I'm 15, and I've been working with weights for a little while now, before now I was just doing body weight workouts and running. I started lifting, dead lifts, power cleans, push-presses, and BOR's, on Thursday. Saturday was a 4-mile competitive run, so Friday was a rest day, and I did nothing strenuous on Friday, and my back was a little stiff. Saturday after the race my back hurt, not a lot, but enough to where I couldn't keep god form when hitting the heavy bag, so what can I do, or what do you do if this happens? Am I doing it with improper form? What are some exercises to strengthen that area of my body to prevent this from happening? Any advice from you all helps, thanks.