Prediction of physical activity intention and behavior in a longitudinal sample of adolescent girls

The purpose of the present study was to investigate a theory of planned behavior model for the prediction of physical activity in adolescent girls using a 1-yr. longitudinal design. A secondary purpose was to examine the moderating influence of intention stability and past behavior on intention-behavior relationships. Participants were 236 12- to 13-year-old adolescent girls who completed measures of the theory of planned behavior and physical activity participation (3-Day Physical Activity Recall) across a 1-yr. interval. The standard theoretical variables predicted intentions, as intention, past behavior, and perceived behavioral control predicted behavior. The temporal stability of intentions and past behavior moderated relationships between intention and behavior. An autoregressive path model showed that intention and perceived behavioral control predicted changes in physical activity and physical activity predicted changes in intention, affective attitude, and perceived behavioral control. This study supports the use of the theory of planned behavior in gaining an understanding of the physical activity intention and behavior of adolescent girls.