Cool and calm under pressure, Aaron Peirsol rose to the big occasion yet again to become the first man in 36 years to retain the Olympic 100m backstroke title.

Slower than his rivals in the early rounds, Peirsol utterly outswam them in Tuesday's final to lower the world record for the fifth time and emulate Roland Matthes of the old East Germany, the last man to win the event twice, in 1968 and 1972.

Peirsol, who picked up the Olympic 200 backstroke silver medal at 17 in 2000, showed his powers were undiminished by carving 0.35 sec from his own world record to win by more than half a second in 52.54.

Aaron Peirsol of the US wears his gold medal after winning the men's 100 meters backstroke swimming final during the Beijing 2008 Olympic Games August 12, 2008. [Agencies]

A golden backstroke double at the 2004 Olympics and six individual world titles on, winning has lost none of its appeal for the 25-year-old American, who admitted he had had doubts after his rivals had performed so strongly in the semifinals.

"It never gets old. It really does feel like the first time. It's an absolutely beautiful feeling," he told reporters. "I'm absolutely elated with how everything went."

Matt Grevers, sitting beside Peirsol after taking the silver, analyzed the strengths of a team mate, whose only significant reverse in the last seven years came when he lost his 200 world crown to fellow American Ryan Lochte in 2007.

"I don't know if it's shoulder strength or what but the amount of water he's able to hold is unbelievable and obviously he's got the right mind for it," Grevers said.

"He's always up to race and he always performs when it matters. I think altogether that makes him a great performer, better than the rest of the world, obviously."

Peirsol faces his next challenge in the 200 backstroke in which victory would make him the only man apart from Matthes to win both Olympic backstroke titles at two Games.

"It doesn't get any easier, to be honest, but certainly the experience and the knowledge that you've done it before helps, knowing hopefully that you can probably do it again... I really wanted to race today," he said.

"I train to pretty much win on my worst day and that's the kind of mentality I use. Honestly, I don't know what goes on in these others guys' heads. I know what I have to do to get my hand on the wall and to do what I have to do."