title: Criterion validity of a 10-category scale for ranking physical activity in Norwegian women.
abstract: BACKGROUND
  Accurate measurement of physical activity (PA) is critical to establish dose-response relationships with various health outcomes. We compared the self-administered PA questionnaire from the Norwegian Women and Cancer Study (NOWAC) with a criterion method in middle-aged Norwegian women.
  
  
  METHODS
  A sample of 177 randomly recruited healthy women attended two clinical visits approximately 4-6 months apart. At each visit, the women completed the NOWAC PA questionnaire (NOPAQ), rating their overall PA level on a 10-category scale (1 being a "very low" and 10 being a "very high" PA level) and performed an 8-minute step-test to estimate aerobic fitness (VO2max). After each visit, the women wore a combined heart rate and movement sensor for 4 consecutive days of free-living. Measures of PA obtained from the combined heart rate and movement sensor, which were used as criterion, included individually calibrated PA energy expenditure (PAEE), acceleration, and hours/day of moderate-to-vigorous intensity PA (MVPA). These were averaged between visits and compared to NOPAQ scores at visit 2.
  
  
  RESULTS
  Intra-class correlation coefficients for objective measures from both free-living periods were in the range of 0.65-0.87 (P < 0.001), compared to 0.62 (P < 0.001) for NOPAQ. There was a moderate but significant (P < 0.001) Spearman's rank correlation coefficient in the range of 0.36-0.46 between NOPAQ and objective measures of PA. Linear trends for the association between the NOPAQ rating scale with PAEE, hours/day of MVPA and VO2max (P < 0.001) were also demonstrated.
  
  
  CONCLUSIONS
  Self-reported PA level measured on a 10-category scale appears valid to rank PA in a female Norwegian population.
authors.affiliation: Department of Community Medicine, University of Tromsø, Norway. kristin.benjaminsen.borch@uit.no
authors.forename: Kristin B
authors.initials: KB
authors.lastname: Borch
authors.forename: Ulf
authors.initials: U
authors.lastname: Ekelund
authors.forename: Søren
authors.initials: S
authors.lastname: Brage
authors.forename: Eiliv
authors.initials: E
authors.lastname: Lund
mesh_terms: D000054:Acceleration; D000328:Adult; D004734:Energy Metabolism / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005260:Female; D006306:Health Surveys; D006339:Heart Rate; D006801:Humans; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology; D009068:Movement / Q000502:physiology*; D009664:Norway; D010101:Oxygen Consumption; D005082:Physical Exertion / Q000502:physiology; D010809:Physical Fitness / Q000502:physiology*; D015203:Reproducibility of Results; D057566:Self Report; D018709:Statistics, Nonparametric; D011795:Surveys and Questionnaires