Get moving: Hearts thrive on exercise
By SALLY ANDERSON

© St. Petersburg Times,
published August 28, 2001


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The concept that physical activity has a positive influence upon people's health is not a new one. Exercise was prescribed for maintaining good health at least 1,500 years ago.

The U.S. Centers for Disease Control and Prevention and the College of Sports Medicine have estimated that 250,000 Americans die each year because of sedentary lifestyles. We now have much more research to document the validity of the relationship of physical activity and fitness to our physiological and psychological health.

It is a shame, with all of our medical advances in treatment, that a simple, low-cost health plan often is ignored. Our genes may to some extent play a role in the development of heart disease, but it is important to remember that how we live our lives can dramatically affect our cardiovascular health.

Cardiovascular disease is a general term for the many diseases of the heart -- "cardio" for heart and "vascular" for blood vessels. Coronary heart disease, in spite of much progress, remains the leading cause of death in our country. A heart attack may appear to occur suddenly, but most are works in progress, with plaque (fatty substances) gradually building up over the years.

Coronary heart disease is most commonly the result of atherosclerosis, a build-up of fatty plaque that, in excess, can cause a thickening and narrowing of the walls of the arteries, including the coronary arteries that supply the heart with blood.

When the fatty plaque clogs the arteries that supply the heart with oxygen, they lose elasticity, and the flow of blood becomes restricted. As the heart's need for oxygen becomes greater than what the coronary artery can supply, myocardial ischemia can occur, which may be a precursor to angina, a feeling of pressure often felt in the chest, left arm or shoulder; cardiac arrhythmias, irregular heart patterns; myocardial infarctions; heart attack; and cardiac arrest, when the heart stops beating. Strokes occur when this disease affects arteries leading to the brain.

In 1993, the American Heart Association included inactivity as a risk factor for the development of coronary artery disease. Already established as primary risk factors were cigarette smoking, elevated blood cholesterol and high blood pressure. The secondary risk factors are obesity, age over 65, being male, family history of coronary heart disease in people younger than 65, diabetes and high stress levels.

Primary risk factors
CIGARETTE SMOKING: Years of smoking can mess up a person's oxygen delivery system. Carbon monoxide, a byproduct of cigarette smoke, decreases the oxygen-carrying capacity of the blood. Smoking releases around 1,200 toxic compounds into the bloodstream, some of which are destructive to the lining of the walls of the arteries. When this occurs, plaque builds up, causing a severe reduction in blood flow. Smoking speeds up the development of atherosclerosis by lowering the "good" cholesterol (HDL) and increasing the "bad" cholesterol (LDL). It also can increase heart rate and blood pressure. It has been said that smoking causes a greater risk of death from heart disease than from lung disease.

HIGH BLOOD PRESSURE: When you have high blood pressure (hypertension), your heart has to work harder, as it is being forced to contract against increased resistance. When you reduce your blood pressure, the workload of the heart decreases. Including moderate physical exercise in your lifestyle is now considered to be a part of the therapy recommended for hypertension reduction. Physically unfit individuals have a 52 percent greater risk of developing hypertension than do more active personalities.

Remember, the key word here is "moderation." Lifting too heavy weights and performing too vigorous a workout may reverse all the exercise advantages. Exercise will help to reduce vascular resistance and also will reduce the resting heart rate; weight control, when needed, is also recommended for hypertensive persons. Performing regular, not just an occasional, physical activity enhances the body's distribution of blood to the muscles, which will decrease the workload of the heart muscle, helping to reduce blood pressure levels.

INACTIVITY: When you begin to exercise, the muscles will begin to use oxygen at a much higher rate, requiring the heart to pump more oxygenated blood to meet the increased demand placed upon it. At rest, the cardiac output, which is the amount of blood being pumped by the heart per minute, is low. During exercise, it can increase to a level about four times that of rest. One of the training effects of this is that the stroke volume, the quantity of blood being pumped, will increase with each heart beat. The heart muscle becomes stronger as it adapts to pumping out more blood with each stroke, it does not have to work as hard, the resting heart rate will be lowered and this reduction of heart rate will permit the heart to have more rest between beats.

CHOLESTEROL: Depending on the TC/HDL ratio, cholesterol can also pose a threat of heart disease. Cholesterol plays a dual role within our bodies. On the positive side, cholesterol is needed and used by all our body cells; on the negative side, the LDL lipoproteins play the role of the "bad guy," and in excess can build up within our arteries and pose a risk for coronary heart disease and other vascular problems. A diet that is too high in fat, particularly saturated fat, and, of course, a sedentary lifestyle can lead to an elevated cholesterol.

Since cholesterol acts as a fatty substance that kind of clumps together like cream on top of milk, it is insoluble in the blood, and in that state, cannot be transported to the cells. When the cholesterol molecules are absorbed by special protein molecules, which are soluble in the blood, they then can be delivered to the cells of the body. This combination of cholesterol and protein molecules is known as lipoprotein (fat and protein).

The two main forms of lipoproteins are low-density lipoprotein cholesterol (LDL), which contains a large amount of cholesterol, and high-density lipoprotein cholesterol (HDL), which contains more protein than cholesterol. Together they are responsible for carrying most of the cholesterol to the body cells, with the LDL leading the way, transporting about 60 to 80 percent of the cholesterol.

Most of our body cells have the unique ability to know when "they are full." When they have taken in the amount of cholesterol they need to perform their bodily function, they will then reject any further entrance of cholesterol. All the surplus LDL will be relegated to the bloodstream. The cells of the inner lining of the arteries do not have a cut-off limit to the amount of cholesterol they take in; therefore, the LDL cholesterol can continue to build up until the inner wall of the artery becomes so filled with plaque that the blood flow becomes restricted.

Now, for the "good guys," the high-density lipoproteins known as "the scavengers." While the LDL cholesterol tries to penetrate the lining of the arteries, the HDL cholesterol comes to the rescue. They will attract the LDL cholesterol and take them on their way, preventing the plaque build-up. The cholesterol is then transported to the liver, where it is metabolized and sent on its way out of the body.

There is a strong relationship between cardiovascular exercise and higher levels of HDL. The best prescription for maintaining a good cholesterol profile is a combination of healthy eating habits, which would include lower consumption of fatty foods, and exercise.

Dr. Dean Ornish, the author of Dr. Dean Ornish's Program for Reversing Heart Disease, believes that active life can slow or stop the process for all but those with serious genetic disorders. He goes on to say that a demanding intervention program consisting of activity, a very low-fat diet and medication, if needed, may even reverse the process.

RATIO OF TOTAL CHOLESTEROL AND HDL: The lower the ratio, the lower the risk. TC/HDL: Divide the two components.

TC (total cholesterol) divided by HDL equals ratio.

Men with a ratio of 3.5 and women with a ratio of 3.0 have a 12 percent risk of cardiovascular heart disease.

Men with a ratio of 5.0 and women with a ratio of 4.5 are at 25 percent risk.

If you have a high ratio, remember that exercise and nutrition can make a difference.