I have a client and a couple of gf’s who suffer from this. They found that swimming, aquatics, and just walking/cycling was the best type of work out.
It’s difficult for people who want to lose weight and have fibromyalgia because of the pain of even using their own body weight or (light weights, constanting moving, cardio work outs). My client also has diabetes type II so it causes swelling on his legs when he is standing for moderate to long periods of time. I have transitioned him over to training in the water due to this.
I have clients with it and know a good number of people with that condition. The one consistent thing I found is that there is no consistency. What works for one person may be wrong for the other. Often a gentle approach with light weights, water and stretching is great, and then you meet somebody who will tell you that only the hard foam roller will do it for them.
I have also noticed that FM is often in the company of anxieties and depression. FM can easily run a person’s life. It is a very multi-faceted condition where one size does not fit all.
The one thing, though, that seems to apply to all is the need to exercise. It is important to encourage clients to listen to their bodies. They may be able to do more one day than another. It requires a great deal of flexibility on the part of the trainer but also understanding and patience.