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A systematic review with meta-analyses of differences in objectively measured physical activity between selected periods of the day and the week in school-aged children

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Brooke, Hannah L 
Corder, Kirsten 
Atkin, Andrew J 
van, Sluijs Esther MF 


Background: Targeting specific time periods of the day or week may enhance physical activity (PA) interventions in youth. The most prudent time-segments to target are currently unclear. Objectives: To systematically review the literature describing differences in objectively-measured PA between selected time periods in young people. Methods: Electronic databases were searched for English language, cross-sectional studies of school-aged children (4-18 years) reporting time-segment specific accelerometer measured PA from 01/1990 to 01/2013. We meta-analysed standardised mean differences (SMD) between time-segments for mean accelerometer counts per minute (TPA) and minutes in moderate-to-vigorous PA (MVPA). SMD is reported in units of standard deviation; 0.2, 0.5 and 0.8 respectively represent small, moderate and large effects. Heterogeneity was explored using meta-regression (potential effect modifiers; age, sex and study setting). Results: Of 54 included studies, 37 were eligible for meta-analyses. Children were more active on weekdays than weekends (pooled SMD (95% CI) TPA 0.14 (0.08;0.20), MVPA 0.42 (0.35;0.49)). On school days, TPA was lower in-school than out-of-school, however, marginally more MVPA was accumulated in-school (TPA -0.24 (-0.40;-0.08), MVPA 0.17 (-0.03;0.38)). TPA was slightly lower on weekends than out-of-school on school days, but a greater absolute volume of MVPA was performed on weekends (TPA -0.10 (-0.19;-0.01), MVPA 1.02 (0.82;1.23)). Heterogeneity between studies was high (I2 73.3-96.3%) with 20.3-53.1% of variance between studies attributable to potential moderating factors. Conclusions: School-aged children are more active on weekdays than weekend days. The outcome measure influences the conclusions for other comparisons. Findings support tailoring of intervention strategies to specific time periods.



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Sports Medicine

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This work was conducted by the Medical Research Council [Unit Programme numbers MC_UU_12015/7] and the Centre for Diet and Activity Research (CEDAR), a UKCRC Public Health Research: Centre of Excellence. Funding from the British Heart Foundation, Economic and Social Research Council, Medical Research Council, the National Institute for Health Research, and the Wellcome Trust, under the auspices of the UK Clinical Research Collaboration, is gratefully acknowledged, CEDAR grant number: RES-590-28-0002.