Article

Subjective and objective measures of physical activity in relationship to bone mineral content during late childhood: the Iowa Bone Development Study

Department of Health and Sport Studies, University of Iowa, Iowa City, IA 52242, USA.
British Journal of Sports Medicine (Impact Factor: 5.03). 08/2008; 42(8):658-63. DOI: 10.1136/bjsm.2008.047779
Source: PubMed

ABSTRACT 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.
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).
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.
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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Available from: Kathleen F Janz, Oct 15, 2014
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    • "However, measurements were performed by trained specialists, using a rigorous approach to gather at least two measurements for each anthropometric parameter, including the sitting height. Moreover, our results on the estimated APHV that requires the sitting height are similar to those provided by previous studies, which involved children of the same chronological age range (Janz et al. 2008; Fairclough & Ridgers 2010). Besides these limitations, the current study indicates that among prepubescent children the influence of biological maturity on gender differences in PA may be a function of how maturity status is determined. "
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    ABSTRACT: AimTo examine: (i) if maturity-related gender differences in moderate-to-vigorous physical activity (MVPA) depend on how maturity status is defined and measured; and (ii) the influence of maturity level on compliance with PA recommendations. Methods The study involved 253 children (139 boys) aged 9.9 0.9 years, with mean stature and weight of 1.39 0.08m and 35.8 +/- 8.8kg respectively. Their PA was evaluated using an Actigraph accelerometer (Model 7164). Maturity was assessed using the estimated age at peak height velocity (APHV) and a standardized APHV by gender (i.e. centred APHV). ResultsBoys engaged in significantly more MVPA than girls (P < 0.0001). There was a significant correlation between the centred APHV and MVPA in boys (r = 0.20; P = 0.016), but not in girls (r = 0.13; P = 0.155). An ancova controlling for the estimated APHV showed no significant interactions between gender and APHV, and the main effect of gender on MVPA was negated. Conversely, there was a significant main effect of APHV on MVPA (F-1,F-249 = 6.12; P = 0.014; (p) (2) = 0.024). Only 9.1% of children met the PA recommendations, including 14.4% of boys and 2.6% of girls (P < 0.01). This observation also applies in both pre-APHV (12.7% of boys vs. 2.4% of girls, P < 0.001) and post-APHV children (23.8% of boys vs. 3.4% of girls, P < 0.0001). No differences in PA guidelines were observed between pre-APHV and post-APHV children. Conclusions Among prepubescent children, the influence of biological maturity on gender differences in PA may be a function of how maturity status is determined. The most physically active prepubescent children were those who were on time according to APHV.
    Child Care Health and Development 06/2012; 39(6). DOI:10.1111/j.1365-2214.2012.01407.x · 1.83 Impact Factor
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    • "During adulthood the Physical Activity Questionnaire for Adults (PAQ-AD), a 7 item version of the PAQ-C/A was used, again, scoring individuals on a five point scale. The PAQ-C/A/AD has been previously reported to be a valid and reliable measure of physical activity levels in children, adolescents and adults [29] [30] [31]. "
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    ABSTRACT: Late maturational timing is documented to be detrimental to bone strength primarily at the distal radius. Studies at the proximal femur have focused on bone mass and the results remain controversial. The purpose of this study was to examine the long term relationship between the onset of maturation and the development of estimated cross sectional area (CSA) and section modulus (Z) at the proximal femur. Two hundred and twenty six individuals (108 males and 118 females) from the Saskatchewan Pediatric Bone Mineral Accrual Study (PBMAS) were classified into maturity groups based on age of attainment of peak height velocity. CSA and Z were serially assessed at the narrow neck (NN), intertrochanter (IT) and proximal shaft (S) sites using hip structural analysis (HSA). Multilevel models were constructed to examine the development of CSA and Z by maturity group. Cross sectional observations indicated that during adolescence, early maturing males had significantly greater CSA and Z than late maturing males at all sites of the proximal femur, while early maturing females had greater Z at the NN and S, and greater CSA at the NN, IT and S sites compared to late maturing females. When age, body size, body composition, physical activity and dietary intake were controlled no significant effects of maturational timing were found at the NN, IT or S regions (p>0.05) in either males or females. In this population of healthy individuals there appears to be no effect of the onset of maturation on estimated CSA and Z development at the proximal femur in both males and females. This may be a result of the proximal femur's loading environment. Future research is required to determine the role of loading on the relationship between maturational timing and bone structure and strength development at the proximal femur.
    Bone 09/2011; 49(6):1270-8. DOI:10.1016/j.bone.2011.08.030 · 4.46 Impact Factor
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    • "The physical activity of children cannot satisfactorily be quantified using the self-evaluation method, since children do not have the cognitive abilities to remember the patterns and details of their activities, while it is precisely physical activity in combination with other factors that has a positive effect on their skeletal system (Rowlands et al., 1997). Nevertheless, Janz et al. (2008) studying a sample which included 449 children, with an average age of 11, and using a questionnaire for the self-evaluation of the physical activities of children (PAQ- C), noted a correlation between body height, body weight and maturity and the bone mineral content (BMC). In addition, they determined that the correlation between everyday physical activity and the BMC was more pronounced in the case of girls than in the case of boys. "
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