First female runner could soon break the 4-minute-mile barrier

"It was the running equivalent to summiting Mount Everest for the first time," said University of Colorado Boulder Integrative Physiology Professor Rodger Kram. "Prior to Bannister, it was considered impossible -- beyond the limits of human physiology."

Seven decades later, a female runner has yet to follow in Bannister's footsteps, and some have questioned whether it's possible. A new study published this week by Kram and his colleagues suggests that with the right strategically timed and placed pacers, the answer is yes -- and Kenyan Olympian Faith Kipyegon is on the brink of doing it.

"We found that if everything went right, under a couple of different drafting scenarios, she could break the 4-minute barrier," said co-author Shalaya Kipp, an Olympic middle-distance runner who earned her master's degree in Kram's lab. "It's extremely exciting that we are now talking about, and studying, the limits of female human performance, too."

From 'Breaking 2' to 'Breaking 4'

In 2016, Kram's lab calculated what was required for a man to break the fabled two-hour marathon barrier.

He and his students determined that, along with intense training, state-of-the-art shoes and an ideal course and weather conditions, drafting -- running behind or in front of another runner to reduce air resistance -- was key.

Informed in part by their research, Nike hosted the Breaking2 Project in May 2017 to create those conditions for Kenyan marathoner Eliud Kipchoge. Kipchoge narrowly missed his goal that day but nailed it in a similarly staged race in Vienna in 2019.

Four years later, Kram watched with interest as Kenyan runner Faith Kipyegon crushed records for the women's 1,500 meter, the 5,000 meter and the mile -- all in less than two months, while raising her daughter.

When Kipyegon smashed the mile world record for women with a time of four minutes, 7.64 seconds, she was just over 3% away from breaking the 4-minute-mile, noted Kram. Coincidentally, when his team first started doing their research, the marathon world record holder was about 3% shy of a two-hour marathon.

Kram and his former students, now spread out at research institutions around the world, reconvened -- this time to explore the limits of female human performance.

The power of drafting

Run alone, even on a still day, and air molecules bump into you as you move through them, slowing you down. Run in the shadow of a pacer or, better yet, with runners in front and back, and you use less energy.

"The runner in front is literally pushing the air molecules out of the way," said Kram.

At a four-minute-mile pace, a runner of Kipyegon's size must overcome a surprisingly large air resistance force -- about 2% of her body weight. The team previously determined that completely eliminating that force would reduce the energy required by about 12%, allowing her to run even faster.

"Anyone from top elite to lower-level runners can benefit from adopting the optimal drafting formation for as much of their race as they can," said Edson Soares da Silva, first author on the new paper.

For instance, da Silva calculated that a 125-pound, 5-foot-7 female runner who typically runs about a 3:35-minute marathon could improve her time by as much as five minutes.

A magic number

For the new study, the team pored over video of Kipyegon's record 1-mile finish in Monaco.

The conditions were ideal, but her pacers ran too fast at first, said Kram, letting the gap between them and her widen. By the last lap, her pacers had dropped out and she was on her own.

Ideally, he said, one female pacer would be perfectly spaced in front, another in back, for the first half mile; then another fresh-legged pair would step in to take their place at the half-mile point. Collectively, previous research suggests, they could cut air resistance by 76%. Using that value, the team calculated her projected finish time: Remarkably, 3:59.37 -- the same time Bannister hit in 1954.

Inspiring scientists and runners

Kipp, now a postdoctoral researcher at the Mayo Clinic, stresses that their study, like many in the field, was based on previous studies that excluded women.

The authors hope that their paper will help spark more interest in studying the physiology of female athletes and inspire interest in female track and field.

They recently sent a copy of the paper to Kipyegon, her coaches and her sponsors at Nike, floating the idea of another staged race, similar to Breaking2.

"Hopefully," the last line of the paper reads, "Ms. Kipyegon can test our prediction on the track."