We’ve long been told that getting physical activity is a good thing. Now, researchers from Tufts Medical Center in Boston are telling us it can increase the risk of having a heart attack.

Well, sort of.

Tufts researchers published an article in the March 23, 2011 issue of The Journal of American Medical Association. The team of researchers sought out to quantify the risk of heart attack caused by physical activity in those who made exercise a habitual activity and in those who rarely get physical activity.

Researchers analyzed data from 14 studies looking at the link between exercise, sex and the risk of heart attacks or sudden cardiac death – a lethal heart rhythm that causes the heart to stop circulating blood.

According to an article published by Reuters, the study found people are 3.5 times more likely to get a heart attack or have sudden cardiac death when they are exercising compared to when they are not.

Furthermore, they are 2.7 times more likely to get a heart attack when they are having sex or immediately afterward compared with when they are not. These findings do not apply to sudden cardiac death because there were no studies looking at the link between sex and cardiac death.

Jessica Paulus, a Tufts researcher who worked on the study, spoke with Reuters in a phone interview after the study was published. Paulus told Reuters that the risk is fairly high as such studies go, but the period of increased risk is brief.

"These elevated risks are only for a short period of time--one to two hours--during and after the physical or sexual activity," Paulus told Reuters in the phone interview.

Because of that, the risk to individuals over the course of a year is still quite small, she said.

"If you take 10,000 people, each individual session of physical or sexual activity per week can be associated with an increase of one to two cases of heart attack or sudden cardiac death per year," Paulus told Reuters.

While the study does provide evidence that acute cardiac events are significantly associated with episodic physical and sexual activity, researchers don’t want people to think they’re propagating exercise is bad.

What researchers hope people take away from their study is that people who do not exercise regularly need to start any exercise program slowly, gradually increasing the intensity of the workout over time.

The risk of heart attack is attenuated among persons with high levels of habitual physical activity.

Yes, sex can kill you, U.S. study shows
http://www.reuters.com/article/2011/03/22/us-heart-exercise-idUSTRE72L6KR20110322

Association of Episodic Physical and Sexual Activity With Triggering of Acute Cardiac Events
http://jama.ama-assn.org/content/305/12/1225.short