When I was in boxing, we used to push ourselves doing a drill that made us punch a lot non-stop and rest for 30 seconds, then jump back in and punch the heavy bag. After about 2 minutes I my muscles felt dead and I had only 10 percent power in my punches. So my question is, does lifting weights promote this burnt-out feeling? And how do I improve on this? Also: Whenever I try a lead side kick I think I explode too hard and it feels like a bone in my knee seperates from the rest; however, there's no pain. When this happens there's a crack or a popping sound, but I read that being explosive in mma, especially boxing was a good thing. Just asking because I'm afraid of getting tendonitis or a condition with my joints.