Lon­don–For­mer world 200m cham­pi­on Ato Boldon says he has sym­pa­thy with ath­letes who fail drug tests by tak­ing sup­ple­ments.But for­mer 100m Olympic and world cham­pi­on Dono­van Bai­ley in­sists there can be no ex­cus­es for ath­letes tak­ing banned sub­stances.Fol­low­ing sprint­ers Tyson Gay and Asafa Pow­ell test­ing pos­i­tive for banned drugs , Boldon said: "An ath­lete does not have a de­gree in phar­ma­col­o­gy."But Bai­ley said: "Ath­letes must know what is on the 'banned' list."And he added it could be time to con­sid­er life bans for those caught tak­ing banned sub­stances.

The Cana­di­an, who will be a BBC Ra­dio 5 live sum­maris­er for the An­niver­sary Games and World Cham­pi­onships, said: "Ul­ti­mate­ly it could be the new false start rule–it doesn't mat­ter who you are, if you false start out of the blocks, you're out."

It is not known which sub­stance Gay, the fastest man in the world this year hav­ing run 9.75 sec­onds, has test­ed pos­i­tive for–that should be con­firmed af­ter the re­sult of analy­sis of his B sam­ple.

Pow­ell, who has clocked 9.88 this year, was test­ed at the na­tion­al tri­als in June and re­turned an ad­verse find­ing for ox­ilofrine (methyl­synephrine), a stim­u­lant that boosts fat-burn­ing.Boldon said it was im­por­tant to make a dis­tinc­tion be­tween blood-dop­ing and "peo­ple try­ing to push the en­ve­lope with their sup­ple­ments".He added: "An ath­lete is trust­ing of the per­son he is buy­ing the sup­ple­ments from, or the coach, or who­ev­er is pro­vid­ing these sup­ple­ments."When you lis­ten to Tyson, he is say­ing he put his faith in some­one and they let him down. That says to me, OK some­body told me you can take this and it will be fine, there will be noth­ing to cause you to have a pos­i­tive test–and ob­vi­ous­ly that was not the case."

Bai­ley, who won Olympic and world 100m gold medals, and has held the 100m world record, has a ze­ro-tol­er­ance pol­i­cy on drug-tak­ing.The 45-year-old said: "Every sin­gle ath­lete is giv­en a banned list and they should look care­ful­ly down it."When mon­ey is in­volved you are go­ing to have cheats, peo­ple who push the en­ve­lope. We are in a sport where one thou­sandth of a sec­ond can be the dif­fer­ence be­tween suc­cess and fail­ure."Ath­letes who take drugs tend to be in­se­cure. They don't be­lieve they have the phys­i­cal and/or men­tal ca­pac­i­ty to do great things so they take an­oth­er route–the phar­ma­ceu­ti­cal route, if you like."On Gay claim­ing he was let down by some­one he trust­ed, Bai­ley added: "You don't go to an ath­let­ics meet­ing to watch the train­er, coach or masseur run a race. The onus is 100 per cent on the ath­lete to take re­spon­si­bil­i­ty for any sub­stances go­ing in­to their body."Boldon sug­gest­ed stim­u­lants and sup­ple­ments are here to stay and said it was naive to think they could be banned. He added: "I think the prob­lem is in try­ing to push the en­ve­lope and get to the edge, sev­er­al of the top names in the sport are falling over the edge."