Relationship between physical activity and bone mineral status in young adults: the Northern Ireland young hearts project

Physical activity during the first three decades of life may increase peak bone mass and reduce future osteoporosis risk. The aim of this study was to determine the extent to which different components of physical activity may influence bone mineral status within a representative population sample of young men and women. Bone mineral density (BMD) and content (BMC) were determined at the lumbar spine and femoral neck in 242 men and 212 women, aged 20–25 years, by dual-energy X-ray absorptiometry. Physical activity was assessed by a self-report questionnaire designed to measure the frequency and duration of physical activity and its components (i.e., work, non-sports leisure, sports-related activities, and peak strain sports activities). Potential confounding factors such as height, weight, diet, and smoking habits were also assessed. In multivariate linear regression models, sports activity and peak strain sports activity undertaken by men were strongly associated with both lumbar spine BMD (β = 0.35 [0.21, 0.49] and β = 0.31 [0.17, 0.44], respectively) and BMC (β = 0.33 [0.21, 0.45] and β = 0.26 [0.14, 0.38], respectively) and femoral neck BMD (β = 0.35 [0.21, 0.48] and β = 0.27 [0.14, 0.40], respectively) and BMC (β = 0.32 [0.19, 0.44] and β = 0.29 [0.17, 0.41], respectively) (all p < 0.01), but work and non-sports leisure activities were not. In women, there were no associations between bone measurements and any component of physical activity. In models involving all subjects the gender/sports activity, but not the gender/peak strain, interaction term was statistically significant. Sports activity explained 10.4% of the observed variance in lumbar spine BMD in men, but