Effects of a Twelve-Week Once versus Twice a Day Power Training Program on Bone Turnover Markers and Bone Quality

Abstract

Physical activity, especially high impact activities, can improve bone. Recently, it has been suggested that increased osteogenic or bone promoting properties may result when high impact training is broken into two sessions per day compared to one. PURPOSE: To compare the effectiveness of performing one vs. two sessions per day of osteogenic-impacting power training on bone in college-aged males and females. METHODS: Nineteen volunteers (8 Males, 11 Females; age 22.1 ± 4.4 yr) were placed into either control (CON, n=4) or exercise groups: 1×/d (n=10) or 2×/d (n=5). Subjects in the exercise groups performed non-linear periodized training on a 3PQ leg press machine 3d/wk for 12 wks. Training groups were matched for total exercise volume but the 2x/d group had a calculated 24% greater osteogenic index by separating same day sessions by 8 hours. Basal serum markers of bone formation (BAP and P1NP) and resorption (CTx and TRAP5b) were evaluated at baseline and 12 wks. Total bone mineral density (BMD), content(BMC) and area (BA) were assessed by pQCT at 4, 38, & 66% of tibial length. Polar strength strain indices (SSIP) were also assessed at the 38 and 66% sites. Baseline and 12 wk one repetition maximum (1-RM) was used to assess changes in overall strength. Repeated measures ANOVA was employed for statistical analysis and significance was set at p<0.05. RESULTS: In all participants, BAP increased significantly over time (pre=22.9±12.6 vs. post= 26.6±13.5 U/L, p<0.03) with no between-group differences. P1NP was suppressed only in the CON group after 12 wks (pre=110±91.4 vs. post=76.2±39.2 ng/mL) (p<0.03). A slight but significant increase in BMD at the 38% site was observed after 12 wks in all participants (pre=916.5±59.1 vs. post=921.5±60.6 mg/cm3) (p<0.03) with no between group differences. Over 12 wks, 1×/d and 2×/d training groups significantly increased their 1-RM with the 2×/d group showing greater improvements (27% vs. 36%, p<0.05). No changes were observed in any groups for bone parameters at the 4 or 66% sites or in markers of resorption. CONCLUSION: Overall engaging in power training was able to maintain bone formation markers with no subsequent effect on bone resorption indices. Although both programs increased BMD, no differences were observed in the measures of bone quality with once vs. twice a day power training programs.