The Effectiveness of a Curricular-Based Exercise Intervention on Bone Health and Body Composition in Swedish Boys and Girls in an Elementary School Setting

Objective: To investigate whether curricular-based physical activity intervention was associated with cortical and trabecular bone microstructure, and fitness parameters among elementary school children. Methods: This was a case-controlled quasi-experimental study to which 79 children were recruited (19 girls and 21 boys attending the intervention school, and 23 girls and 16 boys attending the control school). The curricularbased intervention consisted of two extra weekly classes of 30-45 minutes each, besides the ordinary physical education classes. The assessments included cortical and trabecular bone microstructure and body composition using high-resolution peripheral quantitative computed tomography (HR-pQCT) and dual-energy X-ray absorptiometry (DXA), respectively. Anthropometrics, Tanner and menarchal stages were evaluated on the same occasions. Self-administered questionnaires were used to assess exercise habits and foreign background. Analyses split by gender were done using unpaired t-test and linear regression, adjusted for age, height, weight and pubertal stage. Results: Girls in the intervention school had significantly higher total volumetric BMD (+15.1%; p˂0.01), cortical thickness (+18.7%; p=0.01) and trabecular bone volume fraction (+11.5%; p=0.01), as compared with girls in the control school. The results remained unchanged in linear regression models adjusted for age, height, weight, and Tanner stage. No convincing effects on bone health were found for the boys. There were no significant differences for DXA bone variables when comparing intervention boys and girls with controls. Conclusion: A curricular-based exercise intervention program providing opportunities for elementary school children to be physically active during the school day appear to be associated with bone health among girls, but not boys.