As the mean life expectancy of the population continues to increase, the challenge for individuals is to remain healthy and fit throughout their life span. This review examines the relationships between moderate-vigorous physical activity and sedentary behaviour in relation to the fitness-frailty continuum. The association between increased physical activity and decreased adverse health outcomes is firmly established. A direct association between frailty and moderate-vigorous physical activity has been established to a lesser degree. What has some potential to undermine even these gains is the increasingly recognized relationship between sedentary behaviour and poor health. It now seems likely that sedentary behaviour can have a negative impact on an individual's health, over and above that of meeting the recommendations of moderate-vigorous physical activity. Individuals must consider both increasing their level of moderate-vigorous physical activity and minimizing their level of sedentary behaviour during all aspects of daily life.
