Pistorius, 25, Is First Double-Amputee Sprinter to Compete in Olympic Games

Aug. 4, 2012— -- South Africa's "Blade Runner," Oscar Pistorius, has made good on living up to his other nickname, "the fastest man on no legs."

The four-time Paralympic gold medal winner, 25, qualified for the 400-meter semifinals Saturday, making him the first double-amputee sprinter to compete at the Olympics. He runs on prosthetic legs called Flex-Foot Cheetahs.

Pistorius came in second in his heat, surpassed by Luguelin Santos, 19, of the Dominican Republic. Pistorius ranked 16 in the standings out of the 47 runners who finished their heats Saturday. Twenty-four sprinters advanced to the semi-finals Sunday looking to reach the Monday finals for a chance at Olympic glory.

"Thank you to everyone who has supported me, that was UNBELIEVABLE! Was so amazing to feel the energy from the crowd! Semi-final tomorrow! :)" he tweeted to his followers after the heat.

He ran a seasonal best of 45.44. The 400-meter Olympic record is 43.49, set by American Michael Johnson in 1996 at the Olympic Games in Atlanta.

Pistorius' journey to the top can only be described as miraculous. After he underwent amputation surgery when he was 11 months old, he received his first pair of prosthetic legs at 17 months.

According to his website, Pistorius took up running to bounce back from a rugby injury at the advice of his doctor when he was 16. The next year, he competed in his first Paralympic Games in Athens in 2004 and won a gold medal in the T44 200-meter race, breaking the existing world record in the event where single below-knee amputees and other athletes with equivalent impairments compete.

Of his semi-final qualification at the London 2012 Games, Pistorius took to Twitter to say it felt "surreal."

Additional reporting by ABCNews.com's Kevin Dolak.