(CNN) There wasn't a hint of exhaustion on Ryan Sandes' face during a recent CNN interview with the decorated ultra-athlete in his Cape Town home. You'd never guess he had recently returned from an epic 16-day run along the mostly uncharted mountains of Lesotho's borders -- until he took off his shoes.
For runners, blisters and cracked feet are par for the course; they're practically a source of pride for Sandes and his running partner Ryno Griesel, who together created and subsequently completed Navigate Lesotho on April 27. They covered 1,100 kilometers (684 miles) with over 33,000 meters of elevation gain in 16 days, 16 hours and 56 minutes -- all under extreme weather conditions.
"In some ways it was our toughest challenge, but because of what we've learned in the past, I think our maturity and just the bond we have, made it a lot easier," Sandes told CNN.
The South African duo are no strangers to extreme adventures. Together, they hold the record for fastest known time (FKT) on one of the toughest routes in the world -- the Great Himalaya Trail in Nepal, where they covered 1,504 kilometers (934.5 miles) in 25 says. They also hold the FKT on their home country's renowned Drakensberg Grand Traverse, breaking the previous record by 18 hours.
Even during Covid-19 lockdowns in South Africa, Sandes managed to get in an unofficial 100-mile ultramarathon -- around his house -- which he finished in 26 hours.
"He had done about 140 kilometers (87 miles) and he was like, 'I cannot go any further, this is the hardest thing I've ever done,'" Sandes' wife Vanessa Haywood recounts of the one-man race.
But circumnavigating Africa's "Mountain Kingdom" would prove to be even more grueling.
"Lesotho was definitely the most challenging in terms of conditions, although you don't think about it that way, because it's so close to home," Griesel said, adding that it's a five-hour drive from Johannesburg.
The expedition required two years of planning, or what Griesel likens to "building a puzzle." The pre-production involved plotting unmapped territory, getting sponsors on board, building relationships with locals and scoping out areas of the route they'd later run.
"People often say the hardest part is getting to the starting point and honestly (it) is, and then the rest of the hardest part starts," he said.
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They ran about a marathon and a half each day, trudging through extremely cold, snowy, windy and muddy conditions according to Sandes. In total, Sandes and Griesel crossed 187 rivers.
Temperatures ranged from -5 degrees to 30 degrees Celsius throughout the trip.
Some nights they slept, sometimes they didn't, depending on conditions and keeping on pace with their targeted 17-day finish.
The running duo had to deviate from Plan A quite a few times, and Sandes said they backtracked a few mountains and rivers and took alternate routes due to poor conditions.
Navigating Lesotho proved to be mentally tough as well, but the pair decided early on that giving up was not an option.
"When you've been shivering for two to three days, you can't even think clearly because you haven't slept, you're super hungry, ran out of food two days ago ... there's always 1,000 good reasons to quit," Griesel said, "but once you take that off the table, then you're forced to keep moving towards the goal."
They carried an impressive load in their packs: clothes, food, water, extra socks, GPS trackers, water purification straws, headlamps, hiking poles, sunscreen and more.
And for fuel? Each runner carried a mixture of whole foods and carb-heavy electrolyte mixes, plus one dehydrated meal per day. They estimate they burned 120,000 calories throughout the journey.
Griesel said his favorites foods that got him through Lesotho were hot cross buns and chocolate. "I've always been really bad with diet if you had to look at it from a traditional point of view, but I do believe that the best food[s] on these long projects are what you're looking forward to eating," he added.
They weren't completely alone in their expedition; a support crew on horseback, motorbikes and four-by-fours helped resupply their basic needs and give them cooked food at various pre-planned locations.
Sandes (40) and Griesel (42) met in 2012 at the ultra-trail race Salomon SkyRun South Africa, where Sandes placed first and Griesel third. Two years later, they would run the Drakensberg Grand Traverse together -- and break the FKT record.
"That was definitely where our friendship started," Sandes said, adding "Ryno and I are very different people, but I think we really complement each other."
Sandes joked that Griesel's race gear will be labeled and in order, while his own is in a disorganized pile.
"Even if I look at what we bring to the table, I come from more of a running background and competing on the international circuit, whereas Ryno is more into adventure racing and his mountain skills and navigating [are] next level," he said.
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Sandes is the physical powerhouse and Griesel is the nimble navigator.
"It's all good and well to go fast -- it's ideal to go fast in the right direction and I think that's where we really fit together," Griesel said.
The humble runners balance each other out in more ways than their skillsets. Griesel said Sandes is good at keeping morale going by celebrating the "mini milestones," which helped him push through during their Lesotho run.
"We'll get to the top of [a summit] and I'll be like, 'I still need 10 days to finish this,' and he would be reminding me of where we've come from," Griesel said.
While these two will likely continue going for FKTs, Sandes said the pandemic has created space for him to slow down and appreciate what his home continent has to offer.
"Throughout my career, I've been lucky enough to run on all seven continents and experience a lot of the world, but I feel like I haven't experienced enough of Africa," he said. "And I think being forced to do more locally has made me really grow to love home even more."
The pair are also focused on bringing up the next generation of South African runners through programs like LIV2Run which aims to help uplift people from disadvantaged communities.
"In life we all kind of need that connection to the outdoors," Sandes said. "I think we're so connected to technology, [we need to] break that and to feel free and natural and whole again."