The role of exercise prescription in chronic disease.

T he use of exercise as a medical treatment is an old concept, but one that did not start gaining acceptance until the 20th century. Today, exercise scientists are exploring the limits of exercise as a therapy—of exercise as a medicine. It is not possible to discuss all the ramifications of exercise prescription in a brief article, so I shall take a larger view and illustrate how various kinds of exercise may be useful in patients with a chronic disease and/or a disability. Hippocrates wrote, ‘‘In a word, all parts of the body which were made for active use, if moderately used and exercised at the labor to which they are habituated, become healthy, increase in bulk, and bear their age well, but when not used, and when left without exercise, they become diseased, their growth is arrested, and they soon become old.’’ Medicine’s view of exercise did not progress much in the subsequent two millenia, and exercise was primarily viewed as an activity for healthy people, but not for the chronically ill. The first recorded anecdote of exercise as a treatment for heart disease is thought to be from William Heberden, who wrote of a man with angina pectoris in 1772: ‘‘I knew of one who set himself the task of sawing wood for half an hour every day, and was nearly cured’’. Ironically, Heberden did not know that angina pectoris is a cardiac disorder.