Powell, Emma; Woodfield, Lorayne A; Powell, Alexander J; Nevill, Alan M; Myers, Tony D (MDPI, 2018-09-25)
Despite the known benefits of engaging in daily moderate to vigorous physical activity (MVPA), only 22% of children in England are meeting the recommended guidelines. School break times have been advocated as a key part of children's daily routines in which their MVPA can be increased. The main aim of this study was to evaluate the effect of installing a walking-track on children's MVPA during school break times. A mixed method design was employed which allowed for the quantitative measurement of children's PA at three time points (baseline, mid-intervention (1⁻5 weeks) and follow-up (6⁻9 weeks)), using pedometers (n = 81, 5⁻9 years) and systematic observation (n = 23, 7⁻9 years). A semi-structured interview (n = 1) was also conducted at 10 weeks' follow-up. The installation of the walking-track was grounded in a unique set of theoretical constructs to aid the behaviour change of the teachers. Short term positive increases in girls' and boys' MVPA and longer term increases in boys' vigorous PA (VPA) were found. Qualitative data highlighted that boys dominated the walking-track and the inconsistent behaviour of school staff negatively impacted upon children's MVPA. A set of principles to guide the installment of walking-tracks in school playgrounds are recommended.
Nevill, Alan M; Duncan, Michael J.; Lahart, Ian M; Davies, Paul; Ramirez-Velez, Robinson; Sandercock, Gavin (Wiley, 2017-07-12)
Objectives Both waist circumference (WC) and body size (height) increase with age throughout childhood. Hence, there is a need to scale WC in children to detect differences in adiposity status (eg, between populations and different age groups), independent of body size/height. Methods Using two culturally different samples, 1 English (10–15.9 years n = 9471) and 2 Colombian (14–15 years, n = 37,948), for WC to be independent of height (HT), a body shape index was obtained using the allometric power law WC = a.HTb. The model was linearized using log-transformation, and multiple regression/ANCOVA to estimate the height exponents for WC controlling for age, sex, and any other categorical/population differences. Results In both samples, the power-law height exponent varied systematically with age. In younger children (age 10–11 years), the exponent was approximately unity, suggesting that pre-pubertal children might be geometrically similar. In older children, the height exponent declined monotonically to 0.5 (ie, HT0.5) in 15+ year-olds, similar to the exponent observed in adults. UK children's height-adjusted WC revealed a “u” shaped curve with age that appeared to reach a minimum at peak-height velocity, different for boys and girls. Comparing the WC of two populations (UK versus Colombian 14–15-year-old children) identified that the gap in WC between the countries narrowed considerably after scaling for height. Conclusions Scaling children's WC for differences in height using allometric modeling reveals new insights into the growth and development of children's WC, findings that might well have been be overlooked if body size/height had been ignored.
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