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.
Design 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.
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Contributors KM and FB conceptualised the study and developed the study protocols. KM collected and analysed the data with guidance from SC. KM prepared the draft manuscript. FB and SC assisted in revising the manuscript. All authors read and approved the final manuscript.
Funding This research was funded by Natural England.
Competing interests None.
Ethics approval Loughborough University Ethical Advisory Committee.
Provenance and peer review Not commissioned; externally peer reviewed.
▸ References to this paper are available online at http://bjsm.bmjgroup.com
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