Extension Arm For Light Get Back Extension?

Get back extension? - extension arm for light

dislocaited me a few years ago, and after the rupture of humor, I was in plaster for a few months .. and went to physical therapy, then told me to weight is very light, blah, blah, blah, poor ... if it does not really listen, because he wanted to play sports .. but now my arm is much weaker, and it is my dominant arm .. I followed the sport for sport and play sometimes with friends .. it starts to hurt .. and not working well, as before, and I'm young .. So I am not my whole life .. and suggestions.