Omaha, NE (My Sportsbook) - Katie Hoff continued her impressive run at the U.S. Olympic swimming trials on Monday by winning the women's 400-meter freestyle, one night after setting a world record in the 400-meter individual medley.

The 19-year-old Hoff won the 400m freestyle in a time of 4 minutes, 2.32 seconds, just ahead of Kate Ziegler.

Brendan Hansen secured a spot in the Beijing Olympics by winning the 100m breaststroke in a time of 59.93 seconds, just ahead of Mark Gangloff. The 26-year-old Hansen, the world record holder in the race, won three Olympic medals four years ago.

Christine Magnuson earned her first trip to the Olympics by rallying to win the women's 100m butterfly in a time of 58.11 seconds. Elaine Breeden was second at 58.21 seconds.

Michael Phelps, who celebrated his 23rd birthday on Monday, finished first in his semifinal heat in the 200m freestyle with a time of 1 minute, 45.64 seconds. Phelps, who holds the world record, actually had a time .03 seconds behind Ryan Lochte in the semifinals. The final is Tuesday.

Phelps officially punched his ticket to Beijing on Sunday night in incredible fashion, 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.

In the women's semifinals of the 100m breaststroke, Rebecca Soni had the top time of 1 minute, 6.87 seconds. Jessica Hardy, the American record-holder, had the fifth-best time, while 26-year-old Amanda Beard, trying to qualify for her fourth Olympics, was seventh-best. The final is Tuesday.

Hayley McGregory and Natalie Coughlin had the two best times in the 100m backstroke semifinals with respective marks of 59.48 seconds and 59.74. Earlier Monday, Coughlin quickly regained her world record in the race after McGregory had claimed the mark earlier during heats. Coughlin's time was 59.03 earlier Monday. The final is Tuesday.

Randall Bal led the semifinalists in the men's 100m backstroke with a time of 53.09 seconds. Aaron Peirsol, the defending gold medalist from Athens, had the second-best time at 53.26 seconds ahead of Tuesday's final.