Muscle building supplements are generally just powdered amino acids, which is again why I suspect that FM results in primarily amino-acid metabolism being used, rather than glucose metabolism.

And yes, FM is strange... It, and CFS, and a bunch of other things are what I'd class as "chaotic biochemistry" problems. "Normal" biochemistry has lots of swings and feedback loops, and the eventual result of those loops is a relatively stable configuration. What's clear is that something has broken the "normal" biochemistry loops out of the meta-stable configuration, into a "chaotic" configuration, where loops don't quite loop properly... Hence the butterfly-wing tornado effects. Straight out of chaos/complexity theory.

So "treatment", such as it is, is inherently going to be hit and miss, unless you happen across a magic thing which gets rid of whatever strange-attractor is screwing with the biochemistry.