title: Limited effects of a 2-year school-based physical activity intervention on body composition and cardiorespiratory fitness in 7-year-old children.
abstract: The aim of this study was to assess the effects of a 2-year cluster-randomized physical activity and dietary intervention program among 7-year-old (at baseline) elementary school participants on body composition and objectively measured cardiorespiratory fitness. Three pairs of schools were selected and matched, then randomly selected as either an intervention (n = 151) or control school (n = 170). None of the effect sizes of body composition were statistically significant. Children in the intervention group increased their fitness by an average of 0.37 z score units more than the controls (95% CI:-0.27 to 1.01, P = 0.18), representing an improvement of 0.286 W/kg. Boys had higher fitness (mean(diff) = 0.35 z scores, 95% CI: 0.13-0.58, P = 0.001) than girls, independent of study group, fitness z score at baseline and body mass index. Post hoc analysis showed that the intervention school with the highest fitness z score change was significantly different from two of the lowest control schools (mean(diff) = 0.83 z scores, 95% CI: 0.44-1.21, P < 0.0001 and mean(diff) = 0.70 z scores, 95% CI: 0.29-1.10, P = 0.01), but it was also significantly different from the lowest intervention school (mean(diff) = 0.59 z scores, 95% CI: 0.19-0.99, P = 0.05). The results of this intervention are inconclusive as regards to the effects on fitness, but the intervention did not have any statistically significant effect on body composition.
authors.affiliation: Research Centre for Sport and Health Sciences, School of Education, University of Iceland, Stakkahlid, 105 Reykjavik, Iceland.
authors.forename: Kristjan Thor
authors.initials: KT
authors.lastname: Magnusson
authors.forename: Hannes
authors.initials: H
authors.lastname: Hrafnkelsson
authors.forename: Ingvar
authors.initials: I
authors.lastname: Sigurgeirsson
authors.forename: Erlingur
authors.initials: E
authors.lastname: Johannsson
authors.forename: Thorarinn
authors.initials: T
authors.lastname: Sveinsson
mesh_terms: D001823:Body Composition; D002648:Child; D004032:Diet; D015444:Exercise; D005260:Female; D006293:Health Promotion / Q000379:methods*; D006801:Humans; D007055:Iceland; D008297:Male; D009765:Obesity / Q000517:prevention & control; D010809:Physical Fitness; D012574:Schools; D013334:Students; D016896:Treatment Outcome