I would like to suggest a reason why fluoride poisoning could cause fibromyalgia especially in the case of muscle injury caused by severe overexertion or severe muscle trauma.

Suppose someone is ingesting an amount of fluoride that the body is barely able to deal with. Then the person suffers a severe muscle injury. How could this cause fibromyalgia? If the muscle injury caused a significant decline in kidney function, it would allow for a greater buildup of fluoride in the body, because the kidneys are the main way that the body (slowly) rids itself of fluoride. Check out this link which has to do with exertional rhabdomyolysis in horses. I would like to point out that rhabdomyolysis (would it be fair to call it muscle disintegration?) and kidney damage are both known side effects of fluorine containing statin drugs. Maybe fibromyalgia sufferers wake up feeling so beat up, because they have been - only on a wide-spread but micro scale:

http://shady-acres.com/susan/tying-up.shtml