POLL: physical vs cognitive PEM - same or different?

My OI is relatively mild, especially in cool weather. So let's assume I'm sitting down with my feet up & back supported to minimise that -

Reading will involve using the eye muscles so can trigger physically induced PEM that can easily be confounded with cognitively induced PEM for me.
However, assuming font size, lighting etc isn't an issue, the material I'm reading makes a difference. A fiction novel that I don't need to remember will cause cognitively induced PEM if I read for too long. However, reading legal or technical documents will induce cognitive PEM faster.

Similarly watching TV - a drama programme will induce PEM if watched for too long, but watching a political programme, or an educational one where I have to think about & consider what's being said will trigger PEM much more quickly.

A doctor's appointment by phone is more likely to induce PEM faster than a chat over the phone with someone I know well.

As @Peter Trewhitt says an unfamiliar cognitive task will induce PEM much quicker than a familiar one. If a retailer changes the layout of a website for example. Or when your email provider suddenly decides to give your mailbox a new look & feel.

Interesting. I wrote a lot of reports for work and on average spent many hours writing and typing daily. Yet pain in my hands and fingers was quite an early symptom for me. Although I was used to driving a lot, gripping the steering wheel, changing gear etc became very painful.

I agree trying to build muscle mass just ends up triggering excruciating muscle pain and PEM.

For me - it depends. My fatiguability is variable & depends on everything from the weather to fluctuations of ME

in answer to symptoms after cognitive exertion - I think possibly both but the delayed PEM may be masked by the length of time it takes me to recover. A task like filling in the ESA50 form can wipe me out for weeks or longer. Even when someone else physically fills it in for me.

Re the physical exertion - if it's aerobic, or requires a lot of strength then it may happen straight away. More usually it's delayed by up to 3 days.

 

It depends! I always get both acute (immediate is misleading) and delayed symptoms - but the symptom pattern differs between delayed/immediate and between cognitive/physical exertion.

I don't get physical weakness, nor flu type symptoms (like sore throat, nasal congestion) from cognitive exertion.

But an increase in cognitive symptoms - poor concentration, brain fog etc depend on the task and the level of mental effort involved. To describe experiences during math/science exams: the first hour is foggy, but can push through. Second hour, high level of fog, frequently making mistakes and noticing them, but having difficulty correcting them, regardless of extreme mental effort or not. Third hour, barely know what I am doing at all, no idea whether I am making mistakes or not. A rest for a few hours might bring me back to the second hour level, but this state can persist for several days, even with "good" sleep.

Cognitive symptoms and fatigability depends on the task. Tasks that are less familiar/require more concentration/effort increase the risk.

There are two types of physical exertion, "active" exertion (dynamic exercise) where heart rate and breathing rate are elevated and more passive exertion (including orthostatic effort) where you are strained holding positions for a reasonable period of time (such as reading in bed). Both cause symptoms, including PEM.

Like most others, my muscles always feel stiff, but depending on the level of intensity and duration, I can feel noticeable weakness and sometimes acute unusual pain relatively quickly (after say, 10-15 minutes). This means low performance for a given level of effort on a bike*, or having difficulty getting my arms/fingers to do the right thing/go in the right place - undershoot of position (such as fixing aforementioned bike*). But the key point is this occurs not in all muscles, but only the muscles that have been somehow used during the activity!
In my experience, being more "accustomed" to an activity (such as cycling*) increases the threshold by which the force output is considered intense, but does not diminish the risk of PEM and other symptoms.

Flu-like symptoms such as sore throat, nasal congestion start the next day and last several days. Increased cognitive symptoms also tend to start at least 8 hours later and persist for several days.After a few hours I also note increased symptoms related to poor circulation - pooling in extremities, or feeling of "pins and needles" for example. The poor circulation symptoms seem to persist as long as the cognitive symptoms. I also only experience orthostatic intolerance as a delayed/PEM symptom - if I don't exert myself, I don't experience it on a day to day basis.

Physical weakness/fatigability also persists for several days - but tends to be quite variable, sometimes just a day, sometimes a week or more. (sometimes hard to tell because it requires doing an intense activity to actually reveal the weakness). Increased feeling of stiffness is delayed and tends to be widespread and often worse 2 days after but this stiffness does not predict which muscles will feel weaker or have increased fatigability (or pain during activity). The muscles that have significantly increased weakness/fatigability are (almost) only those which were used in the preceding activities. I also will like to point out that a lot of tasks use many of the muscles in our body, for joint positioning and balancing for example.

If there is any weakness in other muscles, it is only ever associated with poor circulation.

Lastly, I always have a headache, above the front of my head - but note, this does not mean around the forehead or sinus. My neck also gets sore which can radiate up the back of my head, but I don't have this symptom all the time like the other headache. The intensity increases as a result of mental exertion and occurs relatively quickly. Neither mental or physical exertion increases the severity of the headache the next day, but it increases the susceptibility - a lower level of mental exertion will trigger an increase during PEM.

Overall, in my experience, the exacerbation of symptoms seem to be proportional to effort, but aren't necessarily associated with elevated heart rate (or exceeding an "anerobic threshold"). The complex pattern of symptoms in my experience doesn't suggest a simple "switch" being flicked on and off, nor does it suggest a purely brain-based "central metabolic homeostasis governor" or "sickness behaviour" type explanation.

*Also lastly: I have an electric bike with a throttle (and cruise control) - so the bike can do all the work if I need to rest!

 

Could immediate PEM be the result to those who have a very lowered 'energy envelope'?

I didn't experience PEM during the early years of PVFS, my energy envelope was wider because I hadn't caused any 'injury' (yet) from exercising.
I repeatedly went over my limit and this was when my cognitive issues, absorbing and processing information, brain drainage, etc became apparent. I was reading books and talking on the phone everyday with no issues before that. The cognitive PEM began AFTER experiencing physical PEM from exercising.

 

to add . . .

Cognitive impairment is a common and disabling non-motor feature in patients with Parkinson's and other neurodegenerative disorders who experience orthostatic hypotension. And there are many different types of OI with very few specialists who can diagnosis them.

 

That's true as far as I know. I found that in one or more papers.

I think it's normal for activation of the body's immune systems (t-cells, b-cells, maybe others) to activate the brain's immune system (glial cells). The brain is critical, so the rest of the body gives it warning signals just in case the invader is able to cross the BBB. Think of it as an amber alert: be extra alert, but don't go to full attack mode yet. With ME, this alert might trigger an abnormal response, or maybe the mechanism for standing back down from the alert isn't working properly, so our glial cells might remain in an abnormal state. Given how many tasks glial cells are responsible for to maintain normal brain function, it might not take much of a change to cause our symptoms. Googling 'glial types' says that there are 3 different types of glial cells, but that's outdated and there are several more types, and some are highly localized (some are just in part of the hypothalamus) and their complete functions are poorly known, how they're replaced is still poorly understood, and studying these cells and their function is very difficult. This seems like an ideal place for a mysterious dysfunction to be hiding.

Those might not be PEM. Since we don't have any quantitative means of measuring PEM, it's easy to confuse similar symptoms. I'm sure there are plenty of other disorders that cause symptoms soon after exertion, and how can a person know if a feeling of fatigue is from PEM or from circulation problems or nutrient deficiency?

For me, I had PEM from physical exertion, with a consistent 24 hr delay. Cognitive exertion gave what seemed to be the same set of symptoms after a more variable delay, of maybe less than an hour to a couple of hours.

An interesting study would be whether the type of cerebral exertion affects the severity and timing of PEM. Specifically, which parts of the brain are doing the exertion, and does that vary with the individual. I got it from socializing and driving. Have others gotten PEM from math problems, or memorization, or from emotional triggering from books or movies?

I think ME might affect the glial cells in different parts of the brain in different individuals. If the cells in the insula are affected, you might have gut symptoms or poor control of blood pressure or whatever the insula controls. Alterations in another part of the brain might cause the fatiguability. If the glial cells in the retina are affected, you might suffer visual symptoms. I developed double-vision a year of so ago, and I assume it's due to ME affecting certain brain cells involved with keeping eyes aligned.

 

I wonder if stress is a factor in that. Reading a technical document for self-education doesn't involve emotional stress, so it doesn't trigger PEM for me. Filling out taxes or making decisions involving large amounts of money is stressful, and does trigger PEM. Likewise, I think that talking with a doctor or reporting a crime to the police is probably more likely to give me PEM--and more severely--than talking to a friend.

 

Nope. When I had a working brain I thoroughly enjoyed reading technical documents - it was part of my job.

I can't say I'm terribly interested in legal documents but I like getting my head round things. So, even if it's not something I would necessarily want to do, I would still get satisfaction of getting to grips with something. Especially something new.

In fact I thoroughly enjoyed learning. Now, even if it's revisiting schoolgirl French or what have you I'll soon be clobbered by PEM.

Cognitive PEM symptoms are a nightmare. Literally forget how to use a kettle. Sad state of affairs for an engineer.

 

Yes, on PR, several other members stated that they didn't get physical limiting symptoms either. Some of them continued what sounded to me like pretty heavy-duty bodybuilding exercises. There seems to be a subset of ME victims who don't suffer muscle-limiting symptoms. IIRC, at least one member said that they got the physical symptoms, but not the mental ones. There's a wide variety in ME.

I think that it's more likely for the core dysfunction in ME to be in the brain, with various downstream effects on the body, than a body problem that affects the brain. The latter isn't impossible, since there's plenty of feedback from body to brain, but it's harder for such a link to remain hidden. Small abnormalities in brain function are harder and more expensive to find.

 

Normally, I tend to keep my brain, indeed my entire nervous system, inside my body.

It makes keeping it fed, oxygenated and clean much easier, as well as making it easier for both to communicate.

I can understand why some might like to seperate them, but IMO it's not really that practical, or sensible, for the living to do so.

 

On the topic of trying to isolate / understand cognitive induced PEM -

I had forgotten about it but at one point I did use exercises to try to train up my brain.

As I was used to technical problems solving type issues from work and I was clearly struggling to do that I decided to try something related but a bit different. My husband works in a related field but we have different areas of interest so I tried reading some of his training manuals and discussing them and asking questions from him. Nope. Completely wiped me out & I forgot all the new information anyway.

So years on I decided not to focus on learning & the content or problem solving as that was a big part of what I did prior to becoming ill. I reasoned that if the muscles I used to be able to use all day everyday struggled then maybe using the same brain processes might be an issue. I was into yoga and meditation so I decided to use some meditation training techniques.

One example of such a technique (for those unfamiliar) would be to take a simple object, maintain a relaxed physical position and relaxed focus with the eyes, simply observe the object - size, shape, texture, play of light, contact with the surface etc. Then take a small break and the second part involves either writing down or mentally noting what you observed. You start of by allowing a minute or so for each stage and build up, you also start with very simple objects and progress. Still clobbered by PEM.

 

@Invisible Woman

I can barely follow a recipe and forget to add ingredients when it's written right in front of me. And you want to add a timer to that?

 

How about spelling? I was an expert speller because I remembered how the word looked. Now when I start a word, it's a struggle to make it come out right, or...is it right? Cannot tell.

 

I know! I knew no better. Discovering that I could neither do any of the physical activities I previously enjoyed nor the cognitive ones was immensely frustrating. I found it so difficult to believe my life could be reduced by so much, that I could lose so much - job and finances just being a small part of the overall loss.

It sickens me to think how many of us put ourselves through so much unnecessary suffering repeatedly because no one bothered to listen to patients, take it seriously and stop new & old patients repeating the same mistakes.

I don't blame patients - even the ones slow on the uptake like me. When you're desperate to get better & regain some semblance of a life you're going to try anything that seems halfway reasonable at the time.

Not only have the BPSers stifled the research that might have helped & left us at the mercy of quacks, they did their utmost to keep us isolated and prevent us from learning from each other & protecting each other from harm.

 

I reckon this thread is more informative about PEM than some of the published papers out there!

It's also been very helpful to me in trying to answer some of my own questions. As I said earlier, I used to think I got PEM from both cognitive and physical exertion and that the two were much the same. On reflection I started to have doubts, especially because all the PEM events I had considered cognitively-induced had actually involved a mix of different types of exertion.

After a lot of head scratching, here are my tentative conclusions (with all the usual reservations around recall bias):

rapid-onset localised symptoms after very minimal exertion (ROLS)

These start during an activity and necessitate a relatively brief rest before being able to continue. Symptoms relate directly to the activity.

Example (physical): meal preparation has to be broken into several sessions with rest between, symptoms are tiring arm muscles plus orthostatic discomfort from sitting upright with feet down.

This physical activity-rest cycle can be safely repeated a few times throughout the day but repeating too often leads to delayed PEM, presumably due to cumulative effects. This means the PEM threshold is crossed before symptoms appear (apart from the temporary sort like in the example above that don't by themselves lead to PEM).

Example (cognitive): reading an article has to be broken up by rest every few paragraphs as comprehension starts to fail.

This cognitive activity-rest cycle can be safely repeated a few times throughout the day; repeating too often leads to increasing mental fatigue until the brain simply shuts down - but it does not lead to delayed PEM, as far as I can tell.

Some of these ROLS could be mistaken for deconditioning except for the fact that the level of exertion needed to trigger them varies too much and too fast to be fully explained by any training effect.

rapid-onset localised symptoms plus generalised exhaustion* after minor exertion (ROLS++)

Similar to ROLS but after a slightly higher level of exertion. Several hours of rest are needed for symptoms to subside again. Symptoms are more severe but still relate directly to the activity. In addition there is generalised exhaustion.

Example (physical): walking 50m all at once leads to shaky, straining legs, breathlessness and generalised exhaustion. These symptoms gradually improve over some hours of rest but will always be followed by delayed PEM even if the activity is immediately followed by complete rest.

Example (cognitive): I experimented with lying down and listening to a podcast in a language I'm not entirely fluent in while also doing a mental simalteneous translation of it. Predictably that fried my brain in no time at all. Major brain fog and generalised exhaustion for several hours after but no delayed PEM.

* With "generalised exhaustion" I mean more than fatigue. It can include feeling unsteady, dizzy, nauseous and being unable to think straight, a bit like a not quite fit enough marathon runner collapsing after staggering across the finish line, but without the endorphins.

delayed PEM, early phase

Starts 4-6 hours after exertion. Symptoms - irrespective of type of overexertion - feel like immune activation, much like coming down with a cold with a sore throat, feeling in turn hot and cold, and generally feeling off. Timing of early PEM symptoms can overlap with the ROLS++ which can make them difficult to tell apart. The main PEM symptom cluster invariably follows the next day, no amount of rest can stop it (though not resting will make it worse).

Definite triggers: physical & orthostatic overexertion

Likely* triggers: stress & emotional exertion - interestingly ROLS & ROLS++ symptoms after stress & emotional exertion are indistinguishable from those after orthostatic stress

Unlikely* triggers: sensory overload & pure cognitive effort, refer my experiment** above which resulted in major ROLS++ but not in delayed PEM whereas the same level of ROLS++ from physical activity always leads to PEM

* Can't be certain about degree of likely/unlikely because activities involving those potential triggers typically also involve some level of physical and/or orthostatic exertion at the same time.

** Of course my little experiment is an anecdote about a single, not a cumulative, effort of a very specific type of cognitive exertion. Interpret with caution. Oh, and don't experiment yourself, please. Your outcome may be a lot worse than mine. Do as I say, not as I do!

delayed PEM, peak phase

Continuation of the above, symptoms peak 24-36 hours after exertion but take a lot longer to reduce again. Symptoms are much more severe and cover the whole spectrum from flu-like to autonomic and cognitive etc etc.

In summary:

For me, both physical and cognitive exertion lead to localised symptoms immediately or soon after the activity. Symptoms can be significant but I'm not convinced they're PEM. I suspect they reflect the sort of fatiguability a lot of people with other conditions struggle with, too. However many people, within as well as outside the ME community, call these symptoms PEM.

With respect to "classic" delayed PEM, I can only be certain it happens after physical (and orthostatic) overexertion. Symptoms of "classic" delayed PEM are qualitatively different from the ROLS/ROLS++ ones. I can't be sure about "classic" delayed PEM after cognitive exertion but I'm inclined to say I don't get it.

Also, this difference seems important:

If I exert physically to the point of getting ROLS++, I will always get PEM later; the PEM threshold is passed even before appearance of symptoms.

If I exert cognitively to the point of getting ROLS++, I will recover over a few hours and not get PEM the next day.

 

In an ideal world yes. Realistically... glances at to do list, compares to energy envelope, computes... very unlikely to happen , sorry @Trish.

Maybe you could just refer them to this thread in your letter if you haven't sent it yet? The main reason I made the thread a public one was that it might be seen by anyone* with an interest in untangling the concept of PEM.

(*And if that anyone is you, that non-member reading this thread right now and wanting to know even more, or discuss further, there are several other interesting members-only discussions about PEM here on S4ME. Why not join us ?)

 

As @dave30th was interested in this topic and there haven't been that many replies to the poll, I'd very much appreciate if anyone else was to answer the poll or share their experiences.

 

In my own case, I experience PEM as being a state roughly akin to a severe flu (if one could experience flu denuded of fever and rhinorrhoea) which occurs almost solely in response to physical effort or exertion. Mental effort alone, by contrast, can trigger off a state of exhaustion - often severe exhaustion coupled with significantly increased brain fog - but not the severe myalgia or many of the other features specific to the PEM state that leave me with no choice but to spend days in bed. The only other symptoms common to PEM that occur with greater frequency after mental effort, according to the symptom diaries that I once kept, are headache and increased sensory sensitivities, but I have at least three potential causes of such sensitivities (ME, Aspergers, migrainous headaches) and so I cannot say that there is a definite correlation. The post-cognitive exhaustion & brain fog is far more easily triggered and occurs without the typical delay common to PEM, but it is also far easier to recover from; ordinarily, a reasonable night's sleep will bring it under control. This is in stark contrast to the PEM state, from which recovery typically requires days or weeks of rest.

 

Ah,.now here we differ.

Cognitive exertion - even if I take mini breaks immediately at the onset on ROLS (rapid onset symptoms) sill cause delayed PEM. Especially if I repeat that several times during the day and it will be even more pronounced if I were to do that several days in one week.

This is one of the reasons why I struggle so much with filling in the forms for benefits such as ESA. I have to repeatedly concentrate then rest and repeat far too often and filling in the form can easily cost me a couple of months of PEM.