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When it all goes wrong? Longitudinal studies of changes in moderate-to-vigorous intensity physical activity across childhood and adolescence

Reilly, John (2016) When it all goes wrong? Longitudinal studies of changes in moderate-to-vigorous intensity physical activity across childhood and adolescence. International Journal of Exercise Science. ISSN 1939-795X (In Press)

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There is a widespread belief that moderate-vigorous intensity physical activity (MVPA) declines markedly in adolescence, particularly in girls. This belief has led to substantial research and policy effort aimed at reducing the perceived adolescent decline in MVPA. The main aim of this review is to examine belief in the adolescent decline in MVPA critically, by considering 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). Existing systematic review evidence, four recent longitudinal studies from England, and ICAD data, all fail to support the hypothesis that MVPA declines particularly markedly during adolescence, or that an MVPA decline begins at adolescence, or that adolescent declines in MVPA are greater in girls than boys. Systematic reviews, longitudinal studies, and ICAD data in fact suggest that MVPA begins to decline, and sedentary behaviour begins to increase, from around the age of school entry. Recent longitudinal studies also suggest that increasing sedentary behaviour during adolescence displaces light intensity physical activity. An emerging body of evidence from longitudinal studies which use trajectory analysis is providing important new insights on marked between-individual differences in the trajectories of MVPA across childhood and adolescence. While gaps in the evidence remain, particularly from low-middle income countries, and additional longitudinal studies are required, the present review suggests that efforts to promote and /or maintain MVPA should begin well before adolescence.