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For Some, Vigorous Exertion Raises Risk of Sudden Death

WebMD Health News
Reviewed by Gary D. Vogin, MD

Nov. 8, 2000 -- Couch potatoes who try to make up for long periods of inactivity with short, intense bursts of activity may be putting their lives at risk. Vigorous physical exertion appears to dramatically increase the short-term risk of sudden death from cardiac events, especially in people who do not exercise regularly.

But easing into exercise and exercising regularly cuts the risk of such deaths.

Findings from the ongoing Physicians' Health Study, which has been tracking some 22,000 male doctors in the U.S. since the early 1980s, showed that among men who exercised less than once a week, there was a 74-fold increase in the risk of sudden cardiac death during bouts of vigorous exertion, compared to rest. A 10-fold increase was found among those who exercised five or more times per week. Vigorous exertion, as defined in the study published in the Nov. 9 issue of The New England Journal of Medicine,covers a range of activities from racquet sports to heavy yardwork.

But researchers were quick to point out that the absolute risk of sudden death during a particular episode of vigorous exertion was extremely low for both regular and sporadic exercisers -- an estimated one sudden death was reported per 1.51 million incidences of exertion.

"The overwhelming data show that exercise is very beneficial with regard to heart disease," study author Christine M. Albert, MD, of Boston's Brigham and Women's Hospital, tells WebMD. "People should not be discouraged from exercising because of this study. But it shows that those beginning to exercise should start slowly and do it regularly."

Cardiologist Barry J. Maron, MD, of the Minneapolis Heart Institute Foundation, agrees that the short-term hazards of physical activity are outweighed by the wide range of cardiovascular benefits gained. Maron was not involved with the study, but authored an accompanying editorial in which he discussed, "the paradox of exercise."

"Exercise can both increase the short-term risk of sudden death from coronary disease and protect against such deaths in people who exercise regularly," Maron tells WebMD. "There are risks associated with abrupt entry into vigorous exercise programs, especially in sedentary individuals. But there is no doubt that consistent vigorous exercise is a primary prevention strategy for heart disease in at-risk individuals."

In the study reported by Albert and colleagues, a total of 122 sudden deaths occurred during 12 years of follow-up among the doctors enrolled in the study. One in six of the sudden deaths happened during or 30 minutes after vigorous exertion.

It has been suggested that vigorous exercise may increase the risk of heart attack by affecting nerve inputs to the heart or by possibly dislodging plaque in the vessels around the heart. In both cases, Albert suggests, exercising regularly instead of sporadically lowers the risk.

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