title: Reliability and validity of a single-item physical activity measure for adolescents.
abstract: OBJECTIVE
  The aim of this study was to examine the test-retest reliability and concurrent validity of an adolescent single-item physical activity measure by comparing it with the existing Oxford Physical Activity Questionnaire (OPAQ) and accelerometer output.
  
  
  METHODS
  Participants were 123 adolescents (14.7 ± 0.5 years) from three secondary schools in New South Wales, Australia. To determine reliability, participants completed both questionnaires on two occasions separated by 2 weeks. To assess validity, participants wore Actigraph GT3X+ accelerometers for a 7-day monitoring period and completed both physical activity questionnaires. Bivariate correlations between self-reported moderate-to-vigorous physical activity (MVPA) and accelerometer MVPA min/day were calculated.
  
  
  RESULTS
  The single-item (intra-class correlation coefficient (ICC) = 0.75, 95% confidence interval (CI) = 0.64-0.83, P < 0.001) ) and the OPAQ (ICC = 0.79, 95% CI = 0.69-0.86, P < 0.001) were both found to have moderate-to-strong reliability. Correlations between self-reported and objectively measured MVPA were similar for the single-item measure (r = 0.44, 95% CI = 0.24-0.63, P < 0.001) and the OPAQ (r = 0.50, 95% CI = 0.30-0.65, P < 0.001).
  
  
  CONCLUSIONS
  These findings suggest the single-item measure can provide a reliable and valid assessment of youth physical activity.
authors: Priority Research Centre Physical Activity and Nutrition, Faculty of Education and Arts, University of Newcastle, Newcastle, New South Wales, Australia.
authors: Joseph J
authors: JJ
authors: Scott
authors: Priority Research Centre Physical Activity and Nutrition, Faculty of Education and Arts, University of Newcastle, Newcastle, New South Wales, Australia.
authors: Philip J
authors: PJ
authors: Morgan
authors: Priority Research Centre Physical Activity and Nutrition, Faculty of Education and Arts, University of Newcastle, Newcastle, New South Wales, Australia.
authors: Ronald C
authors: RC
authors: Plotnikoff
authors: Priority Research Centre Physical Activity and Nutrition, Faculty of Education and Arts, University of Newcastle, Newcastle, New South Wales, Australia.
authors: David R
authors: DR
authors: Lubans
mesh_terms: D000293:Adolescent; D015444:Exercise; D005260:Female; D006801:Humans; D008297:Male; D009043:Motor Activity; D009517:New South Wales; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires / Q000592:standards*
keywords: adolescent; physical activity; questionnaire; self-report; youth