INDIANAPOLIS — Aaron Peirsol broke the world record in the 200-meter backstroke at U.S. nationals tonight, beating previous owner Ryan Lochte and lowering his second world mark in three days.

The Olympic silver medalist touched in 1 minute, 53.08 seconds, bettering Olympic champion Lochte's old mark of 1:53.94 set in Beijing.

"I'm elated I went that fast, but the real work is in two weeks," Peirsol said, referring to the upcoming world championships in Rome.

Lochte was under his world-record pace in the opening 50 meters before Peirsol took over for good. Peirsol dipped a full second under the mark after 150 meters while wearing an Arena X-Glide suit.

"The last 50 really hurt, so I know the other two guys really, really hurt," he said, referring to Lochte and third-place finisher Tyler Clary.

Lochte took second in 1:54.21. He and Peirsol will swim the event in Rome.

Peirsol dominated the 200 back from the 2000 Sydney Olympics, when he finished second, until finally losing the race and his world record to Lochte at the 2007 world championships in Melbourne.

"It's been a few years since I really felt good racing," said Peirsol, who turns 26 before the world championships begin. "I finally feel pretty good. I want to go faster. Ryan has pushed me quite a bit the last couple of years."

Peirsol reclaimed his 100 back world mark with a time of 51.94 seconds Wednesday.

Cullen Jones lowered the American record in a 50 freestyle swim-off, touching in 21.41 seconds. That bettered the previous record of 21.47 set by Garrett Weber-Gale at last year's Olympic trials.

He edged Weber-Gale in the one-on-one race for the second spot in the event at worlds later this month. Weber-Gale was clocked in 21.70.

"Swimming needs to do more of it. There's so much fun, so many people like to watch it," Jones said. "I don't know how many times since Thursday people came up to me like, 'I can't wait for Saturday. I can't wait to see that race.' It's cool to see that much enthusiasm about swimming.'"

Jones' time was faster than what Nathan Adrian swam in winning the 50 Thursday night, when Jones and Weber-Gale tied for second. Adrian won in 21.52.

Jones switched to a Speedo LZR for the swim-off, abandoning the Jaked polyurethane suit he had worn earlier in the meet. He has a contract with Nike, but the company has gotten out of the competitive suit business.

"We took a — not a gamble, but something different. I tried the LZR. I've always felt comfortable in that since last year," he said. "Jaked, still, I feel is a really great suit for me. They both fit right, so we're going to see what we can do at worlds. I try not to put too much faith in the suit. I put faith in the work I do."

Olympians Jones and Weber-Gale had already qualified for the team in the 400 freestyle relay.

Chloe Sutton, a 17-year-old who competed in the 10-kilometer open water event at the Beijing Olympics, is going to the world championships in a pool event. She won the 800 freestyle in 8 minutes, 29.34 seconds. Haley Anderson took second.

Sutton had never before qualified for a major international pool competition. She typically churns through distance races in lakes and rowing basins, where the often wild and woolly open water events are held.

"I really wanted to make my pool swimming debut here," she said. "Right now my place is in the pool."

Sutton made the switch after she failed to qualify for the open water competition in Rome.

"That wasn't very fun for me," she said. "From now on, I'm only doing things that are fun."

Dana Vollmer qualified for her third individual event in Rome by winning the 100 freestyle, capping a successful meet nearly a year after she failed to make her second Olympic team.

She won in 54.00 seconds, just ahead of Olympian Amanda Weir in 54.03.