The most serious of sex-related injuries is a heart attack. (A penile fracture is dire, we agree, but it's not life or death.) “It takes a certain level of fitness [to have sex], so people with preexisting conditions need to be aware,” says Dr. Moore. If you've had a heart attack in the past or other major cardio issues, check with your doctor to see if you can safely perform the act.
Dr. Moore notes that many heart attack victims have their first one during sex, and that's especially true for men. Signs to look for include a sudden tightening of the chest or pressure in the chest, as well as nausea, dizziness, and shortness of breath. But heart attacks in real life don't always resemble the dramatic clutching of the chest that happens in movies, so if you or your partner has any kind of chest discomfort, play it safe and postpone the action. If it persists or worsens, call 911.