The question: After a rigorous romp, I’m always sweaty and exhausted. But how much of a workout do I really get in the bedroom?

The expert: Bryan Krahn, C.S.C.S., a personal trainer at Complete Body Fitness in New York City

The verdict: “Most guys think they’re outstanding lovers and would never even consider that they might’ve once left a woman or two unfulfilled,” Krahn says. “Not surprisingly, most guys also think that the act itself brings a massive calorie expenditure, on par with running a marathon followed by a Tough Mudder or two.”

But it’s actually more like a quick walk around the corner.

A recent (and totally unfortunate) study published in the New England Journal of Medicine debunked the common belief that having sex burns up to 300 calories. According to the calculations of University of Alabama at Birmingham researchers, a 154-pound man doing the deed burns about 21 calories during an average sex sesh—a mere 3.5 calories per minute.

But ever the optimists, we think it’s worth keeping a few things in mind. Those 21 calories depend on two things: intensity and duration. The study assumes that your sexercise is about as intense as walking at a 2.5-mph pace and that you last about six minutes—the average for most dudes.

For example, another study (did we mention scientists are really into this question?) found that young men burn 101 calories in the sack—granted, they pick up the pace and last a laudable 24.7 minutes. But even if you can’t go quite that long, foreplay counts for something, right?

If you want to up your sex life’s intensity (be it for a better burn or maximum O), mix things up with some standing positions or just focus on doing the pushing, says Krahn, who recommends that you leave the kettlebells at the gym.

But, all bedroom-gym-hybrid fantasies aside, your best bet is to focus on sex in the bedroom and exercise at the gym. That said, if you perform the right moves, your gym time could get you in better naked shape and improve your stamina in the sack. Case in point: our better-sex workout.

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