Eliud Kipchoge has cemented his status as one of the most successful distance runners of all time.

The decorated 32-year-old Kenyan marathoner has nabbed seven first-place finishes in eight career marathons, flashing across finish lines with sub-five-minute splits. His personal best is a lightning-fast 2:03:05.

And yet Kipchoge doesn't exude any of the hubris so common to today's McGregors and Ronaldos. Instead, the self-made millionaire with the megawatt smile exhibits a monklike zen and an unshakable positivity. He approaches the sport with a lionhearted pride, which is exactly how he trains.

Kipchoge's motions are lithe, almost feline, as he runs among his training group. Every move of his 5'6" frame, from arm pump to footstrike, is calculated and exacting. He's about as perfectly built for marathons as a human can be, making him a "unique problem" for sports scientists when he and two other runners—Zersenay Tadese, 35, and Lelisa Desisa, 27—attempted Nike's lofty, moonshot goal of breaking a two-hour marathon.

Nike marathoner Eliud Kipchoge running with training camp

If you watched (or kept up with) the monumental Breaking2 attempt in Monza, Italy, you know that Kipchoge missed 1:59:59 but clocked the fastest (unofficial) time in history with 2:00:25. National Geographic partnered with Nike to narrate Kipchoge's journey. Here's what it took to shave 2.5 minutes from his time, what went into optimizing the "perfect marathon" conditions, and how scientists went about tackling the biggest challenge of all: improving a practically flawless runner.

Finding Kipchoge's "Achilles' heel"

First, it's important to understand why Kipchoge is so talented: He has an above-average exercise capacity, an exceptional VO2 max, and a high lactate threshold, meaning his body more easily transfers oxygen into energy.

So Breaking2's lead physiologist Brett Kirby, Ph.D., focused on the two elements of Kipchoge's game that he could obviously control: nutrition and gear.

"Eliud had the opportunity to improve how he managed energy levels during the marathon," Kirby, a Nike Sport researcher, tells Men's Fitness. "Two strategies we used to make this happen were 1) personalizing Eliud’s Vaporfly Elite shoes, enabling him to maintain race pace at a lower required oxygen cost, and 2) adjusting the carbohydrate amount in Eliud’s drink during both training and racing so he could preserve stored muscle energy levels for longer durations."

Nike marathoner Eliud Kipchoge running

Groundbreaking? Not exactly. Nike didn't set out to drastically change Kipchoge (or any of the runners') diet, regimen, or form—mostly because they didn't have to.

What Kipchoge eats to fuel monster mileage

"Eliud eats a staple Kenyan diet full of Kenyan greens, ugali, and lots of Kenyan tea," Kirby says. Ugali is a polenta-like dish made from cornmeal, sorghum, or millet flour. "In the days leading up to the race, including the morning of the race, Eliud consumed carbohydrate- and nitrate-rich foods, and during the race he consumed a drink mix consisting of both carbohydrates and electrolytes."

Kipchoge's perfected his game-day nutrition to include foods that rev his engine but avoid stomach discomfort. Keeping him well-hydrated was the bigger goal. In fact, all the runners had different hydration beverages and frequencies tailored to their bodies—some bottles had higher amounts of sugar (or a different type of sugar) and some with added caffeine, according to a Nike press release.

Kipchoge's Breaking2 training plan

Kipchoge's regimen was varied and gradually grew more grueling leading up to race day.

"Preseason, Eliud did gym aerobics for one month," Kirby says. "Then, his weekly training included a track workout, a hard, long run, and a fartlek workout with progressive and easy runs mixed in-between."

Kipchoge needed to ramp up his speed to hit the target pace of 2:50min/km. For this, group runs and pacers were essential. He'd set out on distance sessions with as many as 60 locals, pro runners, and coaches, Kirby describes in a Nike press release.

It also helped that Kipchoge’s camp, in Kenya, is at a higher altitude and therefore has less available oxygen. This is optimal for runners because, over time, red blood cells multiply, enabling your body to get oxygen to working muscles more efficiently. Ultimately, you can run farther and faster. It's like a natural blood doping.

Eliud Kipchoge Breaking2 training graphic

Kipchoge's secret weapon isn't a muscle

In a sport where many are subject to burnout, Kipchoge has seen a remarkable amount of consistency and longevity. Yes, he's eating and training right, and putting efforts toward recovery with plenty of sleep and full-body massages. But it's his mental grit and self-confidence that give him an edge.

"Eliud believes that success in sport stems from both a strong heart and a strong mind," Kirby says. "He has both."

Kipchoge's outlook on life centers him and keeps him focused, too. If he's not training, Kipchoge's maintaining his training camp—working on the grounds, pulling water, resting with his teammates. He's grounded in his beliefs and his abilities.

“Marathon is life," Kipchoge says in the documentary Breaking2. "It’s not about the legs, but it’s about the heart and mind."

The faith he has in his trainers, scientists, and friends is unwavering. 

"There’s a formula," Kipchoge says in Breaking2, "100% of me is nothing compared to 1% of the whole team."

Kipchoge resting with training camp

 

What Nike scientists learned from Breaking2

In Monza, Italy, a Tesla car illuminated a green laser pacing line, as well as a clock to indicate the time and current race pace. A pack of 30 pacers ran during Breaking2 to keep Kipchoge, Desisa, and Tadese up to speed, as well as to reduce wind resistance. Six took to the racing track at a time, running in a triangular formation, dropping out after two laps for the next group to fall in. It was like a choreographed dance—at 13mph.

"The drafting and pacing strategy worked extremely well," Kirby says. "If I could modify anything, I might consider adding the entire pool of pacers into the race for the final lap."

And while some experts have come out with their own pacing theories to break the two-hour mark—some suggest going slower for the first half is key, while others believe an all-or-nothing pace is necessary—Kirby stands firm in their strategy.

"Even pacing is my usual preference," he says. "Starting too slow and making up for lost time near the end of a race can be extremely difficult because the body doesn’t get more efficient an hour in, it gets worse. That said, starting too fast makes the rate of energy utilization unsustainable. All that matters is making sure the athlete’s energy supply is matched to the energy demand of the task, and is applied at an average rate."

Nike marathoner Eliud Kipchoge training

So if the calculations suggest Kipchoge is physically capable of hitting 1:59:59, what external elements could've been tweaked to make it happen?

The shoe, for one.

"The Zoom Vaporfly Elite was truly revolutionary, and its impact has changed the shape of marathon running forever," Kirby says. "At Nike, we’re always evolving and striving for better and with that comes change...new technology and innovation will certainly be brought forward."

Will Kipchoge give the sub two-hour marathon another shot?

"I feel that I have a potential inside my heart that I can go beyond human limitations by running under two hours,” Kipchoge says in Breaking2.

This was ahead of Monza, Italy.

"After the race, he noted that, while he missed the 1:59:59 target, he believes this will give hope to another athlete that a two-hour marathon is possible," Kirby says. "He worked extremely hard to shed more than 2.5 minutes from his best time, and that 25-second shave will be achievable by someone in the future."

Portrait of marathoner Eliud Kipchoge

That someone won't be Kipchoge, it seems. And though disappointing, that's OK.

While controversial, this race instigated an eagerness to push human limits—to set the bar higher and say Why not try?

"Barriers are only barriers until they are broken, and often we can only see what we see or know what we know based on life experience," Kirby says. "New ways of living happen when we look beyond current paradigms, imagine different possibilities, then work at making those things happen."

Though it begs the question: If Eliud Kipchoge, one of the best marathoners in history, couldn't pull it off, who can?

National Geographic's Breaking2 documentary premieres September 20. Above is an inside look at Eliud Kipchoge's epic journey, exclusive to Men's Fitness.