Indianapolis:Aaron Peirsol reclaimed his world record in the 100-meter backstroke at the U.S. championships on Wednesday.
The Olympic champion trailed Matt Grevers at 50 meters, then poured it on to win in 51.94 seconds, becoming the first person ever to swim under 52 seconds in the event.
Peirsol's previous mark of 52.54 set at the Beijing Olympics was broken by Spain's Aschwin Wildeboer Faber on July 1. Faber swam 52.38 on the backstroke leg of the 400 medley relay at the Mediterranean Games.
Grevers, the Olympic silver medalist, finished second in 53.11, giving himself another crack at taking down Peirsol in Rome at the world championships this month.
It was the sixth time Peirsol has lowered the world record in the 100 back, an event he has dominated for most of the decade.
Peirsol took back the world record wearing an Arena X-Glide, one of the newer suits approved by FINA. He donned the version that covers his legs.
"I feel like if I would have worn another suit, I probably would have broken the world record anyway tonight by the way I was feeling," he said. "That's one race that's coming a little easier for me, and tonight I just felt really good."