title: Comparison of 3 accelerometer data reduction approaches, step counts, and 2 self-report measures for estimating physical activity in free-living adults.
abstract: BACKGROUND
  Accelerometers have become one of the most common methods of measuring physical activity (PA). Thus, validity of accelerometer data reduction approaches remains an important research area. Yet, few studies directly compare data reduction approaches and other PA measures in free-living samples.
  
  
  OBJECTIVE
  To compare PA estimates provided by 3 accelerometer data reduction approaches, steps, and 2 self-reported estimates: Crouter's 2-regression model, Crouter's refined 2-regression model, the weighted cut-point method adopted in the National Health and Nutrition Examination Survey (NHANES; 2003-2004 and 2005-2006 cycles), steps, IPAQ, and 7-day PA recall.
  
  
  METHODS
  A worksite sample (N = 87) completed online-surveys and wore ActiGraph GT1M accelerometers and pedometers (SW-200) during waking hours for 7 consecutive days. Daily time spent in sedentary, light, moderate, and vigorous intensity activity and percentage of participants meeting PA recommendations were calculated and compared.
  
  
  RESULTS
  Crouter's 2-regression (161.8 ± 52.3 minutes/day) and refined 2-regression (137.6 ± 40.3 minutes/day) models provided significantly higher estimates of moderate and vigorous PA and proportions of those meeting PA recommendations (91% and 92%, respectively) as compared with the NHANES weighted cut-point method (39.5 ± 20.2 minutes/day, 18%). Differences between other measures were also significant.
  
  
  CONCLUSIONS
  When comparing 3 accelerometer cut-point methods, steps, and self-report measures, estimates of PA participation vary substantially.
authors.affiliation: Dept of Health, Human Performance, and Recreation, Baylor University, Waco, TX.
authors.forename: M Renee
authors.initials: MR
authors.lastname: Umstattd Meyer
authors.forename: Stephanie L
authors.initials: SL
authors.lastname: Baller
authors.forename: Shawn M
authors.initials: SM
authors.lastname: Mitchell
authors.forename: Stewart G
authors.initials: SG
authors.lastname: Trost
mesh_terms: D061725:Accelerometry / Q000706:statistics & numerical data*; D056044:Actigraphy / Q000295:instrumentation* / Q000379:methods; D000328:Adult; D005260:Female; D006306:Health Surveys; D006801:Humans; D008297:Male; D008875:Middle Aged; D018670:Monitoring, Ambulatory / Q000379:methods*; D009043:Motor Activity; D009749:Nutrition Surveys; D012044:Regression Analysis; D057566:Self Report; D012959:Socioeconomic Factors; D013997:Time Factors