title: Validity of physical activity monitors in adults participating in free-living activities.
abstract: BACKGROUND
  For a given subject, time in moderate to very vigorous intensity physical activity (MVPA) varies substantially among physical activity monitors.
  
  
  OBJECTIVE
  In the present study, the primary objective, whether time in MVPA recorded with SenseWear Pro(2) Armband (Armband; BodyMedia, Pittsburgh, Pennsylvania, USA), ActiGraph (7164, LLC, Fort Walton Beach, Florida, USA), ikcal (Teltronic AG, Biberist, Switzerland) and ActiReg (PreMed AS, Oslo, Norway) is different compared with indirect calorimetry, was determined. The secondary objective, whether these activity monitors estimate energy expenditure differently compared with indirect calorimetry, was also determined.
  
  
  METHODS
  The activity monitors and a portable oxygen analyser were worn by 14 men and 6 women for 120 min doing a variety of activities of different intensities. Resting metabolic rate was measured with indirect calorimetry. The cutoff points defining moderate, vigorous and very vigorous intensity were three, six and nine times resting metabolic rate.
  
  
  RESULTS
  Time in MVPA was overestimated by 2.9% and 2.5% by Armband and ActiGraph, respectively, and was underestimated by 11.6% and 98.7% by ikcal and ActiReg, respectively. ActiReg (p = 0.004) and ActiGraph (p = 0.007) underestimated energy expenditure in MVPA, and all monitors underestimated total energy expenditure (by 5% to 21%).
  
  
  CONCLUSIONS
  Recorded time in MVPA and energy expenditure varies substantially among physical activity monitors. Thus, when comparing physical activity level among studies, it is essential to know the type of physical activity monitor being used.
authors.affiliation: Department of Sports Medicine, Norwegian School of Sport Sciences, PO Box 4014, Ullevaal Stadion, NO0806 Oslo, Norway. sveinung.berntsen@nih.no
authors.forename: S
authors.initials: S
authors.lastname: Berntsen
authors.forename: R
authors.initials: R
authors.lastname: Hageberg
authors.forename: A
authors.initials: A
authors.lastname: Aandstad
authors.forename: P
authors.initials: P
authors.lastname: Mowinckel
authors.forename: S A
authors.initials: SA
authors.lastname: Anderssen
authors.forename: K-H
authors.initials: KH
authors.lastname: Carlsen
authors.forename: L B
authors.initials: LB
authors.lastname: Andersen
mesh_terms: D000328:Adult; D002151:Calorimetry; D004734:Energy Metabolism / Q000502:physiology; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018670:Monitoring, Ambulatory / Q000295:instrumentation / Q000379:methods*; D012680:Sensitivity and Specificity; D016138:Walking / Q000502:physiology; D055815:Young Adult