SUMMARY INTRODUCTION The COVID-19 pandemic, caused by infections from a novel human coronavirus, has been reported since December 2019 in China but was only made official in March 2020. Since then, it has had an impact worldwide, both due to its aggressiveness and its fast propagation. Society has been facing this pandemic by following the recommendations and determinations of the WHO and the strategies deployed by governmental institutions. Among these, social isolation has been shown to be the most important, because when isolating, society tends to move less, with a consequent increase in physical inactivity and sedentary behavior, affecting its levels of physical fitness. The objectives of this review were: to review the most important effects of physical inactivity and sedentary behavior on the physical fitness levels of the population during the COVID-19 pandemic. CONCLUSION The role of a regular practice of activities on the levels of physical fitness is fundamental to define the balance of quality of life during a COVID-19.