WARNING: Sex Can Kill!

What's one key to safe sex? A healthy heart. That's the word from a new study warning that sudden bursts of moderate to intense physical activity—such as jogging or sex—significantly increase the risk of a heart attack, especially for those who don't get regular exercise. People are 2.7 times more likely to have a heart attack when they are having sex or immediately afterward, Reuters reports. The risk is "fairly high," but only lasts up to two hours after sex, said a researcher.

Individuals are also 3.7 times more likely to have a heart attack during exercise, the study discovered. "What we really don't want is for the public to walk away from this and think exercise is bad," said Tufts University researcher Jessica Paulus. She urged people who don't exercise to start a work out program slowly, and increase the intensity gradually over time.