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

Trying to compile a kind of "where we are with PEM, and investigating it" list, and have this at the moment,
  • fatigue after exertion isn't PEM. We have reduced energy to start with, so it should be an expected response.
  • studies need to look at participants over a longer term - both to establish an individual baseline before any intervention, and to track any effect after.
  • the above point would then allow any effect from travelling to be tested to be seen.
  • given that all of us have different levels at which PEM is triggered, averaging results is a bad idea.
  • different severities and length of illness will tend to affect how people describe their PEM. As will if they pace or not.
Any suggestions/corrections welcomed.
 
I have been trying (unsuccessfully so far) to write an article about harms with GET, and as part of it have written the following:

It is important explain the term PEM clearly, and distinguish it from post-exertional fatigue (PEF) and exercise intolerance.

"Post-exertional malaise (PEM)*—worsening of symptoms after physical, mental, or emotional exertion that would not have caused a problem before the illness. PEM often puts the patient in relapse that may last days, weeks, or even longer. For some patients, sensory overload (light and sound) can induce PEM. The symptoms typically get worse 12 to 48 hours after the activity or exposure and can last for days or even weeks." - IOM 2015 Diagnostic Criteria, CDC website
https://www.cdc.gov/me-cfs/healthcare-providers/diagnosis/iom-2015-diagnostic-criteria.html

PEM and post-exertional fatigue (PEF)
Note that post-exertional malaise is not the same as post-exertional fatigue (PEF) as experienced by people who are healthy or deconditioned who undertake exercise outside their normal level of activity, and which may involve a day or two of feeling tired and achey. The symptoms and duration of PEM should be easily distinguishable from PEF. It is notable that the psychosocial researchers tend to conflate these two distinct phenomena.

Exercise intolerance and PEM
Medical News Today (Hutzen, 2023) explains the difference well:
"The main sign of exercise intolerance is a consistent inability to engage in a reasonable level of physical activity. This may make someone feel exhausted, out of breath, weak, in pain and nauseous."
Huizen explains that this is not the same as being unfit, and lists conditions that cause exercise intolerance where a gradual build up of activity may be possible, including some respiratory, cardiac and metabolic conditions.

People with ME/CFS, and some with post viral fatigue and Long Covid, experience both exercise intolerance and PEM. Because of the delayed onset of PEM people with ME/CFS do not always know when they have exceeded their exertion threshold because of this delayed effect. Exercise therapies that try to push beyond this threshold are counterproductive.
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"PEM and post-exertional fatigue (PEF)
Note that post-exertional malaise is not the same as post-exertional fatigue (PEF) as experienced by people who are healthy or deconditioned who undertake exercise outside their normal level of activity, and which may involve a day or two of feeling tired and achey. The symptoms and duration of PEM should be easily distinguishable from PEF. It is notable that the psychosocial researchers tend to conflate these two distinct phenomena."

My opinion here is that I think we do need to acknowledge that pwME will also experience PEF, and that they will do so quite frequently, but obviously it still isn't PEM.
 
If I were attempting to define or measure something, I'd start by not assigning it a misleading label - or if that ship has sailed, making sure everyone knew that label was misleading.

Shouldn't be hard to shed "malaise" since so few of us live in antebellum Charleston.
 
Andy said:
"PEM and post-exertional fatigue (PEF)
Note that post-exertional malaise is not the same as post-exertional fatigue (PEF) as experienced by people who are healthy or deconditioned who undertake exercise outside their normal level of activity, and which may involve a day or two of feeling tired and achey. The symptoms and duration of PEM should be easily distinguishable from PEF. It is notable that the psychosocial researchers tend to conflate these two distinct phenomena."

My opinion here is that I think we do need to acknowledge that pwME will also experience PEF, and that they will do so quite frequently, but obviously it still isn't PEM.
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Thanks Andy, I agree, and I intended to say that in my section you quoted. People with ME/CFS experience all three of PEM, PEF and exertion intolerance. They are different, and people with some other conditions may experience one or two of them but not all three.
 
Trish said:
I have been trying (unsuccessfully so far) to write an article about harms with GET, and as part of it have written the following:
Click to expand...

Good to hear. Looking forward to seeing that.

I'd also include worsened functioning in addition to worsened symptoms and maybe that PEM severity is out of proportion to the triggering stressor

another useful reference is the NIH CDE description of PEM - compiled from the IOM, CCC, and ME-ICC
 
Trish said:
People with ME/CFS experience all three of PEM, PEF and exertion intolerance. They are different, and people with some other conditions may experience one or two of them but not all three.
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I can appreciate where this may be coming from; none of us likes the cavalier hijacking of an acronym which for years has been considered unique to us, and therefore partially definitional. However, I do think there are a handful of conditions that share it with us. And yes, the other two as well. Channelopathies come to mind.
 
duncan said:
I can appreciate where this may be coming from; none of us likes the cavalier hijacking of an acronym which for years has been considered unique to us, and therefore partially definitional. However, I do think there are a handful of conditions that share it with us. And yes, the other two as well. Channelopathies come to mind.
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Fair point, I'm not excluding other conditions besides ME/CFS/PVFS/LC experiencing PEM. I don't have the medical knowledge or personal experience to do that. I'm just saying we have all 3 of PEM, PEF and exercise intolerance, , whereas some conditions only have one or two of that list.
 
Andy said:
The issue with that is the "can be immediate" part of "An onset that can be immediate or delayed after the exertional stimulus by hours, days, or even longer".
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I see those differently - I think those early symptoms that show up upon overexertion are part of the PEM complex and that if a patient can recognize these early warning signs, they may be able to shorten the duration or severity of the resultant PEM. That's the point of Workwell's timecourse work - at least in their group of patients following physical overexertion - and how they are using it to help patients

Anecdotally, I've observed this in someone I'm close to - head pressure within 30 minutes of reading followed by a headache later on if they kept reading then followed by whole body pain the next day. But recognizing that early head pressure and stopping at that point helped them to lessen the severity of PEM overall including the next day.

Some recent pacing education focuses on helping patients learn to recognize these early symptoms in order to minimize PEM
 
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Medfeb said:
I see those differently - I think those early symptoms that show up upon overexertion are part of the PEM complex and that if a patient can recognize these early warning signs, they may be able to shorten the duration or severity of the resultant PEM. That's the point of Workwell's timecourse work - at least in their group of patients following physical overexertion - and how they are using it to help patients

Anecdotally, I've observed this in someone I'm close to - head pressure within 30 minutes of reading followed by a headache later on if they kept reading then followed by whole body pain the next day. But recognizing that early head pressure and stopping at that point helped them to lessen the severity of PEM overall including the next day.

Some recent pacing education focuses on helping patients learn to recognize these early symptoms in order to minimize PEM
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While I don't disagree with your nuance, the issue we have at the moment is that part of the listed PEM complex is fatigue, so we then get PEM defined by many as "fatigue following exertion".

This isn't helped by such other aspects from the DSQ as

a. Dead, Heavy feeling after starting to exercise,
b. Next day soreness or fatigue after non-strenuous, everyday activities,
c. Mentally tired after the slightest effort,
d. Minimum exercise makes you physically tired and
e. Physically drained or sick after mild activity

being used in which there is, in my opinion, no nuance - those all describe either immediate effects, or normal effects that people who have a reduced level of energy might feel, which isn't specific to pwME.
 
I think the DSQ serves people with ME/CFS very badly.
The list Andy quotes is far from PEM. It describes a mix of immediate fatiguability and PEF, and makes whatever is being described sound very mild.

Where's the delay, the massive ramping up of all symptoms and the severe reduction in function for days or weeks?
 
Andy said:
While I don't disagree with your nuance, the issue we have at the moment is that part of the listed PEM complex is fatigue, so we then get PEM defined by many as "fatigue following exertion".
Click to expand...

Yes, I agree we have a huge problem with those who want to equate PEM as just fatigue after exertion and then dismiss the whole concept of PEM. But I just think we could miss an important nuance if all early symptoms are automatically deemed "not-PEM."

Regarding DSQ
My comments above were only speaking about the nature of PEM and what it is as a symptom, not what instruments are being used today by researchers to identify it. But I do get some of the concerns raised above with the DSQ with the exception of the one above delay of onset of symptoms for the reasons I stated.
 
Andy said:
fatigue after exertion isn't PEM. We have reduced energy to start with, so it should be an expected response.
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Yes. To date very few papers have distinguished adequately between the various exertion and post-exertion phenomena (excessive post-exertional fatigue/pain, excessive fatiguability, exertion intolerance, and post-exertional malaise/post-exertional symptom exacerbation). This makes findings difficult to interpret. The first three phenomena are common in many conditions including in ME; the last is currently only known with any certainty in ME and ME-like LC (but it hasn't been looked for very hard in other conditions so the jury remains out). Hence the need, for now until we really understand what's what, to study the phenomena separately, to compare to a wider range of illness control groups and with better matching of activity levels to untangle findings related to being sedentary or generally ill from findings specific to ME.
Andy said:
  • studies need to look at participants over a longer term - both to establish an individual baseline before any intervention, and to track any effect after.
  • the above point would then allow any effect from travelling to be tested to be seen.
Click to expand...
Yes. Currently the confounding effects of pacing are rarely even considered in studies but they really need to be taken into account properly in study design right from the start. Pacing strongly influences the frequency & intensity of symptoms - a big problem when instruments like the DSQ are used (which I'd prefer they wouldn't use at all but given people who should know better are still using the even worse Chalder Fatigue thingy I'm not holding my breath). Pacing also influences whether a participant's state before an intervention is their baseline or already a state of PEM. Potentially a big confounder.
Andy said:
given that all of us have different levels at which PEM is triggered, averaging results is a bad idea.
Click to expand...
Yes. A design where each participant is their own control and/or where the focus is on the amount of change rather than on absolute values is desirable. I've seen a number of studies using these approaches, especially the latter.

One thing I'm wondering about, in provocation studies, is if it is really necessary to always use identical doses of exertion for each participant or if, at least for some study types, it would be sufficient to just cross over the individual PEM threshold? That would reduce the risks involved for participants at least a little
Andy said:
different severities and length of illness will tend to affect how people describe their PEM.
Click to expand...
Yes, I suggest researchers use the FUNCAP questionnaire to give some structure to patient responses and to increase inter-study comparability
 
On a slightly different tack I wonder whether there is still a confusion between exertion and energy-consuming activity. For a fit young person running down to the sea and jumping into a wave involves no exertion, just activity. For someone with old eyes like me threading a needle requires huge exertion but zero activity.

I am thinking that the exertion is that is the problem in ME is a purely central nervous system property. The battery is the brain. Being run down is not actually an issue of ATP or lactate or aerobic thresholds or any of that. It is more like an increase in 'entropy' of an information processing system. The running down of a battery is also an increase in entropy but it is recognised that there are two sorts of 'entropy'.

Physics entropy relates directly to energy and thermodynamics - free energy rules.
Informational entropy is analogous but not does not actually involve the energy of physics. It can apply to a computation written on a napkin. Cognitive scientists have their own concept of informational 'free energy' (e.g. Karl Friston) which relates to order but not actual thermodynamics.

This may all sound airy fairy but take the travelling thing. It is often mentioned that PWME are exhausted by travelling. Travelling involves exertion. My wife and I have a rule that a day's travelling uses up an extra hour of brain time. Nine o clock at night becomes ten o clock. So jet lag is worse one way and than the other. And of course most travelling involves little or no activity - sitting in a train maybe. The worst thing is driving at night. There is no activity of note but exertion is maximum.

Maybe another analogy is cooking for guests. There comes a point when all the pans, and vegetable knives, and indeed spoons, are in a jumble covered in food debris on the worktop and you have to clear the sink to get enough things clean to move on.

What I see as different about ME is not that there s some unique phenomenon of relation of exertion to symptoms. Normal people encounter travelling fatigue. Normal people with flu get malaise (which I think is a good word because in medicine it spells the serious danger of things like septicaemia or typhoid rather than just fatigue) which is precipitated by exertion (although thinking about it it might in that case be more activity). The difference in ME is that the kinetics are distorted. Like the disturbance of circadian rhythm with jet lag something has put the metaphorical/informational free energy accounting out of line. Like the computer system at the Post Office, it doesn't make sense. It is an unstable kinetics a well as a 'dragged down' kinetics.
 
Ravn said:
Yes. To date very few papers have distinguished adequately between the various exertion and post-exertion phenomena (excessive post-exertional fatigue/pain, excessive fatiguability, exertion intolerance, and post-exertional malaise/post-exertional symptom exacerbation). This makes findings difficult to interpret. The first three phenomena are common in many conditions including in ME; the last is currently only known with any certainty in ME and ME-like LC (but it hasn't been looked for very hard in other conditions so the jury remains out). Hence the need, for now until we really understand what's what, to study the phenomena separately, to compare to a wider range of illness control groups and with better matching of activity levels to untangle findings related to being sedentary or generally ill from findings specific to ME.

Yes, I suggest researchers use the FUNCAP questionnaire to give some structure to patient responses and to increase inter-study comparability
Click to expand...

Has it been confirmed in Long C on a 2nd day CPET or sth?
 
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