Michael Phelps qualified fourth-fastest in the Olympic 200-meter freestyle preliminaries Sunday night, about nine hours after winning a gold medal in the 400 individual medley.
Phelps never led in his heat and touched in 1 minute, 46.48 seconds, well off his world record set at last year's world championships.
"Tonight was just a race to get into tomorrow," he said. "I just try to conserve everything and make it into the semifinal. I try to bank as much rest as I can tonight _ recover and sleep and try to warm down and get out of here as fast as I can, so I'm not getting so run down."
Phelps was still on an emotional high from winning the first swimming medal of these games, and doing so in world-record time. That put him on his way toward breaking fellow American Mark Spitz's record of seven gold medals in a single games.
Dominik Meichtry of Switzerland led the way in 1:45.80, pumping his right arm after winning Phelps' heat. Jean Basson of South Africa was second-quickest in 1:46.31, followed by Canadian Brent Hayden in 1:46.40.
After Phelps returned to his room at the athletes' village, his teammates set him up for Monday morning's 400 freestyle relay final with a world record in the prelims.
Nathan Adrian, Cullen Jones, Ben Wildman-Tobriner and Matt Grevers won their heat in 3:12.23, erasing the old mark of 3:12.46 set by the U.S. at the 2006 Pan Pacific championships in Victoria, British Columbia.
Jones was part of the team that owned the previous record, becoming the first black swimmer to set a long-course world mark.
Jones had the fastest 100 split of 47.61 seconds among his teammates and will likely join Phelps, Jason Lezak and Garrett Weber-Gale in the final.
The U.S. has not won the event at the Olympics since 1996, taking silver in 2000 and bronze in 2004. The Americans will be challenged by France, which qualified second in 3:12.36 and will be trying to win its first relay medal in 56 years.
Like Phelps, Katie Hoff of the United States was back in the pool hours after earning a bronze medal in the 400 IM. She broke Janet Evans' nearly 20-year-old Olympic record in winning her 400 freestyle heat in 4:03.71.
One heat later, world recordholder Federica Pellegrini of Italy took the mark even lower, touching in 4:02.19 to qualify fastest for Monday morning's final.
Rebecca Adlington matched Pellegrini stroke-for-stroke heading into the finish and was second-quickest in 4:02.24. Hoff's time landed her the third spot.
Defending Olympic champion Laure Manaudou of France grabbed the eighth and last spot, qualifying 2.74 seconds behind Pellegrini's time.
Otylia Jedrzejczak of Poland, the silver medalist in Athens, didn't advance, finishing ninth. She also failed to make the 100 butterfly final four years after winning a silver.
Kirsty Coventry of Zimbabwe was the fastest qualifier for the 100 backstroke, where the top four women all swam under 1 minute.
The Olympic record set by American Natalie Coughlin four years ago in Athens was broken in each of the last three heats, with the mark eventually belonging to Coventry, who touched in 59.00 seconds. She was the silver medalist in Athens behind Coughlin. Earlier Sunday, Coventry won a silver medal in the 400 IM.
"I was still running off the adrenaline and hyper from this morning," she said. "I didn't have to build up too much energy."
Reiko Nakamura of Japan was second-quickest in 59.36, while Russian Anastasia Zueva also went under the old Olympic mark in 59.61.
Coughlin, who won a silver medal earlier Sunday in the 400 freestyle relay, advanced to the semifinals in fourth, with a time of 59.69, well off her world record of 58.97.
"I definitely have my work cut out for me," she said. "The 100 back is probably the quickest progressing event in the past year in swimming. There's a lot pressure on me, but I'm going to enjoy it as much as possible."
France's Manaudou, the bronze medalist in Athens, was fifth.
The men's 100 back was fast, too.
American Matt Grevers took down teammate Aaron Peirsol's Olympic record, qualifying fastest in 53.41. Arkady Vyatchanin of Russia was second in 53.64.
Peirsol, like Phelps an old pro at conserving his energy while progressing through the heats, was third in 53.65. The defending Olympic champion is favored to repeat his 2004 sweep of the backstroke events, which the U.S. has won in each of the last three Olympics.
Leisel Jones of Australia qualified first in the 100 breaststroke with an Olympic record time of 1:05.64. She was the bronze medalist in Athens, but is now the world recordholder and the heavy favorite to sweep the breaststroke events.
"I'm quite shocked actually. I had a pretty crazy swim," she said. "That was a little faster than what I expected to do."
Yuliya Efimova of Russia was second in 1:06.08, followed by Mirna Jukic of Austria in 1:07.06.
