For the unprepared, sudden bursts of vigorous exertion--like heavy exercise or shoveling snow--could be dangerous for the heart, according to one new study.

But don't cancel your gym membership just yet. Experts say the findings suggest that regular exercise, rather than sporadic amounts of very vigorous activity, could help prevent problems.

During and shortly after an episode of unusually energetic exertion, healthy men between the ages of 40 and 84 who did not exercise often were found to have a heightened risk of sudden death from a heart problem than men who reported regular exercise.

"But the good news is that by exercising regularly, one can lower this risk substantially," says the study's lead author, Christine M. Albert, MD, MPH, a researcher at Boston's Brigham and Women's Hospital and a cardiologist at Massachusetts General Hospital.

While sudden death was rare in the group studied--one death per 1.51 million episodes of vigorous exertion--it still highlights the benefits of regular exercise, Albert says.

"The message is, if you are going to begin a vigorous exercise program, then build up to it gradually and also ask the advice of your physician before doing so," she says. Start out with moderate levels of exertion, and gradually move to a tougher workout.

Exertion done at work or on weekends counts too, Albert says. "I think what people need to realize is that exercise isn't necessarily just playing sports or participating in a gym ?anything that's really going to cause you to sweat to exert yourself is considered 'vigorous exertion.' And if that's not something that you're used to doing regularly, then that is risky to go out and do it when you haven't been doing it regularly."

But the overall benefits of exercise seem to outweigh the findings of this one study, says Barry J. Maron, MD of the Minneapolis Heart Institute Foundation who wrote an editorial that appears in the November 9 issue of the New England Journal of Medicine along with Albert's study.

"There is overwhelming evidence of the cardiovascular benefits attributable to consistent vigorous exercise as a primary-prevention strategy for coronary disease in asymptomatic middle-aged and older persons," writes Maron.

However, the benefits of exercise don't come without some risk, Maron notes, "particularly when vigorous exertion is undertaken abruptly by untrained or previously sedentary persons." This, he says, makes the relationship between exercise and heart disease "complex and contradictory."

Albert says the body of evidence indicates that exercise is probably not dangerous for most people. "Other studies have found many benefits of exercise, and so that we're not recommending that people don't exercise--we really do want you to still exercise. In fact, we want you to exercise regularly."

(From Medscape)