What could it mean biologically that both physical and cognitive exertion can cause PEM?

I've always wondered how come both physical and cognitive exertion can cause PEM. I'd have thought that moving around would have used very different biological mechanisms and energy expenditures than thinking, on the whole.

There has been talk of 'emotional exertion' causing PEM, even though emotions don't really seem to fit the bill as 'exertion'.

I also wonder whether PwME who have OI and simply remain upright for too long can have PEM (I suspect I can).

Does it indicate anything about the mechanism of ME/CFS that both physical and cognitive exertion can cause PEM?

Is it worth trying to clearly identify other possible triggers of PEM to help point at mechanism?

@Jonathan Edwards (As always!)

 

Our emotions only exist inside our body. As far as the brain goes, it’s kind of like an analog computer (the software aanalogy is wrong). I don’t think the brain cares about what it’s being used for - thoughts and emotions are pretty much the same in that regard.

 

I think it’s worth looking at what very severe patients say give the PEM. Idk where to find any info about it, though.

 

An interesting thought. I would have said emotions only exist in the head - in brain cells. But people use 'emotion' to mean different things.

But I would agree that thoughts wither without emotive content will involve energy usage by brain cells.

What I am not at all sure about is what 'exertion' is. It seems to be largely a subject sense of deliberate usage of faculties, whether mental or physical.

 

I'm wondering whether the level of energy expenditure would be relevant - certainly you'd expect worse PEM with more energy expenditure - but it sounds as though you're not thinking about it in those terms but brain-related for both physical and cognitive activity?

 

That was my initial thought. But then I thought that «Jonathan would probably say that we don’t know if it’s fully contained in the brain», so I went with body.

You and S4ME have made me question my entire reality. Which is a good thing!

 

It means the loop that creates PEM could involve signals going through the brain, or that the mechanism for PEM is present in all organs. I highly doubt PEM is entirely generated from the brain, although the brain can do a lot. But there could be some sort of immune or inflammatory signal that comes from the rest of the body from physical exertion, then goes to the brain, and maybe the brain has some exaggerated response and tells the immune system that there must be an an infection.

 

As far as I understand the discussion on the forum, we don't know any clear answers to the following questions and various different people have offered a wide range of anecdotes:
-Are the symptoms experienced during PEM from exercise exactly the same in PEM experienced from cognitive exertion? Are there specific symptoms related to cognitive exertion that don't occur during physical exertion and vice versa?
-Does PEM experienced from exercise follow the same time course as PEM experienced from cognitive exertion?
-Does the one resolve quicker than the other?
-In the above examples are we sure that things are decoupled from OI?
-What about different severities?

Or perhaps more simpler said
What entails "physical exertion" and "physical PEM" and what entails "cognitive exertion" and "cognitive PEM"? Are they the same for all severities or are there differences? What do these terms mean? As far as I know there has been little to none research on this.

I wander whether it may initially be easier to first discuss "purely cognitive exertion and PEM" (like reading an enjoyable book of thinking about a problem), before discussing "emotional exertion" where things might be even harder to untangle.

I also think different people might sometimes mean different things when the refer to "cognitive exertion" and I don't know how interchangeable those always are. I don't think that thinking harder about something should require more energy than thinking little about something even though it may be draining in a certain sense even for healthy people, so I think the energy metaphor in a physical sense (and in relation to ATP, mitochondria etc) appears to be somewhat of for "cognitive exertion".

I think Rob Wüst has also mentioned that he doesn't have a clear grasp how "cognitive exertion" could for example cause symptoms in the legs.

 

My legs are the first to notice cognitive over-exertion, other than my head. They get really heavy and sluggish.

 

I don't think I ever get PEM from cognitive exertion, but maybe I just haven't noticed. I don't think we have great data on this, but I wonder whether it's common to maybe only get one or the other, and again, whether that points to mechanism.

 

Could you work 100 % from home with something cognitive?

 

I'm not sure I'm answering your question properly but I'm too physically impaired to work for long - even to sit up for long enough to use the computer for long enough to work for anything like normal hours - and I tend to run out of concentration after a certain point but that feels more like mental fatigue more than PEM, isn't delayed, and resolves with rest.

 

That's interesting to think about. Why would one feel drained if not a lack of energy available for the brain? Why can't a healthy person read for 14 hours a day without feeling mentally exhausted? (Actually, do they? Maybe it's a different feeling.)

Is it a damage thing, like using the brain does tiny amounts of damage that need to be repaired, but the repair machinery can't quite keep up with constant use? Is it the brain's requirement for downtime to "consolidate" what it has learned?

 

To me it really feels like any sort of effort past a threshold whatever the nature of that effort is gives me PEM. This even counts for effort where I don’t do anything technically, like “effort” of my body dealing with a virus or the “effort” of my brain dealing with too much stimulus.

As I’m generally clueless about biology, the only thing I know that’s linked between all that is the abstract concept of “energy” (there’s a very physical and mathematical concept of energy used in many fields, but when people say “lack of energy” it’s unclear if the same thing is being described). But its not hard to imagine this “effort” per say involves other bodily systems. Perhaps in ways we don’t know about yet.

 

If, in theory, you could lie in bed and work, the limiting factor would be concentration and/or mental fatigue?
I’m just trying to understand your bottle necks.

 

If I could work via telepathy (!) then yes, the limiting factor would be mental fatigue and I wouldn't get PEM from my cognitive work.

 

Thank you!

I would not be able to do that. I get PEM eventually. I believe the most common symptoms are, they usually come in this order:

1. Tinnitus worsens a lot
2. Legs feeling heavy
3. Body feeling heavy
4. Overheating torso
5. Head gets slower
6. Worse sleep
7. Twitching muscles and invisible internal shaking

I also experience palpatations and increased HR on an irregular basis.

It gets A LOT worse if emotions are involved. A heated argument is a guaranteed way to give me PEM. The last one crashed me for two months.

For reference, I’m bedbound, eat on my own (my parents prepare the meals) and use the bathroom on my own. I walk 50-100 meters/day. All cognitive and emotional tasks are done lying down, so POTS shouldn’t play a part.

 

Damage may not be quite the right word but it might be fair enough.

I think there is an important lesson to learn from the genetic condition Fatal Familial Insomnia. People with this condition cannot refresh their brains by sleep. They sleep less and less and eventually they die. People with ME/CFS don't do that but there may be some indirect connection between what is going on in the two situations.

 

Lately, I've been thinking more that it's related to sleep in ME/CFS as well. It seems so strange that exertion causes insomnia. I think this is common in ME/CFS but I'm not sure.

Just a couple days ago, after spending hours intensely focusing, I couldn't fall asleep until around 4 AM and probably only slept about 5 hours, when usually I fall asleep within about 15 minutes at midnight and sleep at least 7. The next day it was hard to disentangle whether I felt awful from lack of sleep or from PEM - or whether they're separate at all.

Maybe even when people with ME/CFS can sleep a full night after exertion, something about the sleep that we can't yet detect is not quite right, and maybe PEM is very related to that.