Trek-Segafredo's Kiel Reijnen ran 18 miles barefoot after breaking wheel at Unbound Gravel

The 200 miles of lumpy racing amid searing heat at Unbound Gravel is demanding enough without trying to run two-thirds of a marathon in the middle of it.

But that's the situation Trek-Segafredo's Kiel Reijnen found himself in, breaking his wheel after the rim caught a rock but continuing the race anyway.

"Hi my name is Kiel Reijnen and I made some bad choices today," the 35-year-old said in an Instagram video.

"I had some bad luck in a small, technical section and caught the rim on a rock and in retrospect, I think more spacing and backing off a little bit and just really picking your own line is important in this race. And the terrain is just unforgiving, call it a bad line, call it bad luck.

"I broke my wheel, kilometre 46, so not very far into the race. I was in the front group, although the front group was still pretty large at that point. I tried to repair the rim as best I could, I made a splint for it and wrapped that up. That lasted for about a kilometre and a half but turns out that was pretty trash so then I started running. Barefoot."

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One of the rules of the race is that you're not allowed to accept help unless it's help on offer to everybody, meaning Reijnen was hoping to either bump into a stranger or fellow rider who was out of the race and able to lend him a wheel.

"You can accept help from a stranger because in theory [any] help has to be available to everybody else. I started running in the hope that maybe along the way I would run into someone who'd had a different mechanical issue and I could borrow their wheel until the feed zone and change wheels there," Reijnen explained.

"It definitely wasn't an option to have the team van come back and swap wheels with me, that's against the rules.

"I had 56km [until the feed zone]. I would hope most people would call it at that point. I started running, these are the holes in my socks. I don't feel great, I made it about 18 miles, 27 kilometres. I started with my bike on my shoulder and then did some more MacGyver-ing with some tubes and got the wheel straightened up so I could roll it along, which I was very thankful for at the time.

"I was hoping that something would happen along the way and I would get lucky. Find someone who'd cracked in the heat or had a different mechanical issue and lend me a wheel so I could get to the feed zone."

Reijen persevered across sharp rocks, and at one point thought he might make it all the way to the finish, but soon realised he didn't have enough water for how long he'd be out on the course.

"I didn't set any records, I think I had about 8km/h on average. The stones really hurt, they're not round, river rocks," he said.

"Part of me thought: 'Hell, if I just keep trucking maybe I'll get there. After two and a half hours of running, I started doing the calculations and pretty quickly realised it was going to take me four or five hours and I didn't have enough water for that. And the cutoff time is noon, so I would have gotten there close to 1pm or 2pm depending on how much I'd have cracked if I'd had water."

Remarkably, the thing Reijnen is most regretful about is being forced to abandon the event.

"I did something I really didn't want to do today, I quit the race," he said.

"I'm incredibly disappointed with how the day went, I tried to give it my all. It turns out the back 10 per cent of that group are the kindest, most respectful, wonderful people. Every one of them stopped and asked what they could do for me.

"I have a lot of respect for this event, the people doing it. The best part of my day was seeing the people out there doing it who don't have time to train seven days a week, put in 30 hours of training a week, they're out there because they're passionate and want to challenge themselves. I want to say chapeau to all of you."