South Africa’s Oscar Pistorius prepares to start his men’s 400m round 1 heat at the London 2012 Olympic Games at the Olympic Stadium

South Africa's Oscar Pistorius walks on the track prior to his 400 meter heat. (REUTERS/David Gray)

South Africa’s Oscar Pistorius walks on the track prior to his 400 meter heat. (REUTERS/David Gray)

South Africa’s Oscar Pistorius prepares to start his men’s 400m round 1 heat at the London 2012 Olympic Games at the Olympic Stadium August 4, 2012. REUTERS/David Gray (BRITAIN – Tags: OLYMPICS SPORT ATHLETICS)