Feb. 23, 1999 DALLAS -- Physical activity does more than tone up the heart and reduce the risk of heart attacks. Moderate physical activity -- aerobic as well as pumping iron -- fortifies various segments of the cardiovascular system. In an article appearing in Circulation, Journal of the American Heart Association, Roy J. Shephard, M.D., of the University of Toronto and Gary J. Balady, of Boston University Medical Center, say regular, moderate intensive activity reduces the risk of dying from a heart attack or stroke. The effects, however, are broader than many think. An analysis of almost 100 studies has shown:
* Regular physical activity lowers blood pressure and prevents the development of high blood pressure. In someone with mild high blood pressure, physical activity leads to a drop in blood pressure that is sustained for eight to 12 hours. Blood pressure is lower on days when a person is physically active compared to when the individual is not.
* Someone who is very inactive has six times the risk of heart disease as someone who is active.
* An individual who exercises can expect to have a 24 percent drop in blood levels of cholesterol and a 10 percent drop in low-density lipoprotein (LDL), the 'bad' cholesterol, a risk factor for heart disease and stroke. The high-density lipoprotein (HDL) 'good' cholesterol will go up 6 percent. The amount of physical activity needed to reduce cholesterol is not very much, the studies show.
* Physical activity also benefits the blood-clotting system, reducing the body's ability to produce dangerous blood clots that can obstruct blood vessels to the heart, thereby causing a heart attack or stroke. After three months of physical activity by middle-aged, overweight men with mildly elevated blood pressure, one study reported that platelet aggregation was reduced by 52 percent, compared to 17 percent with a control group. Platelets play a role in blood clot formation. A reduction in platelet aggregation leads to a reduced risk of blood clots that can trigger heart attacks and strokes.
* Another benefit is found in the endothelial cells that line blood vessels feeding the heart and brain. Physical activity improves their ability to produce nitric oxide, a substance that causes the blood vessels to relax and contract more efficiently. Physical activity also reduces heart rate variability -- dangerous swings in heart rate -- in patients who suffered from heart attacks.
* Physical training affects both healthy people as well as those with heart disease. After starting an exercise program, moderate physical activity three to five times a week will improve cardiovascular function in eight to 10 weeks as well as improve risk factors for cardiovascular disease and stroke. Experts say that to maintain these health benefits, people need to stick with the program.
* The more strenuous the physical activity, the more beneficial it is -- up to a point. There is a law of diminishing returns with increased exercise. The authors say that it's best to consult with a physician before beginning any exercise program to achieve the maximum benefit.
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