Breaking4

In 1954, Roger Bannister became the first man to break four minutes in the mile, running 3:59.4. That same year, Diane Leather became the first woman to break five minutes with 4:59.6. As of June 2025, according to World Athletics statistics, roughly 2,000 men have broken the four-minute barrier.

No woman has yet broken four minutes. The women's world record is 4:07.64, set by Kipyegon on 21 July 2023. An earlier women's world record, 4:12.56 set by Svetlana Masterkova of Russia in 1996, stood for almost 23 years, with Masterkova being the first woman to break 4:15 at the distance.

Kipyegon also holds the world record over 1500 metres, which at the time was 3:49.04, set in 2024, at the Stade Sébastien Charléty. The time equates to roughly a 4:06 mile pace. Kipyegon's run has led some to speculate that the first women's sub-four minute mile may come within the 21st century.

In January 2025, at the Nike Headquarters in Beaverton, Oregon, Kipyegon did VO2 max testing along with other baseline tests in preparation for the attempt. In February 2025, a scientific study was published in the Royal Society Open Science, stating that Kipyegon could run a mile in approximately 3:59.37 under very specific conditions, achieved through ideal pacesetters and weather conditions.

In April 2025, it was announced that Kipyegon would attempt to become the first woman to run a sub-four-minute mile at a meeting in Paris on 26 June 2025.

The event was run in a similar manner to Nike's previous Breaking2 project for the marathon and the Ineos 1:59 challenge. It was not record eligible because the custom pair of Victory Elite FK spikes Kipyegon wore were not submitted for approval by World Athletics prior to the event.

In addition to the spikes, Kipyegon wore a specially designed speed suit and sports bra.

To break the barrier, she would have to improve on her 4:07.64 personal best by at least 7.65 seconds. Kipyegon fell 6.91 seconds short of the four-minute barrier with an unadjusted time of 4:06.91, which is still faster than her official world record by 0.73 seconds.

Pacers

Breaking4 utilized a dozen male and female pacemakers:

On 26 April 2025, Kipyegon ran 2:29.21 for 1000 metres at the Xiamen Diamond League, a time 0.06 seconds off her personal best of 2:29.15 and 0.23 seconds off Svetlana Masterkova's world record of 2:28.98. This time equates to a 4:00.08 mile pace. Robert Johnson of LetsRun.com considered the attempt to be "ludicrous", since Kipyegon would be required to hold a slightly faster pace for approximately 609 metres longer.

A scientific paper published in the Journal of Applied Physiology in April 2025 concluded that "there is no female athlete presently displaying the physiological characteristics required to run a sub-four minute mile".

The timing adjustment made by Nike to give her a flying start which was not announced before the event and only revealed after questioning from the media, provided another non-official advantage to Kipyegon that most running fans believed Nike should have been up-front about.

The event was streamed live on Prime Video and Nike's YouTube channel, beginning at 7:15 PM local time. The first episode of a docuseries covering the event premiered on 20 June.