Physical activity, sedentary, and non-communicable diseases. Health risk assessment

The lack of physical activity (PA) (inactivity) is recognized as the fourth risk factor for non-communicable diseases (NCD), and the second preventable risk factor after the tobacco use. Nonlinear dose/effect relationships are found between the volume and intensity of PA, and the general or specific mortality and incidence of NCD. A sedentary lifestyle characterized by prolonged periods of very low energy expenditure is also related to general or specific mortality and the incidence of NCD. The deleterious effects of sedentary behavior are especially marked beyond seven hours a day sitting, or three hours a day in watching the television. The deleterious effects of sedentary on mortality and incidence of NCD have been shown to be influenced by the level of PA; in very active people with more than one hour of moderate to high intensity PA daily, the effects of sedentary become imperceptible. All these results underline the importance of having recommendations for reducing sedentary; however, the limits of such recommendations must be known, however, and therefore the preservation of health must be achieved by strengthening the recommendations in PA. (C) 2019 l'Acadernie nationale de medecine. Published by Elsevier Masson SAS. All rights reserved.