title: Activity compensation and activity synergy in British 8-13 year olds.
abstract: OBJECTIVE
  To examine whether children compensate for participating in physically active behaviors by reducing activity at other times (the 'activitystat' hypothesis); or alternatively become more active at other times (activity synergy).
  
  
  METHODS
  In 2002-2006, 345 British children (8-13 years) completed activity diaries and wore accelerometers. This generated 1077 days of data which we analyzed between-children (comparing all days) and within-child (comparing days from the same child).
  
  
  RESULTS
  On week and weekend days, each extra 1% of time in PE/games, school breaks, school active travel, non-school active travel, structured sports and out-of-home play predicted a 0.21 to 0.60% increase in the proportion of the day in moderate-to-vigorous physical activity (MVPA). None of these behaviors showed evidence of reduced MVPA at other times, i.e. activity compensation (all p>0.15). Moreover, each 1% increase in weekday non-school active travel predicted 0.38% more time in MVPA at other times (95% CI 0.18, 0.58). This activity synergy reflected children using active travel for playing and visiting friends.
  
  
  CONCLUSIONS
  Contrary to the 'activitystat' hypothesis, we found no evidence of activity compensation. This suggests that interventions increasing activity in specific behaviors may increase activity overall. The activity synergy of non-school active travel underlines the need for further research into this neglected behavior.
authors.affiliation: London School of Hygiene and Tropical Medicine, London, UK. anna.goodman@lshtm.ac.uk
authors.forename: Anna
authors.initials: A
authors.lastname: Goodman
authors.forename: Roger L
authors.initials: RL
authors.lastname: Mackett
authors.forename: James
authors.initials: J
authors.lastname: Paskins
mesh_terms: D000293:Adolescent; D000294:Adolescent Behavior / Q000502:physiology*; D002648:Child; D002652:Child Behavior / Q000502:physiology*; D004739:England; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D011998:Recreation; D012574:Schools; D013997:Time Factors