In 1996 I took my game on the road and played throughout the USA. I was playing 6 to 10 hours a day sometimes more, a lot more or over six months and had to return home due first to frozen shoulder in my right arm. I'm right handed. I attributed this condition to my Nine Ball break. I was hitting them very hard.
The doctors took x-rays of both shoulders and determined I had an abnormality in the formation of both and with rest I should be okay. A regiment of steroids and physical therapy helped to loosen the shoulder after a couple months but there was no way I could play pool during this time.
I later developed an impingement in my left shoulder. This was anticipated if I continued to play pool. In my case due to the irregular development of my shoulders and the extending of the left arm over the head was the culprit. When leaning over the table this is the position of the arm in relation to the shoulder. The pain associated with this ailment was unbearable. I required surgery, steroids injections with lidocaine, two months of immobilization in a sling, and several months of physical therapy to return my shoulder to normal. To this day any extensive Nine Ball play while breaking the balls with power will cause my shoulder to ache.
Thank God I'm primarily a One Pocket player!
Cheers and good luck,
Tom