Michael Phelps and Katie Hoff got the US Olympic trials off to a spectacular start with world records in the 400-meter individual medleys in Omaha, Nebraska, on Sunday.

Katie Hoff checks the result after the Women's 400m Individual Medley at the U.S. Olympic Swimming Trials in Omaha of the United States, June 29, 2008. Hoff won the title and set a new world record with 4 minutes and 31.12 seconds.(Xinhua Photo)

Officials had promised fireworks during the eight-day competition and the first night produced two world records in three finals.

Phelps, targeting Mark Spitz's record of seven gold medals at a single Game in Beijing, stormed to the wall ahead of good friend Ryan Lochte in a time of four minutes 5.25 seconds, slicing almost a second of his old mark.

"I left everything in the pool," Phelps, who swam in the controversial hi-tech Speedo LZR Racer swimsuit, told reporters. "I would never have been able to do it without Lochte beside me. He is a great friend and a great competitor.

"I definitely started the meet off on the right foot.

"When I heard the crowd I had the feeling something special could happen."

Michael Phelps swims in the Men's 400m Individual Medley at the U.S. Olympic Swimming Trials in Omaha of the United States, June 29, 2008. Phelps won the title and set a new world record with 4 minutes and 5.25 seconds.(Xinhua Photo)

With the arena still buzzing from Phelps's performance, Hoff brought the near capacity crowd of 12,000 to its feet again by powering to the wall in 4:31.12 to reclaim the world record she surrendered to Australia's Stephanie Rice in March.

"It was definitely special for me," said Hoff, who at 15 was the youngest member of the US Olympic team in Athens.

"I was trying to keep that off my mind a little bit because with IMs I kind of pushed and pushed and hyper-focused on them and it really didn't happen for me until I just stopped thinking about it.

"Watching the first race of the meet was definitely inspiring and it gave me chills and got me psyched up for my race."

Like Phelps, Hoff also was wearing the revolutionary Speedo suit, which has been worn for 40 of the 44 world marks set since it was unveiled in mid-February.

Katie Hoff (R) receives interview at the awarding ceremony for the Women's 400m Individual Medley at the U.S. Olympic Swimming Trials in Omaha of the United States, June 29, 2008.(Xinhua Photo)