"Leadville is 3180m above sea level – it's America's highest city," says Red Bull athlete Ryan Sandes. "Big adjustment from South Africa! It's a lot of sucking thin air."
Despite the challenges for the athlete, who lives in South Africa, essentially at sea level, his record at one of North America's most notoriously difficult runs is good: he's run it once, and won it once. That was back in 2011. Now, Sandes is getting ready to try again. To prepare, he's been running at altitude in the US for the past three weeks.
"The first two weeks are very intense! The first run or two isn't that bad… but in the next four or five days, you're completely wiped out. I was taking breaks and even just walking, trying to keep my heart rate down. If you don't push too hard in the early days, you'll acclimatise quickly. But I'll never feel completely normal!"
A big part of any ultra race, where athletes will be on the route long enough to need constant refuelling, is the gear. Ryan takes a minute to give us a quick run-down on his Leadville 100 kit in the video below.
So how does Sandes feel about the upcoming challenge? Confident, optimistic, and realistic. This year sees the return of American ultra marathoner Scott Jurek, local runner Nick Clark, and a unique challenger in Olympian Michael Aish, who is sure to bring speed if not experience and endurance.
Nevertheless, his strategy is simple. He's been over the whole course, which will give him a distinct advantage. "Race the course, not the other runners," says Sandes. "The trails are well-groomed, and very runnable – although at times, you really feel like you're in the wilderness out here!"
The race starts Saturday 17th August. Follow updates at the Leadville 100 twitter.