2024-06-12T20:29:27.911ZSydney McLaughlin-Levrone reacts after setting the world record in the women's 400-meter hurdles at the U.S. Olympic track and field trials. (Patrick Smith/Getty Images)EUGENE, Ore. — Sydney McLaughlin-Levrone knelt a few steps past the Hayward Field finish line and covered her mouth with her right hand, her fingernails tipped with neon-yellow polish. She gazed at the time on the clock, another new frontier in an event she has reorganized, another touchstone of disbelief for the sport she reigns over.The last race at the U.S. Olympic track and field trials rapidly became less competition than the latest salvo of McLauglin-Levrone’s sustained assault on preconceived barriers. She ran away from the other eight fastest 400-meter hurdlers in the nation before the homestretch. As the brick-red chasm grew, twin adversaries she has grown accustomed to surfaced: herself and the limits of human achievement.McLaughlin-Levrone won again. On Sunday night, she broke the world record for the fifth time in a little over three years, resetting it to 50.65 seconds, 1.99 seconds clear of runner-up Anna Cockrell. One year after a knee injury sidelined her for the world championships, McLaughlin-Levrone will head to the Paris Olympics in search of a second individual gold medal that feels like a formality. The reasons to watch will be aesthetic and historic.The path to 50.65 began three years ago at the U.S. trials, where she wrested the world record for good from Dalilah Muhammad in 51.90 seconds. She lowered it to 51.46 at the Tokyo Olympics. In 2022, she dropped it to 51.41 at the national championships, then an unthinkable 50.68 at the world championships.McLaughlin-Levrone’s time Sunday would have beaten four sprinters in last week’s women’s 400-meter final — the one sans hurdles.This is a breaking story and will be updated.