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Purpose - To compare the test-retest reliability, convergent validity, and overall feasibility/usability of activity-based (AB) and time-based (TB) approaches for obtaining self-reported moderate-to-vigorous physical activity (MVPA) from adolescents.

Methods - Adolescents (206 females and 114 males) completed two 3-d physical activity recalls using the AB and TB surveys, which contained identical lists of physical activities. The participants wore an MTI Actigraph® accelerometer for the same period.

Results - The TB instrument took about 3 min longer to complete (P=0.022). Overall 2-d test-retest correlations for MVPA were similar for the two surveys (r=0.676 and 0.667), but the girls had higher reliability on the AB survey than the boys (girls: r=0.713; boys: r=0.568). The overall 3-d correlations for MVPA surveys and Actigraph counts varied by gender (girls: AB=0.265 vs TB=0.314; boys: AB=0.340 vs TB=0.277). Correlations for vigorous physical activity and Actigraph counts were higher for the AB than for the TB (r=0.281 vs 0.162). As the interval between completing the surveys and the days being recalled increased, reliability and validity were lower, especially for the AB survey.

Conclusion - For both genders, either approach is acceptable for obtaining MVPA information on a single day, but the TB approach appears to be slightly favored over the AB approach for obtaining multiple days of MVPA. A 3-d recall period appears to be too long for accurate recall of MVPA information from either instrument. For both genders, the surveys overestimate activity levels; thus, self-reports should be supplemented with objective data.

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