Ya I have noticed at times some pain. When it's in my wrists it is almost always the result of hitting the bag at an odd angle. I've been working on positioning my punches better and haven't had that problem lately. My knuckles occasionally feel sore so I'll generally give them a days rest between workouts. I'll have to try the knuckle pushups, sounds like a good idea. I've been doing regular pushups and I had felt some weakness in my wrists so I'm working on building that up too. The books thing is probably a good idea too. A lot of the technique I have now I learned on the internet. Proper stances, best position to punch at. My friends say my punch has gotten more powerful, I can even hit my 250lb friend hard enough to make him lose his balance and almost fall down.