Sydney McLaughlin on Sunday night broke the world record in the women's 400-meter hurdles.

McLaughlin, 21, who recorded a time of 51.90 seconds, outraced Dalilah Muhammad to earn the victory at the U.S. Olympic trials in Eugene, Oregon. In doing so, she became the first woman to break the 52-second barrier.

Her time crushed the previous record of 52.16 seconds set by Muhammad, who finished second in Sunday's final.

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"Oh my gosh!" McLaughlin stated after she saw the numbers "51.90," upon finishing the race. 

"It's one of those moments you think about and dream about and play in your head that you'll put it together," said McLaughlin, who started working with coach Bobby Kersee in 2020.

Sydney McLaughlin reacts after setting a new world record in the finals of the women's 400-meter hurdles at the U.S. Olympic Track and Field Trials Sunday, June 27, 2021, in Eugene, Ore. (AP Photo/Ashley Landis)

Kersee got McLaughlin focused on improving her form by running shorter hurdles courses. She credited her coach and a renewed sense of faith for her breakthrough.

"It was trusting the process, and a lot of things you can’t really see coming," McLaughlin said. "But just having the childlike faith in trusting everything is going to work out. Bobby’s really good at that."

Her achievement came on a day that temperatures at Hayward Field reached 108 degrees and the surface of the track exceeded 150.

The extreme heat forced USA Track and Field to stop action around 3 p.m. after heptathlete Taliyah Brooks was carted off the track in a wheelchair. McLaughlin's race was delayed by about four hours.

She said the wait "was a little bit of a throw in our plan."

"But we were prepared for that," McLaughlin said. "Bobby always talks about Muhammad Ali, and always having to be ready for that left hook."

In this case, it was another Muhammad — Dalilah Muhammad — who has, in her own way, been preparing McLaughlin for Sunday. It marked the third straight major race in which the two squared off and a world record was set. 

The last two times, it was Muhammad who came out on top. 

The first occurred two years ago on a rainy day in Des Moines, Iowa, at national championships. Then again, a few months after that at worlds in Qatar. McLaughlin ran a 52.23 at worlds -- but lost by .07 seconds. That mark would have been the world record had she run it before Muhammad started rewriting the book that season.

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"Dalilah is a great competitor, and I was growing into my own person," McLaughlin explained when asked if she was deflated after running such good times, only to come in second.

Muhammad said getting to the starting line in a year that began with injuries and a COVID-19 scare – was never a sure thing. She even noted she couldn't break 55 seconds to start the season.

"Almost for a month straight, I kept asking (my coach) every day at practice, ‘Are you sure. Are you sure?’" Muhammad said. "I’m extremely grateful to be here today and so thankful those setbacks are behind me."

Up next is the Olympics. The finals in the 400 hurdles are set for Aug. 4. Muhammad won the gold in Brazil in 2016. Muhammad bested runner-up McLaughlin in the 2019 world championships in Doha.

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"She definitely pushes me," Muhammad said during her interview on the track. She then turned to McLaughlin and said: "Congratulations, you world-record holder. It's going to be a battle in Tokyo for sure."

The Associated Press contributed to this report