I think what Scrap is saying makes sense CC.

I have upper back pain which I didn't get a few years ago.

Now I can only work bags which are moderately hard or soft - not the real old school hard one in my gym because the jarring goes up through my arm straight into my neck.

I never had this problem before I began to have back pain and i think stretching out those tight muscles so they have a bit more give could help.