My shoulder pain is chronic, related to injuries resulting from Tennis and Baseball (old injuries from years ago). I have been fitted to my bike and have raised my handlebar level with the top of my saddle to lessen the pain. It takes a while for the pain to show up and it may be due to weak core muscles as Allegheny Jet has suggested.
I asked about the effect of fitting a carbon handlebar as I understand that carbon offers a better ride than aluminum and thought that it might be beneficial in alleviating my shoulder pain. From your answers it seems that it may have no effect on this condition. I believe I will concentrate on strengthening my core muscles and pay closer attention to my riding posture. Jim