Training tip: Many shoulder & back injuries are related to tightness of the thoracic spine. Try this--Reach your right hand overhead and down your back as far as you can while reaching your left hand up your back as far as possible.
Can you touch your hands together? Are you even close? If not, it’s more than just your shoulders that are tight – your thoracic spine is stiff.
The thoracic spine (T-spine) is the area around your mid- to upper-back that’s built for mobility. When it becomes tight, it limits your shoulders and cause shoulder pain.
To open the T-spine, try exercises like these:
2) Lying Diagonal Reach
3) T-Spine Extension on a Foam Roller: I like this whole video for all his demo exercises,
4) Quadruped T-Spine Extension