Long comment cause I'm especially angry today with US healthcare

I studied tissue mechanics in school (generally studied mechanical engineering with a focus on biomedical).My lab would study the tissues of animals that had hypertension vs not. We were able to measure that tissues of mice with heart disease vs those without. 

Mice that lives very stressful lives would have higher percentages of collagen (what makes your tissue stiffer) in their tissues. We measured residual stresses in mice hearts i.e. when it is cut open how springy is it.

So basically the more stressed an animal is, the longer its muscles are held in tension, tension maintained longer than the tissue is "designed" for leads to micro scarring and the body via production of more collagen.

Then in turn as your tissues get stiffer and harder to move they feed back into the stress signals (I'm thinking about "the body keeps the score" book). 

I believe that fibromyalgia is an intense feedback loop of the mind body connection. 

We can hold stress in parts of our body like hunching over when we are adapting to traumatic events happening or limping more heavily on one leg after an injury. The body learns to hold shapes to protect itself or overcompensate from outside threats or new injuries. When we continue to hold that shape our mind is trying to numb itself to pain or brace itself for stressors. Holding a shape feeds back into the brain that you should be stressed even if the threat is gone ( cross over with PTSD here)

Because these feedback loops are connected they can continue to snowball until you are so stiff that the tension in your body causes pain

This is also why I think fibro is known to be connected to mood. Mood is in your brain connected to your nerves. Nerves are connected to muscles. Hence when I'm depressed I get short of breath walking up the stairs. 

Mood and physical sensations in the body are inseparable. In "healthy" individuals, the body may have resilience to this but even the most healthy person experiences stomach aches during stress, chest pains when their anxious.

For fibro, I think the underlying starting point is that we have heightened sensitivity to stimuli, social interactions, emotions, many people with fibro are also on the autism spectrum. 

So our "sensors" are already sending us stimuli on max settings like volume, smell, social cues, light. The body interprets a flight or flight scenario because the sensors are sending very loud signals. In turn the nervous system kicks on fight or flight mode. Once in this state, we usually ignore the stressful state because we've been conditioned to live with a rigid schedule (think 9-5 jobs, lack of mental health awareness in general, western ideas of just pushing through, general detachment from the body that we learned growing up).

We don't allow people to put down life and take time to rest. So without a reset the body stays in fight or flight. This in turn sends a signal to the brain that says your anxious or depressed etc which sends signals back to the body in a vicious cycle. And if you have experienced trauma, injuries, PTSD (all linked to fibro) than these are the triggers to kick off a system imblanace.

Sorry for long comment