Exercise is medicine: a historical perspective.

Much of the early information about exercise and medicine appeared in the ancient, medieval, and Renaissance medical literature in the context of the "six things nonnatural." These were the things that were under everyone's own control, directly influenced health, and became the central part of the new "physical education" movement in the early 19 century in the United States. They were known then as the "Laws of Health." Until the early 1900s, "physical education" was dominated by physicians who specialized in health and exercise. However, physical education changed to a games and sports curriculum led by coaches who introduced competition and athletic achievement into the classroom. As that happened, physicians disappeared from the profession. Through the last half of the twentieth century, as exercise became more central to public health, the medical community began to view exercise as part of lifestyle, a concept embracing what was once called the "six things nonnatural."