The role of supervision and motivation during exercise on physical and mental health in older adults: a study protocol for a randomized controlled trial (PRO-Training project) oleh Paola Gómez-Redondo, Pedro L. Valenzuela, Óscar Martínez-de-Quel, Coral Sánchez-Martín, Mónica Cerezo-Arroyo, David Moreno-Manzanaro, Luis M. Alegre, Amelia Guadalupe-Grau, Ignacio Ara, Asier Mañas