title: Validity and reproducibility of motion sensors in youth: a systematic update.
abstract: OBJECTIVE
  To review recently published studies on the reproducibility, validity, and feasibility of motion sensors used to assess physical activity in healthy children and adolescents (2-18 yr).
  
  
  METHODS
  On October 2004, a systematic literature search in PubMed, EMBASE, and PsycINFO was performed. This search has been updated on October 2007. In this update, the clinimetric quality of three pedometers (Digi-Walker, Walk4Life, and Sun TrekLINQ) and nine accelerometers (ActiGraph, BioTrainer, StepWatch Activity Monitor, Actiwatch, Actical, Tritrac-R3D, RT3, ActivTracer, and Mini-Motionlogger) has been evaluated and compared using a checklist.
  
  
  RESULTS
  Thirty-two recently published clinimetric studies have been reviewed. All 12 motion sensors have been validated in youth in one or more studies. There is strong evidence for moderate validity of the StepWatch in children and adolescents (4-18 yr) and moderate to good validity of the ActiGraph in preschool children and young children (2-8 yr). There is less evidence for the reproducibility and feasibility of the 12 motion sensors. Strong evidence exists for good reproducibility of the ActiGraph in preschool children (2-4 yr).
  
  
  CONCLUSIONS
  Compared to the review performed in 2004, there is increased evidence for the clinimetric quality of pedometers and accelerometers in youth. Most motion sensors seem reproducible, valid, and feasible in assessing physical activity in youth.
authors.affiliation: Department of Physical Activity and Health, TNO Quality of Life, Leiden, The Netherlands. sanne.devries@tno.nl
authors.forename: Sanne I
authors.initials: SI
authors.lastname: De Vries
authors.forename: Helmi W J E M
authors.initials: HW
authors.lastname: Van Hirtum
authors.forename: Ingrid
authors.initials: I
authors.lastname: Bakker
authors.forename: Marijke
authors.initials: M
authors.lastname: Hopman-Rock
authors.forename: Remy A
authors.initials: RA
authors.lastname: Hirasing
authors.forename: Willem
authors.initials: W
authors.lastname: Van Mechelen
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D006801:Humans; D008991:Monitoring, Physiologic / Q000295:instrumentation*; D009068:Movement; D054928:Validation Studies as Topic