Appropriate for the Olympics season is this very interesting piece from Scientific American, "Magic Blood and Carbon-Fiber Legs at the Brave New Olympics," in which Daid Epstein addresses some of the same questions I considered in "Cheating is the American way" way back in 2012.
Epstein's answers? He doesn't have any, any more than I did. In addition to drugs, athletes have available performance-enhancing biomechanical limbs and genetic manipulation and high-tech training kit available. ("Well-endowed" these days refers to one's training budget.)
No set of rules can accommodate all the possibilities; better to abolish rules altogether, and may be the best, well, whatever win.