title: Estimating minutes of physical activity from the previous day physical activity recall: validation of a prediction equation.
abstract: BACKGROUND
  This study was designed to develop a prediction algorithm that would allow the Previous Day Physical Activity Recall (PDPAR) to be equated with temporally matched data from an accelerometer.
  
  
  METHODS
  Participants (n = 121) from a large, school-based intervention wore a validated accelerometer and completed the PDPAR for 3 consecutive days. Physical activity estimates were obtained from PDPAR by totaling 30-minute bouts of activity coded as ≥4 METS. A regression equation was developed in a calibration sample (n = 91) to predict accelerometer minutes of moderate to vigorous physical activity (MVPA) from PDPAR bouts. The regression equation was then applied to a separate, holdout sample (n = 30) to evaluate the utility of the prediction algorithm.
  
  
  RESULTS
  Gender and PDPAR bouts accounted for 36.6% of the variance in accelerometer MVPA. The regression model showed that on average boys obtain 9.0 min of MVPA for each reported PDPAR bout, while girls obtain 4.8 min of MVPA per bout. When applied to the holdout sample, predicted minutes of MVPA from the models showed good agreement with accelerometer minutes (r = .81).
  
  
  CONCLUSIONS
  The prediction equation provides a valid and useful metric to aid in the interpretation of PDPAR results.
authors.affiliation: Dept of Health, Nutrition, and Exercise Sciences, North Dakota State University, Fargo, ND, USA.
authors.forename: Jared M
authors.initials: JM
authors.lastname: Tucker
authors.forename: Greg
authors.initials: G
authors.lastname: Welk
authors.forename: Sarah M
authors.initials: SM
authors.lastname: Nusser
authors.forename: Nicholas K
authors.initials: NK
authors.lastname: Beyler
authors.forename: David
authors.initials: D
authors.lastname: Dzewaltowski
mesh_terms: D061725:Accelerometry / Q000592:standards; D000293:Adolescent; D000465:Algorithms; D002138:Calibration; D002648:Child; D015444:Exercise / Q000502:physiology*; D005260:Female; D006293:Health Promotion / Q000379:methods*; D006801:Humans; D008297:Male; D011939:Mental Recall; D055686:Metabolic Equivalent / Q000502:physiology; D012572:School Health Services; D057566:Self Report; D011795:Surveys and Questionnaires / Q000592:standards*; D013997:Time Factors