Sport practice is conditioned by different factors; previous studies have shown that the attitude towards physical activity and sports practice is largely conditioned by the individual. This study proposes to examine whether the classic model of the theory of planned behaviour reinforces the main motivations for people to adhere to a sport practice. An empirical model based on the classic model of the theory of planned behaviour was proposed, adding three motivational variables to sport practice. A sample was composed of 1008 valid questionnaires collected online in Spain and Colombia. The analysis of the data was performed using the partial least squares technique using the Smart PLS 3.0 statistical programme. The proposed model presents a statistical validity that proves that the practice of physical and sporting activity is determined by the individual’s evaluation of their abilities and perceptions and their relationship with the motivations generated by continuing the practice of physical or sports activity, consequently how adherence is generated. © 2020, Associação Brasileira de Psicologia.