"The exercise high does exist," says Toby Mündel, a senior lecturer in the School of Sport and Exercise at Massey University. He teaches a paper on 'the exercising brain'.
So how do you get it - you know, that buzzy feeling of euphoria? You've got do prolonged exercise, Mündel says, like running, swimming or biking long distances. This will propel you beyond feeling "pumped", which is something a weight-lifter might feel after a short and intense workout.
Mündel says part of an exercise high is due to an increase in brain activity (increased pressure and blood flow to the brain), like shifting up through gears on a car.
Men and women also experience an increase in different hormones (for men it's adrenaline; women it's oxytocin) in response to stressful situations, of which exercise can be seen as one, that puts them in a different "state".
Both sexes also release endorphins which scientists once thought were solely responsible for the high. But further tests in animals show endorphins don't easily pass the blood/brain barrier and so cannot be the only reason for euphoria. Mündel likens endorphins to a type of "morphine", which "numbs pain and creates an euphoric state"; our internal opiate.
"The body releases something similar to cannabis and gives you that euphoric feeling," he says, adding that he realises this may "sound daft, but it's true".
The university expert says that relatively recent research shows that another area too is responsible for this euphoria, called "the endocannabinoid system", which essentially modulates sensations of pain and mood in the brain. Prolonged exercise also raises serotonin and dopamine - neurotransmitters that send messages around the brain - to increase feelings of "reward" during prolonged exercise, much like many get from drugs, alcohol or sex.
However, the exercise high is not the same experience for everyone. People get different levels - or rather respond differently - to it. Just like how some people might respond differently to smoking actual cannabis, says Mündel.
And he also warns that the more you exercise does not equal a greater high. He says the same dose of exercise does not give you the same "hit" all the time, and typically the more you do something then the less the high might become.
Chasing too much of a high can also become addictive, with people exercising more and more to try and feel the same way they once felt. Exercising for five hours is not usual for non-elite athletes, says Mündel. He says for most people they just want to lose weight, look good or manage stress - like him - and the exercise high might make them feel floaty now and again.
However, if you're addicted to any "high", then perhaps the exercise high is the better one to indulge in. Just make sure you don't push yourself too far.