During sex, the heart races, blood pressure rises and the breath quickens, sometimes to a pant. Muscles tense and euphoric feelings flood the brain.

This is not a time to be thinking, “I hope my heart doesn’t stop.”

But according to cardiologists, male patients over 50 during checkups sometimes ask what the chance is of a heart attack or sudden cardiac arrest during sexual intercourse. The concern is based on the heightened physiology experienced (racing heart, contracted muscles, etc.), but also the misconception that sex, even the steamy kind, is physically demanding. A 2013 study in PLOS One discovered that people tend to think they expend more energy during sex than they really do.

Is sex comparable to, say, performing strengthening exercises for 40 minutes, or walking a treadmill for 30 minutes? Not quite. Sex involves moderate exertion for a brief period, says Sumeet Chugh, a cardiologist and coauthor of a study on cardiac arrest and sex published in November in the Journal of the American College of Cardiology. Sex is “comparable to climbing two flights of stairs,” he says.

Sex won’t keep you physically fit, but it does have physical consequences. The study in PLOS One, which involved young adult men and women, equated the energy expenditure of sex to moderate intensity for a short duration. Men in the trial burned on average 101 calories and women 69 calories during sex (including foreplay and intercourse), which is about the number of calories in one or two whole-grain bisquits. These same men and women burned 276 calories and 213 calories, respectively, during 30 minutes on a treadmill.

So sex is marginal exercise and won’t make you thinner, but the good news is that it’s unlikely to stop your heart, either – regardless of your age, the study in American College of Cardiology found.

The paper looked at results from the Oregon Sudden Unexpected Death Study that examined sudden cardiac arrests, or SCAs, in the region of Portland, Ore., from 2002 to 20015. SCAs involve a short circuit in the heart causing “electrical chaos” and is lethal 90 percent of the time, Chugh says. In the United States, 300,000 people die each year from SCAs. The condition is different from a heart attack, which involves a plumbing problem in the organ.

Of the 4,500 adults suffering SCA, 34 occurred during or minutes after sex. Thirty-two were men, mostly middle aged and with a history of heart disease. These were more likely to be African-American men when compared to the overall SCAs in the study.

Among people having a SCA, 1 in 100 men and 1 in 1,000 women might experience the attack during or soon after sex, the study found. “We expected low risk, but our findings indicate that risk of sudden cardiac arrest with sexual activity is extremely low — a most reassuring finding that will help healthcare providers communicate with concerned patients based on real data,” Chugh says.

Though this study looked only at SCAs, other studies have shown that the risk of having a heart attack during or soon after sex is also very low.

“The individuals most at risk are those who have some severe form of heart disease and who are not habituated to exercise,” Chugh says. “Mostly this includes patients over 50.”

An additional risk for SCA or heart attack involves the sexual circumstances, though this wasn’t part of Chugh’s study. A cheating spouse wining and dining his lover ups the ante of a heart episode.

“A large proportion of these encounters occur with extra-marital partners and often happen in the setting of alcohol and food intake,” Chugh says.