Sudden Exercise Poses Heart Risk for Sedentary People

If you don't exercise regularly, a sudden bout of energetic activity can trigger a heart attack, and may even kill you, according to a new study published in JAMA, the journal of the American Medical Association.  

It sounds like the scene from a movie: a flabby, out-of-shape guy has a heart attack while running to catch a train, or maybe he drops dead while having sex. Now, there's some scientific evidence to support that fictional scenario.

Researchers at Tufts University near Boston combined the results of 14 studies that looked at the link between what they call episodic physical activity and heart attack and other cardiac events.

Regular exercise may be beneficial, but co-author Jessica Paulus says that among more sedentary people, there was a short-term increase in the danger.

"There's a link between episodic physical activity and sexual activity with the risk of heart attack and death from sudden cardiac events," she says. "During a very short window of time along the order of one to two hours following physical activity and sexual activity and sexual activity."

The researchers found that the episodic physical activity roughly tripled the risk of heart attack, but because a sudden burst of activity is rather uncommon among otherwise-sedentary people, the risk of having a heart attack while running to catch a train is actually small.

And lead author Issa Dahabreh says regular physical activity can reduce the risk. "Individuals who exercise regularly while involved in these activities overall experience a much smaller increase in their risk of having a heart attack."

Even regular exercise just once a week can significantly reduce the risk. The researchers found that a person's risk of heart attack decreased by almost half, and the risk of sudden death dropped by about one-third, for every weekly exercise session.