I'm with l00p in thinking that there have been some artificial muscle producers in Nadal's past, but I don't know if I would say he is still using.
However, either way, if they test for stuff in the future, I don't think that Nadal will have a long career because I think his body won't be able to hold up without assistance.
He has more nagging injuries than people say Djorkealkgthoith has.