Background/Purpose The decline of physical activity (PA) during adolescence is greater in girls than boys (Dumith et al., 2011). The purpose of this study was to examine the direct and moderating effects of age and gender in the prediction of PA intention and behavior, using the Theory of Planned Behavior (TPB; Azjen,1991).
Method Children and adolescents (n=4,653) aged 9-15 years (M=12.3, SD=1.2) completed a self-report questionnaire measuring TPB constructs (attitude, subjective norm, perceived behavioral control and intention) and a self-report measure of PA. Relationships were tested using multiple hierarchical regression analyses and significance tested at p=.05.
Analysis/Results All TPB constructs were significant predictors of intention (R²change=.642). Intention was a significant predictor of behavior (R²change=.067), but perceived behavioral control was not significant. The gender*intention interaction term added significantly, but trivially, to the prediction of behavior (R²change=.002). The age*intention interaction term was not significant.
Conclusions From these results, it appears that attitudes, subjective norms, and perceived behavioral control explain intention to be physically active, and that intention explains PA behavior. Additionally, gender moderates the relationship between intention and PA behavior. These findings have important implications for promoting PA in children and adolescents. For example, physical activity programs may need to target the TPB constructs, in addition to providing PA opportunities. Research priorities include evaluating interventions that investigate whether change in these determinants predicts change in PA behavior.