From Ben Johnson to Marion Jones, the world of sprinting has been blighted by numerous high-profile doping scandals.u00a0Its reputation was further sullied following Sunday’s startling revelations of positive tests returned by two of the four fastest men in history, Tyson Gay and Asafa Powell. Here AFP looks back at some of sprinting’s most notorious drug cases:

Tyson Gay (right) and Asafa Powell celebrate after the mens 100 metres final during the British Grand Prix at Gateshead International Stadium on July 10, 2010. PIC/Getty Images