Associations between three measures of physical activity and selected influences on physical activity in youth transitioning from elementary to middle school

Measurement of physical activity is challenging, and objective and subjective methods can be used. The purposes of this study were to apply structural equation modeling in: 1) examining the associations between three distinct measures of physical activity and three factors that are often found to be correlated to physical activity in children, and 2) examining the associations of the combination of three measures with the same correlates in a cohort of youth followed from 5th to 7th grade. A total of 409 children (45% boys) had complete physical activity data derived from accelerometers, self-report by youth, and proxy-report by parents. The potential correlates of physical activity included self-efficacy, physical activity support, and facilities for physical activity. Structural equation models were used to assess the relationship between physical activity and the correlates. The structural equation models examining associations between individual measures of physical activity and selected correlates showed that parent-reported and child self-reported physical activity were associated with parental support for physical activity and self-efficacy. Objectively measured physical activity was associated only with facilities for physical activity. A structural equation model showed that a composite expression of physical activity, based on the inclusion of all three individual measures, was associated with all three correlates of physical activity. In conclusion, combining measures of physical activity from different sources may improve the identification of correlates of physical activity. This information could be used to plan more effective physical activity interventions in children and youth.