@article{ref1,
title="Exploring the adolescent fall in physical activity: a 10-yr cohort study (EarlyBird 41)",
journal="Medicine and science in sports and exercise",
year="2015",
author="Metcalf, Brad S. and Hosking, Joanne and Jeffery, Alison N. and Henley, William E. and Wilkin, Terence J.",
volume="47",
number="10",
pages="2084-2092",
abstract="INTRODUCTION: Contemporary adolescents are deemed inactive, especially girls, but whether for biological reasons associated with their maturation, changes in their behaviour or because of environmental constraints, is uncertain. We examined the trends in physical activity (PA) in relation to both biological and environmental factors in an attempt to establish what drives activity patterns from childhood through to adolescence. <br><br>METHODS: PA (7d Actigraph accelerometry) was measured annually from 5y-15y in a single cohort of some 300 UK children. Total PA (TPA - in-school and out-of-school separately and combined as whole day) and intensity-specific PA (sedentary, light and moderate-and-vigorous [MVPA]) were analysed. Biological age (years before/after measured peak height velocity) and pubertal stage (self-reported pubic hair development - Tanner staging) were also measured, as was socio-economic status (post-code derived index of multiple deprivation [IMD]). <br><br>RESULTS: TPA was stable from 5y-8y (trend p=0.10) but fell progressively from 9y-15y (by ∼30% in girls and ∼20% in boys, both p<0.001; sex interaction p<0.01). Half of this fall was attributable to light intensity PA, only a quarter to MVPA. The decline in PA was related similarly to chronological and biological age, while pubertal stage explained the more rapid PA decline in girls (puberty adjusted sex interaction, p=0.51). TPA fell to the same extent for in-school and out-of-school settings (both p<0.001), and for lower and higher IMD areas (both p<0.001). TPA tracked moderately-to-strongly from childhood into adolescence (r=0.58, p<0.001). <br><br>CONCLUSIONS: The adolescent decline in physical activity is consistent across different environmental settings, attributable to falls in light-intensity/habitual activity and influenced by puberty, suggesting that the inactivity of adolescence may, in part, be under biological control.<p /> <p>Language: en</p>",
language="en",
issn="0195-9131",
doi="10.1249/MSS.0000000000000644",
url="http://dx.doi.org/10.1249/MSS.0000000000000644"
}