Yam-powered Jamaican Bolt to strike again

It's Bolt's favoured event, and he predicted when he smashed his world record in winning the 100m that he would repeat the double last achieved by Carl Lewis in 1984.

The 21-year-old Bolt owns the three fastest 200m times this season, ran an effortless semi-final on Tuesday and joked afterwards he was only jogging.

"I was just trying to make sure I was in a good position, keeping an eye on the board and seeing where everyone else was," he said, but indicating Michael Johnson's world record of 19.32 seconds may be out of reach.

"I'm not really worried about the world record," Bolt said. "I'm just coming here to win. That's the aim for me."

Defending champion Shawn Crawford and 100m bronze medallist Walter Dix, both members of a US track team that has failed to excel in Beijing, figure as Bolt's main rivals.

Perhaps to catch up they may have to copy Bolt's eating habits with the Jamaican attributing his speed to his diet.

He dined on chicken nuggets before breaking the 100m world record here, and said his food staple when growing up was his mother's yam mash.

On day 13, one of the quietest days at the Olympics, there are ony 11 finals in six sports - athletics, sailing, open-water swimming, synchronised swimming, taekwondo and wrestling.

China continues to hold a commanding lead on the medal's table with 44 compared to 26 for the the United States and 16 for Great Britain with 94 finals remaining before the Games close on Sunday.

But none of the leading sports nations are likely to stop Jamaica getting its second Bolt gold and third of the Games in the day's feature event.

Russian open water superstar Larisa Ilchenko entered the record books as the first women's 10km swimming marathon champion when the sport made its debut on Wedndesday.

Ilchenko, unrivalled in open water swimming for the past four years, overtook Great Britain's Keri-Anne Payne in a sprint finish to win the gruelling event in just under two hours in the water.

South Africa's Natalie du Toit, the first amputee to qualify for the Olympic Games, finished 16th in the 25 strong field and pledged to be back in 2012 to do better.

"I don't even think about not having a leg and if I want to keep competing I will have to continue to qualify with the able-bodied. For me it's not about the disability at all," said du Toit who lost her left leg in a motorcycle accident seven years ago.

Yin Jian lifted China further ahead on the medal's table, winning the women's windsurfing, but the Games hosts had no luck in a preliminary round baseball match when crushed 17-1 by Cuba with the match called off in the seventh inning under the sport's mercy rule.

Sheena Tosta and Tiffany Ross-Williams front as the best USA prospects on the track in the women's 400m hurdles final,

BMX racing made its Olympic debut with American professional Mike Day coming out tops from the men's qualifying rounds.

The cosmopolitan last 16 will be composed of three Americans, two Australians, a New Zealander, a Colombian, two Latvians, two Dutchman, one Italian, Swiss, French and Argentine rider, and one South African.

The Games have been largely devoid of controversy, and the International Olympic Committee insisted Wednesday the low number of positive doping cases was proof they were winning their battle against drug cheats.

From 4,133 tests conducted, only four positive cases have been detected and only one involved a podium finisher - North Korean shooter Kim Jong-Su, a minor medallist.

Before the Games began, IOC president Jacques Rogge said he expected 30 to 40 positive tests.