Drafting can save marathoners minutes, make an official sub-2 possible

On September 25, Kenyan marathoner Eliud Kipchoge broke his own world record by 30 seconds, crossing the finish line of the Berlin Marathon in 2:01:09 and closing in on the sport’s holy grail: running 26.2 miles in under two hours in an officially sanctioned race.

New CU Boulder research published in Journal of Applied Physiology.

Even better, this racing strategy can save three to five minutes for moderate hikers as well, including those competing in Boulderton 2022 or this weekend’s Chicago Marathon.

“Our study confirms that blueprinting can make a big difference,” said senior author Roger Crum, emeritus associate professor of integrative physiology. “Even elite marathoners don’t take full advantage of it.”

Much discussion, little research

Run alone, even on a still day, and the air molecules bump into you as you move through them, slowing your speed. Run in the aerodynamic shadow of another runner, also known as drafting, and they push those molecules out of the way, so you don’t have to work as hard.

How much energy runners can save by sprinting has been debated since 1970, when British physiologist Griffith Pugh published a study suggesting that runners expend about 8% of their energy just pushing air. It suggests that an elite marathon runner can shave six minutes off his time with some clever drawing. But the study involved only one subject who ran on a treadmill in wind tunnel. A subsequent study with three runners estimated the energy cost to be about half that.

Crum and co-authors Edson Soares da Silva of the Federal University of Rio Grande do Sul in Brazil and Wutter Hugkamer of the University of Massachusetts at Amherst set out to set the record straight.

“This is the first study to reliably measure the benefits of stretching based on physiology,” Crum said.

The team recruited 12 male runners to complete six 5-minute trials on a treadmill at a pace of six to eight minutes per mile. First, they ran normally. Then, instead of having the wind blowing on them, they had a rubber strap that pulled them back with a force of 4 or 8 newtons (about the weight of one or two full beer cans) to simulate aerodynamic drag running with or without pacers (other runners to lean on).

Among other things, Crum and his team measured the runners’ oxygen consumption, or how much energy they expended in each scenario.

Bottom line: Pugh was right.

“Our number ended up being very similar to what he found with that single runner,” Crum said.

Researchers conclude that runners can theoretically increase their power by about 6% per 1% of their strength body weight in the absence of any wind resistance.

Realistically speaking, even the most ideal circuit can only eliminate about 85% of this resistance. And especially, for reasons that are unclear, some running backs seem to benefit more from the draft than others.

For a runner of Kipchoge’s size and speed, that means just adding up can save you from 3:42 to 5:29.

Surprisingly, slower runners can achieve about the same time savings. For example, he calculated that Silva, a 125-pound, 5-foot-7 runner who typically runs a marathon around 3:35, could improve her time by as much as five minutes.

“Anyone, from the top elite to lower-level marathoners, could benefit from adopting optimal training form for as much of their race as possible,” da Silva said.

An underrated secret weapon

Crum said that for a mere mortal runner looking for a personal best, it’s just a matter of ducking behind taller runners for a while. (Caution: on a hot day this can backfire by blocking the cool breeze).

For Kipchoge, the challenge now is to find the perfect draft formation and players who can keep up with him longer.

Under normal road racing rules, a a runner can only have three pacers starting with them. In Berlin, three pacers ran ahead of him and flew away at the 15-mile mark. The authors report that if the pacers could hold on to Kipchoge for another 10 kilometers, he could shave off another minute.

During Kipchoge’s famous Ineos 1:59 in 2019, he used spinning pacers to help him break two hours, in addition to wearing the perfect shoes and running on the perfect course, all factors that can make a big difference, according to by Kram’s previous research.

But the organized event was not an official race, so the running milestone had not yet been officially achieved, according to World Athletics.

Krum is confident that day will come, and it could be soon.

“Mass participation marathons are back, and there’s a lot of interest again in trying to run a two-hour marathon,” he said. “Kipchoge only needs to shave a minute. More disciplined drafting could easily get him there.”