TOKYO -- Sydney McLaughlin broke the world record.

Dalilah Muhammad broke it, too.

Only one of the world's best hurdlers could win the Olympic gold medal, however, and McLaughlin came out ahead in the latest installment of the best rivalry in track.

Muhammad's time of 51.58 also beat McLaughlin's old record of 51.9, set at the Olympic trials in June.

"I think that's really iron sharpening iron,'' McLaughlin said.

Muhammad first broke the mark at U.S.

McLaughlin broke that record earlier this summer at Olympic trials, running her 51.90 to become the first woman to crack 52 seconds.

Starting from Lane 7, Muhammad came out of the blocks and made up the lag quickly as they cruised down the backstretch.

Olympic team in one of the most stacked events on the program, Muhammad, already in her prime, won a gold medal in Rio de Janeiro.

"Bobby always talks about Muhammad Ali, and always having to be ready for that left hook," McLaughlin said earlier this summer when asked how she deals with the unexpected.

In this case, it was another Muhammad -- Dalilah Muhammad -- who stood in the way of McLaughlin's goal.

Decathlon world record holder Kevin Mayer of France, the Olympic silver medalist from Rio and world champion in 2017, is in fourth spot with 2,662 points