ROME (AP) — Five world records were set Monday at the world swimming championships.

No surprise there.

Aaron Peirsol failed to make the finals of 100-meter backstroke.

Now that’s a stunner.

Peirsol, the world record-holder and two-time Olympic champion in the 100-meter backstroke, was stunningly knocked out in the semifinals. He was caught off guard by the lightning-quick times that dealt another beating to the record book on the second day of the world swimming championships.

“It’s just a huge miscalculation,” said Peirsol, the three-time defending world champion in the 100 back. “I thought I was in a much better place, but if you’re looking straight up you don’t see much.”

Michael Phelps was taking no chances in his first individual event of the meet.

He breezed through the semifinals of the 200 freestyle, but looks to have quite a challenge waiting in Tuesday’s final. Germany’s Paul Biedermann, who already knocked Ian Thorpe out of the record book, was fastest qualifier with a time that was less than a second off Phelps’ world record.

“I thought Phelps would do better,” Biedermann said. “I didn’t give it my all in the last 50 meters. It’s going to be a close race.”

There’s been a staggering 11 world records set at the final major meet for high-tech bodysuits, with six more days still to go. The suits – some made of 100 percent rubber — will be banned starting in 2010, but that’s not soon enough for swimming purists who believe this Roman speed show is nothing more than a sad spectacle ruining the integrity of the sport.

Peirsol was wearing one of those newfangled suits, but it sure didn’t help. His time of 53.22 seconds was nearly a full second behind the top qualifier, Japan’s Junya Koga, and a tenth of a second out of the eighth spot, the last that advances to the final.

Peirsol lingered in the water, staring at the scoreboard in disbelief. Finally, he climbed out of the pool and walked across the deck, hands on hips and clearly disgusted. Less than three weeks earlier, he had pushed the world record to 51.94 at the U.S. nationals.

In Rome, he couldn’t even make the final. Matt Grevers was the only Americans to get through, after barely making it out of the morning prelims when his suit ripped.

“I’m going to put this one behind me and just move on, cheer for Matt and aim for the 200 (back),” Peirsol said. “It is what it is.”

Biedermann already won the 400 free, breaking Thorpe’s 7-year-old record, and he’ll have the prime No. 4 lane for the 200 final after breezing through the semis in 1 minute, 43.65 seconds — within striking distance of Phelps’ world record of 1:42.96.

The winningest Olympian won his semifinal heat in 1:45.23, then watched Biedermann’s performance from the deck. Phelps was clearly impressed.

“He’s dropped a lot of time,” Phelps said. “Usually you don’t see six seconds dropped in the 400 in a year. I think he was in the final of the 200 free last year (at the Olympics) and he’s dropped like three seconds in that, so he’s having a good meet. He’s having a good year. Tomorrow is going to be a good race.”

After the morning prelims, Biedermann said he didn’t expect to put up much of a fight against Phelps. The German sounded a lot more confident following the semis.

There’s another factor that can’t be overlooked. Biedermann is wearing an Arena X-Glide, a polyurethane suit that is considered faster than Speedo’s once revolutionary LZR Racer.

Speedo gave all its swimmers the option of switching to another suit if they felt it would improve their chances, but that wasn’t really an option for Phelps, who’s been sponsored by the company since he was a teenager and earns millions for wearing its suits.

Biedermann believes the Arena suit improves his times by as much as two seconds, a staggering edge in a sport often decided by hundredths of a second.

“You guys heard me the first day. I said I wasn’t going to talk about the suit,” Phelps said after his race. “I’m here to swim at the world championships, so keep asking questions about suits and you’re going to get the same exact answer.”

Phelps’ coach Bob Bowman said all the talk about suits could spur his swimmer.

“Michael loves a challenge,” Bowman said.

The record breaking carried on at a staggering pace Monday.

-Brenton Rickard of Australia set a world standard in the very first event, winning the 100 breaststroke in 58.58 to take down Kosuke Kitajima’s mark of 58.91.

-Sweden’s Sarah Sjostrom broke the record she set a day earlier in the semifinals of the 100 butterfly at 56.06, shaving nearly four-tenths off the 24-hour-old record.

-Ariana Kukors provided a rare bright spot for the struggling American team in the 200 individual medley, beating Olympic champion Stephanie Rice of Australia in 2:06.15. That was nearly a full second faster than Kukors’ record swim in the semis, and even more amazing when one considers she didn’t even qualify for this event at the U.S. nationals. Kukors got the spot when Elizabeth Pelton dropped out to concentrate on the 100 back, a move that backfired when the teenager didn’t even make the final.

-Rebecca Soni of the U.S. and Russia’s Anastasia Zueva both set world records in the semis. Soni’s time of 1:04.84 in the 100 breaststroke beat Leisel Jones’ three-year-old record of 1:05.09, while Zueva won her heat of the 100 back in 58.48, wiping Kirsty Coventry’s mark of 58.77 off the books.

“This is just ridiculous,” said 42-year-old Dara Torres, who has pretty much seen it all during her career.

Australia’s Dawn Fraser, who won gold medals at three Olympics, said the record times should be “rescinded immediately” because the suits give swimmers extra buoyancy, allowing them to glide along the top of the water.

“The world championships are a laughingstock to the world of swimming,” she said.

The Americans are off to a disappointing start. They’ve won two golds but have no other medals, having already finished fourth — just off the stand — four times through the first eight finals, along with a fifth place.

Eric Shanteau, who put off cancer treatment to compete at the Beijing Olympics, was the latest to miss. He took fourth in the 100 breaststroke, failing to improve on his top qualifying time from the semifinals.

“The men are hurting right now,” Bowman said. “We need to get going. As a team, we’ve had a lot of fourth places that needed to be medals, and that’s not due to the suits. We need to step up. Where we have a chance to win, we need to win.”