Of all of the things that you can do to break a sweat, sex is probably up there with one of the most fun. Why was sex a better workout for the guys? Not as many as you think—but you can up your burn by doing it a certain way. One study in the New England Journal of Medicine found that the average bout of sex lasts just six minutes although that number did not include foreplay. After all, super-fit celebrities like model Miranda Kerr , reality star Khloe Kardashian , and actor Charlie Hunnam have sworn that they stay in shape by having a lot of sex. This is the same as 55 minutes of swimming or playing an entire football match. You can always go for a run afterwards. Coming up onto your feet, almost as if you're in a squatting position, can also help work your bum, legs and hips. Especially among older couples in long-term relationships, sex is unlikely to crank your heart rate or energy output. In a study , a team from the University of Montreal compared the calories used running to that of sex and found that running was far better at burning them off. On top of that, there's a million different ways to have sex, with different partners, and in varying intensities. And after entering all your details, the tool offers suggestions on how you can step up your in order to take it up a level. It asks you to put in your partner's gender note that it only puts male or female, and doesn't specify genitals , your gender, both of your weights, what position you're doing it in, for how long, and what your role is top or bottom. Doing this will help flex your core muscles and deliver a similar workout to ab crunches. Men should use your arms to hold yourself up as if you are doing a plank at the gym but hopefully this will be more fun and you should thrust with your pelvic muscles rather than your lower back. A team from the University of Montreal compared the calorie expenditure of running to that of sex and found that—no surprise—running far outpaced the latter.