Bone Turnover Across 16-Weeks of Training in Functionally Limited Seniors

Abstract

Exercise has a positive impact on bone turnover in young adults, however, the influence of exercise training on bone turnover in older individuals is not as apparent. Limitations in functional ability may reduce daily activity, further inhibiting bone turnover. PURPOSE: This study was designed to determine whether bone turnover changes in response to different modes of training in functionally limited older adults. METHODS: Functionally limited elders (n=174; 126F, 48M; 64–94 yr) were randomly divided into one of four treatment groups: aerobic training (AER; 28F, 16M), resistance training (RES; 36F, 14M), aerobic plus resistance training (AR; 33F, 11M) or control (CON; 29F, 7M). Fasting, morning blood samples were collected at baseline, 8-weeks and 16-weeks of training. Serum samples were stored at −70°C; each subject's samples were analyzed on the same ELISA plate. Bone formation was measured by osteocalcin (OC; ng/mL) and bone specific alkaline phosphatase (BALP; U/L) and bone resorption by cross linked N-telopeptides (NTx; nM BCE). Bone turnover was expressed as the uncoupling index (UI), calculated by subtracting the z-score of the mean resorption values from the z-score of the mean formation values. For analysis purposes, subjects were placed into age groups by decade (60 – 69 yr, 70 – 79 yr, etc.). Data were analyzed separately for men and women with a repeated measures ANOVA, utilizing treatment group and age group as between subjects factors. RESULTS: In the women, OC increased slightly over time while BALP decreased slightly. Bone resorption (NTx) did not change over time, but was greater in AR than CON. OC, BALP and NTx were all significantly greater in the 80–89 yr olds when compared to the 60–69 and 70–79 yr olds. There were no significant differences in the men over time or between treatment or age groups for any of the bone turnover variables. CONCLUSION: These data indicate that both bone formation and resorption are elevated in individuals in their 9th decade. Although 16 weeks of training does not appear to improve markers of bone turnover in functionally limited men and women, perhaps a regular exercise program will attenuate negative bone turnover responses.