title: Evaluation of 2 self-report measures of physical activity with accelerometry in young adults.
abstract: BACKGROUND
  The purpose of this paper is to evaluate self-reported physical activity of young adults using 1-week and 1-year recall measures with an accelerometer as the criterion measure.
  
  
  METHODS
  Participants were a subsample (N = 121, 24 ± 1.7 yrs) from a large longitudinal cohort study. Participants completed a detailed 1-year physical activity recall, wore an accelerometer for 1 week and then completed a brief 1-week physical activity recall when they returned the accelerometer.
  
  
  RESULTS
  Mean values for moderate-to-vigorous physical activity (MVPA) from the 3 instruments were 3.2, 2.2, and 13.7 hours/wk for the accelerometer, 1-week recall, and 1-year recall, respectively (all different from each other, P < .001). Spearman correlations for moderate, vigorous, and MVPA between the accelerometer and the 1-week recall (0.30, 0.50, and 0.40, respectively) and the 1-year recall (0.31, 0.42, and 0.44, respectively) demonstrated adequate validity.
  
  
  CONCLUSIONS
  Both recall instruments may be used for ranking physical activity at the group level. At the individual level, the 1-week recall performed much better in terms of absolute value of physical activity. The 1-year recall overestimated total physical activity but additional research is needed to fully test its validity.
authors.affiliation: Department of Epidemiology and Community Health, University of Minnesota, Minneapolis, MN, USA.
authors.forename: John Ronald
authors.initials: JR
authors.lastname: Sirard
authors.forename: Peter
authors.initials: P
authors.lastname: Hannan
authors.forename: Gretchen J
authors.initials: GJ
authors.lastname: Cutler
authors.forename: Dianne
authors.initials: D
authors.lastname: Nuemark-Sztainer
mesh_terms: D061725:Accelerometry / Q000523:psychology* / Q000706:statistics & numerical data*; D000293:Adolescent; D001837:Body Weights and Measures; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D011939:Mental Recall; D044469:Racial Groups; D015203:Reproducibility of Results; D057566:Self Report; D012737:Sex Factors; D012959:Socioeconomic Factors; D013997:Time Factors