Sex isn't only a pleasurable experience, with some reports claiming the act also has health benefits that can be compared to those of exercise.
In fact, the physiological response to sex is similar to that of exercise. Landmark studies in the 1960s showed people having sex had an increase in their respiratory rate, heart rate and blood pressure.
These are all signs the body is working at an elevated rate, similar to that experienced during exercise.
More recently, these findings have been replicated by a number of researchers using less obtrusive, miniaturised and wireless equipment, enabling more realistic results.
Again, they found a significant increase in markers of physiological stress, such as heart rate and blood pressure.
Comparing this to what happens during exercise, they showed sexual activity elicits a moderate level of physical stress - up to 75 per cent of maximal exercise.
But they also noticed these physiological stress levels were intermittent. Much of the average time of sexual activity recorded (33 minutes) was spent at lower stress levels.
A more recent study of young Canadian heterosexual couples showed a bout of sexual activity was akin to moderate physical activity (such as brisk walking) when energy expenditure was measured.
Sex is kind of like exercise
So sex is exercise? Well yes and no. It depends on your definition of exercise. If you compare the two purely by the physiological change that occurs then yes, because sex elicits a change in human physiology akin to exercise.
But if you believe exercise should change human physiology for the better, in the long term, then perhaps no. This is because, for most of us, sex isn't sustained long enough nor occurs frequently enough for a true physiological change to happen in the long term.
Also, we haven't really explored the other benefits of exercise and contrasted them with sex. For instance, muscular health is recognised as a major component of a person's health.
We know lots about gaining muscular health through resistance training and other exercises. But does sex give enough of a workout to change muscular health? Well ... I sense a research project in the pipeline.
The studies mentioned above also reported a distinct difference between responses in males and female participants. The reasons for this difference - whether men are more physically active during sex compared to women or whether different sexual positions place a greater demand on the human body - have yet to be explored.
What about masturbation? Increases in heart rate and systolic blood pressure have been reported during masturbation. But both the level and duration of these increases weren't as high or long as with intercourse.
Judging by measurements of heart rate, masturbation really only equates to light exercise, such as slow walking.
How exercise affects sex and vice versa
In many cases, exercise can also be helpful to sex. Research into pelvic floor exercises in women with pelvic pain, for instance, has shown they improve sexual function. Women reported increased control, confidence, heightened sensation and less pain.
While in men, exercises that train the perineal muscles in front of the anus help with premature ejaculation.
And what about how sex affects exercise? Should professional sportspeople, for instance, refrain from sex before a competition?
Not if they wait long enough after sex. Sex has been shown to have no negative effect on sports performance but can have a negative effect on recovery if you compete within two hours of having it. This means athletes could take longer to recover from one bout of exercise to another.
So in answer to the question of whether sex is really exercise. Kind of. But you can test it out for yourself and see how you feel.
Kevin Netto is an Associate Professor of Physiotherapy and Exercise Science at Curtin University.
This article originally appeared on The Conversation.