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Professional runner Faith Kipyegon in her attempt to break the four-minute mile earlier this year. 

In June 2025, during a Nike-sponsored event, world champion and Kenyan middle- and long-distance runner Faith Kipyegon  to break the four-minute mile barrier. She finished just over the goal with a time of 4:06.42.

But a CU �Ǹ�Թ� lab calculated that it is possible to break the four-minute barrier. CU physiologist Rodger Kram, who focuses on biomechanics involved with human locomotion, was part of the team that helped Kenyan long-distance runner Eliud Kipchoge historically break the two-hour marathon in 2019. While Kram was not directly involved in the Kipyegon attempt, his lab published a study earlier this year that found a champion runner like Kipyegon could clock a time of 3:59.37 under ideal conditions. Strategies include coordinated pacing and drafting, which involves a runner following closely behind pacers to reduce air resistance.

Kram and his team, Edson Soares da Silva, Wouter Hoogkamer and Shalaya Kipp (IntPhys’14; MS’17), also calculated that rotating pacers — runners who set a steady speed to help others reach a goaltime and block the wind — could have provided an elite racer with just enough of an edge to dip under the barrier.

Nike’s execution this year took a different approach.

“They used 13 pacers in a very unusual formation,” said Kram. “Our model involved only two pacers at a time.”

Still, Kram believes the four-minute mile barrier will fall.

“I still think it’s possible, with two teams of female pacers who trade out halfway,” he said.

Royal Society Open Science published Kram’s  in February 2025.

What’s next for Kram? “We’re cooking up some outrageous next experiments,” he said. “But they’re top secret for now.”

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Photo by Christophe Ena/The Associated Press