Cöster Marcus E, Rosengren Björn E, Karlsson Caroline, Dencker Magnus, Karlsson Magnus K
Clinical and Molecular Osteoporosis Research Unit, Department of Orthopedics and Clinical Sciences, Lund University, Skåne University Hospital, SE-205 02 Malmö, Sweden.
Clinical and Molecular Osteoporosis Research Unit, Department of Orthopedics and Clinical Sciences, Lund University, Skåne University Hospital, SE-205 02 Malmö, Sweden.
Bone. 2016 Dec;93:139-145. doi: 10.1016/j.bone.2016.09.021. Epub 2016 Sep 24.
Physical activity (PA) in childhood is associated with musculoskeletal benefits while the effect on fracture risk is yet to be determined. The aim of this study was to evaluate whether extension of a PA intervention leads to improvement in musculoskeletal traits with an accompanied reduced fracture risk. We hypothesized that the PA program would have beneficial effects in both sexes, but more so in girls since they tend to be less physically active than boys during this time frame.
In one elementary school we increased physical education (PE) from 60 to 200min per school week and followed 65 girls and 93 boys from a mean age of 7years until a mean age of 15years. Thirty-nine girls and 37 boys in three other schools continued with 60min of PE per week during the same years and served as controls. We measured bone mineral content (BMC), areal bone mineral density (aBMD), and bone area annually with dual energy X-ray absorptiometry, and leg muscle strength with a computerized dynamometer. In 3534 children within the same PE program (1339 in the intervention and 2195 in the control group) we registered incident fractures during the 8-year study period and estimated annual sex-specific fracture incidence rate ratios (IRRs).
Girls in the intervention group annually gained more total body less head aBMD, spine aBMD (p<0.01), femoral neck BMC (p<0.05), lumbar vertebrae size (p<0.05), and knee flexion strength (p<0.05) than girls in the control cohort. In boys we found no group differences. There was an inverse correlation between number of years with extra PE and the annual IRR of sustaining fractures in both girls (r=-0.90 (95% CI -0.98 to -0.51); p<0.001) and boys (r=-0.74 (95% CI -0.94 to -0.02); p<0.05).
In this 8-year pediatric school-based moderate exercise intervention program there is an inverse correlation in both sexes between annual IRR and each additional year of extra PA. A sub-cohort of girls in the intervention group had greater gains in bone mass, bone size, and muscle strength, which could possibly explain the inverse correlation between years within the PA program and fracture risk, while in boys the reason for the inverse correlation remains unknown. It should be noted that differences in unreported factors such as skeletal maturity status, diet, and spare time PA could confound our inferences. That is, true causality cannot be stated.
儿童时期的身体活动（PA）对肌肉骨骼有益，但对骨折风险的影响尚待确定。本研究的目的是评估延长PA干预是否能改善肌肉骨骼特征并降低骨折风险。我们假设PA计划对两性均有有益影响，但对女孩的影响更大，因为在此时间段内女孩往往比男孩身体活动少。
在一所小学，我们将每周的体育课（PE）时间从60分钟增加到200分钟，并跟踪了65名女孩和93名男孩，他们的平均年龄为7岁，直至平均年龄15岁。在同一年中，其他三所学校的39名女孩和37名男孩继续每周进行60分钟的体育课，并作为对照组。我们每年用双能X线吸收法测量骨矿物质含量（BMC）、骨面积骨矿物质密度（aBMD）和骨面积，并用计算机测力计测量腿部肌肉力量。在同一体育课程的3534名儿童中（干预组1339名，对照组2195名），我们记录了8年研究期间的新发骨折情况，并估计了每年按性别划分的骨折发病率比（IRRs）。
与对照组女孩相比，干预组女孩每年全身（不包括头部）aBMD、脊柱aBMD（p<0.01）、股骨颈BMC（p<0.05）、腰椎尺寸（p<0.05）和膝关节屈曲力量（p<0.05）增加更多。在男孩中，我们未发现组间差异。额外体育课年限与女孩（r=-0.90（95%CI -0.98至-0.51）；p<0.001）和男孩（r=-0.74（95%CI -0.94至-0.02）；p<0.05）骨折年发病率比之间呈负相关。
在这个为期8年的基于儿科学校的适度运动干预计划中，两性的骨折年发病率比与每年额外的PA年限之间均呈负相关。干预组中的一个女孩亚组在骨量、骨大小和肌肉力量方面有更大的增加，这可能解释了PA计划年限与骨折风险之间的负相关，而在男孩中，负相关的原因尚不清楚。需要注意的是，未报告因素如骨骼成熟状态、饮食和业余时间的PA差异可能会混淆我们的推断。也就是说，无法确定真正的因果关系。
