PEM discussion thread - post-exertional malaise

[Hutan]

I don't think so but I do think cortisol is heavily involved in stress and energy production and thus could relate to (over)exertion.

Yes. I don't think there is any good evidence of cortisol levels that are abnormal (given the average lifestyle of people with ME/CFS - waking later, no morning rush) or that the production of cortisol in response to stressors is abnormal. I see that @arnoble has been directed to our thread on cortisol here already, on another thread, but link it here again for completeness.

I suppose bursts of cortisol may contribute to the effect of adrenalin in activating t-cells - I haven't looked to see if it does cortisol does that too.

 

[MeSci]

Years ago a friend with ME did the ACTH stimulation test and it came back normal. She didn't have insomnia either.

I've done the ACTH stimulation test which came back normal, but I do (often) have insomnia. Also, during the test, my gut swelled up severely, I think because I was told to sit still, and it was very uncomfortable.

 

[Mij]

I've done the ACTH stimulation test which came back normal, but I do (often) have insomnia. Also, during the test, my gut swelled up severely, I think because I was told to sit still, and it was very uncomfortable.

Yes, it can make some people feel nauseated too.

 

[poetinsf]

But if it is the basis of a symptom that patients are expected to recognise it has to be subjective.

Why? A symptom being subjective doesn't mean that the cause of the symptom has to be subjective as well. Your feeling pain because a car ran over you does not mean the weight of the car is subjective. Or the sound of the backfire from the passing vehicle that triggered the PTSD symptom.

We should talk of power (calories per time would be power) or of total energy usage. So far I don't think we have established even which of those is relevant - and they are very different in implications.

Calories by itself does not cause enough stress/damage. For healthy people anyway. Just living and breathing consumes about 1 cal/min, which means over 1000 cal/day. But you will surely feel the next day the damage from 1000 cal spent in an hour.

The stress from burnt calories gets relieved/cleared at a certain rate. It accumulates rapidly as the arrival rate approaches/exceeds the clearance rate if we view it as an MM1 queue. This is probably why slowing down by 5-10% allows athletes run/skate/swim twice as far. My theory is that the accumulated stress, or working against it, is what causes damage and subsequent PEM. This model could explain things like pacing (slowing down and incorporating rest) letting you walk much further without triggering PEM and the illusion of lowered threshold from accumulation effect in rolling PEM, etc.

I've modeled it mathematically using R and fitbit minute-by-minute data and had some success with it. Then Google deprecated the authentication API and replaced it with OAUTH2 protocol which R did not support then. I couldn't find ways to improve the model anyway, so I shelved it at that time. I've been meaning to resurrect it, but I haven't so far. Now I'm too distracted with making up for what I've missed now that I have my life back. But it's still on my list of things to do...

 

[poetinsf]

Subjectively it feels that a simple measure like calories per unit of time does not correspond to what ever culminates in triggering PEM. Other things interact like the novelty of the activity, additional sensory stimuli or orthostatic issues.

There could be several triggers for PEM, with physical exertion being but one. Mental exertion or sensory stimuli could be other. We could take just the physical exertion portion, of it, since that is the simplest to objectify, and then establish the relationship between physical exertion and PEM. There could be other factors like emotion, but we could treat them as noises in the model that lowers correlation.

 

[poetinsf]

Meaning that if PEM has something to do with the processes which increase utilization of different fuel sources (be that AMPK phosphorylation, increased glucose uptake, fatty acid mobilization, etc), this will look different between tissues.

But you do need recovery from mental exertion (I know how my mental ability degrades after 1 hour of thinking), and there is no reason to preclude such stress/damage as the possible trigger for PEM. And how hard you think, and how tired you are afterward, got to be proportional to the amount of expended for thinking within the given time period.

 

[Jonathan Edwards]

Why? A symptom being subjective doesn't mean that the cause of the symptom has to be subjective as well. Your feeling pain because a car ran over you does not mean the weight of the car is subjective. Or the sound of the backfire from the passing vehicle that triggered the PTSD symptom.

Those examples are not equivalent. PEM is defined as a worsening following exertion. Whether or not it is caused by exertion is a different issue. It is elicited as a temporal symptom profile in which the apparent trigger is a subjective sense of having done a lot or 'exerted' and the time relation is nearly always subjective in that when PEM is elicited by a physician in clinic or in a questionnaire nobody really knows whether any particular exertion was what the worsening followed.

As to what causes PEM, that is a biological issue that would do well to keep well away from terms like 'exertion'.

But you will surely feel the next day the damage from 1000 cal spent in an hour.

Maybe but from what members say, the length of time at that rate is also relevant. So we seem to need a complex measure of a high work rate for a certain length of time. I agree that total work done is not going to cut it but nor is just work rate. So we are likely to need some new measure that so far nobody has calculated. And if nobody has calculated it I do not see how anyone can know what it is from experience to be honest. People may get very good at predicting what will cause trouble but so far no formal measure that reflects that has been devised.

 

[Jonathan Edwards]

My theory is that the accumulated stress, or working against it, is what causes damage and subsequent PEM.

What would 'stress' be here? It is another lay term that may not help I suspect.

I continue to think that what may trigger PEM is some cumulative tissue response to microtrauma - like the response to using your hands that leads to calluses on your palm. It is partly the intensity of force involved and partly the duration, but not a simple multiplication of the two.

 

[poetinsf]

Does @poetinsf have something with the idea of tolerance?

To me, none of it seems like inputs and outputs. It's a substantial, often variable, and sometimes devastating reduction in tolerance to almost everything—perhaps caused by some kind of biological brake being applied.

I wouldn't be surprised if the tolerance/sensitivity is highly variable in some cases. Some people report oscillation between remission and relapse after all. That's an ultimate case of tolerance variability. Your guess is as good as mine as to why. I'm mainly interested in a steady state response to physical exertion though, mainly because that is the easiest to establish, and that will probably help the most since PEM from physical exertion is universal in ME/CFS.