Post-Exertional Malaise - a discussion including defining and measuring PEM

Which also includes cognitive impairment for pwME that worsens over time from PEM.

 

Thanks, @Trish. That's surprisingly good.

 

Why it's important that PEM is not fatigue
https://mecfs.substack.com/p/why-its-important-that-pem-is-not

 

Maybe nitpicking but: not necessarily. It's just what happens when muscles are used beyond their current ability. It happens when someone who hasn't lifted weight for years does a few series with 15 lbs, and it also happens when someone who is doing so regularly goes from 150 lbs to 160 lbs.

So it's associated with exercise, but I'd say it has nothing at all to do with deconditioning. It is conditioning, but happens whether someone is going from 0 to 1, or from 50 to 51, whatever those numbers might mean, they're just illustrative.

Of course since most people never train enough to get there, they're only familiar with the "haven't trained in a while, feeling sore" scenario, but this is just the process of strengthening muscle. For that reason I don't think it should be discussed, it's a side show. And if anything, when people like Carson bring it up as a sort of gotcha, it only displays their ignorance about PEM, which it has zero to do with.

 

So here's where I'm confused...
@Ravn above noted:

And the point of Workwell's Timeline slide is that pwME can learn early signs of overexertion, they can reduce or stop a PEM event. That was the case for the pwME that I described - that symptom preceded PEM on the days when she had not yet learned to watch for it. And it's the basis of pacing

Putting those together would suggest that at least some of those symptoms that occur following onset of the exertion are due to that process that drives PEM kicking in.

Am I correctly interpreting this to be saying that all the symptoms that occur immediately or in less than 12 hours following the exertion are due to exercise intolerance and fatiguability and are not associated with that process that drives PEM?

Can we really attribute those early symptoms to exercise intolerance and fatiguability?

Excuse me if I'm not articulating that clearly. Long day heads down in papers

 

I do not see a clear distinction between exertion intolerance and PEM. If we are using exertion intolerance to describe a worsening of symptoms post exertion, and not just a decreased capacity to exert, then I think this can match PEM.

I have never found the delayed portion of PEM particularly compelling. 12 hours is a very arbitrary cut off and without knowing the cause we can't say that symptoms within 12 hours aren't the same thing. I think it is plausible that headaches, light and sound sensitivity and other symptoms that might occur shortly after exertion are driven by the same processes that drive symptoms after 12 hours. Are there people with ME/CFS who can go for a run, feel completely normal for 12 hours and then suddenly have symptoms?

I see some use in a term like PEM to try and differentiate symptom of this condition from other diseases. However, I also think it adds confusion. I don't like using the term as I think it doesn't adequately explain my symptoms. I would much prefer to tell doctors thing like I get headaches, dizziness, pressure in my head, light and sound sensitivity ect. after exertion.

I think the other issue with PEM is that there may be multiple process that drive PEM. Given that PEM is a broad description of symptoms, people may have different issues causing their symptoms while still really having PEM. There are people all the time who have some form of PEM but later find out their condition is not ME/CFS. Because of this, I think it is unlikely we will find a single cause of PEM.

 

The complication is that I suspect these processes interact with triggering PEM, early fatiguability is a warning to stop the activity as there is a risk of subsequent PEM. Sometimes if I react in time I can experience some immediate fatigue effects but avoid subsequent PEM.

Also I suspect if experiencing these immediate symptoms then either the threshold for triggering PEM is reduced or they also add the process of triggering PEM, just as when experiencing OI, sensory intolerances or food intolerances then there is an increased risk of triggering PEM. Then in turn when in PEM early fatiguability and the various intolerances have lower trigger thresholds, just as subsequent further PEM is more likely.

So in real life these various phenomena are not necessarily independent in people with ME, but interact with each other, perhaps the main distinction is that occasionally in ME but more generally in conditions other than ME they can occur without any subsequent PEM.

Perhaps it is splitting hairs, but I can label increased fatiguability when it happens but I don’t know if it is a precursor to or contributing to subsequent PEM until that does or does not happen, just as it can be hard to know if PEM itself is really PEM or the early stages of a virus or an infection until it has progressed or resolved.

 

I don't think this is an issue of distinguishing processes but distinguishing effects.

I think it is saying: 'all the symptoms that occur immediately or in less than 12 hours following the exertion are called exercise intolerance'. They may or may not be associated with a process that can also produce symptoms later and longer. In my periods of post Covid illness I have had major exercise intolerance and apparent fatiguability but never what I would regard as PEM in the sense of a 'crash' - the long snake part of snakes and ladders.

Fatiguability, as Snow Leopard points out, is something different. You may notice it or it may only show up on a CPET machine. The CPET measures a loss of physiological function rather than symptoms. That loss might be associated with a process of crashing but certainly my case was not.


I am quite sure it is good policy for PWME to pace to try to avoid crashes. On the other hand I get a strong feeling that we do not actually have any clear idea what should guide pacing. It may be that heart rate is a useful indicator but it may be that it just correlates roughly with what actually matters and people find it 'seems to work' whereas in fact it is not reliable. It might even be misleading. I am not aware that Workwell or anyone else has any useful data on this.

My suspicions are linked to the way physios say they can tell what treatments work for individual patients - when in fact the PACE data show they couldn't possibly identify the benefits, which either aren't there or are too small to distinguish from natural variation. Physios and sports medicine people love to think they can see cause and effect going on in their treatments and people love to think they can identify cause and effect in their daily lives but a lot of the time it is wishful thinking.

What if the effort of trying to pace actually contributes to a crash? That may sound ridiculous but I think we understand so little about the link between exertion and pay back that it should be totally discounted. I would be very wary of using physiological data on fatiguability to build theories of how to manage the illness when therapists building theories has been the worst thing for ME all along.

 

Some of us don't experience symptoms at all during the activities, in fact I sometimes get an adrenaline boost which is tricky in itself b/c it's pushing me to do more. I could go for a 45 min run and feel fine for the next 12-14 hours. I sleep well and feel ok the next morning and then the onset of delayed PEM nightmare begins. It's very distinctive and has been for the last 20+ years.

I feel that OI is the main source of my fatiguability that forces me to lie down for an hour or so to recover and then I can keep going for a bit more. No PEM and this for both cognitive and physical recovery. Of course there's a point when I need to stop or I'll get wired up and won't be to relax or sleep.

Some pwME experience 'rolling PEM". I've never experienced this.

 

@Trish

I've read about several similar experiences over the years.

I also didn't experience PEM or delayed PEM until several years after onset and this was during the time period when I didn't have cognitive issues or OI either. This is why I feel most of my immediate "fatiguability" is from OI or some form of dysautonomia.

 

Late to the party, as usual, sorry.

Or, the delay mechanism could be a normal physiological process and the PEM mechanism is reacting to a later event in that normal process. The PEM mechanism then does not necessarily have to start at the time of exertion. In that view, PEM would be a reaction to the products of exertion rather than exertion itself.

 

I understood by "rolling PEM" as multiple instances of PEM after an exertion. I looked up and found that some people equate it to "compounding PEM" or accumulation over multiple exertions. (Rolling PEM: What It Is and How to Avoid It - Ticked Off Codess). Maybe people are using the term to mean different things?

 

That link is a good explanation from what I've read from pwME who don't have a known or obvious baseline. They can monitor their symptoms and pace to avoid worsening.

I don't experience many symptoms, but during allergy season and immune/viral or whatever is going on can bring on immediate PEMish symptoms w/o cognitive issues but not as horrible as delayed PEM. The onset of immediate PEM feels similar but doesn't progress and only lasts a few hrs.

 

The second description seems to be more common, but people do use and understand terms differently.

Rolling PEM is really common in mildly affected people. I had it almost continuously when I was working; I was exceeding my capacity every day during the week, and resting up at weekends just about enough to be able to start again the following week.

I still get some of it, but it's better managed now I'm not working. Occasionally I want to do two things that fall on consecutive days, and as long as they're not too extreme and I can schedule recovery time afterwards, I choose to cope with it.

You might even argue that, in some respects, ME actually IS rolling PEM (probably wouldn't be particularly helpful, though!)

 

I don't think there is. It reminds me a lot of driving a wheelchair-adapted van.

They have to reduce the size of the fuel tank (invariably by an unspecified amount) to accommodate the lowered suspension, so you never actually discover what the dashboard indicator shows when you've only got a few miles'-worth of diesel left until you run out. The best you can do to manage it is be cautious.