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To run the first women’s sub-four-minute mile in Paris on Thursday night, Faith Kipyegon needed to chase a set of green Wavelight pacing lights that flashed around the inner curb of the track at precisely the right pace. Through two of the four laps, she was even with the lights. Towards the end of the third lap, she fell a step behind, but it was still close halfway through the fourth and final lap. Could she use her fearsome finishing kick to claw back the difference?

“I gave everything,” Kipyegon said after the race. “And I think the Wavelights also gave everything. It was the Wavelight’s time today.” Indeed, the lights telescoped away in the final straight as Kipyegon’s torrid pace finally took a toll. She fought to the finish line in a final time of 4:06.42, more than a second faster than her world-record mark of 4:07.64. This time won’t count as a new women’s record, since it was an exhibition race using male pacemakers—but it was still an eyepopping performance. You can watch the race:

Leading up to the race, there was lots of speculation about how Kipyegon and the Nike scientific team that organized the event would be able to shave more than seven seconds off her best time. The three keys seemed to be newly designed racing spikes, a space-age aerodynamic racing suit, and a team of pacers placed to block as much wind as possible. During the testing phase, another Nike-sponsored elite runner ran two one-mile time trials, one with her current racing kit and the other wearing the new speedsuit and running behind pacemakers in the planned drafting formation. She was three percent faster in the latter case, giving Nike’s scientists confidence that Kipyegon could dip under four.

The final drafting formation involved 13 pacemakers, including 11 men and two women, all of them decorated international runners—including Olympic medalists Georgia Hunter Bell and Grant Fisher. They were divided into two groups: a five-person “shield” running in front of Kipyegon, and a seven-person “spoiler” running beside and behind her. Theoretically, such a formation should be capable of turning a 4:07 mile into a 3:59 mile. But the real world is messy, and in the chaos of the 14-person pack circling the track at Charléty Stadium, it was hard to tell whether the pacing formation was tight enough to give Kipyegon maximum benefit. Still, Brett Kirby, who headed Nike’s scientific team, gave the pacers high marks afterwards: “It was really close to what we wanted.”

According to the unofficial splits shown on the finish-line clock, Kipyegon passed through 400 meters in 1:00.20, 800 meters in 2:00.75, and 1,200 meters in 3:01.84, which suggests she was still on a 4:03 mile pace with a lap to go. It’s not clear what splits she was aiming for—Kirby would only reveal that the team’s intended plan “starts out fast, and then it progresses faster and faster.” But those splits look good for a sub-four attempt.

Despite the number on the clock, the mood in the stadium after the race was upbeat. After crossing the finish line, Kipyegon crumpled to the track and lay there for a minute, covered by a Kenyan flag. But she soon popped up and acknowledged the cheering crowd. Left lingering in the air was the obvious question: would she take another shot? Missing by six seconds sounds like a long way, but another way of looking at it is that she was very close to being on pace for 1,400 of the 1,609 meters. Kipyegon still seems drawn to the challenge. “I will say that this was the first trial,” she told reporters afterward. “We learned many lessons from this race. I think going forward, I will go back to the drawing board.”

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