title: Effectiveness of intervention on physical activity of children: systematic review and meta-analysis of controlled trials with objectively measured outcomes (EarlyBird 54).
abstract: OBJECTIVE
  To determine whether, and to what extent, physical activity interventions affect the overall activity levels of children.
  
  
  METHODS
  Systematic review and meta-analysis.
  
  
  METHODS
  Electronic databases (Embase, Medline, PsycINFO, SPORTDiscus) and reference lists of included studies and of relevant review articles.
  
  
  METHODS
  Design: randomised controlled trials or controlled clinical trials (cluster and individual) published in peer reviewed journals.
  
  
  METHODS
  incorporated a component designed to increase the physical activity of children/adolescents and was at least four weeks in duration.
  
  
  RESULTS
  measured whole day physical activity objectively with accelerometers either before or immediately after the end of the intervention period.
  
  
  METHODS
  INTERVENTION effects (standardised mean differences) were calculated for total physical activity, time spent in moderate or vigorous physical activity, or both for each study and pooled using a weighted random effects model. Meta-regression explored the heterogeneity of intervention effects in relation to study participants, design, intervention type, and methodological quality.
  
  
  RESULTS
  Thirty studies (involving 14,326 participants; 6153 with accelerometer measured physical activity) met the inclusion criteria and all were eligible for meta-analysis/meta-regression. The pooled intervention effect across all studies was small to negligible for total physical activity (standardised mean difference 0.12, 95% confidence interval 0.04 to 0.20; P<0.01) and small for moderate or vigorous activity (0.16, 0.08 to 0.24; P<0.001). Meta-regression indicated that the pooled intervention effect did not differ significantly between any of the subgroups (for example, for total physical activity, standardised mean differences were 0.07 for age <10 years and 0.16 for ≥ 10 years, P=0.19; 0.07 for body mass index across the entire range and 0.22 for exclusively overweight/obese children, P=0.07; 0.12 for study duration ≤ 6 months and 0.09 for >6 months, P=0.71; 0.15 for home/family based intervention and 0.10 for school based intervention, P=0.53; and 0.09 for higher quality studies and 0.14 for lower quality studies, P=0.52).
  
  
  CONCLUSIONS
  This review provides strong evidence that physical activity interventions have had only a small effect (approximately 4 minutes more walking or running per day) on children's overall activity levels. This finding may explain, in part, why such interventions have had limited success in reducing the body mass index or body fat of children.
authors.affiliation: Department of Endocrinology and Metabolism, Peninsula College of Medicine and Dentistry, Plymouth University Campus, Plymouth, UK. brad.metcalf@nhs.net
authors.forename: Brad
authors.initials: B
authors.lastname: Metcalf
authors.forename: William
authors.initials: W
authors.lastname: Henley
authors.forename: Terence
authors.initials: T
authors.lastname: Wilkin
mesh_terms: D000293:Adolescent; D002648:Child; D002986:Clinical Trials as Topic; D015444:Exercise; D005260:Female; D006293:Health Promotion / Q000379:methods*; D006801:Humans; D008297:Male; D009043:Motor Activity; D009765:Obesity / Q000517:prevention & control