title: Reliability and validity of self-reported physical activity in the Nord-Trøndelag Health Study (HUNT 2).
abstract: BACKGROUND
  To validate the physical activity (PA) questionnaire in Nord-Trøndelag Health Study (HUNT 2).
  
  
  METHODS
  The questionnaire was administered twice to a random sample of 108 men aged 20-39 and validity by comparing results with VO(2max) and ActiReg, measuring PA and energy expenditure and with the International Physical Activity Questionnaire (IPAQ).
  
  
  RESULTS
  Spearman correlation coefficients indicated poor and moderate significant agreement by test-retest (light activity, r = 0.17, and hard activity, r = 0.50). We found a moderate significant correlation r = 0.46 (p < or = 0.01) between hard PA and VO(2max) and n.s for light activity (r = -03). Metabolic equivalent (METs) values 6+ from ActiReg most strongly correlated with hard PA r = 0.31 (p < or = 0.01), though associations of other measures obtained from ActiReg with questionnaire measures were weaker. Occupational activity was strongest correlated for METs 3-6 r = 0.48 (p < or = 0.01) by ActiReg.
  
  
  CONCLUSIONS
  The HUNT 2 question for "hard" LTPA has acceptable repeatability and appears to be a reasonably valid measure of vigorous activity, as reflected in moderate correlations with several other measures including VO(2max), and with corresponding results from IPAQ and ActiReg. The HUNT 2 question on occupational activity had good repeatability and appears to best reflect time spent in moderate activity, with moderate associations with measured time at intermediate intensity levels. The "light" activity question from HUNT 2 had poor reproducibility and did not correlate well with most of the comparison measures. Thus, the "hard" PA and the occupational activity question should be useful measures of vigorous PA, if time and space allow only very brief assessment. The utility of the "light" PA questions remains to be established.
authors.affiliation: HUNT Research Centre, Department of Public Health and General Practice, Faculty of Medicine, Norwegian University of Science and Technology, Neptunveien 1, 7650, Verdal, Norway. nanna.kurtze@sintef.no
authors.forename: Nanna
authors.initials: N
authors.lastname: Kurtze
authors.forename: Vegar
authors.initials: V
authors.lastname: Rangul
authors.forename: Bo-Egil
authors.initials: BE
authors.lastname: Hustvedt
authors.forename: W Dana
authors.initials: WD
authors.lastname: Flanders
mesh_terms: D000328:Adult; D015444:Exercise; D006801:Humans; D007899:Leisure Activities; D008297:Male; D010809:Physical Fitness; D015203:Reproducibility of Results; D018709:Statistics, Nonparametric; D011795:Surveys and Questionnaires