title: How many days of monitoring are needed to reliably assess SenseWear Armband outcomes in primary school-aged children?
abstract: OBJECTIVE
  To identify the number of hours and days or nights of monitoring required to reliably estimate energy expenditure (EE), steps, waking sedentary time, light- (LPA), moderate- (MPA), vigorous- (VPA), moderate- to vigorous-intensity physical activity (MVPA), time in bed and total sleep time using the SenseWear Armband.
  
  
  METHODS
  Cross-sectional study.
  
  
  METHODS
  One hundred and two children (50% boys) aged 8-11 years from six schools wore a SenseWear Armband (BodyMedia Inc, USA) for eight consecutive days (seven consecutive nights). Hourly increments of valid day wear time criteria were examined (days/week; 8h/day-14h/day). Intra-class correlation coefficients estimated the reliability for any individual day for each wear time criteria. The Spearman-Brown prophecy formula was used to determine the number of days/nights of monitoring needed to achieve reliability estimates of 0.7, 0.8 and 0.9.
  
  
  RESULTS
  Fewer monitoring days were needed as the valid day criteria became more stringent. For example, at least 12h of wear time on at least 2 days was required to achieve a reliability of 0.7 for EE. In contrast, at least 8h/day on 5 days resulted in reliable estimates (0.7) for MPA, VPA and MVPA. Between 6 and 7 nights of monitoring were required to reliably estimate children's time in bed and total sleep time, respectively.
  
  
  CONCLUSIONS
  A 7-day monitoring protocol in primary school-aged children would provide acceptable reliability for the assessment of EE, waking sedentary time, LPA, MPA, VPA, MVPA, time in bed and total sleep time, as assessed by the SenseWear Armband.
authors.affiliation: Centre for Physical Activity and Nutrition Research, Deakin University, Australia. Electronic address: nicky.ridgers@deakin.edu.au.
authors.forename: Nicola D
authors.initials: ND
authors.lastname: Ridgers
authors.affiliation: School of Science and Health, Western Sydney University, Australia.
authors.forename: Jill A
authors.initials: JA
authors.lastname: Hnatiuk
authors.affiliation: Centre for Physical Activity and Nutrition Research, Deakin University, Australia.
authors.forename: Grace E
authors.initials: GE
authors.lastname: Vincent
authors.affiliation: Centre for Physical Activity and Nutrition Research, Deakin University, Australia.
authors.forename: Anna
authors.initials: A
authors.lastname: Timperio
authors.affiliation: School of Health and Social Development, Deakin University, Australia.
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Barnett
authors.affiliation: Centre for Physical Activity and Nutrition Research, Deakin University, Australia.
authors.forename: Jo
authors.initials: J
authors.lastname: Salmon
mesh_terms: D056044:Actigraphy / Q000295:instrumentation / Q000379:methods*; D001315:Australia; D002648:Child; D003430:Cross-Sectional Studies; D004734:Energy Metabolism; D005260:Female; D006801:Humans; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D015203:Reproducibility of Results; D012574:Schools; D013334:Students / Q000706:statistics & numerical data; D013997:Time Factors
keywords: Energy expenditure; Measurement; Physical activity; Sedentary behaviour; Youth