Resistance training and bone mineral density during growth

This study examined the efficacy of two different resistance training programs in enhancing bone modeling and bone mineral density (BMD) in maturating rats. One exercise mode involved lifting a lighter weight with more repetitions (LI), while the other regimen involved lifting a heavier weight with fewer repetitions (HI) where the total volume of work between exercise programs was equivalent by design. Twenty-three male rats were randomly divided into control (Con, n = 8), LI (n = 7), and HI (n = 8) groups. The LI and HI groups were conditioned to climb a vertical ladder with weights appended to their tail 4 days/wk for 6 wks. After training, serum osteocalcin (OC) was significantly (p < 0.05) higher in both HI (45.2 ± 1.7 ng/ml) and LI (39.1 ± 2.2 ng/ml) when compared to Con (29.9 ± 0.9 ng/ml). Left tibial BMD was significantly (p < 0.05) greater for HI (0.231 ± 0.004 g/cm ²) when compared to both LI (0.213 ± 0.003 g/cm²) and Con (0.206 ± 0.005 g/cm²) with no significant difference between LI and Con. The results indicate that both HI and LI are effective in elevating serum OC, implicating an osteogenic response; however, only HI resulted in a significant elevation in BMD.