The first study, with a systematic review, sought to investigate the relationship between the practice of physical activities and the mental health of the adult population in the most diverse contexts, by searching the PsycINFO, LILACS, SciELO and PePSIC databases, where they were selected, finally, 44 articles. The data suggest an association relationship between physical activity and mental health in adults, with the type and strength of association varying in the different samples. The second study presents a non-systematic review of the literature on the benefits of physical activity for physical and mental health during Pandemic. With the outbreak of COVID-19, measures such as social isolation have been adopted by the world in order to contain the spread of the virus and, due to this, interventions have been carried out to help, in a safe and effective way, issues related to physical and mental health of the population. Considering that physical inactivity / inactivity has increased even more during the pandemic, physical activity has been considered a good strategy and has been recommended by health entities, which present the ideal time and intensity of practice for each age group, in addition to present several exercise options that can be done during this period. The third, empirical study sought to assess mental health indicators in practitioners and non-practitioners of physical activities during the social isolation of COVID-19 in a sample of 701 participants, of which 71.5 percent were women (n = 501), 28, 4 percent men (n = 199) and 0.1 percent who preferred not to inform biological sex (n = 1) (M = 31.08; (SD = 11.28). The results indicated significant differences between groups for women that is, lower levels of anxiety, depression and stress and higher levels of positivity and quality of life were found in participants who practiced physical activities during the social isolation period of COVID-19. These data contribute to a broader understanding of the relationship between the practice of physical activities and mental health, in general.