Cardiac benefits of sport
When asked about his personal recipe for old age, Winston Churchill used to answer: "First of all: No sports." While being a visionary figure in world politics researchers in cardiovascular exercise science today would unanimously reply to his medical hypothesis: "Sorry, you are wrong."
A large number of long-term observational studies clearly documented that increased levels of average daily physical activity were correlated to a reduced rate of coronary heart disease and reduced cardiac and all-cause mortality. Moderately active persons were 30-40% less likely to die from heart disease as compared to the inactive "couch potato." Despite this solid epidemiologic evidence, the proportion of people who do not engage in sports at all is ever increasing: About two thirds of all Americans, for example, do not participate in regular leisure-time physical activity. This lack of sports is closely related to the epidemic of other risk factors for future heart attacks: Obesity, diabetes, high blood pressure, and elevated cholesterol levels. Together, these inactivity-related diseases cost about US$76 billion per year to treat in the US.
But physical activity is not only beneficial in healthy people to prevent cardiovascular diseases. Also patients with stable coronary artery disease can extend their life-expectancy by engaging in sports: A recent meta-analysis revealed a significant 27% reduction of total mortality among training patients and a significant 31% reduction in cardiac mortality. Even when compared to sophisticate interventional procedures, exercise training is surprisingly effective in improving the patient's well-being. In a recent study which randomized patients with coronary 1- or 2-vessel disease to either the standard interventional treatment or to regular exercise training, we found a higher event-free survival in the training group and a similar improvement of cardiac symptoms. This finding confirms again that there is no cardiac gain without the pain of changing your inactive lifestyle.
But how does such a non-specific intervention as exercise training achieve these impressive results? Atherosclerosis – the chronic disease process finally leading to coronary narrowings and heart attacks – begins as a vascular malfunction before plaques develop. Normally, a healthy vessel dilates and gets larger with increases of blood flow, which is especially important during activity to meet the increased demand for oxygen by the working muscles. In atherosclerosis, the artery loses its ability to dilate under these conditions, which leads to reduced blood supply during exercise. The key mediator which regulates vessel diameter is nitric oxide (NO), which is generated in endothelial cells by a special enzyme called "endothelial nitric oxide synthase" or eNOS. It has been found that NO production is reduced and NO degradation is increased in the early stages of heart disease – leading to endothelial dysfunction.
Exercise training and sports lead to repetitive increases in shear stress on the endothelium and can thereby stimulate the eNOS enzyme to produce more NO. Endothelial dysfunction is rare among active people and occurs later in life as compared to inactive individuals. In the last years we found that patients with stable coronary artery disease often have severe endothelial dysfunction, which can be dramatically improved by a four week training program – to an extent which is comparable with the effects of established medications such as lipid-lowering drugs (i.e. statins). This improvement of vessel dilation increases blood flow to the myocardium and thereby reduces clinical symptoms. In addition, endothelial dysfunction is regarded as the initial step toward atherosclerosis and plaque formation. By treating endothelial dysfunction with regular exercise training we can therefore retard the development of new coronary stenoses.
The key message emerging from these clinical studies is that sports and exercise – in addition to preventing obesity and diabetes – directly improve vascular function and reduce atherosclerosis. Considering that the majority of people do not engage in regular physical activities one can only say: The health of your heart is in your own hands. If you want to protect it: First of all, engage in regular sports activities!
Source: Eurekalert & othersLast reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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