Construct validity of selected measures of physical activity beliefs and motives in fifth and sixth grade boys and girls.

OBJECTIVE Scales used to measure selected social-cognitive beliefs and motives for physical activity were tested among boys and girls. METHODS Covariance modeling was applied to responses obtained from large multi-ethnic samples of students in the fifth and sixth grades. RESULTS Theoretically and statistically sound models were developed, supporting the factorial validity of the scales in all groups. Multi-group longitudinal invariance was confirmed between boys and girls, overweight and normal weight students, and non-Hispanic black and white children. The construct validity of the scales was supported by hypothesized convergent and discriminant relationships within a measurement model that included correlations with physical activity (MET • min/day) measured by an accelerometer. CONCLUSIONS Scores from the scales provide valid assessments of selected beliefs and motives that are putative mediators of change in physical activity among boys and girls, as they begin the understudied transition from the fifth grade into middle school, when physical activity naturally declines.