title: Sources of variation in habitual physical activity of children and adolescents: the European youth heart study.
abstract: The present study examined the influence of gender, maturity state, seasonality, type of measurement day and socioeconomic status (SES) on habitual physical activity in 8-10-year-old children and 14-16-year-old adolescents (n=1318). Physical activity was assessed objectively by accelerometry. The results showed a significant effect of the type of measurement day on physical activity with a general pattern of lower activity levels in weekends compared with weekdays. Furthermore, higher physical activity levels were observed during the months of spring/summer compared with the months of autumn/winter for the 8-10-year-olds, whereas no significant effect of months was observed for the 14-16-year-olds, possibly due to exam preparations and lack of physical activity registration during the months of summer for this cohort. SES was unrelated to physical activity in the 8-10-year-olds, whereas an inverse association was observed in the 14-16-year-olds. However, a post hoc analysis provided strong evidence that this latter result was biased by the accelerometers inability to pick up bicycling activities. Finally, boys were more physically active compared with girls, and maturity state was unrelated to physical activity. The results could prove useful for working out strategies to prevent inactivity and for adjusting for temporal sources of variation in physical activity in future studies.
authors.affiliation: Institute of Sports Science and Clinical Biomechanics, University of Southern Denmark, Odense M, Denmark. plkristensen@health.sdu.dk
authors.forename: P L
authors.initials: PL
authors.lastname: Kristensen
authors.forename: L
authors.initials: L
authors.lastname: Korsholm
authors.forename: N C
authors.initials: NC
authors.lastname: Møller
authors.forename: N
authors.initials: N
authors.lastname: Wedderkopp
authors.forename: L B
authors.initials: LB
authors.lastname: Andersen
authors.forename: K
authors.initials: K
authors.lastname: Froberg
mesh_terms: D000054:Acceleration; D000293:Adolescent; D000367:Age Factors; D002648:Child; D005060:Europe; D005260:Female; D015438:Health Behavior; D006801:Humans; D008019:Life Style; D008297:Male; D009043:Motor Activity; D011634:Public Health; D012741:Sexual Maturation; D012923:Social Class; D012959:Socioeconomic Factors