[Role of physical activities in a public health policy].

A gradual decrease in energy output for adults in the Western countries has been observed through the XXth century. The mechanization in industrial societies result in a decline of customary physical activity and consequently in the potentially vicious spiral of inactivity leading to deconditioning and thence, via loss of physiological capacity, to a further reduction in activity. The sedentary life has injurious effects on the health of individuals and specially increase the risks of cardiovascular disease. Furthermore there is a supposed relation between inactivity with obesity and hyperlipemia in young people and with osteoporosis in elderly. In contrast, many papers showed that high levels of physical activity have been associated with a diminished occurrence of hypertension, coronary artery disease, non insulin-dependent diabetes, colon cancers... In addition physical fitness is obviously related to the quality of life. Because of all these reasons several developed countries have elaborated plans of physical reconditioning for their people. In France some experimental actions have been completed but any national programme has been determined. Moreover it is now crucial to promote scientific researches about the fundamental biological mechanisms which explain the beneficial effects of physical training on the prevention and/or the treatment of several illness.