title: Estimating physical activity in children: impact of pedometer wear time and metric.
abstract: BACKGROUND
  The purpose of this study was to provide a practical demonstration of the impact of monitoring frame and metric when assessing pedometer-determined physical activity (PA) in youth.
  
  
  METHODS
  Children (N = 1111) were asked to wear pedometers over a 7-day period during which time worn and steps were recorded each day. Varying data-exclusion criteria were used to demonstrate changes in estimates of PA. Steps were expressed using several metrics and criteria, and construct validity was demonstrated via correlations with adiposity.
  
  
  RESULTS
  Meaningful fluctuations in average steps per day and percentage meeting PA recommendations were apparent when different criteria were used. Children who wore the pedometer longer appeared more active, with each minute the pedometer was worn each day accounting for an approximate increase of 11 and 8 steps for boys and girls, respectively (P < .05). Using more restrictive exclusion criteria led to stronger correlations between indices of steps per day, steps per minute, steps per leg length, steps per minute per leg length, and obesity.
  
  
  CONCLUSIONS
  Wear time has a meaningful impact on estimates of PA. This should be considered when determining exclusion criteria and making comparisons between studies. Results also suggest that incorporating wear time per day and leg length into the metric may increase validity of PA estimates.
authors.affiliation: School of Kinesiology and Recreation, Illinois State University, Normal, IL.
authors.forename: Kelly R
authors.initials: KR
authors.lastname: Laurson
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Welk
authors.forename: Joey C
authors.initials: JC
authors.lastname: Eisenmann
mesh_terms: D056044:Actigraphy / Q000379:methods*; D000293:Adolescent; D049628:Body Size; D002648:Child; D005260:Female; D006801:Humans; D008297:Male; D009765:Obesity; D010349:Patient Compliance; D016138:Walking