My understanding is that fibromyalgia is the nerves in the muscles and RSD is the communication between the brain and sympathetic nervous system. When I overdid exercies (lunges; same as I had done b4 RSD) I had more than soreness in my muscles; I felt like someone had taken a cheese grater to the ones in my thighs. I couldn't move for 3 days. With RSD, I have burning and stabbing pain in random places of my injured side. Hope this helps a bit. Prayers.