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Effects of an 8-year childhood physical activity intervention on musculoskeletal gains and fracture risk

Cöster, Marcus E. LU ; Rosengren, Björn E. LU ; Karlsson, Caroline LU ; Dencker, Magnus LU and Karlsson, Magnus K. LU (2016) In Bone 93. p.139-145
Abstract

Background 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. Methods In one elementary school we increased physical education (PE) from 60 to 200 min per school week and followed 65 girls and 93 boys from a mean age of 7 years until a mean age of 15 years. Thirty-nine girls and 37 boys in three other schools... (More)

Background 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. Methods In one elementary school we increased physical education (PE) from 60 to 200 min per school week and followed 65 girls and 93 boys from a mean age of 7 years until a mean age of 15 years. Thirty-nine girls and 37 boys in three other schools continued with 60 min 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). Results 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). Conclusion 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.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Bone mineral density, Children, Growth, Muscle strength, Physical activity
in
Bone
volume
93
pages
7 pages
publisher
Elsevier
external identifiers
  • Scopus:84989192081
  • WOS:000386987500015
ISSN
8756-3282
DOI
10.1016/j.bone.2016.09.021
language
English
LU publication?
yes
id
25d45522-e26e-493b-aa0f-0f36db2875f4
date added to LUP
2016-10-12 09:57:24
date last changed
2017-01-30 13:27:25
@article{25d45522-e26e-493b-aa0f-0f36db2875f4,
  abstract     = {<p>Background 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. Methods In one elementary school we increased physical education (PE) from 60 to 200 min per school week and followed 65 girls and 93 boys from a mean age of 7 years until a mean age of 15 years. Thirty-nine girls and 37 boys in three other schools continued with 60 min 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). Results Girls in the intervention group annually gained more total body less head aBMD, spine aBMD (p &lt; 0.01), femoral neck BMC (p &lt; 0.05), lumbar vertebrae size (p &lt; 0.05), and knee flexion strength (p &lt; 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 &lt; 0.001) and boys (r = − 0.74 (95% CI − 0.94 to − 0.02); p &lt; 0.05). Conclusion 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.</p>},
  author       = {Cöster, Marcus E. and Rosengren, Björn E. and Karlsson, Caroline and Dencker, Magnus and Karlsson, Magnus K.},
  issn         = {8756-3282},
  keyword      = {Bone mineral density,Children,Growth,Muscle strength,Physical activity},
  language     = {eng},
  month        = {12},
  pages        = {139--145},
  publisher    = {Elsevier},
  series       = {Bone},
  title        = {Effects of an 8-year childhood physical activity intervention on musculoskeletal gains and fracture risk},
  url          = {http://dx.doi.org/10.1016/j.bone.2016.09.021},
  volume       = {93},
  year         = {2016},
}