A Radical Solution for the World’s Greatest Marathoner
- October 30, 2025
There are few firsts left for marathon GOAT Eliud Kipchoge. The New York City Marathon is the near equivalent of his last frontier. This November 2, 2025, will be his debut in the race, the only world major he has yet to run.
Typically a first tester for Nike’s latest footwear innovations, Eliud will take on NYC with a tool borrowed from a different toolbox: a custom Nike Radical AirFlow top, a material innovation introduced in this summer’s trail running season through All Conditions Gear (ACG). The origin for the one-of-one top is simple. In July of 2025, a team of Nike product experts were preparing to fly to Eliud’s training camp in Kenya to show him new product. What if he tried a Radical AirFlow top, they thought? The same kind worn by All Conditions Racing Department athlete Caleb Olson for the 2025 Western States 100-Mile Endurance Run, where he ran the second-fastest course time in the race’s history.
What happened next is familiar to anyone who’s followed Eliud’s relationship to product. He ran in the top. He liked it enough to scribe pages and pages of his signature handwritten notes, drawings and annotations on how it performed. And he believed in the top so much, he said he’d wear it for one of the few remaining firsts of his career.
“The journey of how this project went from prototype to race-day ready for Eliud was very much in the spirit of just doing it,” says Scott LeClair, VP/GM, Nike ACG. “Serve the athlete and don’t let anything get in the way.”
Eliud’s reputation as a devout wear tester is storied across Nike Running. Designers call him a product line manager on the ground. His humble sketchpads turn into maps that lead to goldmines. From unboxings to post-workout debriefs, Eliud is always ready to share his direct experience with the innovation at hand.
[Left] Eliud’s notes often double as training logs, contextualizing his product testing with the workout at hand. [Right] The most notable changes to Eliud’s top include two additional side vents.
After a week of running in the top, Eliud was shocked at the perceptible cooling effect over his body, and he liked how the knit material moved freely across his skin without chafing. He offered one suggestion that might increase the cooling effect: an additional side vent at the garment’s ribs, betting on the chance for even more ventilation.
Designers back at Nike’s PHK headquarters got to work creating an updated prototype. At the LeBron James Innovation Center, experts from Nike’s NXT Apparel teams used Eliud’s digitized body scans from the Nike Sport Research Lab to hit exact measurements for his 5’7” build. Along with creating the side vents, designers made more adjustments to get the top race-ready. They reverted the hemline to a normal height (the trail version of Radical AirFlow is cropped to allow room for a fuel belt). Based on Eliud’s feedback, they also adjusted the drape to make the top fit a little tighter to his body, to prevent it from swinging excessively from side to side.
“Every alteration we made for Eliud was based on his feedback,” says Emily DeLess, Apparel Innovation, Product Management. “Thanks to our research history, we already have a language of development with him, so we can give him exactly what he needs.”
“The material is wonderful, friendly to the skin and absorbs moisture very fast.”
Eliud Kipchoge on his custom Radical Airflow top, in notes to the Nike Running team
Another of Eliud’s suggestions, shown at right, was to tighten the fit just slightly to avoid excess swinging while he runs.
When Eliud received his top in August, he put it to the test on roads outside his training camp in Western Kenya.
His comments after these long runs kept returning to the notion that the sweat across his body was, somehow, being turned into a cooling agent, not a distraction. “The magic of this top,” says Eliud, “is how it evaporates the sweat.”
Soon, Eliud had the validation he needed. In a text thread with Tony Bignell, Chief Innovation Officer, Eliud remarked that his 40-kilometer run that day was the right time to close the feedback loop on his prototype. I think the top is ready to go, he texted, adding a flex emoji. Then: ACG has a great future.