By Laura Smith-Spark, CNN
LONDON (CNN) – Olympic athletes and spectators are set for the biggest day of action yet at the London 2012 Games, with 25 gold medals up for grabs in 11 different sports on what has been dubbed “Super Saturday.”
The world’s fastest man, Jamaican sprinter Usain Bolt, got his 100-meter campaign under way on day eight of the Games, in front of a packed stadium. After what he described as a poor start, he strolled over in 10.09 seconds — good enough to win his heat.
He faces a challenge from teammates Yohan Blake, who has stolen some of his thunder this year and won his heat in 10.0 seconds, and Asafa Powell, who also crossed the line first in his race.
It was also a good morning for Team USA, with Justin Gatlin and Ryan Bailey getting off to a scorching start, each with sub-10 second times, while teammate Tyson Gay also won his heat.
Judging by the heats, spectators can look forward to lightning-fast 100-meter semifinals and finals Sunday.
But former 100-meter world champion Kim Collins of St. Kitts and Nevis did not run in the heats after apparently falling out with his team over seeing his wife.
The sprinter, who carried the flag for the tiny Caribbean state at the opening ceremony, tweeted: “My fans. I won’t lie. Won’t be running later tonight.” In another tweet, he said: “Even men in prison get their wives to visit.”
The St. Kitts-Nevis Times said that on Facebook Collins had written: “Hours before my 5th 100m olympic race, i now find out i cant run, all because i was in a hotel with my wife/coach.”
Jamaicans Shelly-Ann Fraser-Pryce, Kerron Stewart and Veronica Campbell-Brown run in the women’s 100-meter final Saturday night, going for gold against American Carmelita Jeter.
Also on the track, double-amputee sprinter Oscar Pistorius, who runs on special carbon fiber blades and is nicknamed “The Blade Runner,” came an impressive second in his heat of the men’s individual 400-meter race, qualifying for Sunday’s semifinals.
He is the first person to compete in the able-bodied Olympics using prosthetic legs — and he will also compete in the Paralympics later this summer.
The four-time Paralympic Games gold medalist, whose legs were amputated below the knee when he was 11 months old because of a bone defect, has also been named in South Africa’s 4×400-meter relay team.
In a disappointment for the Americans, though, defending 400-meter champion LaShawn Merritt pulled up injured in his heat.
The home crowd is cheering on Jessica Ennis, seeking gold in the heptathlon after a strong start Friday. After high scores in long jump and javelin Saturday, she is well placed to take a medal after the final 800-meter run.
Over on Centre Court at Wimbledon, Serena Williams won Team USA’s second gold of the day in the Olympic women’s tennis singles, making it look easy as she beat Russia’s Maria Sharapova 6-0, 6-1.
Earlier, Victoria Azarenka of Belarus beat Russia’s Maria Kirilenko to take bronze in the women’s singles.
The men’s doubles final also takes place Saturday, pitting top-seeded American brothers Bob and Mike Bryan against the French pairing of Michael Llodra and Jo-Wilfried Tsonga.
The Team GB duo of Andy Murray and Laura Robson won through to the semifinals of the mixed doubles, also to be played Saturday, a day after Murray defeated Novak Djokovic to earn a place in the men’s final Sunday against Roger Federer.
Team USA claimed its first gold medal in a shooting event Saturday, as Jamie Lynn Gray set a new Olympic record in the women’s 5-meter rifle three positions.
Meanwhile, the International Olympic Committee announced the exclusion of Russian cyclist Victoria Baranova and provisionally suspended Colombian 400-meter runner Diego Palomeque Echavarria, pending further analysis, after they tested positive for banned testosterone.
There was an early gold to celebrate at Eton Dorney for Team GB’s rowers in the men’s four, defending their Beijing title, with Australia second and Team USA taking bronze.
Another gold for the home nation swiftly followed, with an emphatic victory in the women’s lightweight double sculls for Sophie Hosking and Katherine Copeland. China took silver and Greece bronze.
Denmark stormed through in the last 100 meters to beat Team GB to the gold in the men’s lightweight double sculls, leaving the British duo visibly devastated. New Zealand took bronze.
Gold in the women’s single sculls, the last rowing event of the Games, went to the Czech Republic’s Miroslava Knapkova after a commanding performance, with Denmark taking silver and Australia bronze.
Later Saturday, U.S. swimming legend Michael Phelps will swim in his last race, as part of the U.S. men’s 4×100-meter medley relay team. He promised to retire after this competition.
On Friday, he clinched the 100-meter butterfly to capture his third gold medal of the London Games and the 17th gold of his career.
Phelps wasn’t the only American to make history in the pool Friday. Missy Franklin, 17, from Pasadena, California, earned her third gold medal, and fourth medal overall, in the women’s 200-meter backstroke, smashing the world record in the process.
Another American teenager, 15-year-old Katie Ledecky, also earned gold in impressive fashion, besting her nearest competitor by more than four seconds in the women’s 800-meter freestyle.
The women’s triathlon started Saturday morning with the swim in the chilly waters of the Serpentine, a lake in the middle of Hyde Park more usually home to swans, followed by the cycle and run elements on the roads around the park.
Switzerland’s Nicola Spirig won the gold after a photo finish with Sweden’s Lisa Norden, who was just squeezed into silver, while Australia’s Erin Densham took bronze. Great Britain’s Helen Jenkins went into the race one of the favorites but only managed fifth. Team USA’s Sarah Groff came in fourth.
Early rain left the tarmac slick, bringing unwelcome drama in the form of crashes to the cycle stage.
The scandal-hit women’s doubles badminton comes to an end with a Chinese duo playing for the gold medal — but not world No. 1 pair Yu Yang and Wang Xiaoli, who were among eight players expelled this week for trying to lose their matches to get a better draw for future rounds.
The gold medal contest pits China’s Yunlei Zhao and Qing Tian against Japan’s Mizuki Fujii and Reika Kakiiwa. Russians Nina Vislova and Valeria Sorokina beat Canadians Michelle Li and Alex Bruce to take bronze.
Medals also will be awarded Saturday in the women’s singles competition, where three of the four contenders are from China.
The United States’ excellence at the Aquatics Center helped them pass China for the most gold medals on Friday. Americans have 25 golds and 46 medals total, compared with 43 for the Chinese.
Great Britain has rocketed up the medal count chart, thanks to one of its athletes’ best days yet on Friday and the Saturday rowing competitions. The host nation brought its gold medal total for the Games to 10, the third highest among the nations.
CNN’s Steve Almasy and Dominque Van Heerden contributed to this report.