Factors associated with Physical Activity in adolescents in Qazvin: an application of the theory of planned behavior

Physical inactivity is prevalent among adolescents around the worlds. This study tested the ability of the theory of planned behavior)TPB(to predict Physical Activity)PA(among adolescents in a 4-weeks longitudinal study. 623 adolescents were randomly selected from eight high schools in Qazvin. TPB measures, and a revised International Physical Activity Questionnaire were measured at baseline and 1-month follow-up. Hierarchical regression analyses were conducted regressing Physical Activity at Time 2 onto TPB. the mean age of the adolescents was 15.5 years and the most of them were girls(51.2 %(. Past behavior accounted for a significant 57% of the variance in Physical Activity in Step 1of analysis. In Step 2, TPB accounted for an additional 7% with attitude, subjective norms and perceived behavior control as a significant predictor. The analysis resulted in a significant amount of incremental variance accounted for by the intention (Step 3(. The results of this study demonstrated the theory of planned behavior successfully predicted the most of physical activity's variance among adolescents. Our results suggest that theory-based interventions should be based on the TPB with a targeting on PBC.