Probably a dumb question, but why aren't wrestlers constantly covered in bruises?  Fake or not, they still hit things awfully hard if for no other reason than gravity. If I even tried something as simple as running the ropes I'm pretty sure my back and sides would be black and blue the next day

I think it comes down to "learning to fall" and spreading out the force of the impact over a larger area.  Lots of times you DO see guys with bruises on their back and legs from a particularly stiff match against someone like a Low-Ki who kicks you hard for fun, but really WWE rings have been softened for the better to the point where there's probably not a lot of focused damage to parts of the body specific enough to cause bruising.  Plus often when guys get bruised up from an Elimination Chamber or whatever, they'll get a day or two off to heal up or just hide it under a suit or shirt or whatever.  The sport really has gotten 1000 times safer even since the 80s, for as much s--- as we give the PG era.