title: Validation of thigh-based accelerometer estimates of postural allocation in 5-12 year-olds.
abstract: OBJECTIVE
  To validate activPAL3™ (AP3) for classifying postural allocation, estimating time spent in postures and examining the number of breaks in sedentary behaviour (SB) in 5-12 year-olds.
  
  
  METHODS
  Laboratory-based validation study.
  
  
  METHODS
  Fifty-seven children completed 15 sedentary, light- and moderate-to-vigorous intensity activities. Direct observation (DO) was used as the criterion measure. The accuracy of AP3 was examined using a confusion matrix, equivalence testing, Bland-Altman procedures and a paired t-test for 5-8y and 9-12y.
  
  
  RESULTS
  Sensitivity of AP3 was 86.8%, 82.5% and 85.3% for sitting/lying, standing, and stepping, respectively, in 5-8y and 95.3%, 81.5% and 85.1%, respectively, in 9-12y. Time estimates of AP3 were equivalent to DO for sitting/lying in 9-12y and stepping in all ages, but not for sitting/lying in 5-12y and standing in all ages. Underestimation of sitting/lying time was smaller in 9-12y (1.4%, limits of agreement [LoA]: -13.8 to 11.1%) compared to 5-8y (12.6%, LoA: -39.8 to 14.7%). Underestimation for stepping time was small (5-8y: 6.5%, LoA: -18.3 to 5.3%; 9-12y: 7.6%, LoA: -16.8 to 1.6%). Considerable overestimation was found for standing (5-8y: 36.8%, LoA: -16.3 to 89.8%; 9-12y: 19.3%, LoA: -1.6 to 36.9%). SB breaks were significantly overestimated (5-8y: 53.2%, 9-12y: 28.3%, p<0.001).
  
  
  CONCLUSIONS
  AP3 showed acceptable accuracy for classifying postures, however estimates of time spent standing were consistently overestimated and individual error was considerable. Estimates of sitting/lying were more accurate for 9-12y. Stepping time was accurately estimated for all ages. SB breaks were significantly overestimated, although the absolute difference was larger in 5-8y. Surveillance applications of AP3 would be acceptable, however, individual level applications might be less accurate.
authors: Early Start Research Institute and Illawarra Health and Medical Research Institute, Faculty of Social Sciences, University of Wollongong, Australia. Electronic address: cmtvl646@uowmail.edu.au.
authors: Christiana M T
authors: CM
authors: van Loo
authors: Early Start Research Institute and Illawarra Health and Medical Research Institute, Faculty of Social Sciences, University of Wollongong, Australia.
authors: Anthony D
authors: AD
authors: Okely
authors: School of Mathematics and Applied Statistics, University of Wollongong, Australia.
authors: Marijka J
authors: MJ
authors: Batterham
authors: Deakin University, Geelong, Australia, Institute for Physical Activity and Nutrition (IPAN), School of Exercise and Nutrition Sciences.
authors: Trina
authors: T
authors: Hinkley
authors: Norwegian School of Sports Sciences, Norway; MRC Epidemiology Unit, University of Cambridge, United Kingdom.
authors: Ulf
authors: U
authors: Ekelund
authors: MRC Epidemiology Unit, University of Cambridge, United Kingdom.
authors: Søren
authors: S
authors: Brage
authors: University of Strathclyde, School of Psychological Sciences and Health, Scotland.
authors: John J
authors: JJ
authors: Reilly
authors: Early Start Research Institute and Illawarra Health and Medical Research Institute, Faculty of Social Sciences, University of Wollongong, Australia.
authors: Rachel A
authors: RA
authors: Jones
authors: University of Strathclyde, School of Psychological Sciences and Health, Scotland.
authors: Xanne
authors: X
authors: Janssen
authors: Early Start Research Institute and Illawarra Health and Medical Research Institute, Faculty of Social Sciences, University of Wollongong, Australia.
authors: Dylan P
authors: DP
authors: Cliff
mesh_terms: D061725:Accelerometry / Q000295:instrumentation*; D002648:Child; D002675:Child, Preschool; D006801:Humans; D009068:Movement; D011187:Posture
keywords: Accelerometry; Breaks; Child; Physical activity; Sedentary behaviour; activPAL