title: Objective measurement of levels and patterns of physical activity.
abstract: OBJECTIVE
  To measure the levels and patterns of physical activity, using accelerometers, of 11-year-old children participating in the Avon Longitudinal Study of Parents and Children (ALSPAC).
  
  
  METHODS
  Cross-sectional analysis.
  
  
  METHODS
  ALSPAC is a birth cohort study located in the former county of Avon, in the southwest of England. This study used data collected when the children were 11 years old.
  
  
  METHODS
  5595 children (2662 boys, 2933 girls). The children are the offspring of women recruited to a birth cohort study during 1991-2. The median age (95% CI) of the children is now 11.8 (11.6 to 11.9) years.
  
  
  METHODS
  Physical activity was measured over a maximum of 7 consecutive days using the MTI Actigraph accelerometer.
  
  
  METHODS
  Level and pattern of physical activity.
  
  
  RESULTS
  The median physical activity level was 580 counts/min. Boys were more active than girls (median (IQR) 644 (528-772) counts/min vs 529 (444-638) counts/min, respectively). Only 2.5% (95% CI 2.1% to 2.9%) of children (boys 5.1% (95% CI 4.3% to 6.0%), girls 0.4% (95% CI 0.2% to 0.7%) met current internationally recognised recommendations for physical activity. Children were most active in summer and least active in winter (difference = 108 counts/min). Both the mother and partner's education level were inversely associated with activity level (p for trend <0.001 (both mother and partner)). The association was lost for mother's education (p for trend = 0.07) and attenuated for partner's education (p for trend = 0.02), after adjustment for age, sex, season, maternal age and social class.
  
  
  CONCLUSIONS
  A large majority of children are insufficiently active, according to current recommended levels for health.
authors.affiliation: Sport and Exercise Science, School for Health, University of Bath, Bath, UK. cjr27@bath.ac.uk
authors.forename: Chris J
authors.initials: CJ
authors.lastname: Riddoch
authors.forename: Calum
authors.initials: C
authors.lastname: Mattocks
authors.forename: Kevin
authors.initials: K
authors.lastname: Deere
authors.forename: Jo
authors.initials: J
authors.lastname: Saunders
authors.forename: Jo
authors.initials: J
authors.lastname: Kirkby
authors.forename: Kate
authors.initials: K
authors.lastname: Tilling
authors.forename: Sam D
authors.initials: SD
authors.lastname: Leary
authors.forename: Steven N
authors.initials: SN
authors.lastname: Blair
authors.forename: Andy R
authors.initials: AR
authors.lastname: Ness
mesh_terms: D002648:Child; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D004522:Educational Status; D005260:Female; D015438:Health Behavior; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D009043:Motor Activity; D050177:Overweight; D010290:Parents; D012621:Seasons; D012923:Social Class; D006113:United Kingdom