Higher step count is associated with greater bone mass and strength in women but not in men

In this cross-sectional study, peripheral bone traits were examined relative to total daily steps measured with pedometer. Higher number of steps was associated with greater bone values at the calcaneus and tibia in women, but not in men. In women, dose-dependent associations at the radius were congruent with the weight-bearing bones. Introduction Habitual physical activity measured as daily steps may contribute to bone density and strength at the calcaneus and other weight-bearing bones. Methods Subgroups of 705-837 women and 480-615 men aged 31-46 years from the Cardiovascular Risk in Young Finns Study participated in the present study. Participants were instructed to use pedometer for 1 week, and the total daily steps, divided into tertiles, were evaluated relative to quantitative ultrasound-measured bone traits at the calcaneus and peripheral quantitative computed tomography-measured bone traits at the tibia and radius. Analysis of covariance was used to examine the between-group differences. Results In women, significant dose-dependent between-group differences were found in the weight-bearing bones and in non-weight-bearing radius. The differences in broadband ultrasound attenuation and speed of sound at the calcaneus were 3.8 and 0.5% greater in women within the highest tertile of daily steps compared to the lowest tertile (p values for trend <= 0.04). In tibia, women in the highest tertile (> 8765 steps/day) had on average 1-5.4% greater bone cross-sectional area, bone mineral content (BMC), trabecular density, and bone strength index at the distal site and 1.6-2.7% greater bone areas, BMC and strength strain index (SSI) at the shaft compared to women with less daily steps (p values for trend <= 0.02). Similarly, in radius, BMC and BSI at the distal site, and bone cross-sectional areas, BMC and SSI at the shaft were 1.7-3.4% greater in women within the highest tertile of daily steps compared to their peers (p values for trend <= 0.04). In men, the differences in calcaneal, tibial, and radial bone traits were mainly non-significant between the tertiles of daily steps. Conclusion Observed significant positive associations between daily steps and various bone traits at the calcaneus, tibia, and radius in women suggest that habitual physical activity may benefit skeletal health in adulthood.