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On Thursday, Lausanne will host the 100m showdown between Justin Gatlin, Asafa Powell and Tyson Gay.

All are contenders for World Championship gold, but they've also all served drugs bans. All deny any intention to cheat. While Powell, whose six month ban was the shortest of the three, proved his failed test was down to a batch of contaminated supplements, Gay, who admitted using creams containing testosterone and human growth hormone, says each case is different and, unless that's explained, the sport will suffer.

Tyson Gay's been speaking to our Athletics Commentators Ed Harry.

(Image: Tyson Gay. Credit: Getty Images)