title: Secular and longitudinal physical activity changes in population-based samples of children and adolescents.
abstract: The aims of this study were to investigate whether physical activity (PA) and sedentary time (ST) in 9- and 15-year-olds differed between 2005-2006 and 2011-2012 (secular change), and to investigate changes in PA and ST from age 9 to 15 (longitudinal change). In 2005-2006, we invited nationally representative samples of Norwegian 9- (n=1470) and 15-year-olds (n=1348) to participate. In 2011-2012, we invited a new nationally representative sample of 9-year-olds (n=1945), whereas 15-year-olds (n=1759) were invited to participate either based on previous participation in 2005-2006 or from a random sample of schools. We assessed PA and ST objectively using accelerometers. In 2011-2012, both 9- and 15-year-olds spent more time sedentary (≥35.7 min/d, P<.001) and less time in light PA (≥35.2 min/d, P<.001) compared to their peers in 2005-2006. Nine-year-old girls also spent less time in moderate-to-vigorous PA (MVPA) (4.2 min/d, P=.041). In both age groups, the proportion accumulating an average of 60 min/d of MVPA did not differ between the two cohorts. From age 9 to 15, girls and boys decreased their time spent in LPA (≥106.7 min/d, P<.001) and in MVPA (≥20.8 min/d, P<.001). During the same period, ST increased by a mean of >2 h/d (P<.011). We observed an adverse secular change in PA from 2005-2006 to 2011-2012 among 9- and 15-year-olds, and a large decline in PA in the participants followed longitudinally from age 9 to 15 years.
authors.affiliation: Department of Sports Medicine, the Norwegian School of Sport Sciences, Oslo, Norway.
authors.forename: K E
authors.identifier: http://orcid.org/0000-0002-4401-301X
authors.initials: KE
authors.lastname: Dalene
authors.affiliation: Department of Sports Medicine, the Norwegian School of Sport Sciences, Oslo, Norway.
authors.forename: S A
authors.initials: SA
authors.lastname: Anderssen
authors.affiliation: Department of Sports Medicine, the Norwegian School of Sport Sciences, Oslo, Norway.|Department of teacher Education and Sport, Sogn and Fjordane University College, Sogndal, Norway.
authors.forename: L B
authors.initials: LB
authors.lastname: Andersen
authors.affiliation: Department of Sports Medicine, the Norwegian School of Sport Sciences, Oslo, Norway.
authors.forename: J
authors.initials: J
authors.lastname: Steene-Johannessen
authors.affiliation: Department of Sports Medicine, the Norwegian School of Sport Sciences, Oslo, Norway.
authors.forename: U
authors.initials: U
authors.lastname: Ekelund
authors.affiliation: Department of Sports Medicine, the Norwegian School of Sport Sciences, Oslo, Norway.
authors.forename: B H
authors.initials: BH
authors.lastname: Hansen
authors.affiliation: Department of Sports Medicine, the Norwegian School of Sport Sciences, Oslo, Norway.
authors.forename: E
authors.initials: E
authors.lastname: Kolle
mesh_terms: D061725:Accelerometry; D000293:Adolescent; D002648:Child; D003430:Cross-Sectional Studies; D015444:Exercise; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D009664:Norway; D057185:Sedentary Behavior; D013997:Time Factors
keywords: 
  MVPA
  ; accelerometer; prospective; sedentary