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November 9, 1999
Web posted at: 4:52 PM EST (2152 GMT)

By Sarah Yang

(WebMD) -- People whose idea of exercise is lifting the television remote control may want to think twice before they consider jogging, shoveling snow or engaging in other sudden, strenuous activities, new research suggests.

According to a study published in this week's issue of the Journal of the American Medical Association, people living a sedentary lifestyle are up to 30 times more likely to suffer a heart attack when they push their physical limits. Sedentary men who also have multiple risk factors for heart disease -- obesity, high cholesterol and smoking -- may be particularly vulnerable, said Satyendra Giri, M.D., lead author of the study and a fellow in cardiology at Hartford Hospital in Hartford, Connecticut.

"Exercise is a double-edged sword," Giri said. "It's definitely protective if it's done in a gradual fashion. But if you've never exercised and then do something abrupt, it can lead to a heart attack."

During the study, researchers examined 640 heart attack patients at Hartford Hospital, asking them about their activities at the onset and one hour before the heart attack. Results show that 10 percent of the attacks were triggered by heavy exercise.

The researchers also grouped patients into four categories from very low active to highly active, based upon the estimated amount of time they had spent doing various physical activities over the previous day, month and year. Patients who had heart attacks not related to exercise, results show, were more likely to be moderately or highly active compared to those who suffered exercise-related heart attacks -- 34 percent and 16 percent respectively.

"We found that people who have exercise-related heart attacks paradoxically are people who do not exercise," Giri said.

Previous studies have shown that for those not used to breaking a sweat, sudden, heavy exertion can be dangerous. But exactly what happens during an exertion-related heart attack is still unclear. Researchers have reported that the increased blood pressure and heart rate related to exercise may rupture cholesterol-filled plaques, allowing a clot to form rapidly and cause a heart attack.

Just as playing tennis or biking quickly could trigger an attack, so could running several blocks to catch a bus, pushing a stalled car or moving heavy furniture around.

"A couch potato that's a middle-aged male is synonymous with a walking time bomb," said Phil Sokolof, president of the National Heart Savers Association. "The message has been out there many times before. Nevertheless, [the study] provides an opportunity to say it again."

A recent report by the American Heart Association shows that heart disease is still the leading cause of death in the United States, accounting for about one in five deaths in 1996. And national health experts have reported that physically inactive people can increase their risk for heart disease by more than two times, with as many as 25 percent of Americans living a sedentary lifestyle.

Rita Redberg, M.D., an associate professor at the cardiology division of the University of California, San Francisco, said the study emphasizes the importance of regular exercise.

"It's always good to drive home that point," Redberg said, explaining that regular aerobic activity has already been shown to decrease a person's risk for heart disease.

Sokolof, an outspoken health advocate who has spent $10 million of his own money to educate Americans on heart disease risks, said the consequences of doing nothing are clear.

Rather than shy away from exercise, people should embrace it, he said. They should simply follow common-sense advice: See a doctor and start slowly.

"It's never too late to start," he said. "It can be as little as walking a few blocks a day. Any little bit helps."