I talked about it here
We've circled around adrenalin (epinephrine I think is usually the term for exogenous adrenalin) as a possible cause of PEM. I can't remember how much of this has been said before.
Exercise definitely increases adrenalin. Cognitive effort can too, especially if it is demanding or there is time pressure. Hot temperatures do. Being upright and not getting enough blood to the brain increases adrenalin.
And adrenalin activates CD8+ t-cells. It seems to result in an increase of them in the blood, followed by them going into tissues. I think we haven't quite worked out how the CD8+...
Exercise/being upright/heat/ mental exertion >adrenalin > activates t-cells >
activated T cells produce interferon, among other things that might contribute to PEM
There's a study in mice.
I'm happy to have it explained why it can't be a mechanism for PEM.
one thing I've been increasingly conscious of, both (I think) in creating PEM and when in PEM, is that there is the orthostatic and there is the just supporting one's own body - and in that the more upright but also if for example you have a supportive chair which supports arms, neck, back. My car seat for example is a pretty good fit, and is a best fit for supporting everything I need it to support if it is pretty upright, and stops doing so once recline and so I'd find I was better off with it being upright evne though orthostatic is sort of a big thing for me too.
I think* that this was a thing when I was less ill as by the end of a day in the office it was that desperate feeling of needing to rest my head on the back of the chair, and when I got home getting head and face supported by a pillow. I mention this because I'm conscious these days so many would assume it is just me 'being ill but having to be out of bed' or of course that ole deconditioning assumptions. But it was there, just slower to catch up with me, when I was having to live a life where noone sensible could have claimed it was a vicious circle of deconditioning because I was having to 'act normal' so claiming other healthy people who did the same as me were somehow free of this because they did more was nonsense (unless you were the type who assumed I was wrong in what I was saying)
I will say though that I definitely used 'momentum' (a term I'm stealing from
@Sean because it was spot on) in getting through any day where I wasn't at home. Whether that was adrenaline specifically I don't know but certainly I'd feel better walking that bit fast to get it done, and schzuzz it up vs doing it slowly sometimes, and if I couldn't sit I'd have to move (orthostatic issues) and that probably doesn't help that it was pushing through a sense of exhuastion and maybe sleepiness so keeping a bit focused if I could. On the other hand I'm not sure in
creating PEM that did me much good - hence why these trying to be clever 'how to manage fatigue' type documents we've started seeing that are giving out exactly this same advice I know is just making the problem worse/denying it (complete misunderstanding of what the issue is and using that short-term coerce people into performing x and 'see it's better' even though you know in your body what you are doing) longer-term.
So I'm kind of intrigued what kind of measures an app type thing could come up with that can distinguish the change in whatever it is that happens due to orthostatic and how some of us are having to then compensate it and the above (body wanting to slump and lie down) with things that stop us collapsing when we are in situations when we can't. And how if we can control for things and isolate these different scenarios and reactions how they relate to what PEM /later effect someone gets on another day.
And now of course when I'm more ill it is a case of when in PEM I
might be able to eventually get a little bit less than flat if I can get pillows supporting my whole body and limbs, and if on a better day then the clock starts when out of bed and it feels it runs down much much faster if I'm sitting and not supported vs maybe just a little reclined (but not enough to really make a difference to orthostatic, just gravity/weight) and very supported in all the areas I need.
As it would be quite likely to be correlated with these situations also happenning on days where I'm having to do more of 'something else' on this list, eg obviously this automatically interacts with orthostatic because I'm also 'more upright' (although slumped by the end of it) but might be having to do it to speak to someone or do an appointment it is hard to unpick.