[nanomonkey]

Umm...have you had a broken leg? Sure, it needs to be immobilized (set and put in a cast). But after that you're body does all of the work, which requires proper nutrition. And then after that you need a great deal of exercise to rebuild muscle and relearn neural musculature control.

But more to the point, a well trained body will hardly ever get into a state where it needs medical attention. Most broken bones are due to poor muscle control and lack of strength later in life (think hip fractures). This can be mitigated by strength training that involves similar dynamic movements.