Physical activity has been shown to maintain bone mineral density (BMD) through the effects of mechanical loading on bone metabolism. However, the effects of exercise on the calcium-regulating hormones and other metabolic variables are not known. The purpose of this study was to compare the effects of strength and endurance exercise on blood pH, total serum calcium, ionized calcium, parathyroid hormone (PTH) and calcitonin (CT) between males of different physical activity. Experimental group consisted of 9 very active males (runners) and the control group consisted of 10 males with no regular exercise within a year. Subjects were asked to perform both strength (eccentric action) and endurance exercises (VO2 peak). The blood pH, total serum calcium, ionized calcium, PTH and CT were measured before and after exercise. A two-way ANCOVA was used for data analysis. The results were as follow:(1)High physical activity with regular exercise can increase cardiovascular function and muscle strength.(2)Exercise with weights helps to maintain and increase bone density.(3)When low level of physical activity male did anaerobic exercise, the free ionized calcium will increase significantly (p<.o5).(4)Mode and intensity of physical activities have no significant effect on body’s regulating hormones.(5)Physical activity level is the major factor on bone density. High level of physical activity plus strength exercise can have additive effect on bone density. Conclusions: Regular high intensity exercise will help increase bone density. Strength exercise can maintain bone density not only through mechanical loading, but also through biochemical changes in free ionized calcium, blood pH which can positively affect bone density.