For many chronic conditions, rest has long been the standard of care, but today we are witnessing a true paradigm shift: scientific studies show that physical activity (PA) has indisputable benefits for people with chronic diseases. These benefits are all the greater when PA is introduced early after diagnosis. Consequently, physical activity—even among patients in advanced stages of their diseases—must be an integral part of the treatment of chronic diseases. It should be prescribed systematically and as early as possible in the care pathway for each of the conditions studied. Even more impressive, the scientific literature now demonstrates with certainty that certain conditions can be cured through physical activity alone, provided that the patient adopts it on a long-term basis. The expert panel of the French National Institute of Health and Medical Research (Inserm) recommends that physical activity be prescribed before any drug treatment—that is, as a first-line treatment for mild to moderate depression, type 2 diabetes, obesity, and peripheral arterial disease.