Static and dynamic functional connectivity in patients with CFS...

[RogerBlack]

You can't conclude that from your experience. I do not share your experience at all, and do not get muscle pain from mental exertion.

Still, your experience could be explained by depletion of the ATP pool (your brain gobbles up a lot of energy) and increase in oxidative stress. Or, the stress of having to focus in a low energy scenario could lead to muscle tension.

I do not tense up when thinking hard.
I should have been clearer - there are certainly multiple different subtypes of ME/CFS.
As to ATP - no.
There is 'no' circulating ATP in the blood - ATP is generated in each cell. My blood glucose is normal during a crash.

 

[Woolie]

Yeah, my cognitive crashes are confined to cognitive and neurological symptoms. I can't think straight, but I'm not getting muscle pain from it, etc. Conversely, my physical crashes hit me cognitively as badly as the cognitive crashes do.

That's pretty much my experience too, @Valentijn. Physical exertion causes cognitive fatigue for me, but cognitive exertion doesn't cause physical fatigue, its confined to cognitive stuff.