Nike’s latest high-end running shoe, the Zoom Vaporfly 4%, lives up to its name, according to a new study from researchers at the University of Colorado.
Researchers at CU’s Locomotion Lab in Boulder found that the shoe reduced the energetic cost of running by an average of 4 percent during treadmill tests.
Four percent in energy savings might not sound like a big deal. But for elite runners, who are trying to shave mere fractions of a percent off of their running times in pursuit of the two-hour marathon barrier, it could be a breakthrough, the researchers said.
“If you look at how the world record in marathon evolved over the last years, over 30 years we got 3 percent faster,” said Wouter Hoogkamer, a postdoctoral researcher who led the study at the Locomotion Lab. “And all of a sudden you have a shoe that gives you 4 percent energy savings.”
“People are going to holler at us for saying that,” said Rodger Kram, a professor of integrative physiology who was also an author on the study. Many factors can affect a runner’s performance: wind, nutrition, turns on the course, hills.
“These shoes reduce the energy you need to run at a certain speed,” he said. “But if you wear these shoes and don’t drink any water for 26 miles, it’s not going to be the shoes that explain why you didn’t run in under two hours.”
The current world record for marathon stands at 2 hours, 2 minutes and 57 seconds. But during Nike’s Breaking 2 project, in which some of the world’s fastest marathoners worked with coaches and a “science team” from Nike to try to break the two-hour barrier, Kenyan runner Eliud Kipchoge ran a faster marathon, though not for the world record. In May, drafting off a team of runners switching in to help him and other runners for the attempt on a Formula One track in Italy, Kipchoge crossed the line at 2 hours and 25 seconds. He was wearing the 4%s for the attempt.–More recently, Shalane Flanagan won the New York City Marathon wearing the 4%s.—
The retail price of the shoe is $250.
The shoes themselves aren’t a radical departure from what running companies have created over the years: they have a carbon fiber plate (Kram noted that other brands have used plates in the past, and that spiked track shoes often have a plate) and a cushy foam midsole. “It’s a combination of existing technologies put together in an ambitious way,” Hoogkamer said.
The foam in the midsole of the 4% is lighter, thicker and returns more energy than other shoes, Kram said. “It’s like if you run on a sandy beach — it’s soft, but it doesn’t give you any of that energy back. And the foam that’s used in this shoe is the foam that returns the most energy, I think ever, in shoes.”
Hoogkamer and other researchers in the Locomotion Lab tested 18 male runners, all of whom wore a men’s shoe size 10. “All had recently run a sub-31 minute 10-km race at sea level, a sub-32 minute 10-km race at the local altitude, or an equivalent performance,” according to the study, which was published in the journal “Sports Medicine.”
Study participants ran in three different shoes for the test; the other two shoes were “baseline marathon racing shoes,” the Nike Zoom Streak 6 and the Adidas Adizero Adios Boost 2.
Researchers collected physiological data, measuring rates of oxygen consumption, carbon dioxide production and rate of metabolic energy consumption in the runners. The energy savings ranged from 2 to 6 percent but averaged 4 percent, and every runner saw savings. “What’s really notable to me is, we had 18 subjects, and every single one of the 18 saved energy,” Kram said. “That’s unusual.”
Nike funded the study, and Kram is on the company’s scientific advisory board. But the authors said this had no influence on the study’s results, and Nike paid to make the study available in its entirety online so other researchers can conduct their own tests and try to replicate the study. “We are really confident if people would replicate it, they would see the same thing that we saw,” Hoogkamer said.
They aren’t done studying the Zoom Vaporfly 4%. This study didn’t find a significant difference in biomechanics with this shoe, but Hoogkamer suspects it must be there. They’ve already started another study. “We’ve taken the next step of taking it to a more advanced biomechanical study where we look at the force,” he said.
“So far, we saw minor changes from before, and as we look closer and closer, we add up all those, and probably we can see why that energy difference works,” he said.