1. Regular aerobic exercise causes cardiovascular, neural, humoral and metabolic changes. Many of these are likely to influence cardiovascular risk and the changes vary according to the level and duration of increased physical activity.
2. The case for exercise exerting beneficial effects derives from epidemiological data showing that sedentary subjects have, on average, double the risk of cardiovascular disease of active individuals. Post-infarct rehabilitation studies are also consistent with a beneficial effect of exercise. Large randomized controlled intervention studies have not been performed.
3. These benefits may be due to the effects of regular exercise on risk factors, direct effects on atheromatous vessels, or improvement in survivability in established coronary heart disease by reducing arrythmias or increasing tolerance of ischaemia.
4. There are direct effects of regular exercise on blood pressure (BP) and lipid profiles. These occur at different levels of physical activity. Other changes which would be expected to reduce cardiovascular risk include increased insulin sensitivity, reduced sympathetic activity and increased gain of the baro-receptor-heart rate reflex and increased arterial compliance.
5. In hypertensives these changes may improve outcomes, irrespective of the reduction in BP reported in some randomized controlled intervention studies.