hi all,
it became quite apparent to me that as the day wore on, my thoracic spine became tighter as more muscles went into spasm. one way i was able to control this time clock was when i started wearing a shoulder brace. before the brace it was a case of the more i used my affected arm the worse the thoracic tightness would get.
if i had a function that i had to go to i would place my arm in a sling to stop me using those muscles in my upper back that cause the thoracic tightness. other things that i found slowed down the onset were- not eating, laying on a bolster and using medication which stopped chest breathing.

best wishes towelhorse