effort aimed at reducing the perceived decline in MVPA during adolescence. The main aim of this review is to critically examine the belief that MVPA declines during adolescence. Methods: Review of evidence from studies with objective measures of physical activity, systematic reviews of longitudinal studies, insights from recent longitudinal studies, and evidence from the International Children's Accelerometry Database (ICAD). Results: Existing systematic review evidence, four recent longitudinal studies from England, and ICAD data all failed to support the hypothesis that MVPA declines particularly markedly during adolescence, or that an MVPA decline begins at adolescence, or that declines in MVPA during adolescence are greater in girls than in boys. Systematic reviews, longitudinal studies, and ICAD data in fact suggest that MVPA begins to decline, and sedentary behavior begins to increase, from around the age of school entry. Recent longitudinal studies also suggest that increasing sedentary behavior during adolescence displaces light-intensity physical activity. An emerging body of evidence from longitudinal studies that use trajectory analysis is providing important new insights into marked between-individual differences in the trajectories of MVPA across childhood and adolescence. Conclusion: Although gaps in the evidence remain, particularly from low- to middle-income countries, and additional longitudinal studies are required, this review suggests that efforts to promote and/or maintain MVPA should begin well before adolescence.Mediating role of television time, diet patterns, physical activity and sleep duration in the association between television in the bedroom and adiposity in 10 year-old childrenBorghese MM,Tremblay MS,Katzmarzyk PT,Tudor-Locke C,Schuna Jr J,Leduc G, Boyer C, LeBlanc AG, Chaput J-P 2015Background: Having a TV in the bedroom is associated with adiposity in children. It is not known how lifestyle behaviours (television viewing time, diet patterns, physical activity, and sleep duration) mediate this association. The objective of this study was to examine the mediating role of these lifestyle behaviours in the association between TV in the bedroom and percent body fat (% BF). Methods: Cross-sectional data from 1 201 children (57.3 % female; mean age = 9.8 years) from Ottawa, Canada and Baton Rouge, USA were examined. % BF was directly measured. Accelerometers were used to determine physical activity and sleep duration (24-h, 7-day protocol). Questionnaires were used to assess TV viewing time and healthy/unhealthy diet patterns (derived using factor analysis from food frequency questionnaire data). Results: Canadian boys and girls with a TV in their bedroom had a higher % BF, watched more TV and had unhealthier diets. American boys and girls with a TV in their bedroom watched more TV, while boys had a higher % BF and a more unhealthy diet, and girls had less MVPA. In Canadian girls, TV viewing time mediated the association between having a TV in the bedroom and adiposity, independent of diet patterns, MVPA, and sleep duration. Other lifestyle mediators were not significant in Canadian boys or in US children. Conclusion: TV viewing is a mediating lifestyle behaviour in the association between TV in the bedroom and adiposity in Canadian girls. Future research is needed to identify lifestyle behaviours as intermediate mediators.The PitSTOP study: a feasibility cluster randomized trial of delirium prevention