When Arnold Schwarzenegger admitted to steroid use (http://en.wikipedia.org/wiki/­Arnold_Schwarzenegger#Steroid_­use), he said it was about muscle maintenance, not muscle growth. Regardless of whether you believe him, he does bring up a good point. Tennis players put tremendous strain on their bodies. Doping would be most effective when reducing recovery time between tournaments. This is also the real danger - constant touring encourages doping, rather than prime time performance.

An interesting perspective, but ultimately, size and strength are increased. Body builders do not compete with strength.

Tennis requires a different set of attributes than power lifting, but strength is important. A tremendous amount of strength is required to cut corners and change direction of travel.