Rio Olympics: Usain Bolt Fires Starting Gun on Games Super Saturday

Usain Bolt strode calmly through the 100m preliminaries on Saturday as Michael Phelps prepared to take his final Olympics bow on a bumper Super Saturday at the Rio Games.

Britain's women's team pursuit cyclists set a sizzling world record and Juan Martin del Potro won a thriller with Rafael Nadal to reach the men's tennis final.

Day eight in Rio had 21 gold medals on offer, including the climax of the swimming competition and the heptathlon, men's long jump and men's 10,000m at the Olympic Stadium.

It will be the last day of any Olympics with both Bolt and Phelps in action, with the Games' two top stars insisting they won't be extending their careers to the Tokyo 2020.

Russian athlete fights ban

Behind the scenes, there was more controversy as Darya Klishina, dope-tainted Russia's only track and field competitor, fought a late ban by world body the IAAF.

Bolt stole the show at the athletics as he glided smoothly past the field to win his opening 100m race, looking across the line at his straining competitors as he crossed the line.

"I'm feeling good. I'm happy," said Bolt, after launching his bid for the 'treble-treble' -- winning 100m, 200m and 4x100m gold for three Olympics in a row.

"So now it's all about execution and getting it right when it comes to the finals."

Bolt-Gatlin showdown

Arch-rival Justin Gatlin, the fastest man this year, led the way at 10.01sec. Bolt was slower out of the blocks but easily ran down Bahrain's Andrew Fisher to clock 10.07.

Germany's Christoph Harting won discus gold to keep the title in the family after his brother Robert, the 2012 champion, ruined his chances by straining his back while turning off a light with his foot.

And Belgian pretender Nafi Thiam snatched a five-point lead over defending champion Jessica Ennis-Hill after the long jump to set up an exciting conclusion to the heptathlon.

Thiam long-jumped 6.58 metres to reach 5,018 points. British star Ennis-Hill only made 6.34m, increasing the pressure going into the final two disciplines, the javelin and 800m.

Appeal for calm

At the velodrome, Britain's Katie Archibald, Laura Trott, Elinor Barker and Joanna Rowsell-Shand smashed the women's team pursuit world record for the second time in 48 hours to take gold, beating world champions USA to defend their title.

And the Netherlands' Elis Ligtlee pulled off a shock when she won the women's keirin, beating Britain's Becky James with Australian legend Anna Meares third.

Brazil and Argentina's basketball captains appealed for calm among their rival fans before the visitors won a gripping and tightly guarded contest 111-107 after double overtime.

Murray in final

In tennis, Andy Murray shrugged off a code violation for directing the word "stupid" at the umpire to crush Japan's Kei Nishikori 6-1, 6-4 and move one win away from becoming the first player to win back-to-back Olympic singles titles.

The world number two and reigning Wimbledon champion will face the resurgent Juan Martin del Potro, who edged 2008 champion Rafael Nadal 5-7, 6-4, 7-6, (7/5) -- after knocking out world number Novak Djokovic in the first round.

Olympic rowing ended on Saturday with Great Britain winning the men's eight gold to top the medal table for the third successive Games.

Doping controversy

Doping controversies continued to cast a shadow as long-jumper Klishina, the only Russian track and field given leave to compete, was handed an 11th-hour ban by world athletics body.

"I am a clean athlete," insisted the US-based 25-year-old, as she launched an appeal against the decision.

The Olympic spotlight will now switch to the final swimming battles where Phelps is expected to go out with a 23rd gold medal, in the 4x100 medley relay. It is an event the United States have never lost at the Olympics.