Think CrossFit, Bikram yoga, Tough Mudder-type challenges and ultramarathons.

They're same, same but different to your average exercise.

Average exercise we might describe as 'fun' whereas flogging yourself fitness is more about self-flagellation.

It's not just being stuck in a stinky sauna and flicked with  someone else's sweat while you workout (looking at you Bikram).

Overheating, vomiting, enduring electric shocks, dehydration, bruises, cuts, kidney-failure and cardiac damage are just some of the potential risks of such high-intensity forms of fitness. 

So why are people drawn to them in droves?

Some put it down to our instant gratification, go hard or go home culture.  Others suggest that extreme exercisers are sensation-seekers who enjoy the bragging rights earned by doing (arguably) insane yet unique activities.

"It's psychologically more rewarding than plodding away on a treadmill," points out Dr Jeremy Adams, a psychologist with a PhD in sport and exercise psychology. "People get psychological benefits from feeling like they've achieved something."

Plus, he adds, there's often novelty factor, challenge and the bonding that tends to go on within niche fitness cultures.

"They're really tribal," he says of Bikram and CrossFit. "Exercise with others when you find it rewarding and you will get massive benefits."

The physical catharsis of these types of exercise is huge.

But as much as they are physical activities, the feel-good factor seems to lie largely in the mental benefits.

A 2013 study by Australian researcher Eric Brymer found that the challenge of mind over matter - in this case our bodies - can be mentally and emotionally "transformative".

As we break through physical and mental  barriers and, often, face our fears we experience "a sense of personal liberation", Brymer wrote in the study which was published in the Journal of Health Psychology.

As well as a sense of liberation, extreme exercise can bring a greater sense of control, new research suggests.

"What we're finding is that when people are feeling a loss of control, they're particularly likely to go for these high-effort things like very intense workouts because it makes them feel empowered," the co-authorof the study, Dr Keisha Cutright told Time.

“You feel like you’re in charge of the desired outcome,”  Cutright added of the results, which were published in the Journal of Consumer Research. “You find a certain amount of control over your life, and that feels good.”

While there are benefits associated with stretching ourselves through sport and exercise, there can also be a dark side.

And it's not just the risk that people will become, as Adams puts is, "zealots about a particular brand of exercise".

A 2011 study conducted by University of Queensland psychologists found that those who felt guilt in their life were more prone to  punish themselves through pain.

“Going on a hard run is perhaps a convenient way to make ourselves feel better after we’ve behaved badly,” Brock Bastian, the study's co-author, explained. “It makes us feel like the scales of justice have been rebalanced.”

There is also the more obvious dark side of pushing ourselves to our limit.

"It might have instant rewards but there is also the potential for massive injury," Dr Adams says.

Potential injury and the potential to become obsessed with exercise.

Adams says there are certain criteria that make it "pretty obvious" that someone's approach to exercise has become unhealthy.

These include not taking rest days, exercising through injury or ill health, subscribing to "logic fallacies" like two hours of exercise must be better than one, becoming upset and irrational when their exercise routine is broken and putting exercise before all else.

For the most part, however, getting hooked on exercise and pushing our limits here and there is healthy. Particularly given that we're becoming more sedentary as a population.

"Provided we have plenty of rest, have good instruction, diets and sleep, you can have high intensity work outs," Adams says. "They give better mood benefits.

"The harder you work out, the better - to a point. If you vomit, you won't feel good."