title: StepWatch stride counting: accuracy, precision, and prediction of energy expenditure in children.
abstract: BACKGROUND
  Accuracy and precision of the StepWatch (SW) was tested in typically developing youth (TDY) with the prediction of oxygen consumption derived from stride counts.
  
  
  METHODS
  Ten TDY (5 boys, 5 girls) with an average age 14.1 years (SD=2.2) enrolled. Participants underwent treadmill cardiopulmonary exercise testing (CPET) wearing two SW devices at 1, 2, 3, and 4 miles per hour (mph).
  
  
  RESULTS
  Average sign-corrected disagreement for strides counted between the 2 monitors was 0.4 (0.52), 0.2 (0.42), 0.1 (0.32), and 0.1 (0.32) for 1, 2, 3, and 4 mph, respectively. The ratio of SW counts to observed manual counts averaged 100.03% with ICC=0.995. Oxygen consumption equations were derived from resting and walking VO(2), age, gender, and stride counts.
  
  
  CONCLUSIONS
  Excellent accuracy and precision was documented for treadmill walking speeds up to 4 mph while VO(2) per number of strides taken appears to decrease with age and is lower in girls.
authors.affiliation: Developmental Medicine, Seattle Children's Research Institute, University of Washington, Seattle, WA, USA. kristie.bjornson@seattlechildrens.org
authors.forename: Kristie F
authors.initials: KF
authors.lastname: Bjornson
authors.forename: Delphine
authors.initials: D
authors.lastname: Yung
authors.forename: Kevin
authors.initials: K
authors.lastname: Jacques
authors.forename: Robert L
authors.initials: RL
authors.lastname: Burr
authors.forename: Dimitri
authors.initials: D
authors.lastname: Christakis
mesh_terms: D061725:Accelerometry / Q000295:instrumentation / Q000379:methods; D000293:Adolescent; D000367:Age Factors; D002648:Child; D019719:Diagnostic Equipment / Q000592:standards*; D061827:Dimensional Measurement Accuracy; D004734:Energy Metabolism / Q000502:physiology*; D004867:Equipment Design; D005080:Exercise Test / Q000295:instrumentation / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008422:Materials Testing / Q000379:methods; D010101:Oxygen Consumption / Q000502:physiology*; D012737:Sex Factors; D016138:Walking / Q000502:physiology