This study was conducted to determine if physical activity and cardiorespiratory fitness (CRF) at baseline influence the likelihood of gaining bone mineral density (BMD) at the hip and lumbar spine over 6 years. Another aim was to ascertain the effect of several potential confounding factors. In a prospective study of 244 women (baseline age range 35-45 years), physical activity volume (PAv) and intensity (PAi) were measured using accelerometers at baseline. CRF indexed by VO2max was estimated using a graded, maximal treadmill test at baseline. BMD was measured using DEXA. Risk ratios were used to show the likelihood of BMD gains (> 75th percentile) between different levels of PAv, PAi, or CRF at baseline. Mean hip BMD change was -0.015 + 0.045 g/cm2. Women with high PAv were 2.50 times (95% CI: 1.19-5.24), and women with moderate PAv were 2.20 times (95% CI: 1.08-4.45), more likely to experience significant hip BMD gains than women with low PAv. Adjusting for potential confounders had little effect on the results. Baseline PAi and CRF were not related to changes in hip BMD. None of the relationships between PAv, PAi, and CRF, and changes in spine BMD, was statistically significant. Middle-aged women with moderate or high levels of PAv are more likely to experience significant gains in hip BMD over time compared to those with low levels of PAv.



College and Department

Life Sciences; Exercise Sciences



Date Submitted


Document Type





Physical Activity, Fitness, Bone, BMD