My husband survived a mild case of polio, and I watch for signs of post-polio syndrome. He has struggled with coordination ever since the polio, and I notice that his handwriting is deteriorating. He is also more fatigued. I am convinced that post-polio syndrome and fibromyalgia are two very different things.
As for fibro being an overdoer's disease, I'm not sure. There are mitochondrial factors, RNA factors and more that are physical puzzlers. I ask myself why one person can be an overdoer and end up with fibro, but another overdoer does not. This is just my guess, but perhaps there is a physical predisposition to fibro that does not manifest until it's ready to show itself.