title: Direct observation is a valid criterion for estimating physical activity and sedentary behavior.
abstract: BACKGROUND
  Physical activity and sedentary behavior measurement tools need to be validated in free-living settings. Direct observation (DO) may be an appropriate criterion for these studies. However, it is not known if trained observers can correctly judge the absolute intensity of free-living activities.
  
  
  OBJECTIVE
  To compare DO estimates of total MET-hours and time in activity intensity categories to a criterion measure from indirect calorimetry (IC).
  
  
  METHODS
  Fifteen participants were directly observed on three separate days for two hours each day. During this time participants wore an Oxycon Mobile indirect calorimeter and performed any activity of their choice within the reception area of the wireless metabolic equipment. Participants were provided with a desk for sedentary activities (writing, reading, computer use) and had access to exercise equipment (treadmill, bike).
  
  
  RESULTS
  DO accurately and precisely estimated MET-hours [% bias (95% CI) = -12.7% (-16.4, -7.3), ICC = 0.98], time in low intensity activity [% bias (95% CI) = 2.1% (1.1, 3.2), ICC = 1.00] and time in moderate to vigorous intensity activity [% bias (95% CI) -4.9% (-7.4, -2.5), ICC = 1.00].
  
  
  CONCLUSIONS
  This study provides evidence that DO can be used as a criterion measure of absolute intensity in free-living validation studies.
authors: Dept of Kinesiology, University of Massachusetts, Amherst, MA.
authors: Kate
authors: K
authors: Lyden
authors: Natalia
authors: N
authors: Petruski
authors: John
authors: J
authors: Staudenmayer
authors: Patty
authors: P
authors: Freedson
mesh_terms: D000328:Adult; D002153:Calorimetry, Indirect / Q000295:instrumentation* / Q000379:methods; D006801:Humans; D008404:Massachusetts; D009043:Motor Activity; D015588:Observer Variation; D057185:Sedentary Behavior; D013997:Time Factors