GOLF? Why would any golfer be doping?
Anyway, back to the subject. I don't think doping is that big a problem in tennis, though once players start putting in abnormally hard work into what they do then accusations start floating around. I personally believe that hard work coupled with a healthy diet can get you pretty far, even as far as the top guys are. One must also remember that not every person is built roughly the same genetically. One guy has an easy time getting all muscly and buff like Nadal while a guy like Federer is more of the lean type. Heck, all the Roman gladiators had were dried fruits, beans and cereals, and once (if) they won, their super-buff (or rather thick as they actually were, but still muscly) bodies would let them have fun at orgies later (that might get cleaned up by TT mods).
Also Senti, I read somewhere a while ago that the long distance thing was a genetic thing, probably due to adaptation and spending time on high altitude or something. Makes me wonder why I'm not that great of a long-distance runner being 50% African...