title: Waist-Worn Actigraphy: Population-Referenced Percentiles for Total Activity Counts in U.S. Adults.
abstract: BACKGROUND
  Accelerometer-derived total activity count is a measure of total physical activity (PA) volume. The purpose of this study was to develop age- and gender-specific percentiles for daily total activity counts (TAC), minutes of moderate-to-vigorous physical activity (MVPA), and minutes of light physical activity (LPA) in U.S. adults.
  
  
  METHODS
  Waist-worn accelerometer data from the 2003-2006 National Health and Nutrition Examination Survey were used for this analysis. The sample included adults ≥ 20 years with ≥ 10 hours accelerometer wear time on ≥ 4 days (N = 6093). MVPA and LPA were defined as the number of 1-minute epochs with counts ≥ 2020 and 100 to 2019, respectively. TAC represented the activity counts acquired daily. TAC, MVPA, and LPA were averaged across valid days to produce a daily mean.
  
  
  RESULTS
  Males in the 50th percentile accumulated 288 140 TAC/day, with 357 and 22 minutes/day spent in LPA and MVPA, respectively. The median for females was 235 741 TAC/ day, with 349 and 12 minutes/day spent in LPA and MVPA, respectively.
  
  
  CONCLUSIONS
  Population-referenced TAC percentiles reflect the total volume of PA, expressed relative to other adults. This is a different approach to accelerometer data reduction that complements the current method of looking at time spent in intensity subcategories.
authors.affiliation: Dept of Kinesiology, Recreation, and Sports Studies, The University of Tennessee, Knoxville, TN.
authors.forename: Dana L
authors.initials: DL
authors.lastname: Wolff-Hughes
authors.forename: Eugene C
authors.initials: EC
authors.lastname: Fitzhugh
authors.forename: David R
authors.initials: DR
authors.lastname: Bassett
authors.forename: James R
authors.initials: JR
authors.lastname: Churilla
mesh_terms: D061725:Accelerometry / Q000295:instrumentation / Q000592:standards*; D056044:Actigraphy / Q000379:methods; D000328:Adult; D004734:Energy Metabolism; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology*; D009749:Nutrition Surveys; D014481:United States; D055815:Young Adult