Batman is a master warrior and all around tough guy, so he's easily able to handle the stress of his lifestyle, right?

Wrong, according to science.

E. Paul Zehr, a kinesiologist and author of popular science books Becoming Batman and Becoming Iron Man, lays out exactly what would happen to Bruce Wayne, even if he just went around beating up muggers every night instead of getting his back broken by Bane:

Every time we do anything our muscles, bones, skin and other tissues experience mechanical stress and mechanical strain. The biological tissues that make up our bodies are just like lots of other materials. With extended use they can weaken. And it all accumulates over time.

In other words, unless Batman takes long breaks between fights, and makes sure his training schedule gives him time to heal, his body will accumulate enough damage that essentially he'd get injured far more easily than your average couch potato.

On the other hand, your average couch potato isn't Batman, so...