title: Determinants of change in physical activity in children and adolescents: a systematic review.
abstract: BACKGROUND
  Data are available on correlates of physical activity in children and adolescents, less is known about the determinants of change. This review aims to systematically review the published evidence regarding determinants of change in physical activity in children and adolescents.
  
  
  METHODS
  Prospective quantitative studies investigating change in physical activity in children and adolescents aged 4-18 years were identified from seven databases (to November 2010): PubMed, SCOPUS, PsycINFO, Ovid MEDLINE, SPORTDdiscus, Embase, and Web of Knowledge. Study inclusion, quality assessment, and data extraction were independently validated by two researchers. Semi-quantitative results were stratified by age (4-9 years, 10-13 years, and 14-18 years).
  
  
  RESULTS
  Of the 46 studies that were included, 31 used self-reported physical activity; average methodologic quality was 3.2 (SD=1.2), scored 0-5. Of 62 potential determinants identified, 30 were studied more than three times and 14 reported consistent findings (66% of the reported associations were in the same direction). For children aged 4-9 years, girls reported larger declines than boys. Among those aged 10-13 years, higher levels of previous physical activity and self-efficacy resulted in smaller declines. Among adolescents (aged 14-18 years), higher perceived behavioral control, support for physical activity, and self-efficacy were associated with smaller declines in physical activity.
  
  
  CONCLUSIONS
  Few of the variables studied were consistently associated with changes in physical activity, although some were similar to those identified in cross-sectional studies. The heterogeneity in study samples, exposure and outcome variables, and the reliance on self-reported physical activity limit conclusions and highlight the need for further research to inform development and targeting of interventions.
authors.affiliation: MRC Epidemiology Unit, Institute of Metabolic Science and UKCRC Centre for Diet and Activity Research, Addenbrooke's Hospital, Cambridge, United Kingdom.
authors.forename: Christopher
authors.initials: C
authors.lastname: Craggs
authors.forename: Kirsten
authors.initials: K
authors.lastname: Corder
authors.forename: Esther M F
authors.initials: EM
authors.lastname: van Sluijs
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Griffin
mesh_terms: D000293:Adolescent; D000367:Age Factors; D002648:Child; D002675:Child, Preschool; D016208:Databases, Factual; D015444:Exercise; D005260:Female; D006293:Health Promotion; D006801:Humans; D008297:Male; D009043:Motor Activity; D020377:Self Efficacy