J. Sports Med. Phys. Fitness J. Sports Med. Phys. Fitness Application of stages of change model to adolescents' physical activity in relation to psychological variables Abarca-Sos Alberto Universidad de Zaragoza Bois J.E. Generelo Lanaspa Eduardo Universidad de Zaragoza Julian Clemente J.A. Universidad de Zaragoza Zaragoza Casterad Javier Universidad de Zaragoza 2015 research-article