On the morning of October 12, Eliud Kipchoge, the best marathoner on Earth, will set off from the Reichsbrücke Bridge in Vienna, Austria, with the goal of traversing 26.2 miles—42.165 kilometers—in less than two hours, almost half a minute faster thanany person in history.
A little less than 120 minutes later, the world will know whether he succeeded.
The sub-two hour marathon is the last great barrier in distance running. Elite athletes have been closing in on the milestone for more than a century, but only in the past few years have they started to come close. Kipchoge holds the official world record of 2:01:39, which he set at the Berlin Marathon in 2018.
But as the running world (and its sponsors) have grown obsessed with breaking the two-hour barrier, they’ve sought to engineer the perfect race to finally see if a human could do it. And in that ideal-marathon bubble, Kipchoge has gotten even closer than 2:01:39.
In 2017, the Kenyan attempted to break the two-hour barrier at Italy’s Formula One race track, in Monza. He came agonizingly close, completing the race in 2:00:25, too slow by an average of less than one second per mile. An exhibition event sponsored by Nike, conditions in Monza had been so carefully controlled that the race was ineligible for world record consideration. Still, Kipchoge had come closer than many thought possible. As he said after the race: “The world now is just 25 seconds away.”
On Saturday, at 8:15 am local time (2:15 am ET), Kipchoge will make his second attempt at a sub-two-hour marathon at another exhibition event, this one organized by global manufacturing company Ineos. And while no one can predict the future, it looks like he has a solid chance of pulling it off. Conditions Saturday morning in Vienna look to be even more favorable than in Monza. Assuming he runs a smart, injury-free race, the following four factors will dictate Kipchoge’s success—or his failure.
The first time Kipchoge chased the sub-two-hour marathon, he did it wearing a special edition of Nike’s Vaporfly 4%, a shoe the company claimed could make runners 4 percent more efficient on their feet. In the past two years,peer-reviewedstudiesand analyses byWIREDandThe New York Timeshave confirmed that, for many runners, the shoes perform as advertised.
But maybe not all runners. Some people respond less to the shoes than others. What’s more, 4 percent more efficient does not necessarily translate to 4 percent quicker. Some simple math confirms this: If the Vaporfly gave runners a 4 percent speed boost, every marathoner capable of running 2:05 or better (a rarified club, to be sure, butone with at least 10 members in 2019 alone) would need only slip on a pair to break two hours.
Yet since the shoes made their debut, several marathoners have posted shocking personal bests, the most recent example being Ethiopian Kenenisa Bekele, who last month won the Berlin Marathon in 2:01:41, a mere two seconds shy of Kipchoge’s world-best time.
Bekele ran that race in the latest version of Nike’s Vaporfly, a pair of shoes the company says saves runnerseven more energy than its predecessor. Kipchoge, meanwhile, has beenspiedpracticingin Vienna in a Vaporfly prototype rumored to be more energy efficient than anything he’s worn since Monza.
One of the things that will make Kipchoge’s attempt in Vienna ineligible for official record consideration is the pacing strategy. In official marathons, pacers must start from the beginning of the race, and they can only shield the frontrunners from wind for as long as they’re physically able. The upshot is that pacers typically burn up and drop out long before the race is over, leaving competitors to run the last, most arduous miles unshielded.
On Saturday, Kipchoge will be protected by alternating teams of elite pacers, who will rotate in and out of formation throughout the entirety of the race. A rotating cast of runners protected him at Monza, too, but the pacers for Saturday’s race—many of whom Kipchoge has rehearsed with at his training camp in Kenya—have spent more time practicing and thereforelook to be better preparedthan the ones from 2017.
“I think pacing had the biggest impact on Kipchoge’s performance at Monza,” says Michael Joyner, an expert in human performance whoin 1991 theorizedthe ideal athlete running under perfect conditions could complete a marathon in 1:57:58. “And not just because of the wind break. Pacers relieve the psychological burden of keeping your tempo up and your pace steady. Having someone to suck off of, as we say in running, makes a huge difference.”
Two years ago, anindependent analysisfound the benefit provided by the pacers at Monza probably was, in fact, huge, and might have shaved several minutes from Kipchoge’s overall time. The phalanx of runners protecting him on Saturday could buy him even more speed.
Hills and turns slow runners down. For as flat as the circuit in Monza was, and for as gentle its curves, the course in Vienna looks to be even more ideal.
Kipchoge will spend the majority of the race running back and forth along the Hauptalee, an arrow-straight stretch of freshly paved road that intersects the city’s historic Prater park. He’ll span the out-and-back loop just over four times with the help of two roundabouts: a large one at the straightaway’s northwestern terminus and a smaller one at the southeastern terminus.
Analyses suggest the gradual curves that bookend the Vienna circuit will go easy on Kipchoge. “When you run in a turn you use slightly more energy, but the roundabouts in Vienna are big-radius turns, and Kipchoge will only have to run them nine times over the entire race,” says Wouter Hoogkamer, coauthor on a recently publishedpreprint analysisof the Prater course. “If you compare it to a perfectly straight line, the Vienna course is just half a second slower over 26.2 miles.”
Changes in the course’s elevation could be less kind. The Vienna loop rises and falls about 10 feet every lap, which Hoogkamer and his colleagues estimate could cost Kipchoge 10 seconds over the course of the race. (Generally speaking, runners lose more time ascending hills than they gain descending them.)
Here’s the good news: To get to the Prater loop, Kipchoge will start his run from Reichsbrücke Bridge and descend over 40 feet in the first three-quarters of a mile. That’s a big drop. Hoogkamer and his colleagues estimate the downhill start will allow Kipchoge to bank about six seconds—and because he’ll never have to run back up the bridge, Kipchoge won’t have to pay those seconds back.
The researchers weren’t able to track down reliable elevation data for Monza, so they never modeled the effect of that course’s undulations, but Hoogkamer has heard anecdotally that Monza had a comparable change in elevation per lap. But Kipchoge ran 17 laps at Monza, compared to the four he’ll run in Vienna. According to Hoogkamer’s back-of-the-napkin calculations, the extra 13 loops might have cost Kipchoge an additional 26 seconds, compared to the Vienna course. Which means that if Kipchoge had staged his first attack on the two-hour mark in Austria instead of Italy, he might have broken the barrier in 2017.
Finally, a small but important note on weather: Conditions in Vienna will be cooler and drier than they were in Monza, which exercise physiologists think will help keep Kipchoge’s body running more efficiently throughout the race.
None of the above factors matters if the person running the race isn’t up for the challenge. Kipchoge is regarded around the world as the best—and most consistent—marathoner in history. Since his unofficial race at Monza, he’s gone on to post personal bests at official marathons, as well, including his world-record performance at the Berlin Marathon in 2018.