The Tour de France is gruelling enough, with its punishing mountain climbs and brutal descents in a three-week pursuit of the feted yellow jersey.
But how about tackling all of that with a fractured pelvis?
That's the agonising situation Welshman and Sky team member Geraint Thomas finds himself in, following a spectacular crash near the finishing line during the opening stage of cycling's most prestigious event.
Thomas, a dual Olympic track cycling gold medallist, went over his bars and landed on his back on the narrow roads leading into Bastia, after the Australian team's Orica GreenEdge bus became lodged under a banner at the finishing line.
With riders bearing down, race organisers temporarily moved the finishing line back three kilometres before restoring the route once the bus was removed. There were several pile-ups amid the confusion.
Thomas, 27, underwent scans on Saturday night and was cleared to ride the following day.
He climbed back into the saddle, only to endure what he described as "one of the worst days I've ever had on a bike", finishing 17 minutes and 35 seconds down on the leaders.
A further MRI scan on Sunday night revealed a small fracture to his pelvis.
But, in what sounds like a mind-boggling decision to most people, Thomas has vowed to battle on through the epic endurance event with a fractured pelvis.
On Monday, he needed help to lift his leg over his bike's crossbar before the start.
Even his mother thinks he's mad.
"I'm going to continue, to give it a good go even if my mum doesn't want me to," Thomas said following stage three of the Tour.
"I have not come here just to do a lap of France.
"I've done so much to lose weight and get fit for this.
"I'm not going to give up straight away.
"The experts have said I am not going to do any more damage by riding. It is just a matter of if it improves."
James Heathers, an applied physiologist at the University of Sydney, said Thomas' vow to battle on exemplified the single-mindedness of world class athletes compared to everyone else.
"It's very difficult for 'normal' people who don't have that mindset to understand how impossibly competitive and single-minded you have to be to succeed at something like this," Mr Heathers said.
He said he did not know the extent of Thomas' injury, and it was possible that "it may sound worse than it is". But world-class athletes were extremely driven.
He pointed to a scientific study, the Goldman Dilemma, carried out in the 1980s and 90s by American physician and journalist Bob Goldman.
In the study, Goldman asked world-class athletes whether they would be prepared to take a drug that guaranteed them an Olympic gold medal, but also would result in their death in five years.
Goldman reported that about half of the athletes surveyed would be willing to accept the gold-for-death deal.
"I think you have to understand the mindset of someone who's truly competitive," Mr Heathers said.
"For Thomas, it's not a matter of whether it hurts, it's whether it interferes directly with his ability to do his job in the team."
That is the sentiment that Thomas expressed following Monday's stage three.
"Like I said, it's the Tour. It's not your average race. I'm definitely going to keep fighting," he said.
"It felt a lot better today than yesterday and it felt a lot better [at the finish] than at the start today. But I've got a crack on my bone so it's always going to hurt."
Sky team principal David Brailsford praised Thomas' efforts.
"We all have different tolerances to pain but the determination and level of suffering required to ride on a course like this, with its twists and turns where you can never get into any kind of rhythm, was really considerable," he said.
"He suffered an awful, awful lot. He deserves every bit of recognition and support for his suffering."
- Sydney Morning Herald