In a race for the ages, the United States' Dalilah Muhammad held off countrywoman Sydney McLaughlin to win her first IAAF World Championships title in the 400m hurdles and break her own world record in 52.16.

McLaughlin's runner-up time of 52.23 is not only a significant personal best, but the fastest time in the world by anyone not named Dalilah Muhammad. It's also, clearly, the fastest losing time in world history.

Dalilah Muhammad leaves us speechless again...52.16...how...

pic.twitter.com/evOOm5vmfl

— FloTrack (@FloTrack) October 4, 2019

The two Americans were the only women in the world to run under 53 seconds this year and after trading major wins throughout the season, were expected to make the final a two-woman race—which they did. 

Muhammad, the 29-year-old reigning Olympic champion, and McLaughlin, the 20-year-old hurdle prodigy, both got out well and immediately starting making up the curve on their competitors. It was clear as they neared the final curve that Muhammad had gone out slightly faster. On the homestretch, McLaughlin gained ground on her more experienced compatriot but Muhammad's stride never faltered and she successfully earned her first world gold to go with her world silver medals from 2013 and 2015.

Muhammad shocked the world in late July at the USATF Championships, when she captured gold in 52.20—breaking the 16-year-old world record—ahead of McLaughlin, whose then-PR of 52.75 was the fastest time in the world in 2018. But Muhammad hasn't been bulletproof all summer—she lost the Bislett Games, part of the IAAF Diamond League series, to McLaughlin in June, then placed just third in the IAAF Diamond League final, the biggest race of the year besides worlds, behind McLaughlin and another American, Shamier Little.

Before this year, the world record in the women's 400m hurdles was 52.34 by a Russian woman named Yuliya Pechonkina, and the event itself was one of the after-thoughts in a bloated track and field schedule. Thanks to Muhammad and McLaughlin's rivalry, that is certainly no longer the case.

This story will be updated with quotes from the mixed zone.