Sydney McLaughlin shattered Dalilah Muhammad's 400m hurdles world record Sunday in the event's final at U.S. Olympic Trials in Eugene, Oregon, becoming the first woman to run under 52 seconds in the event's history.

The 21-year-old clocked 51.90 to make her second U.S. Olympic team, shaving more than a quarter-second off Muhammad's 52.16 winning time from the 2019 World Championships.

"Waking up today, I knew it was going to be a great day," McLaughlin said. "I will cherish this for the rest of my life."

Muhammad, the reigning Olympic and world champion, finished second in 52.42 to also make her second Olympic team. Anna Cockrell, this year's NCAA champion, was third in a personal-best 53.70. She'll make her Games debut.

McLaughlin was the top qualifier in both the prelims (54.07) and semifinals (53.03) and entered Trials as the fastest in the world this year, having put down a 52.83 earlier this month – at the time, her third-best 400m hurdles race ever.

The New Jersey native said she knew the race was going to be fast and competitive but had been precisely training for those conditions.

"I think great competition always pushes you," she said. "It helps to have such an amazing camp of women in the U.S. to get those times. With my training we were able to put one together. I'm excited for what the future holds."

And Muhammad, too, had a gut feeling something big was on its way.

"I definitely said [the world record] coming," she said. "[McLaughlin] looked so good in the rounds. Absolutely saw it coming."

McLaughlin didn't make it past the semifinals at the 2016 Rio Games, finishing 15 spots overall behind gold medal-winner Muhammad just a week after turning 17 years old. Now she'll return to the Olympics a favorite to win the title.

Sunday marked yet another chapter in this already storied U.S. clash between two of the nation's best overall female track and field athletes who just happen to compete in the same event.

And despite the noise surrounding the duo and their fierce head-to-head showdowns, they respect each other. McLaughlin reflected on the relationship after her record-breaking performance.

"Iron sharpens iron. There's no animosity or hard feelings. We have to have each other to have these world records," she said.

"It's an honor. So many amazing women have come before me and will come after me. The glory isn't forever."

As for Muhammad, who dealt with injury in 2021, she's looking forward to next month.

"It's very discouraging when setbacks happen to you. You don’t know how the season will go," the 31-year-old Queens, New York, native said. "I think there's more in store for me and Tokyo will be good for me."

She twice broke the world record in 2019, first when capturing her fourth national title in 52.20 and then in the final at the world championships in 52.16. Her times are now the second- and third-fastest ever recorded.

Muhammad’s 2016 Olympic title was Team USA's first gold in the women's 400m hurdles. She and McLaughlin also won 2019 world titles in the 4x400m relay and will likely be in the pool for the Tokyo team.