Time Segment Specific Physical Activity During School Hours In Six- Nine- And 15-year-olds

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It is recommended that youth spend ≥60 min/d in physical activity (PA) of moderate-to-vigorous intensity (MVPA). Because the vast majority of children attend school, this environment can provide an ideal arena for PA promotion and it has been argued that schools should provide opportunities to accumulate ≥30 min/d of MVPA (i.e., ≥50% of recommended daily minimum). However, the current knowledge of MVPA accumulated during school is limited by small sample sizes, short duration of observation and inaccurate segmentation of periods during the school day. PURPOSE: To examine time segment specific MVPA during school hours, using accurately segmented accelerometer data collected over a full school week in a representative, population-based sample of 6-, 9-, and 15-year-olds attending a diverse sample of schools. METHODS: We used accelerometer data (ActiGraph GT1M/GT3X+) from a sub-sample of the PA among Norwegian Children Study. Participants attended 34 different schools (82 classes) that provided class schedules describing the exact start and end time of the school day, recess periods and physical education (PE) classes. To classify time segment specific MVPA, we summed all 10 sec epochs within the different time segments containing >333 activity counts (vertical axis). We applied random effects linear regression models, accounting for the clustered nature of the data. RESULTS: Among 6- (n=166), 9- (n=296) and 15-year-olds (n=323), 57%, 35% and 9% accumulated ≥30 min of MPVA per school day, respectively. Boys accumulated significantly more MVPA than girls during school hours, recess and PE (adjusted for wear time (WT) and month, p≤0.011). We found an inverse association between age and school hour MVPA (p<0.001), whereas the association was inverted and J-shaped with age (adjusted for WT, month and sex, p<0.001) for recess MVPA. We found no association between age and MVPA during PE (p≥0.154). Onclusion: Low proportions of 6-, 9- and 15-year-olds accumulated ≥30 min of MVPA during school hours, and girls accumulated less MVPA than boys throughout the school hours in all age groups. Our results indicate that self-organised MVPA (recess), but not teacher organized MVPA (PE), declines with age. This suggest that schools should provide opportunities for structured PA during recess, especially for adolescents and girls.