On an Edinburgh Fringe stage scattered with suitcases, plastic bottles and a Persian rug, Sohrab Haghverdi is hopping about naked with a sock covering his penis. His show charts his experience of attempting to gain US citizenship as an Iranian, and also surviving testicular cancer as a teenager. At this precise moment, he is playing his childhood urine; minutes later he reappears as his adult sperm. But neither appearance is as shocking as when Haghverdi pulls his penis from his trousers, points it into a bottle, urinates, and then drinks it.

It’s one of a conspicuous number of shows at this year’s Edinburgh Festival Fringe that features a performer using their body in strange and punishing ways. Plays are taking place on bikes, treadmills and reformer Pilates benches. Others involve stomach-turning stunts. One sees the same song sung over and over for the duration of its hour-long run – testing the stamina of the audience as much as the performer.

Are these exploits gimmicky ways of standing out amid the fierce competition of the festival’s oversaturated market – one in which intimate confessions, tears and even nudity are so commonplace they don’t cut through the noise? Or a way for artists to express themselves, pushing their mental and physical limits for the sake of their art?

When I catch up with Haghverdi after his show, he insists the “moments of physical hardship” are “a means of self-expression” – a commitment to his art and a celebration of his freedom and life following his illness.

Having previously performed at fringe festivals in Philadelphia and Denver, Haghverdi believes he’s “developed some sort of tolerance” to the stunt, but admits urinating on demand and swallowing whatever liquid he produces for 24 nights this August may prove challenging.

Elsewhere in the same complex, another artist has his own Everest to climb each night. Australian comedian Connor Daroil, better known by his stage name Conk, is performing his show .

The song in question is an irritatingly sunny country-rock number, which Conk has asked me not to name in order to savour the surprise. “It’s kind of perfect because everyone knows it, but no one really knows it,” he says. “It starts really bombastically – it’s like a slap in the face.” Coming to Edinburgh as part of a wider tour, Conk reckons he’s sung the song around 780 times already, and will hit 1,000 by the end of the month.

Each round of the song is slightly different, with Conk adding props (bananas, placards, a recorder), removing clothing or changing up the choreography. Somehow, enthusiasm among the crowd never wanes the night I watch: each time Conk pulls a party popper to mark the completion of another round, there are cheers for more. “It brings people together in a really weird way,” he says with a laugh. Performances are filling up most nights, with many people, including an Australian couple I find myself sitting next to, having booked it as a priority. Once the hour is complete, there are even calls for “one more song!”

With the arrival of the all-new Sauna Theatre, audiences can experience some physical endurance of their own. Already popular in pockets of northern Europe, aufguss – a multisensory theatrical experience that unfolds inside a sauna with a fusion of movement, sound and scent – is still a novelty in the UK. For many, including myself, the Fringe’s Sauna Sessions Arts Club marks a first encounter with the art form.

Stripped down to our swimwear, we take our seats on wooden benches surrounding three large trays of white-hot rocks, our skin instantly glistening in the 50°C to 60°C heat. Several shows are running in the space but I’m here for a production of Virginia Woolf’s . As we listen to an audio patchwork of particularly evocative passages from the novel, a pair of “sauna masters” pat ice onto the rocks to generate puffs of steam, wave around towels and waft incense towards us. Between each 12–15 minute act, there’s a break for audiences to cold plunge outside.

Visitor wellbeing is a top priority. “When we have eye contact, it’s part of the performance but it’s also to make sure [the audience] are safe,” says sauna master Hannah, who became an aufguss artist after working as a personal trainer. “If someone stands up and wants to leave, you stop the performance and take them outside to make sure they’re okay.” On my visit, one woman leaves before the third act because she’s struggling with the heat, but the rest stick it out until the end.

The sauna masters here perform in loose-fitting vests and trousers. They’re used to the heat, but it’s still a physical challenge. Hannah says electrolytes, water and sleep are her coping methods.

We’re all sweating profusely by the end, but not as much as the actor of the next show I see. Ben Norris is a former GB long-distance runner, and he delivers his mostly autobiographical one-hour play while running on a treadmill. It’s a spectacle, certainly, but though Norris’s athleticism is mesmerising to watch, it never overshadows a rich narrative. He takes us through the significant races, rigorous training regime, and strict diet of his teenage years, all while pounding steps and changing in and out of sweat-soaked vests.

This is not the first piece Norris has brought to the Fringe, but he admits the physicality involved is making it a more strenuous affair. “I’m kind of having to behave like I’m an elite athlete again,” he says. “I’ve had many Fringes that have been quite boozy, and this one is much more monastic.”

The risk of injury is high with moving equipment involved. On the night I watch, Norris slips off the machine momentarily, without missing a beat. Were he to fall and hurt himself though, it could mean suspending performances.

It would be a similar case for Conk if he lost his voice, or Haghverdi were he unable to urinate on demand. While each of these shows is greater than its gimmick, and each performer would undoubtedly find a way through, these brave feats are unofficially factored into ticket sales.

Norris is not the first artist to perform on a treadmill at the Fringe (though says he’s been working on the idea for 13 years). Bikes have also been incorporated into shows at the festival before. But playwright and actor Eddie Thornton may well be the first to bring a play set across a pair of reformer Pilates benches to Edinburgh.

In , she and Anna Glendenning play women sizing each other up while performing lunges, planks and stretches on Pilates carriages – which for anyone unfamiliar with the cultishly popular workout, look a little like leather-clad medieval torture racks. “I’ve tried to structure it as closely to a real class as I could,” says Thornton, who managed to buy the benches from Aldi for roughly £150 each. As a trained dancer, she makes the moves look effortless.

Glendenning, meanwhile, has the potentially hazardous challenge of playing an uncoordinated beginner for comic effect. “Pretending to be bad is quite challenging,” she laughs. Even though she’s a keen yogi, “my legs are jelly [and afterwards] I’m genuinely full of endorphins”.

Of course, in order to deliver a feat of endurance on stage, a gruelling rehearsal period is required. To practise talking while running, Norris would call a friend while jogging on a treadmill at his local gym. As the show neared, he would bring his iPad and recite his 65-minute monologue out loud, ignoring the stares of his fellow gym-goers. Haghverdi, meanwhile, saved drinking his urine until the dress rehearsal, but needed to do it at least once to know that he could.

But each of these acts raises the question of whether, in our attention economy, there’s too much pressure on artists to shock and titillate audiences who have seen it all before, and are becoming increasingly desensitised. So much pushing to extremes will likely take its toll eventually, be it through torn muscles, infections or sheer exhaustion.

For veteran Fringe director Scott Hurran, who developed shingles while staging a play at the 2015 festival, hearing stories of artists pushing their mental and physical boundaries for the sake of impressing audiences raises alarm bells. “I think the Fringe can put enormous pressure on artists precisely because it’s become one of the only places where [they] feel they still have permission to take a risk,” he says.

Among the artists I interview, though, the most strenuous part of their show is not its obvious act of fortitude. For Conk, singing the same song on repeat isn’t nearly as tiring as the Instagram Live stunt he pulled to raise the money to be here. “I danced the Macarena for every dollar that I raised, and ended up performing it 2,500 times over seven and a half hours,” he says. “It hurt!” And in the show itself, it’s also a nausea-inducing moment in which he performs star jumps shortly after downing a pint of beer that the comedian finds hardest.

Similarly for Norris, climbing and swinging from the metal scaffolding encasing his treadmill is “way more outside of my comfort zone than the running”. He managed to make hanging from one arm look effortless, but says it’s taken him months to perfect. “I’m in so much pain here,” he says, pointing to his biceps.

Looking back on his own experience, Hurran can see there was “an enormous amount of mental and physical strain during the Fringe and in the lead up”. It led to him having to take days away from the show mid-run. Ultimately, it “made me think much more seriously about my wellbeing, and physical health, and what a sustainable career in the industry actually looks like”.

Hurran’s experience is not unique. While most escape with something akin to Freshers’ Flu, serious injuries happen too. Several years ago, Douglas McFarlane, who now runs UK Theatre Network, injured his back while lifting ladders in a production of Mack and Mabel, and says he’s had recurring back problems ever since. “It has made me very aware that the industry can depend enormously on people pushing themselves physically and mentally, often without much of a safety net when something goes wrong,” he says.

But Hurran stresses that “it shouldn’t be that artists become less ambitious, or stop taking work to Edinburgh… it should be about how we can create the conditions that allow theatre-makers to be ambitious without damaging themselves in the process”.

‘Foreigner’ is on to 31 August; ‘Man Sings the Same Song Over and Over Again for an Hour’ is on to 31 August; the Sauna Theatre is on to 31 August; ‘The Distance’ is on to 31 August; ‘Reformer’ is on to 29 August.