Moderate to vigorous physical activity and impact loading independently predict variance in bone strength at the tibia but not at the radius in children

Objectives: To assess if daily minutes of moderate-to-vigorous physical activity (MVPA) or vigorous physical activity (VPA) and impact counts (acceleration peaks ≥3.9g) would independently predict variance in bone strength in children and youth. Second, to estimate bone strength gain associated with increases in daily MVPA, VPA or impact counts. Methods: We recorded 7-day activity of 49 participants, mean age 11.0; SD 1.7 years, using accelerometers and estimated radius and tibia bone strength using peripheral quantitative computed tomography. We used linear regression models adjusted for sex, body mass and muscle area to address objectives. Results: Daily MVPA (mean 50, SD 23 min) and VPA (17, 11) or impacts (71, 59 counts) did not predict variance in radius strength. Daily VPA (β=0.24), predicted variance in tibia strength at the distal and shaft sites, shaft strength was also predicted by MVPA (β=0.20) and impact counts (β=0.21). Our models estimated a 3-6%, 4%, and 4-11% gain in tibia strength after increasing daily MVPA by 10-20 min, VPA by 5 min, or impacts by 30-100 counts, respectively. Conclusions: Daily minutes MVPA, VPA and impact counts were independent predictors of tibia but not radius strength. Objective recording of activities associated with forearm bone strength and trials testing efficacy of increasing daily MVPA, VPA and related impacts on bone strength development in children and youth are warranted.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author