Jamaican sprinter Usain Bolt has raced to the second fastest 100 m ever with a superb 9. 63 s. He is the first man to win back to back Olympic titles on the track. The brilliant display silenced the doubters who predicted his hamstring problems would open the door for his rivals in one of the most eagerly anticipated races in history. World champion Yohan Blake made it a Jamaican 1-2 when he won silver. 2004 Olympic champion Justin Gatlin of the United States grabbed bronze. Asafa Powell pulled up a groin injury near the end to ruin a potential Jamaican sweep. Bolt now stands alongside Carl Lewis as the only men with two 100 m golds. Meanwhile, Oscar Pistorius who made history as the first amputee to participate in a track event at the Olympic Games, only managed last place in his 400 m semi-final. Pistorius finished in 46.54 s, more than a second slower than his qualifying time on Saturday. His semi-final was won by Grenada’s Kirani James, last year’s world champion in 44,59 s. Pistorius bowed out waving to the crowd in gratitude for their support. The 25 year old will take part in the men’s 4 x 4 relay on Thursday.