title: Impact of accelerometer epoch length on physical activity and sedentary behaviour outcomes for preschool-aged children.
abstract: BACKGROUND
  The Canadian Health Measures Survey uses accelerometry to collect physical activity and sedentary behaviour data. Between cycles 2 and 3, a transition was made from 60-second to 15-second epochs in accelerometry data for children aged 3 to 5. This study examines the impact of epoch length on physical activity and sedentary behaviour outcomes.
  
  
  METHODS
  Twenty-nine children aged 3 to 5 wore two accelerometers at the same time, one initialized to collect data in 60-second epochs, and the other, in 15-second epochs. Comparisons between epoch settings were made for several physical activity variables.
  
  
  RESULTS
  Compared with the 60-second epoch setting, the 15-second setting captured more moderate-to-vigorous physical activity (MVPA) and sedentary time, but fewer steps and less light and total physical activity. The correlation between epoch settings was high for all variables except steps.
  
  
  CONCLUSIONS
  The epoch length used in accelerometer data collection affects physical activity and sedentary behaviour data for preschool-aged children.
authors.affiliation: Health Analysis Division, Statistics Canada, and Children's Hospital of Eastern Ontario Research Institute, Ottawa, Canada.
authors.forename: Rachel C
authors.initials: RC
authors.lastname: Colley
authors.affiliation: Children's Hospital of Eastern Ontario Research Institute, Ottawa, Canada.
authors.forename: Alysha
authors.initials: A
authors.lastname: Harvey
authors.affiliation: Children's Hospital of Eastern Ontario Research Institute, Ottawa, Canada.
authors.forename: Kimberly P
authors.initials: KP
authors.lastname: Grattan
authors.affiliation: Children's Hospital of Eastern Ontario Research Institute, Ottawa, Canada.
authors.forename: Kristi B
authors.initials: KB
authors.lastname: Adamo
mesh_terms: D061725:Accelerometry; D002170:Canada; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D008297:Male; D009043:Motor Activity; D057185:Sedentary Behavior; D013997:Time Factors
keywords: Ambulation; pediatric; stepping; walking