Equal BMD after daily or triweekly exercise in growing rats

The purpose of this study was to examine the efficacy of continuous resistance training (3 days/wk) compared to interrupted resistance training where 20-24 h separated an exercise bout (i. e. 6 days/wk) for enhancing bone mineral density (BMD) in growing male rats. The total volume of work performed per week between the two resistance training programs was equivalent by design. Young male rats were randomly divided into Control (Con, n=9), 3 days/wk resistance trained group (RT3, n=9), and 6 days/wk resistance trained group (RT6, n=9). The RT3 and RT6 groups were conditioned to climb a vertical ladder with weights appended to their tail for a total of 6 wks. After 6 wks, BMD (assessed via DXA) from the left tibia was significantly greater for RT3 (0.242+/-0.004 g/cm (2)) and RT6 (0.244+/-0.004 g/cm (2)) compared to Con (0.226+/-0.003 g/cm (2)). Further, serum osteocalcin (oc, in ng/ml) was significantly greater for RT3 (75.8+/-4.4) and RT6 (73.5+/-3.8) compared to Con (53.4+/-2.4). There was no significant difference in BMD or serum OC between RT3 and RT6 groups. The results indicate that both resistance training programs were equally effective in elevating bone mineral density in young, growing rats.