The knowledge about the effects of exercise, physical and sport activities on general well-being has been advanced thanks to pioneering studies in several medical conditions and in rehabilitation from the 1980s onwards [1].However, a noteworthy contribution to improving standard tools hallowing to measure of how much exercise, physical and sport activities could affect the quality of life (QoL) of the elderly and adults came mainly from the studies on their effects on depression and mental health [2 -4].First, the new perspectives have made it possible to establish the level of QoL, which cannot be considered as a simple variable depending on the state of health: actually, there are consolidated evidence of a complex relationship between health, QoL, exercise, physical and sport activities [5,6].Second, this complex vision of physical and psychosocial health has benefited from the concepts of well-being and QoL applied, first of all, like "extended" outcome measures to the studies on the use of exercise, physical and sport activities in depression [7,8].
The Brain-Derived Neurotrofic Factor (BDNF) is one of the most important neurotrophins in the brain and it is suggested influences the activity of the serotonergic, noradrenergic and dopaminergic pathways. In the last few years, it has been hypothesized that BDNF level is related with depression and sleep. Several studies show that depressive subjects present low levels of BDNF in the brain. Poor sleep quality is also related with alterations in the BDNF concentration. Some authors argue that most of the cases show that impaired sleep quality increases the stress and, consequently, the vulnerability to depressive disorders, suggesting that there is a relationship between sleep, depression and BDNF levels.
