Purpose: Physical activity (PA) promotion among youth is a public health priority, and there is a need for robust surveillance systems to help support such initiatives. Existing youth PA self-report instruments that are used for surveillance lack information regarding the types and contexts of activity. Further, these instruments have limited validity with accelerometry. The purpose of the present study was to develop a self-report instrument, with sound psychometric properties, for monitoring compliance with PA guidelines in youth.
Methods: In focus groups, 162 middle school students identified 30 forms of PA that are highly prevalent in that age-group. We incorporated these activities into three preliminary forms of a self-report instrument. An independent sample of middle school students (n = 537) was randomly assigned to complete one of the three preliminary versions of the instrument. Rasch analysis was applied to the responses to the three formats, and a yes/no plus frequency format emerged as the preferred method. A third sample of 342 middle school students then completed the yes/no plus frequency instrument twice after a 7-d period during which they wore an accelerometer. Using both Rasch analysis and traditional correlational methods, validity and reliability of a 14-item instrument were established. Data were collected during 2012-2015.
Results: Spearman correlation coefficient for the association between the cumulative score for the 14 items and minutes per day of accelerometry-derived moderate-to-vigorous physical activity was 0.33 (95% confidence interval = 0.22-0.43, P < 0.001). The sensitivity and specificity values of the 14-item instrument were 0.90 and 0.44, respectively.
Conclusions: The study produced a PA self-report instrument for youth that was found to be reliable (r = 0.91), valid versus accelerometry (r = 0.33), and with acceptable specificity and sensitivity in detecting compliance with PA guidelines.