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Exercise May Improve Heart-Protecting Chemicals | |
| By IRA DREYFUSS Associated Press Writer WASHINGTON - Older men and women who exercise improve their abilities to create natural drugs that fight heart attack, a study finds. And the levels of these body chemicals are higher when they are most needed - in the morning, when the risk of a heart attack is highest, the study said. The research looked at tissue plasminogen activator, TPA, an enzyme that dissolves clots. A clot that narrows or blocks a coronary artery can cut off blood flow to the heart muscle, leading to a heart attack. It also measured levels of plasminogen activator inhibitor, PAI-1, which dissolves TPA, acting as a balance against too much of the anti-clotting enzyme. Researchers in Seattle studied 16 men and nine women with an average age of 66 who were sedentary at the start of the six-month study. The study participants stayed overnight at a clinic, and blood samples were drawn while they slept. They then began a program of walking, jogging or bike riding three times a week. The exercisers started with 30-to 45-minute workouts at a moderate 50 percent to 60 percent of their projected maximums as measured on a heart test; they worked up to a vigorous 45 minutes at 85 percent of their maximums. At the end of the study, they stayed again at the clinic for more overnight blood samples. In the men, PAI-1 levels dropped 37 percent while TPA was unchanged, said the report in the American College of Sports Medicine's journal, Medicine and Science in Sports and Exercise. The drop in PAI-1 means the activity of the clot-busting TPA in the men's bloodstreams was less likely to be impeded, said reseacher Wayne L. Chandler of the University of Washington. In the women, TPA levels were up 20 percent, but PAI-1 levels were unchanged, the study said. This means the women also had more clot-busting protection, Chandler said. Chandler could not explain why men had more PAI-1 but women had more TPA. "It was a little unexpected," he said. But the bottom line in terms of protection against blood clots was apparently the same, regardless of the apparent mechanism, he said. The findings fit the idea that exercise increases TPA levels and may in part account for endurance exercise's well-established protection against heart disease, Chandler said. "That's what's kind of fun," he said. "Everybody tells you (exercise) is good for you and, all of a sudden, we are finding real biochemistry for it." The TPA levels that resulted from exercise were far below those given as drugs to heart attack victims, Chandler said. A drug dosage might be 1,000 to 10,000 times the body's normal levels, he said. Older people who want to boost their exercise as a way to boost their body chemicals should be sure first that they are up to the strain, Chandler said. Leaping into intense exercise can trigger previously hidden health conditions, possibly leading to a heart attack. However, other studies have shown that moderate exercise reduces the risk of death from many causes, including heart disease. And Chandler suspected that lower amounts of exercise might create some beneficial changes in TPA or PAI-1. But his study did not look at lower intensity or less time working out. The study raises some interesting points, but does not prove that the body chemical changes actually reduce heart attacks, said a separate researcher, Dr. Joseph P. Broderick of the University of Cincinnati Medical Center. The changes in TPA and PAI-1 levels may be real, but there were too few study participants to be sure the results were not a result of unrelated variations in the levels of the chemicals, Broderick said. And the differences in the way men and women in the study reacted to exercise need explanation, he said. Copyright 1996 Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed. | |