In 2019, Kenyan long-distance runner Eluid Kipchoge became the first person to run a marathon in under two hours. This achievement had held an almost mythical status—existing, as some physiologists projected, at the edge of a human body’s capabilities. But in the years leading up to Kipchoge’s feat, he and other elite athletes had squeezed their marathon times ever closer. Finally, four years ago, in an unsanctioned event along a flat six-mile loop in Vienna, Kipchoge cruised at record speed, completing 26.2 miles in one hour, 59 minutes, and 40 seconds.
Officially, the two-hour marathon barrier has not been broken, according to World Athletics, the organization that keeps race records. For one, there were no other competitors in Kipchoge’s event. Plus, he wasn’t alone. He ran in a pack with several expert runners, known as pacers or “rabbits,” creating an aerodynamic shape around him. Wind tunnel tests and computer simulations helped the team finesse the formation: Five pacers positioned in front made a V, like the inverse of a flock of geese, while two additional racers ran slightly behind the marathoner, at his left and right flank. After each loop, the pacers rotated out for a fresh set of legs. With this protection from headwinds, Kipchoge completed the distance more than a minute faster than he ever had.
But as it turns out, there may be an even better drafting formation for running a marathon—or so says a team of researchers at École Centrale in Lyon, France, who recently tested multiple shapes by placing miniature manikins in a wind tunnel. They’ve proposed an arrangement, somewhat resembling a swordfish’s body, that would reduce drag forces by 60 percent on a runner. It would result in marathon times about a minute quicker than the Vienna V, they claim. Using the swordfish shape, it “may be possible to run the fastest marathon ever,” the study authors write in a paper recently published in the journal Proceedings of the Royal Society: A.
But the scientists who helped develop and verify the buzzed-about 2019 configuration dispute that assertion, citing flaws in the new study’s wind tunnel setup and the proportions of the mini model runners used to explore it. “The paper itself shows huge differences between present results and those from previous studies,” says Bert Blocken, a professor of civil engineering at KU Leuven in Belgium, who used computer and wind tunnel simulations to analyze drag reduction in the Vienna race. While the Proceedings paper indicates that a V-shape reduces drag by 50 percent, Blocken says that past work found it was closer to 85 percent.
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The benefits of marathon formations are not in dispute here. Aerodynamics researchers agree that packs offer an advantage to going solo, especially at the pace elite runners travel. The drag force acting on an object is proportional to the object’s speed squared, points out Pietro Salizzoni, a professor of fluid mechanics and an author of the new study. In other words, the faster you go, the more extreme headwinds you face. On a leisurely stroll, these disturbances are essentially undetectable. But at the speed Kipchoge ran at for his record—an average of 4.5-minute miles or 13 miles an hour, which would feel like a sprint to most people—pushing air out of the way becomes a literal drag.
For Vienna, three studies pointed to a V-shaped pack, Blocken says: a UK consultancy company’s tests of 110 formations using fluid dynamics simulations; his team’s own computer simulations of 15 formations; and wind tunnel experiments involving 10 formations. (Confidentiality clauses from INEOS, the British chemical company that sponsored Kipchoge’s race, means those reports have not been published.) “All three detailed previous studies gave the same outcome,” Blocken explains: The configuration with a “V-shape in front of the target athlete and two runners behind him” produced the lowest aerodynamic drag.
Salizzoni and his coauthors independently tested eight formation styles, including the INEOS V-shape, by mounting stationary 6.5-inch manikins in an indoor wind tunnel. Their goal was to measure air resistance proportional to what a marathoner would experience. Ultimately, they also found a benefit to placing two pacers in the back. The force acting on a running target “is the sum of the pressure on the front and on behind,” Salizzoni notes—those in the rear help minimize any pressure drops. “You want to control the wake you are producing,” he says, similar to the back wings on a Formula One race car.
Where the new findings differ substantially is in the positions of the pacers out front. Salizzoni’s team concluded the most effective was a swordfish-profile shape: a lone pacer, followed by four other pacers forming a skinny diamond four feet behind, and finally the target athlete less than five feet behind the diamond’s rear. The “narrower wedge” in this formation could allow runners to “sort of slice through the air,” University of Colorado Boulder physiologist Rodger Kram, who wasn’t part of the research team, told Science News.
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Blocken remains unconvinced—he argues that the team’s manikins were inappropriately proportioned. “The model used in the study by the present authors seems to be some sort of small cartoon model that is very different from the geometry of a real human body,” he says, referring to the unrealistic chest-belly ratio and sharp edges of the models’ poseable joints. Blocken’s studies used smooth and solid manikins based on scans of real human marathoners.
Salizzoni counters that their figurines had a “equivalent area and an equivalent form” to an athlete, and that using moveable models helped provide more accurate data. After all, humans in motion don’t have their arms and legs fixed in place. This “could still give a realistic result for the single runner,” Blocken say, but he points out that the fluid dynamics of formations are much more sensitive to subtle changes. In fact, as the New Yorker noted at the time, the configuration for the 2019 race was so precisely tuned that if Kipchoge moved five inches out of place, he would be much more exposed to aerodynamic drag.
It may be some time before a top marathoner puts another pack run to the test. Kipchoge typically only competes in two marathons a year. His second race of 2023 will be in Berlin in September, where he officially set the world record in 2022—without the help of a formation—at 2:01:09.
