Twenty weeks of weight training increases lean tissue mass but not bone mineral mass or density in healthy, active young women

Twenty young women (20.3+/-1.0 years) participated in a weight training program in which upper and lower body exercises were done twice per week for 20 weeks. Ten other women (20.2+/-0.4 years) served as a control group. Training resulted in significant (p<0.05) increases in arm curl (73%), bench press (33%), and leg press (23%) lifting performance. Whole body (3.7%), trunk (3.0%), arm (9.7%), and leg (3.3%) lean tissue mass also increased significantly, based on measurements made by dual energy x-ray absorptiometry (DEXA). Changes in the control group were small and nonsignificant. In contrast, training did not increase DEXA-measured bone mineral content (BMC) and density (BMD) in a whole body measure nor in arm, leg, ribs, thoracic and lumbar spine, and pelvis segments. Similarly, hip BMC and BMD at femoral neck, trochanter, intertrochanter, and Ward's triangle sites, and total hip did not increase with training. The data indicate that a resistance training program that effectively increases strength and lean tissue mass in young women may fail to increase BMC or BMD over a 20-week training period.