The exercise doesn't have to be all that strenuous to reduce your risk of heart trouble, says Dr. William Kraus, an associate professor of medicine at Duke University Medical Center and leader of a group reporting the findings in tomorrow's issue of The New England Journal of Medicine.
This new study has two significant differences from many of the countless others showing that exercise is good for the cardiovascular system, Kraus says. Most studies just ask people if they exercise, then correlate their answers with the incidence of heart problems. This one was carefully controlled, with different groups of people selected because they were overweight, inactive and had high cholesterol levels. They were then assigned to carefully measured rations of exercise or to inactivity.
The blood tests they had at regular intervals were also out of the ordinary -- sophisticated, high-tech measurements looked at subtle and specific changes not only of blood cholesterol levels but also at the nature of the cholesterol-carrying lipoproteins in the blood.
The participants were divided into four groups. One was assigned to vigorous exercise, the caloric equivalent of 20 miles of jogging a week, a second to the equivalent of 12 miles of jogging a week, a third to the equivalent of 12 miles of brisk walking, and the fourth to doing nothing in particular.
"One major point is that the inactive folks deteriorated at a rate faster than we would have predicted," Kraus says. "They gained an average of three pounds in six months, and their cholesterol levels also deteriorated."
"A second finding was that anyone assigned to an exercise group did better. Even a low amount of exercise prevented that deterioration. Some exercise is better than none, and more is better than less," he says.
"Third, we found that one need not focus on weight change. Even in the absence of significant weight loss, people got a benefit from being in an exercise group," he adds.
The exact nature of that benefit was shown by the advanced blood tests used in the study. Standard blood tests showed a reduction in LDL cholesterol, the "bad" kind that clogs arteries, only for the people doing more vigorous exercise. The newer blood tests looked not only at overall LDL cholesterol levels but also at the nature of the lipoprotein particles that carry cholesterol in the blood.
"What we have known for a while is that small and dense particles are more dangerous than light, fluffy particles," says Dr. Richard A. Stein, a professor of clinical medicine at Weill Cornell Medical Center in New York City and a spokesman for the American Heart Association. "What this study showed was that even moderately intensive exercise improves the ratio of fluffy particles to small, dense particles."
By exercising, Stein says, "what you are doing is moving your LDLs from the very dense forms that are likely to cause heart disease to less dense forms. This is why regular, moderate exercise is a dramatic way to reduce the risk of having a first or second heart attack."
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