Remember how that doc diagnosed you with "Nintendinitis" back in the 1990's? Well, now he's got another fun "itis" for you. Yep, the Wii is actually so great that you can get a sports-like injury from it.
Personally, I see this as another great Wii selling-point; if it can provide the injuries of non-virtual athletics, it can also provide the physical benefits of non-virtual athletics. Heck, there have already been a number of stories on exercise benefits of the Wii.