Athletes 'suspect' Russian doping
Wales' former hurdles world champion Dai Greene, 28, says fellow athletes suspect their Russian counterparts of cheating, describing doping allegations as "disturbing".
A German television documentary has claimed to present evidence of systematic doping in Russian sport.
The president of the Russian Athletics Federation has threatened legal action against "the slanderous allegations".
The claims do not surprise Greene: "My first thought was, here we go again."
"The athletes that have been successful for Russia in recent years, many of them who are going to be implicated in the scandal, I think athletes in general knew," he added.
"You'd know as athletes who you suspect because you don't see them on the circuit, you see them maybe just at championships.
"They train and compete maybe just in Russia all year and then all of a sudden they turn up at major championships and they're one of the best in the world.
"You have to be very sneaky to catch these people. The current testing regime isn't good enough. It's all very disturbing."
The German documentary, broadcast on Wednesday, also contended that the corruption extends beyond Russia and alleged that the International Association of Athletics Federations (IAAF) could be involved in a cover-up.
The IAAF said it had "noted a number of grave allegations" and revealed that an investigation into some of the claims is "already ongoing".
The BBC has not independently verified the documentary's allegations and is awaiting responses from athletes targeted in the programme.
The claims have been rejected as "a pack of lies" by Valentin Balakhnichev, president of Russian Athletics Federation, who said in a statement on Friday that the documentary was "a planned attempt to create an ugly scandal within Russian athletics and Russian sport in general".