after running on the treadmill in different intensities. It was found that in comparison with the control group, Ca 2+ ATP ase activities of quadriceps and gastrocnemius significantly decreased by 60.60% and 57.53% ( P <0.01), respectively, after middle intensity exercise, whereas they varied slightly after high intensity exercise. Therefore, it is suggested that the decrease in activ...