A comparison of resistance and aerobic training for mass, strength and turnover of bone in growing rats

To determine the effects of resistance versus aerobic exercise on the mass, strength and turnover of bone, thirty Sprague Dawley rats (4 weeks of age) were assigned to one of three experimental groups: sedentary, running or j umping. In the jumping group, the trunk was kept upright during electricall y stimulated jumping exercise for 1 h every other day. The running rats ran at speeds of 24 m/min for 1 h every other day. After 4 weeks, the jumping rats exhibited increases in the mass and strength of the lumbar vertebrae a nd of the mid-diaphysis of the femur (mid-femur), and increases in the cros s-sectional morphology of these bones: the trabecular bone volume per bone surface, the trabecular thickness, the trabecular bone formation rate per b one surface (BFR/BS). In addition, they exhibited reduced trabecular separa tion and the area of osteoclast surface per bone surface. The running and s edentary rats showed no such changes. With regard to the mid-femur, in both the jumping and running rats the periosteal BFR/BS was increased. However, only the jumping rats showed a reduction in the BFR/BS at the endocortical surface. These results suggest that resistance exercise accelerates cortic al drift and increases the bone mass and strength by stimulating bone forma tion more efficiently than does aerobic exercise.