I have HMS but don't have too many problems - just the 'usual' aches and pains that are pretty much constant. I went to a spa recently for a treat, and the masseur was amazed at how tight my back and shoulder muscles were - in her words, my back was 'like a rock'. She kept asking if I worked at a desk (no) and if I was under a lot of stress (no). She ended up working on my back for then entire hour instead of the 'whole body massage' I had originally booked!
I was wondering if my back muscles were tense from holding my spine in place - and if that was really a bad thing. The masseur thought it wasn't good, but then she did admit she didn't know anything about HMS. I have pretty much constant lower back pain anyway.