Does anyone have times where your arms and legs suddenly feel like cement, and you can't move? I've had fm for about 18 months, and one of the first things I noticed was that my muscles felt like they were going to give out (and sometimes they did and I couldn't walk). No doctors have really addressed this problem. Any suggestions as to what it is or how to stop this from happening? My fm was triggered by a whiplash in a car accident.