Influence of a School-based Physical Activity Intervention on Cortical Bone Mass Distribution: A 7-year Intervention Study.

Jesper Fritz,Timo Rantalainen,Rachel L Duckham,Robin M Daly,Björn E Rosengren,Magnus K Karlsson

doi:10.1007/s00223-016-0174-y

Jesper Fritz, Timo Rantalainen + Show 4 more

Open Access

https://doi.org/10.1007/s00223-016-0174-y

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Abstract

Cortical bone mass and density varies across a bones length and cross section, and may be influenced by physical activity. This study evaluated the long-term effects of a pediatric school-based physical activity intervention on tibial cortical bone mass distribution. A total of 170 children (72 girls and 98 boys) from one school were provided with 200 min of physical education per week. Three other schools (44 girls and 47 boys) continued with the standard 60 min per week. Tibial total and cortical area, cortical density, polar stress–strain index (SSI), and the mass and density distribution around the center of mass (polar distribution, mg) and through the bones cortex (radial distribution subdivided into endo-, mid-, and pericortical volumetric BMD: mg/cm3) at three sites (14, 38, and 66 %) were assessed using peripheral quantitative computed tomography after 7 years. Girls in the intervention group had 2.5 % greater cortical thickness and 6.9 % greater SSI at the 66 % tibia, which was accompanied by significantly greater pericortical volumetric BMD compared to controls (all P < 0.05). Region-specific differences in cortical mass were also detected in the anterior, medial, and lateral sectors at the 38 and 66 % tibial sites. There were no group differences at the 14 % tibia site in girls, and no group differences in any of the bone parameters in boys. Additional school-based physical education over seven years was associated with greater tibial structure, strength, and region-specific adaptations in cortical bone mass and density distribution in girls, but not in boys.

Highlights

Regular participation in moderate to high impact sports during growth has been associated with greater bone mass, structure, and strength [1,2,3], traits associated with a reduced risk of fracture [4]
This study is a secondary analysis of a 7-year schoolbased physical education (PE) intervention in which we have previously reported that girls engaged in the intervention experienced greater gains in total body and spine bone mineral density (BMD) and had greater tibial cortical thickness at the 66 % site, while no beneficial effects were detected in boys [7]
After the initiation of the intervention and during the entire 7-year study period, the total amount of physical activity was on average 1.9–3.2 h per week higher in the girls and 2.0–3.1 h per week higher in the boys in the intervention compared to the control group (Table 2)

Summary

Introduction

Regular participation in moderate to high impact sports (e.g., gymnastics, basketball, volleyball) during growth has been associated with greater bone mass, structure, and strength [1,2,3], traits associated with a reduced risk of fracture [4]. There are few long-term intervention studies [9, 10] examining the effects of more generalized, school-based physical education (PE) programs on cortical bone structure and the mass/density distribution during growth. This is important because increased loading can induce small localized cortical bone adaptations to resist fractures at sites subjected to the greatest loads (strains) that are not necessarily detected using techniques that measure whole cortical bone mass or structure [11]. Bone modeling is the primary factor associated with exercise-induced changes in cortical bone

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