Scientists at the University of Colorado say their research helped Nike name its new running shoe that reduces a runner’s energy use by an average of 4 percent.

Nike debuted limited quantities of the $250 Zoom Vaporfly 4% in July, and Shalane Flanagan of the U.S. and Geoffrey Kamworor of Kenya wore the shoe when they each won New York City Marathon titles on Nov. 5.

Prior to the shoe’s release, scientists at the University of Colorado’s Locomotion Lab in Boulder recruited 18 male runners to help test the shoe. All participants were in their 20s, had run a 10K race in less than 31 minutes and wore a size 10 shoe.

Over the course of three days, the runners rotated through the Nike Vaporfly 4% (which hadn’t yet been named) and two other high-performance running shoes —the Nike Zoom Streak and Adidas Adios Boost 2—while running on a treadmill. To make sure shoe order or weight didn’t affect the results, the runners reversed the order in which they wore the shoes and researchers also put lead pellets in the Vaporfly 4% so they’d be the same weight as the others.

By measuring the runners’ oxygen consumption and determining the number of calories burned, the researchers were able to determine that the runners used between 2 percent and 6 percent less energy while wearing the Vaporfly 4% shoe, with an average energy savings of 4 percent—thus giving the shoe its name.

Prototypes of the shoes were also worn by elite marathoners Eliud Kipchoge, Zersenay Tadese and Lelisa Desisa when they attempted to break the 2-hour barrier for the marathon at Nike-backed time trial in Italy last May. Kipchoge finished in 2:00:25, but it was not a record-eligible time because of the preferential conditions.

The researchers say the energy savings will allow runners to decrease their run times, bringing a 2-hour marathon within reach.  The current world record, set in 2014, is 2:02:57.

VIDEO: Watch the “Breaking2” Marathon Documentary

“Our extrapolations suggest that with these shoes the technology is in place to break the 2-hour marathon barrier,” said the study’s lead author, Wouter Hoogkamer, a postdoctoral researcher in the Locomotion Lab at CU-Boulder. “Now, it is up to the athletes to make it happen.”

The Vaporfly 4% shoe features high-tech foam cushioning that researchers say “stores and returns twice as much energy” as the other shoes studied, as well as a carbon-fiber plate that some have argued works as a spring, giving runners an unfair advantage. Hoogkamer says the plate works more like a lever than a spring, but an ongoing study is taking a closer look at how it works with the other materials.

READ MORE: The Denver Channel