Drafting behind other runners can help marathoners, including those running Boulderthon or the Chicago Marathon this weekend, shave minutes off their time, according to new CU Boulder research. It could also play a critical role in helping world champion Eliud Kipchoge officially break the sub-2 marathon record some day.
“Our study confirms that drafting can make a huge difference,” said senior author Rodger Kram, associate professor emeritus in the Department of Integrative Physiology. “Even elite marathoners are not taking full advantage of this.”
When runners run, even on a still day, air molecules bump into them, slowing them down. If they run in the aerodynamic shadow of another runner, a.k.a. drafting, that runner pushes those molecules out of the way, reducing resistance.
With Kipchoge edging closer to breaking the 2-hour marathon milestone at an officially sanctioned race, Kram and co-authors Edson Soares da Silva, of the Universidade Federal do Rio Grande do Sul in Brazil, and Wouter Hoogkamer, now at the University of Massachusetts, Amherst, sought to determine just how much energy a runner can save by drafting.
“This is the first study to reliably measure the performance benefits of drafting based on physiology,” said Kram.
The team recruited 12 male runners to complete six five-minute trials on a treadmill at six to eight minutes per mile. First, they ran normally. Then, they ran with a rubber strap pulling them back with either 4 or 8 newtons of force (about the weight of one or two full beer cans) to simulate the aerodynamic drag of running with or without pacers (other runners to draft off of).
Researchers measured the runners’ oxygen consumption, or how much energy they expended under each scenario.
They found that runners could theoretically increase their power by about 6% per 1% of their body weight in the absence of any air resistance (e.g. running in a vacuum). Realistically, even the most ideal drafting can probably only eliminate about 85% of that drag. And some runners appear to benefit more from drafting than others.
For a runner the size and speed of Kipchoge, drafting alone can potentially save between 3 minutes and 42 seconds and 5 minutes and 29 seconds, according to the authors.
Because a slower runner, like a 4-hour marathoner, is on the course much longer, they can achieve about the same time savings. Just ducking behind taller runners during a race can make a difference.
“Anyone from top elite to lower-level marathoners could benefit from adopting an optimal drafting formation for as much of their race as they can,” said da Silva.
For Kipchoge, the challenge now is to find the perfect formation and professional pacers who can keep up with him longer.
On Sept. 25, Kipchoge beat his own world record at the Berlin Marathon in 2:01:09. Kipchoge has run 26.2 miles in under two hours at a staged run but not at an officially sanctioned race.
In Berlin, his three pacers peeled off at the 15-mile mark. If pacers could stick with Kipchoge for another 10 kilometers, the authors report, he could shave off at least another minute.