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

Medfeb said:
Another question to clarify - is there a standard definition for exercise intolerance? I ask because it seems that some LC clinical guidance and research studies equate PEM to exercise intolerance and then use that to leap to exercise as treatment. Of course, assuming they mentioned PEM at all
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I found this article helpful:
Jennifer Huizen: What is exercise intolerance?, Medical News Today, Updated on September 20, 2023
https://www.medicalnewstoday.com/articles/exercise-intolerance#symptoms

Some quotes:
Exercise intolerance is a reduced ability to exercise at a level that is typical for someone’s age and size. Individuals with exercise intolerance may not be able to exercise as vigorously as they used to, or they may get tired or out of breath very quickly after they start exercising.
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Examples of conditions that cause exercise intolerance include lung and heart conditions and ME/CFS.

Exercise intolerance and PEM
PEM is similar to exercise intolerance in that it can prevent someone from exercising or being physically active. However, where exercise intolerance makes it difficult to begin or continue exercising in the present, PEM causes a delayed reaction.

With PEM, a person’s preexisting medical symptoms get worse around 12–48 hoursTrusted Source after they exert themselves. It can last from days to weeks, and because of the delayed onset, people do not always know when they have done too much physical activity.
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Exercise intolerance and PEM are hallmark symptoms of ME/CFS.
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Medfeb said:
Thanks, @Trish. That's surprisingly good.
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I think to complete the picture of what happens to people as a result of exertion, we need to also include PEF and DOMS

So here's my summary:

PEF - Post exertional fatigue: fatigue lasting minutes, hours or a day or two in healthy people, particularly associated with deconditioning
DOMS - Delayed Onset Muscle Soreness: Feeling sore/aching the next day following more exercise than usual, also associated with deconditioning.

In ME/CFS PEF and DOMS are likely to occur, but they are not the same as PEM. Promoters of the psychosomatic view of ME/CFS, including the PACE triallists, wrongly attribute ME/CFS symptoms to deconditioning and interpret PEM as exaggerated perception of symptoms of PEF and DOMS.

Exercise intolerance - reduced ability to exercise, eg in heart and lung conditions. Includes symptoms such as breathlessness and fatigue.

Exertion intolerance / Fatiguability in ME/CFS. An immediate and cumulative response to physical and/or cognitive exertion that reduces ability to continue exertion, and leads to an immediate increase in ME/CFS symptoms, including not just increasing fatigue, but other symptoms such as muscle pain, OI, congnitive dysfunction etc. Takes longer than in healthy people to return to pre-exertion symptom level, but if sufficient rest between activities, not followed by PEM the next day/days.

PEM - Post-exertional malaise (PESE, crash)
Results from physical, cognitive and or social exertion outside the individual's current capacity. May be a single trigger or cumulative effect of too much exertion.
Delayed onset (12+ hours), lasts more than a day, usually longer, often more than a week, increase in symptoms plus additional symptoms, much reduced capacity to function.

pwME are likely to have all of the above, but as far as we know PEM only occurs in ME/CFS and some people with Long Covid.
 
Trish said:
DOMS: Feeling sore/aching the next day following more exercise than usual, also associated with deconditioning
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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.
 
rvallee said:
So it's associated with exercise, but I'd say it has nothing at all to do with deconditioning.
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I agree with you, but it also happens to people who are deconditioned at a much lower level of activity than in athletes because their level of fitness is lower, so that's the aspect I focused on in my comment. I nearly added 'and in athletes' but that wasn't the point I was making.

I think it should be discussed because we need to know that BPS people conflate PEM with PEF and DOMS. Only by understanding them can we refute them.
 
Trish said:

Exertion intolerance / Fatiguability in ME/CFS. An immediate and cumulative response to physical and/or cognitive exertion that reduces ability to continue exertion, and leads to an immediate increase in ME/CFS symptoms, including not just increasing fatigue, but other symptoms such as muscle pain, OI, congnitive dysfunction etc. Takes longer than in healthy people to return to pre-exertion symptom level, but if sufficient rest between activities, not followed by PEM the next day/days.

PEM - Post-exertional malaise (PESE, crash)
Results from physical, cognitive and or social exertion outside the individual's current capacity. May be a single trigger or cumulative effect of too much exertion.
Delayed onset (12+ hours), lasts more than a day, usually longer, often more than a week, increase in symptoms plus additional symptoms, much reduced capacity to function.
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So here's where I'm confused...
@Ravn above noted:
if we accept exertion is the trigger for PEM then logically the underlying PEM mechanism has to start at the time of exertion even if it takes time to build up or run through a cascade of downstream processes before signs & symptoms become obvious.
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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.
 
Medfeb said:
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?
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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.
 
Medfeb said:
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?
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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.
 
Medfeb said:
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
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My distinction between exertion intolerance and PEM is based on symptoms and functional capacity purely. I was not hypothesising about physiology. I have no idea whether they are physiologically distinct or part of a continuum.

So what I am saying is, from my experience, and reading what a lot of other people describe, all exertion increases some symptoms at the time, and we are forced to stop and rest by function worsening, eg can't find words, legs getting heavy and more painful and gait unstable.

If we can rest sufficiently, and don't push to over exert, we may be able to repeat the same level of activity each day. Even in mild ME when not deconditioned, daily total activity and individual strenuous activities are restricted by at least half. That is what I call exertion intolerance. pwME are physically and/or cognitively unable sustain a normal level of exertion.

I think pacing is not just about avoiding PEM. I don't just stop and rest because I'm afraid continuing to walk may make me sicker tomorrow, I stop and sit down because my legs are getting harder to keep upright and take the next step. I don't lie down to read and type because of fear of PEM tomorrow. I lie down because my symptoms and function worsen when I try to do it sitting up.

PEM is different symptomatically and functionally from that daily experience of fatiguability/exertion intolerance. It feels more like a sudden onset of flu, or crashing down the ME severity scale from one day to the next to a much lower level. The at least 12 hour delay often cited may relate to the intervention of night. So for me, PEM is often something I wake up with next morning àfter a day or more of cumulatively pushing to do increased activity.

The length of delay from the specific exertion we attribute PEM to may be partly by the retrospective nature of attribution. Eg was it the hour spent sitting and chatting with a visitor that triggered PEM starting the next day, or was it the cumulative effect of several days tidying up, bathing, baking etc in advance of the visit - was it the cumulative effect of several days extra exertion? All we may deduce is that something about those extra exertions probably contributed to the week in bed feeling horribly ill and barely able to think or eat that started a day or so after the visit.

I know it's not clear cut in many instances.
 
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.
 
Mij said:
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.
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I wonder how common your experience is. I don't think I've come across anyone else with that pattern.
 
@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.

Ravn said:
On the first point, if we accept exertion is the trigger for PEM then logically the underlying PEM mechanism has to start at the time of exertion even if it takes time to build up or run through a cascade of downstream processes before signs & symptoms become obvious.
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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.
 
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.
 
poetinsf said:
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.
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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!)
 
Jonathan Edwards said:
On the other hand I get a strong feeling that we do not actually have any clear idea what should guide pacing.
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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.
 
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