No pain, no gain. It's a mantra to push exhausted runners through that extra mile or swimmers down one last length of the pool.
It'll all be worth it, won't it? It's a theory Charlotte Roach tested to its limits - and rejected.
The former Olympic hopeful, whose chance of going to the London 2012 Games was ended after a near-fatal cycling accident, says people too often hate their fitness routines. But it doesn't have to be that way, she insists.
Roach, 27, says the fitness industry has been selling pain, and repetitive and isolating exercise - and making people feel guilty if they didn't shape up.
So she founded Rabble, a business that extols the virtues of getting fit by having fun - from playground games such as British Bulldog and Stuck in the Mud, to Frisbee and dodgeball.
Players sign up online, paying monthly or for one-off events.
Rabble's aim is summed up in the name. "We're a rowdy, energetic community, disrupting the fitness community and bringing some fun to an unnecessarily dull industry," says Roach.
The company's success would seem to reflect fundamental changes in attitudes to fitness, underlined by the growth of social exercising via such activities as Zumba and outdoor activities like military boot camps. People want to get fit - but not necessarily in a gym.
Olympic gold medallist Dame Kelly Holmes, who mentored Roach as a young athlete, is a fan. "You forget you're exercising," she told the BBC. "If you can promote social interaction through physical activity, people see the fun, and in turn show commitment to more regular exercise."
But Rabble would never have happened if Roach hadn't suffered her accident.
"I was in my second year at Cambridge University, running and swimming competitively, and was invited to join the training programme for the Olympic 2012 triathlon squad," says Roach. She left Cambridge for the Loughborough training base.
But in 2009, during a group cycling event, her life changed.
"A Land Rover travelling in the opposite direction hit me," she says. "All I could feel was pain. My back was in agony, I was struggling to breathe."
A passing motorist stopped to help. Luckily, it was Julie Hayton, a physiotherapist with Leicester Tigers rugby team and trained in resuscitation.
"I was gargling blood and Julie, realising I had a short window to survive, sat me up. It was risky, I could have been paralysed due to my back injury but it saved my life," Roach says.
Roach had sustained horrific injuries. Both lungs collapsed, her back was broken in 12 places along with her collarbone and ribs. She spent a week in intensive care.
Roach recalls the frustration of being inactive, but within a few months forced herself back into training, still with pins in her back.
"I could feel the metalwork jarring when I ran and I had some nasty spasms," she says. "Looking back I don't know how I did it, but I guess deep down I wanted to prove to myself that I could still race."
Incredibly, in 2010 Roach came fourth in the European Cup, competing for Great Britain. But the training eventually became too much, and she returned to Cambridge to finish her neuroscience degree.
Bored at the gym
After university, Chester-born Roach worked for a construction company in London. She enjoyed the challenge, and working on a variety of different projects kept the boredom at bay.
But after work, Roach went to the pub more than the gym. "Without a goal I found the gym boring," she says. "I didn't see the point of sweating with a group of silent strangers in spinning classes. It just felt weird.
"I wanted to meet up with a group at times that suited us, and do something active and fun."
The idea for Rabble was born. Roach quit her job and ploughed her savings into the business. "I decided to live off fear," she says.
She organised the first Rabble game, in January 2014, on social events site Meet Up and 15 participants turned up to their hired basketball court.
'Breath of fresh air'
Initially, events were free, to gauge popularity. "By the end of 2014 we had 150 players a month. The money was running out, but the games were going well so I applied for funding," she says.
Through angel investors and money from Cambridge University's Downing Enterprise start-up competition, Roach raised £210,000.
One investor, John Yeomans, chairman of Cambridge Angels, normally backs tech start-ups. But he was "blown away" by her business presentation.
"She was a breath of fresh air," he says. "An investor wants to know that the person they're investing in has vision and determination. Charlotte clearly had both in abundance."
And her athletic background was important. "Top athletes often make good entrepreneurs; they're determined, persistent and will push," Mr Yeomans says.
He initially invested £10,000, subsequently topping up his funding twice.
Roach says Rabble is on track to make its first profit in 2017. There are currently around 850 players across several UK cities and its popularity is catching on fast. There are big expansion plans, possibly by franchising the operation.
"Rabble isn't for everyone," she admits. "But we want to make exercise accessible, especially for adults who haven't necessarily been sporty before."
It's an approach supported by sports psychologists.
Middlesex University's Dr Rhonda Cohen, author of Sport Psychology: The Basics, says: "Exercise as play captures the essence of who you were as a child. That spirit of freedom and fun is a useful way of motivating people into doing exercise."
Ray Algar, founder of Oxygen Consulting, which advises the fitness industry, thinks established gym brands are recognising the growth potential of firms like Rabble. Pure Gym, for example, has partnered with boot camp group British Military Fitness.
"I recently spoke to a Zumba class, asking them why they went. One person said, 'Because it makes me feel fabulous.' This is the antithesis of gyms, which seem to have the mantra that fitness is hard work."
There is an alternative, says Roach, and it's emblazoned across Rabble's website. "Stop exercising, start playing."