Clad in featherlight spikes, a custom 3D-printed sports bra and an aerodynamic speed suit, Kenyan Olympian Faith Kipyegon will step onto a Paris track this week and try to become the first woman to run a sub-4-minute mile.

The attempt comes four months after CU Boulder researchers published a paper suggesting she could do it, particularly if Kipyegon used strategically timed and placed pacers to block the wind coming at her.

They ended their paper with the words: “Hopefully Ms. Kipyegon can test our prediction on the track.”

This Thursday, they’ll be watching intently.

“I've been making hypotheses since about 1984, and none of them have been anywhere near this publicly tested,” said study author Rodger Kram, an associate professor emeritus in the Department of Integrative Physiology and an expert in running physiology and biomechanics. “It's a little bit scary, but it's also super exciting.”

The “Breaking4” event, hosted by Nike, resembles the 2017 Breaking2 Project, in which Nike set out to create the perfect conditions for Kenyan Eliud Kipchoge to break the two-hour marathon barrier. (He missed it but nailed it in a similar event in 2019).

Reportedly, Nike first started planning Breaking4 some 18 months ago.

Like Breaking2, Breaking4 has been informed by CU Boulder research.

“Our study found that if everything went right, under a couple of different drafting scenarios, Faith Kipyegon 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.”

The Mount Everest of running

When Roger Bannister ran the first sub-4-minute-mile on May 6, 1954, it made international news and inspired a new generation of male runners.

“It was the running equivalent to summiting Mount Everest for the first time,” said Kram. “Before that, it was considered beyond the limits of human physiology.”

But progress in women’s running was slower to come.

When Diane Leather became the first woman to run a sub-5-minute-mile just 23 days after Bannister’s race, it received little attention.

From 1928 to 1960, women were prohibited from running anything longer than 200 meters in the Olympics, due to unfounded concerns that it could harm their reproductive health. And women weren’t permitted to run the Boston Marathon until 1972.

We’ve come a long way, the researchers say, with women now outnumbering men in U.S. running races as a whole. But women still participate less in middle- and long-distance running than men do globally.

“The 4-minute-mile was an elusive barrier for humankind, and now if we actually had a woman do it, it would give a whole new generation of track athletes something to go after,” said Kipp.

The power of drafting

Not all are convinced Kipyegon will succeed.

Some have publicly expressed their doubts that the 31-year-old mother can carve 7.64 seconds off her already lightning-fast mile record set in Monaco in 2023.

“She’s not going to break four and it’s not going to be particularly close,” wrote one skeptic.

But Kram contends that while others focus on how much energy she must expend, his team’s research emphasizes how much energy she can save by drafting—or using other runners to push the air molecules out of the way, reducing resistance.

First author Edson Soares da Silva, who traveled from the Universidade Federal do Rio Grande do Sul in Brazil to work in Kram’s lab, notes that migratory birds often fly in formation, using drafting for energy-efficient locomotion. Humans can learn something from them.

“Anyone from top elite to lower-level runners can benefit from drafting,” he said. “But, the faster the speed, the more air resistance a runner faces, and the more drafting matters.”

In the case of Kipyegon running a 4-minute-mile pace alone, just pushing against the air eats up 13% of her energy, according to the team’s calculations.

The study forecasts that if she used just two female pacers, which switch out at the half-mile point, Kipyegon could reduce that drag by about 76%, enabling her to run a 3:59:37.

A promotional video from Nike suggests that a pack of both male and female elite runners will pace Kipyegon Thursday, with some of the male runners sticking with her the entire mile—which could reduce air resistance even more, Kram said. (He notes that Bannister also used pacers for his historic run).

“On Thursday, she will have better than 70% drafting and all of these other contributing factors like the shoes and the clothing,” he said. “I think there is a really good chance that she will break four minutes.”

Watching history in the making

He’ll spend Thursday on Zoom with Kipp and co-author Wouter Hoogkamer, watching the attempt together.

Meanwhile, da Silva, now a doctoral student in France, will be in the stadium in Paris cheering her on.

“Since I live just three hours away, I feel like I am in the right place at the right time to witness the testing of our hypothesis and to see history in the making,” he said.

What if she doesn’t make it?

“As we have seen over the years in running and in other fields, one sure-fire way to motivate a woman to do something is for people to tell her she cannot do it,” said Kram. “It’s only a matter of time.”

The Breaking2 Event will be streamed live on Prime Video and Nike’s YouTube channel beginning at 1:15 PM ET Thursday, subject to weather conditions.