To develop a reliable and valid physical activity screening measure for use with adolescents in primary care settings.
We conducted 2 studies to evaluate the test-retest reliability and concurrent validity of 6 single-item and 3 composite measures of physical activity. Modifications were based on the findings of the 2 studies, and a best measure was evaluated in study 3. Accelerometer data served as the criterion standard for tests of validity.
In study 1 (N = 250; mean age, 15 years; 56% female; 36% white), reports on the composite measures were most reliable. In study 2 (N = 57; mean age, 14 years; 65% female; 37% white), 6 of the 9 screening measures correlated significantly with accelerometer data. Subjects, however, had great difficulty reporting bouts of activity and distinguishing between intensity levels. Instead, we developed a single measure assessing accumulation of 60 minutes of moderate to vigorous physical activity. Evaluated in study 3 (N = 148; mean age, 12 years; 65% female; 27% white), the measure was reliable (intraclass correlation, 0.77) and correlated significantly (r = 0.40, P<.001) with accelerometer data. Correct classification (63%), sensitivity (71%), and false-positive rates (40%) were reasonable.
The "moderate to vigorous physical activity" screening measure is recommended for clinical practice with adolescents.