The role of exercise in the primary and secondary prevention of coronary artery disease.

Over the past 30 years, mortality rates from coronary artery disease (CAD) have decreased by more than 30% in the United States. However, CAD remains the major public health problem in this country. There is now substantial evidence linking exercise training to a reduced risk for CAD and for mortality after myocardial infarction. The actual mechanism by which physical activity aids in reducing the risk for developing or dying from CAD has still to be elucidated. Several highly plausible mechanisms have been postulated, including decreased myocardial oxygen demand, increased myocardial oxygen supply, reduced propensity toward ventricular arrhythmias, reduced platelet aggregation, increased plasma fibrinolytic activity, and modification of multiple CAD risk factors. Irrespective of the precise mechanism, it now appears that lower levels of physical activity are needed to reduce the risk for CAD than are needed to optimize cardiorespiratory fitness. In this regard, we recommend that the type, frequency, intensity, and duration of exercise training be modulated to achieve a weekly energy expenditure of between 14 and 20 kilocalories per kilogram of body weight. Although aerobic activities should be emphasized, muscle strengthening and flexibility exercises should also be incorporated into the training program in order to promote musculoskeletal health.