The association between physical activity during growth and bone microarchitecture at peak bone mass.

Childhood and adolescence are critical periods for skeletal development in establishing peak bone mass (PBM), an important determinant of lifelong fracture risk. This study investigates the relationship between cumulative physical activity during growth and bone density and microarchitecture attained surrounding PBM. BMD and microarchitecture properties were obtained in 226 individuals (142 females; 84 males) surrounding PBM (aged 18-35 years) using HR-pQCT at the distal radius and tibia, and DXA at the lumbar spine and femoral neck. Physical activity during growth up to PBM was captured with the bone-specific physical activity questionnaire (BPAQ). Spearman's partial correlations, adjusted for age, height, and weight were used to determine sex-specific associations between bone properties and physical activity during growth. Higher physical activity during growth quantified by the BPAQ (gBPAQ) was associated with higher tibia failure load and femoral neck areal BMD, in both sexes (ρ = 0.27-0.38, p ≤ .02). Higher gBPAQ scores were also associated with better trabecular BMD and bone volume fraction at the tibia in both sexes, where associations were stronger in males (ρ = 0.40-0.41, p < .01) than in females (ρ = 0.24-0.26, p < .05). Males additionally had significant associations with trabecular bone microarchitecture properties, including number, separation, and inhomogeneity at both the radius (ρ = 0.30-0.34, p ≤ .01) and tibia (ρ = 0.31-0.42, p ≤ .02). In contrast, gBPAQ scores were not associated with cortical bone properties at PBM for either sex or site. Physical activity during growth is associated with greater BMD and failure load at PBM, 2 predictors of lifelong fracture risk. However, compartment-specific differences indicate that trabecular bone, as opposed to cortical bone, is more responsive to physical activity during growth.