Based on the theory of planned behaviour and self-determination theory, the objective of the present study was to analyse the relationship between (i) parents' and peers' autonomy support, and (ii) exercise intention in adolescents, while also considering the mediating role of attitude, control, subjective norms, and descriptive norms. A total of 428 secondary school students, aged between 13 and 19 years old (Mage = 15.30, SD = 1.15), filled in a questionnaire assessing the variables of interest. The relationships between the study variables were examined through a mediation model with bootstrapping technique (20,000 samples) using Mplus v. 7 software. The results showed that the perception of parents' autonomy support was positively and statistically significant associated with exercise intention; this occurring indirectly through attitude and control both in boys and girls, as well as through subjective norms in the case of girls. Conversely, the perception of peers' autonomy support was positively and statistically significant associated with exercise intention; this occurring directly both in boys and girls, as well as indirectly through attitude in the case of girls. These findings suggest that, by involving a form of pressure (i.e., subjective/descriptive norms), perceptions of autonomy support may play a more important role than other forms of social influence in predicting exercise intention in adolescents.
Keywords: adolescence; autonomy support; descriptive norms; exercise; mediation model; subjective norms.