Efficacy of a physical activity intervention on physical activity levels of patients with chronic low back pain (PAy-BACK trial): study protocol for a randomised controlled trial - Oliveira, Crystian [UNESP]; Franco, Marcia [UNESP]; Damato, Tatiana [UNESP]; Silva, Fernanda [UNESP]; Araujo, Giulia [UNESP]; Azevedo, Bruna [UNESP]; Cantarela, Caio [UNESP]; Morelhao, Priscila [UNESP]; Gobbi, Cynthia [UNESP]; Christofaro, Diego [UNESP]; Zambelli, Rafael (Human Kinetics Publ Inc, 2018)