title: Can a single question provide an accurate measure of physical activity?
abstract: OBJECTIVE
  The 'single-item measure' was developed as a short self-report tool for assessing physical activity. The aim of this study was to test the criterion validity of the single-item measure against accelerometry.
  
  
  METHODS
  Participants (n=66, 65% female, age: 39±11 years) wore an accelerometer (ActiGraph GT3X) over a 7-day period and on day 8, completed the single-item measure. The number of days of ≥30 min of accelerometer-determined moderate to vigorous intensity physical activity (MVPA) were calculated using two approaches; first by including all minutes of MVPA and second by including only MVPA accumulated in bouts of ≥10 min (counts/min ≥1952). Associations between the single-item measure and accelerometer were examined using Spearman correlations and 95% limits of agreement. Percent agreement and κ statistic were used to assess agreement between the tools in classifying participants as sufficiently/insufficiently active.
  
  
  RESULTS
  Correlations between the number of days of ≥30 min MVPA recorded by the single-item and accelerometer ranged from 0.46 to 0.57. Participants underreported their activity on the single-item measure (-1.59 days) when compared with all objectively measured MVPA, but stronger congruence was observed when compared with MVPA accumulated in bouts of ≥10 min (0.38 days). Overall agreement between the single-item and accelerometry in classifying participants as sufficiently/insufficiently active was 58% (k=0.23, 95% CI 0.05 to 0.41) when including all MVPA and 76% (k=0.39, 95% CI 0.14 to 0.64) when including activity undertaken in bouts of ≥10 min.
  
  
  CONCLUSIONS
  The single-item measure is a valid screening tool to determine whether respondents are sufficiently active to benefit their health.
authors.affiliation: School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, Leicestershire, UK, LE11 3TU. k.milton@lboro.ac.uk
authors.forename: Karen
authors.initials: K
authors.lastname: Milton
authors.forename: Stacy
authors.initials: S
authors.lastname: Clemes
authors.forename: Fiona
authors.initials: F
authors.lastname: Bull
mesh_terms: D000293:Adolescent; D000328:Adult; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018670:Monitoring, Ambulatory / Q000295:instrumentation; D057566:Self Report; D011795:Surveys and Questionnaires; D013997:Time Factors; D055815:Young Adult