WASHINGTON (AP) -- Fifty-four studies' combined data put the weight of evidence behind the benefit of aerobic exercise to control blood pressure.
Exercise pushes down blood pressure, regardless of age, weight, or what blood pressure was when the person started to exercise, according to a statistical analysis of the studies.
The average reduction was 3.8 milligrams of mercury in systolic pressure -- the measurement taken when the heart contracts and pushes blood through the arteries. The average diastolic reduction, taken when the heart relaxes, was 2.58 milligrams of mercury lower.
''If we can reduce systolic pressure by 3.8, we can reduce a lot of risk of cardiovascular disease, stroke -- everything,'' said Dr. Jiang He of Tulane University.
Being physically inactive raises the risk of developing high blood pressure. And federal surveys find 25 percent of all adults are not active at all. About a quarter of American adults have high blood pressure, and the risk of problems resulting from the condition gets worse as pressure rises.
Normal blood pressure in an adult is lower than 130 systolic, 85 diastolic. High blood pressure is 140 over 90 or above. Readings between those are considered borderline.
The report in the April issue of Annals of Internal Medicine examined studies involving 2,419 participants.
The researchers pooled cases from smaller studies in which some people did aerobic exercise and others did not. The scientists counted on the resulting larger number of cases to give a more accurate assessment of the effect of aerobic exercise on blood pressure. Evidence on the size of the effect had been inconsistent in the smaller groups, they said.
The pooled figures showed the extent of the drop in blood pressure was fairly consistent regardless of what form of exercise the participants did.
''For someone who is sedentary, even small things like walking or riding a bike, the study shows, can significantly reduce their blood pressure,'' said researcher Seamus P. Whelton of Princeton.
It also did not make a difference whether the participants were overweight or at normal weight. ''Blood pressure was significantly reduced even in participants who did not lose weight overall,'' the report said.
The benefit was there whether the participants had high blood pressure or normal blood pressure. And the extent of the reduction from exercise was greater than what was found in similar studies on reducing salt in the diet or reducing alcohol use.
The reduction cited in the paper is modest but valuable, said Dr. Gerald Fletcher of the Mayo Clinic in Jacksonville, Fla., who is also a spokesman for the American Heart Association.
''It's a good additional bit to know for our pitch on lifestyle changes rather than taking pills or other things that may give side effects,'' Fletcher said.
The benefits of exercise may vary among individuals, but the paper in the journal ''probably shows us the average to expect,'' Fletcher said. Overweight people, for instance, may draw reassurance from the paper's finding that their blood pressure can improve from physical activity even if they don't lose weight, he said.
On the Net:
American Heart Association exercise page: http://www.americanheart.org/presenter.jhtml?identifier1200013
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