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Subjective and objective measures of physical activity in relationship to bone mineral content during late childhood:
K F Janz1, H C Medema-Johnson, E M Letuchy
1Department of Health and Sport Studies, University of Iowa, Iowa City, IA 52242, USA. kathleen-janz@uiowa.edu
Insights
Objective physical activity measurement using accelerometry is more effective than self-report for assessing bone mineral content in children, especially girls. This highlights the importance of objective tools for understanding physical activity and bone health.
Area of Science:
- Pediatric Bone Health
- Physical Activity Measurement
- Childhood Development
Background:
- Bone mineral content (BMC) is crucial for skeletal health in children.
- Accurate assessment of physical activity (PA) is essential for understanding its impact on BMC.
- Objective measures like accelerometry may offer greater accuracy than subjective self-report methods.
Purpose of the Study:
- To compare accelerometry (Actigraph) with self-report (PAQ-C) for assessing PA in relation to BMC in children.
- To evaluate the differential effectiveness of these PA measures in boys versus girls.
Main Methods:
- Cross-sectional study of 449 children (mean age 11 years).
- PA assessed via accelerometry (Actigraph) for 3-5 days and self-report questionnaire (PAQ-C) for 7 days.
- BMC measured at the hip, spine, and whole body using dual-energy x-ray absorptiometry (DXA).
Main Results:
- Accelerometry (Actigraph) and self-report (PAQ-C) were significantly associated with BMC in boys.
- Only accelerometry (Actigraph) showed significant associations with hip and whole body BMC in girls.
- Objective PA measurement was more consistently associated with BMC across sexes.
Conclusions:
- This study supports the link between everyday physical activity and bone mineral content in children.
- Objective measures of physical activity, particularly accelerometry, are more effective than self-report in detecting these associations, especially in girls.
Objective:
This study compared accelerometry to self-report for the assessment of physical activity (PA) in relation to bone mineral content (BMC). In addition, we compared the ability of these measures to assess PA in boys versus girls.
Methods:
Participants in this cross-sectional study included 449 children (mean age 11 years) from the Iowa Bone Development Study. PA was measured via 3-5 days of accelerometry using the Actigraph and 7 day self-report questionnaire using the Physical Activity Questionnaire for Children (PAQ-C). Hip, spine, and whole body BMC were measured via dual energy x ray absorptiometry (DXA).
Results:
Partial correlation analysis (controlling for height, weight, and maturity) showed the Actigraph was significantly associated with hip (r = 0.40), spine (r = 0.20), and whole body (r = 0.33) BMC in boys, as was the PAQ-C (r = 0.28 hip, r = 0.19 spine, and r = 0.22 whole body). Among girls, only the Actigraph was significantly associated with hip (r = 0.18) and whole body (r = 0.16) BMC. Both the Actigraph and PAQ-C were significant in hip, spine, and whole body multivariable linear regression models (after controlling for body size and maturity) in boys. Only the Actigraph entered hip BMC regression model in girls.
Conclusions:
Our study supports previous work showing associations between everyday PA and BMC in older children. These associations are more likely to be detected with an objective versus subjective measure of PA, particularly in girls.
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