Daily physical movement and bone mineral density among a mixed racial cohort of women

Purpose: The impact of lifestyle physical activity on bone mineral density (BMD) is unclear. We examined the influence of physical activities typical of everyday life on BMD among 151 women (52.0 ± 0.9 yr). These women were of low socioeconomic status, and 57.6% were Hispanic, 17.2% black, and 24.5% white. Methods: BMD was measured at the calcaneus by ultrasound with a Hologic Sahara sonometer. We measured physical activity with two questions from the Yale Physical Activity Survey that assessed h·d^-1 spent in motion typical of the past month and number of flights of stairs climbed up daily. Multivariate ANCOVA adjusted for adiposity and nutrients and medications known to influence BMD determined whether BMD differed between categories of physical activity (<2 vs ≥2 flights·d^-1 and <7 vs ≥7 h·d¹), menopausal status (pre- vs post-), and ethnic group (white vs nonwhite). Results: Among the premenopausal women (N = 63, 43.2 ± 0.9 yr), adjusted mean calcaneal BMD and BMD T-score were similar between categories of stair climbing and accumulated daily movement regardless of ethnic origin (P > 0.05). Among the postmenopausal women (N = 88, 58.1 ± 1.0 yr), adjusted mean calcaneal BMD (0.561 ± 0.019 g·cm^-2 vs 0.503 ± 0.016) (P = 0.022) and BMD T-score (-0.172 ± 0.166 vs -0.695 ± 0.143) (P = 0.020) were higher with more flights of stairs climbed daily in the Hispanic and black women only. Similarly, calcaneal BMD (0.579 ± 0.023 g·cm^-2 vs 0.505 ± 0.014) (P = 0.010) and BMD T-score (-0.020 ± 0.209 vs -0.678 ± 0.129) (P = 0.010) were higher with greater amounts of daily movement in only the older Hispanic and black women. Conclusion: Lifestyle physical activity positively impacted BMD indicators in a mixed racial cohort of postmenopausal women. Older Hispanic and black women should be encouraged to engage in physical activities typical of everyday life to attenuate age-related bone loss.