title: The validity of the GENEActiv wrist-worn accelerometer for measuring adult sedentary time in free living.
abstract: OBJECTIVE
  Based on self-reported measures, sedentary time has been associated with chronic disease and mortality. This study examined the validity of the wrist-worn GENEactiv accelerometer for measuring sedentary time (i.e. sitting and lying) by posture classification, during waking hours in free living adults.
  
  
  METHODS
  Fifty-seven participants (age=18-55 years 52% male) were recruited using convenience sampling from a large metropolitan Australian university.
  
  
  METHODS
  Participants wore a GENEActiv accelerometer on their non-dominant wrist and an activPAL device attached to their right thigh for 24-h (00:00 to 23:59:59). Pearson's Correlation Coefficient was used to examine the convergent validity of the GENEActiv and the activPAL for estimating total sedentary time during waking hours. Agreement was illustrated using Bland and Altman plots, and intra-individual agreement for posture was assessed with the Kappa statistic.
  
  
  RESULTS
  Estimates of average total sedentary time over 24-h were 623 (SD 103) min/day from the GENEActiv, and 626 (SD 123) min/day from the activPAL, with an Intraclass Correlation Coefficient of 0.80 (95% confidence intervals 0.68-0.88). Bland and Altman plots showed slight underestimation of mean total sedentary time for GENEActiv relative to activPAL (mean difference: -3.44min/day), with moderate limits of agreement (-144 to 137min/day). Mean Kappa for posture was 0.53 (SD 0.12), indicating moderate agreement for this sample at the individual level.
  
  
  CONCLUSIONS
  The estimation of sedentary time by posture classification of the wrist-worn GENEActiv accelerometer was comparable to the activPAL. The GENEActiv may provide an alternative, easy to wear device based measure for descriptive estimates of sedentary time in population samples.
authors.affiliation: Centre for Research on Exercise, Physical Activity and Health (CRExPAH), School of Human Movement Studies, The University of Queensland, Brisbane, Australia. Electronic address: t.pavey@uq.edu.au.
authors.forename: Toby G
authors.initials: TG
authors.lastname: Pavey
authors.affiliation: Centre for Research on Exercise, Physical Activity and Health (CRExPAH), School of Human Movement Studies, The University of Queensland, Brisbane, Australia.
authors.forename: Sjaan R
authors.initials: SR
authors.lastname: Gomersall
authors.affiliation: Centre for Research on Exercise, Physical Activity and Health (CRExPAH), School of Human Movement Studies, The University of Queensland, Brisbane, Australia.
authors.forename: Bronwyn K
authors.initials: BK
authors.lastname: Clark
authors.affiliation: Centre for Research on Exercise, Physical Activity and Health (CRExPAH), School of Human Movement Studies, The University of Queensland, Brisbane, Australia.
authors.forename: Wendy J
authors.initials: WJ
authors.lastname: Brown
mesh_terms: D061725:Accelerometry; D000293:Adolescent; D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D057185:Sedentary Behavior; D055815:Young Adult
keywords: Accelerometer; Adults; Objective; Posture; Sedentary