title: Standardising the 'after-school' period for children's physical activity and sedentary behaviour.
abstract: OBJECTIVE
  Studies examining children's after-school physical activity (PA) and sedentary behaviours (SB) often use arbitrary times to signify the period start and end. A standardised time is required for future research examining this period. The aim of the present study was to compare children's after-school behaviour using three definitions of the after-school period, namely (1) end of school to 6 pm; (2) end of school to dinner time; and (3) end of school to sunset, to determine the extent of variability in PA and SB during the after-school period depending on the definition used.
  
  
  METHODS
  Children (n=308; aged 8 years) from the Melbourne Transform-Us! intervention wore an accelerometer and a subsample (n=112) wore an activPAL inclinometer in 2010. The end of school bell time was obtained from the child's school, parents completed a 2-day log reporting their child's dinner time and sunset times were obtained from Geoscience Australia. ActiGraph accelerometers assessed the proportion of time spent sedentary (SED) and that spent in light (LPA), moderate (MPA) and moderate-to-vigorous (MVPA) PA during the three time periods; activPAL inclinometers assessed the proportion of time spent sitting (SIT).
  
  
  RESULTS
  Apart from the end of school time (3:30 pm), dinner (range 3:30 pm-8:40 pm) and sunset (range 5:07 pm-7:34 pm) times varied. Despite this, there were no significant differences in estimates of the proportions of time children spent in SED, LPA, MPA, MVPA or SIT between the three after-school periods examined.
  
  
  CONCLUSIONS
  Given the small differences in SED, PA and SIT during the after-school period regardless of the definition (6 pm, sunset or dinner time), it appears that applying a standardised definition of end of school to 6 pm is acceptable for defining children's PA and SB during the after-school period. So what? The use of a standardised after-school definition (end of school to 6 pm), will enable future studies exploring children's after-school PA and SB to be more comparable.
authors.affiliation: School of Exercise amd Nutrition Sciences, Deakin University, Burwood, Australia. lauren.arundell@deakin.edu
authors.forename: Lauren
authors.initials: L
authors.lastname: Arundell
authors.forename: Jo
authors.initials: J
authors.lastname: Salmon
authors.forename: Jenny
authors.initials: J
authors.lastname: Veitch
authors.forename: Eoin
authors.initials: E
authors.lastname: O'Connell
authors.forename: Trina
authors.initials: T
authors.lastname: Hinkley
authors.forename: Clare
authors.initials: C
authors.lastname: Hume
mesh_terms: D061725:Accelerometry / Q000295:instrumentation; D002648:Child; D005260:Female; D015438:Health Behavior; D006801:Humans; D008297:Male; D009043:Motor Activity; D057185:Sedentary Behavior; D013997:Time Factors; D014739:Victoria