title: Calibration of self-report tools for physical activity research: the Physical Activity Questionnaire (PAQ).
abstract: BACKGROUND
  The utility of self-report measures of physical activity (PA) in youth can be greatly enhanced by calibrating self-report output against objectively measured PA data.This study demonstrates the potential of calibrating self-report output against objectively measured physical activity (PA) in youth by using a commonly used self-report tool called the Physical Activity Questionnaire (PAQ).
  
  
  METHODS
  A total of 148 participants (grades 4 through 12) from 9 schools (during the 2009-2010 school year) wore an Actigraph accelerometer for 7 days and then completed the PAQ. Multiple linear regression modeling was used on 70% of the available sample to develop a calibration equation and this was cross validated on an independent sample of participants (30% of sample).
  
  
  RESULTS
  A calibration model with age, gender, and PAQ scores explained 40% of the variance in values for the percentage of time in moderate-to-vigorous PA (%MVPA) measured from the accelerometers (%MVPA = 14.56 - (sex*0.98) - (0.84*age) + (1.01*PAQ)). When tested on an independent, hold-out sample, the model estimated %MVPA values that were highly correlated with the recorded accelerometer values (r = .63) and there was no significant difference between the estimated and recorded activity values (mean diff. = 25.3 ± 18.1 min; p = .17).
  
  
  CONCLUSIONS
  These results suggest that the calibrated PAQ may be a valid alternative tool to activity monitoring instruments for estimating %MVPA in groups of youth.
authors.affiliation: 235 Forker Building, Ames, IA 50011, USA. pedrosm@iastate.edu.
authors.forename: Pedro F
authors.initials: PF
authors.lastname: Saint-Maurice
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Welk
authors.forename: Nicholas K
authors.initials: NK
authors.lastname: Beyler
authors.forename: Roderick T
authors.initials: RT
authors.lastname: Bartee
authors.forename: Kate A
authors.initials: KA
authors.lastname: Heelan
mesh_terms: D000293:Adolescent; D035843:Biomedical Research; D002138:Calibration; D015444:Exercise; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D008991:Monitoring, Physiologic; D012574:Schools; D057566:Self Report / Q000592:standards*; D011795:Surveys and Questionnaires; D013997:Time Factors