Physical activity is a behavior that offers protection against various chronic diseases and is associated with numerous important health indicators. A sedentary lifestyle, on the other hand, is a risk factor for chronic diseases, and reducing it is associated with health benefits. Physical activity is a hot topic in the fields of health promotion and disease prevention. Its health benefits are now well documented, and although the mechanisms of action remain to be elucidated, its effects have been demonstrated regardless of age and gender. As a result, physical activity is now included in most health promotion recommendations and is of interest to numerous sectors (health, social services, sports, urban planning, environment) which, if they collaborate, can make a significant impact. Indeed, the concept of physical activity is very broad and includes almost all types of movement, allowing each sector to approach movement from a different angle. Physical activity is characterized by a number of measurable parameters (frequency, duration, intensity, type of activity), the combination of which makes it possible to determine the level of physical activity across a population. Based on these observations, it is possible to implement targeted promotional actions or strategies. Indeed, there are disparities in physical activity practices, particularly by gender, socioeconomic status, and place of residence. Sedentary behavior, meanwhile, has gradually become more widespread and now affects most countries, regardless of their level of development. It represents a major risk factor in our society, where it is now considered the leading non-communicable cause of mortality worldwide (World Health Organization [WHO], World Health Day, April 2002). A sedentary lifestyle is not merely the absence of physical activity; it also involves engaging in activities that require little movement and result in low energy expenditure. It is important to emphasize here that physical activity is not the opposite of a sedentary lifestyle; the relationships between them are complex and still poorly understood. To improve health, it is therefore necessary to both limit sedentary behavior and promote physical activity. The development of promotional policies on nutrition and physical activity has grown significantly in recent years, both at the national level through the National Nutrition and Health Program (PNNS) and at the European (European Platform for Action on Diet, Physical Activity and Health, European Network for the Promotion of Health-Enhancing Physical Activity) and international (World Health Organization: Global Strategy on Diet, Physical Activity and Health) levels.[excerpt from chapter introduction]