I know any kind of exercise can incite a flare but since I started doing Tai Chi (beginner) where you gently move your body and dont push it I have been able to breath better and face the day better. It dosnt seem to aggrevate my TOS...there are some things in the video I cant do yet but mostly it helps..maybe some kind of thoracic strech you could do to loosen those muscles up a bit without making the TOS worse. Also some kinds of medicine can cause muscles to tense. I know this from experience. Check side effects of your meds and see if its not a possiblity...Amy