At the other place I started a thread (Feeling very heavy - symptom that rarely gets mentioned) with this post: " I have come across anecdotal mention of this symptom but never seen it included in any diagnostic criteria I can remember. It is something that I regularly experience a lot, particularly as part of PEM. At the very beginning, I struggled to push the duvet off me in bed. Nowadays, it is a sure sign that I am overdoing it as everything becomes much heavier. My whole body, particularly my legs; anything I try to lift feels as if it's quadrupled in weight. It's as though someone has increased gravity. I'm 5'6 and weigh 8stone but at times it's like I'm more than twice that. Just wondered how common it was and what reason there might be for it?" I think 'lead limbs' (or something like that) is included in Jasons PEM diagnostic questionnaire. But I was thinking about this again. When I am in bed I sort of can tell how good/bad I am depending on how heavy the duvet feels (particularly in the morning/when I wake up). So I am not talking about heavy limbs after 'exercise' or 'mollasses fatigue'. I just wondered if maybe this 'symptom' could be used (particularly in the severe/very severe) to gauge severity/fluctuation/PEM. Not sure how.