Anybody notice how when Nadal comes back from the hollies at the beginning of the year his biceps are 10X as massive as the end of the year before, then by July Wimbledon their all skinny again? Just sayin... Is juice legal in Spain?
My guess would be all of the additional cardio he has to do throughout the season. Ever seen a big marathon runner? All of the running he is doing while playing and training will eat the muscle off of anyone.