Phelps - Doping or gifted ?

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After Tour-de-France doping affairs our confidence in sports achievments are not doubtless anymore. What do you think ? Is a person able to boost his accomplishment in a way Phelps is showing us right now ? Or is this only possible because of doping, the inspectors are not able to detect nowadays ? Can it be true that a person without chemical help is able to be the best olympic player all times ? Or is he just gifted ? What is you opinion ?