title: Accelerometer-derived physical activity levels of preschoolers: a meta-analysis.
abstract: OBJECTIVE
  This study synthesized the published estimates of daily moderate-to-vigorous physical activity (MVPAd(-1)) of preschooler-age children (3-5 years).
  
  
  METHODS
  Meta-analysis of previously published studies reporting accelerometer-derived estimates of daily MVPA of preschoolers.
  
  
  METHODS
  A comprehensive literature review was conducted to identify studies published by March 2010 that reported daily minutes of accelerometer-derived MVPA in preschool-age children (3-5 years). Random effects point estimates and 95% confidence intervals (95% CIs) were calculated based on study weighted means and standard deviations of raw accelerometer counts per minute (cpm) and reported minutes of MVPA and/or percentage of time spent in MVPAd(-1).
  
  
  RESULTS
  29 articles representing 6309 preschoolers were included. Overall, preschoolers engaged in 42.8 min (95% CI 28.9-56.8) of MVPAd(-1), and 54.4 min (95% CI 29.9-78.9) and 45.4 min (95% CI 25.2-65.6) for boys and girls separately. This translated into approximately 5.5% (95% CI 3.7-7.2%) of time spent in MVPAd(-1), and 7.1% (95% CI 3.9-10.3%) for boys and 6.3% (95% CI 3.9-8.7%) for girls. Studies (76%) using ActiGraph accelerometers reported an average of 714 cpm (95% CI 678-751), with boys and girls having 783 cpm (95% CI 753-813) and 696 cpm (95% CI 665-727), respectively.
  
  
  CONCLUSIONS
  Interpretation of accelerometer-derived MVPA is confounded by differences in cutpoints applied within a study. Great care, therefore, should be taken when interpreting the activity levels of preschoolers to inform policy decisions, such as the development of physical activity guidelines. Hence, considerable attention is required to unify accelerometer-derived MVPA so that unbiased comparisons across studies can be made.
authors.affiliation: Department of Exercise Science, University of South Carolina, USA. bornstei@mailbox.sc.edu
authors.forename: Daniel B
authors.initials: DB
authors.lastname: Bornstein
authors.forename: Michael W
authors.initials: MW
authors.lastname: Beets
authors.forename: Wonwoo
authors.initials: W
authors.lastname: Byun
authors.forename: Kerry
authors.initials: K
authors.lastname: McIver
mesh_terms: D002675:Child, Preschool; D005260:Female; D006801:Humans; D008297:Male; D018670:Monitoring, Ambulatory / Q000295:instrumentation*; D009043:Motor Activity / Q000502:physiology*; D015203:Reproducibility of Results