Omaha, NE (My Sportsbook) - Natalie Coughlin and Aaron Peirsol each re-set their own world records to highlight Tuesday's results at the U.S. Olympic swimming trials.

Coughlin set the world mark in the 100-meter backstroke final, as the time was whittled down for the third time during this event. She held the mark coming in, with a time of 59.21 seconds.

But in Monday's preliminary heats, Hayley McGregory broke the record in 59.15, only to have Coughlin take the record back in the next heat in 59.03 seconds. Then, in Tuesday's final, Coughlin set the mark again with a time of 58.97 seconds, wrapping up an Olympic spot in the process.

Margaret Hoelzer placed second (59.21), while McGregory finished in third (59.42).

Peirsol held the world mark for the men's 100-meter backstroke coming into the event, at 52.98 seconds. Though it wasn't broken several times, he improved the time in Tuesday's final as well.

Peirsol won the race in 52.89 seconds to set the new mark and earn an Olympic berth, while Matt Grevers took second place (53.19). Randall Bal, who was the top seed entering the final, finished a distant fourth in 53.45.

In other final results, Michael Phelps won the men's 200-meter freestyle and Jessica Hardy took first in the women's 100-meter breaststroke.

Hardy, the American record holder, locked up a spot on her first Olympic team with a winning time of 1:06.87, in a tight race. Megan Jendrick took second in 1:07.50, while Tara Kirk was just 1/100th of a second behind Jendrick to take third. Rebecca Soni -- the top seed for the final -- placed fourth in 1:07.80.

Phelps, the world record-holder in the event, won in 1:44.10, almost two seconds ahead of second-place finisher Peter Vanderkaay (1:45.85). Ryan Lochte qualified as the first seed in Monday's semifinals to focus on the 100-meter backstroke -- to no avail, however, as Lochte finished in third behind Peirsol and Grevers.

Phelps additionally posted the top time in the 200-meter butterfly semifinals, in 1:54.02. It was well off his world-record time of 1:52.09, but Phelps will be the favorite going into Wednesday's final.

Davis Tarwater had the second-best time, while Gil Stovall, Bobby Bollier, Dan Madwed, Matt Patton, Alex Vanderkaay and Mark Dylla all also qualified for the final.

Phelps, who celebrated his 23rd birthday on Monday, already secured a spot for Beijing on Sunday by winning the 400-meter individual medley with a world- record time. Phelps is entered in eight events at the trials. A winner of six gold medals and two bronze in 2004, Phelps could be sizing up the Olympic record of seven gold medals won at a single Summer Games, which was accomplished by Mark Spitz in Munich in 1972.

Katie Hoff, who has already won two events this week -- the 400-meter freestyle and 400-meter individual medley, setting a world record for the IM -- continued to swim well. She had the top time in semifinals for the 200- meter freestyle and 200-meter individual medley.

In the freestyle, her time of 1:57.10 was enough to give her the top time heading into Wednesday's final. Allison Schmitt, Julia Smit, Caroline Burckle, Kim Vandenberg, Dana Vollmer, Kara Lynn Joyce and Christine Marshall all also posted qualifying times.

In the individual medley, her time of 2:09.94 was almost a second better than Arian Kukors' 2:10.85. Coughlin, the American record holder, had the third- best time of 2:11.72. Caitlin Leverenz, Ava Ohlgren, Whitney Myers, Kaitlin Sandeno all qualified, while Elizabeth Beisel and Dagny Knutson finished in a tie for the eighth spot.