Drugs in Sport

Correct Shoco, this is known as microdosing, where lads take small amounts of banned drugs, carefully calibrated with the aid of dieuretics (also usually banned) to make sure they are clean before a race. The trick isn't to overload on the drugs, or peak at a certain time, it is keeping it just the bare minimum below the legal amount, and maintaining it at that level, so that any improvement will probably be small and can be explained by a remarkable consistency when the accusations start flying. 

Farah, probably guilty, but sure even if he isn't, one or 2 of his competitors will be soon, as they can't beat him as things stand, and somebody will get fed up of it & go for the next step. I don't really know or care much about Farah, but the whole Gatlin thing is just a massive piss take, athletics version of cycling's Chris Horner. Losing battle I'm afraid & always will be, but we could really do without the piss takers if we want to be someway convincing that the competition is even. 

some people call it marginal gains

Do ye think this hasn't already happened ?? 

Start by taking a look at the line up from the 1992 100M mens final in Barcelona, not that is it the only single race of obvious dopers in history or anything, but it firmly resides in the piss taking category of drug taking. A bunch of lads who wouldn't look out of place in the WWE running sub 10 second times.