Are you able to get some hands on massage or trigger point work to help release the muscles along with the injections?
Can you do some very gentle stretches and range of motion without it reactivating the flare ups?

I have found that posture awareness and working towards better posture for my upper body does help.
If I let my shoulders roll forward or let my head jut or tilt forward - my neck muscles & upper back pay for it.
I can feel the tightness start in my pec muscles too- they will shorten and tighten and the back muscles will lengthen and weaken.

useful threads/posts -
http://neurotalk.psychcentral.com/post87845-18.html
http://neurotalk.psychcentral.com/thread55183.html
http://neurotalk.psychcentral.com/thread43297.html