title: Validation and calibration of the activPAL™ for estimating METs and physical activity in 4-6 year olds.
abstract: OBJECTIVE
  Examine the predictive validity of the activPAL™ metabolic equivalents equation, develop an activPAL™ threshold value to define moderate-to vigorous-intensity physical activities, and examine the classification accuracy of the developed moderate-to vigorous-intensity physical activities threshold value in 4- to 6-year-old children.
  
  
  METHODS
  A sample of forty 4- to 6-year-old children from the Illawarra region in New South Wales, Australia were included in data analysis.
  
  
  METHODS
  Participants completed a ∼ 150-min room calorimeter protocol involving age-appropriate sedentary behaviors, light-intensity physical activities and moderate-to vigorous-intensity physical activities. activPAL™ accelerometer counts were collected over 15s epochs. Energy expenditure measured by room calorimetry and direct observation were used as the criterion measure. Predicted metabolic equivalents were calculated using the activPAL™ metabolic equivalents equation (activPAL™ software version 5.8.0). Predictive validity was evaluated using dependent-samples t-tests. Participants were randomly allocated into two groups to develop and cross-validate an intensity threshold for moderate-to vigorous-intensity physical activities. Receiver operating characteristic curve analysis was used to determine moderate-to vigorous-intensity physical activities threshold. The classification accuracy of the developed threshold was cross-validated using sensitivity, specificity, and area under the receiver operating characteristic-curve.
  
  
  RESULTS
  The activPAL™ metabolic equivalents equation significantly overestimated metabolic equivalents during sedentary behaviors and significantly underestimated metabolic equivalents for light-intensity physical activities, moderate-to vigorous-intensity physical activities and total metabolic equivalents compared to measured metabolic equivalents (all P<0.001). The developed threshold of ≥1418 counts per 15s resulted in good classification accuracy for moderate-to vigorous-intensity physical activities.
  
  
  CONCLUSIONS
  The current activPAL™ metabolic equivalents equation requires further development before it can be used to accurately estimate metabolic equivalents in preschoolers. The developed threshold exhibited acceptable classification accuracy for moderate-to vigorous-intensity physical activities; however studies cross-validating this moderate-to vigorous-intensity physical activities threshold in free-living preschool-aged children are recommended.
authors.affiliation: Interdisciplinary Educational Research Institute, University of Wollongong, Australia. Electronic address: xj512@uowmail.edu.au.
authors.forename: Xanne
authors.initials: X
authors.lastname: Janssen
authors.affiliation: Interdisciplinary Educational Research Institute, University of Wollongong, Australia.
authors.forename: Dylan P
authors.initials: DP
authors.lastname: Cliff
authors.affiliation: School of Psychology and Health, University of Strathclyde, United Kingdom.
authors.forename: John J
authors.initials: JJ
authors.lastname: Reilly
authors.affiliation: Centre for Physical Activity and Nutrition Research (C-PAN), Deakin University, Australia.
authors.forename: Trina
authors.initials: T
authors.lastname: Hinkley
authors.affiliation: Interdisciplinary Educational Research Institute, University of Wollongong, Australia.
authors.forename: Rachel A
authors.initials: RA
authors.lastname: Jones
authors.affiliation: Centre for Statistical and Survey Methodology, University of Wollongong, Australia.
authors.forename: Marijka
authors.initials: M
authors.lastname: Batterham
authors.affiliation: Department of Sport Medicine, Norwegian School of Sport Sciences, Norway; MRC Epidemiology Unit, Institute of Metabolic Science, Addenbrooke's Hospital, United Kingdom.
authors.forename: Ulf
authors.initials: U
authors.lastname: Ekelund
authors.affiliation: MRC Epidemiology Unit, Institute of Metabolic Science, Addenbrooke's Hospital, United Kingdom.
authors.forename: Søren
authors.initials: S
authors.lastname: Brage
authors.affiliation: Interdisciplinary Educational Research Institute, University of Wollongong, Australia.
authors.forename: Anthony D
authors.initials: AD
authors.lastname: Okely
mesh_terms: D000465:Algorithms; D002138:Calibration; D002151:Calorimetry; D002648:Child; D002675:Child, Preschool; D004734:Energy Metabolism; D015444:Exercise / Q000502:physiology*; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D055686:Metabolic Equivalent; D008954:Models, Biological
keywords: Accelerometry; Activity monitor; Inclinometer; MVPA; Room calorimetry; Young children