What is fatigue?

[Snow Leopard]

However, just 'fatigue' in the context we are interested in has a completely different meaning - a symptom cluster. People with myasthenia gravis do not suffer from 'fatigue' despite fatiguability of muscle being the origin of their symptoms. People with myasthenia report 'weakness'. Yes, some people with ME report an actual sense of weakness but they report it as weakness or inability to do things.

It is true that patients may not use the word 'fatigue', but that is beside the point. There are also a variety of presentation biases that must be considered. Many ME patients likewise don't complain of "fatigue" unless they have come across medical literature or discussions describing their experiences as 'fatigue'.

When I suffered from bilateral acute flaccid paralysis due to motor axonal neuropathy, that was the symptom for which we (I wasn't an adult) sought help for, since it was the most alarming. At the time I was unfamiliar with the language around 'fatigue' and I likely described any other symptoms clumsily or not at all (and never used the word fatigue), but that doesn't mean I didn't also suffer from the 'fatigue' associated symptom cluster you are alluding to. And guess what, twitch interpolation EMG studies of GBS patients show a similar same pattern to CFS patients - central fatigue.

Back to the point you mentioned though, people with Myasthenia do suffer from a similar 'fatigue' related symptom cluster. The association with reporting of symptoms that we associate with fatigue and fatigue itself is no mere coincidence.

"Fatigue in patients with myasthenia gravis. A systematic review of the literature"
https://www.nmd-journal.com/article/S0960-8966(20)30160-7/fulltext

Although a hallmark of MG is muscle fatigability due to dysfunction of the neuromuscular junction (peripheral fatigue), a large number of MG patients also report symptoms of central fatigue, defined as an experienced lack of energy, physically and/or mentally.

"Fatigue and its impact on patients with myasthenia gravis"
https://pubmed.ncbi.nlm.nih.gov/10951443/

We have examined fatigue in myasthenia gravis (MG) by administering a measure of cognitive and physical fatigue to patients and control subjects before and after administration of a lengthy cognitive battery. Subjects also completed a scale that assessed the impact of fatigue on physical, social, and cognitive function. Results of the study revealed that MG patients experience significantly more cognitive and physical fatigue than do control subjects, and the patients' perceptions of both cognitive and physical fatigue increased significantly following completion of demanding cognitive work.

"Fatigue in myasthenia gravis: is it more than muscular weakness?"
https://bmcneurol.biomedcentral.com/articles/10.1186/1471-2377-13-132

Norwegian ethnic patients with MG have higher levels of fatigue and a higher prevalence of chronic fatigue than controls, even in patients in full remission.

Unfortunately, no one seems to have bothered conducting twitch interpolation EMG studies on Myasthenia patients, but I'm willing to bet if such a study was conducted, it would find that central fatigue would play a significant role.

Anyway, the point I'd like to make is many medical practitioners and researchers need to stop assuming that supraspinal phenomena is magically independent of peripheral phenomena - despite the fact we know they are inherently linked through the nervous system. I am also suggesting that there may be parallels with the regulation of the appetite and gut too.

 

[Subtropical Island]

I too think that the term fatigue is not just ones experience or sensation but a word that describes some form of actual wear (like metal fatigue, but in a medical sense). It’s not just about sickness behaviour. It’s something not working.
I can absolutely be fatigued without realising it. (Story of my life these days - learning to recognise when it’s happening or about to).
Intrigued by the detail described here.

And bothered that so many seem to accept that fatigue = tired/sore/want to rest. Sometimes I might experience it that way but fatigue is more.

(This isn’t quite what I want to say but can’t get it to work so stopping)

 

[Mithriel]

This discussion highlights the problem with the word "fatigue". One of the problems with CFS is that most healthy people feel they are fatigued too and people with MS and other diseases claim to be fatigued as well.

They usually mean they do not have the energy they would like and things can feel like an effort instead of easy. It has a colloquial meaning that detracts from its use as a medical term.

We would be served better by giving up the term and trying to find words that are more specific because as it stands the patient means one thing and the doctor another and a different patient and doctor could have another set of ideas.

 

[Jonathan Edwards]

I too think that the term fatigue is not just ones experience or sensation but a word that describes some form of actual wear (like metal fatigue, but in a medical sense).

There is a medical sense of that sort - as in so-called fatigue-fracture when the shin bone cracks after repeated use. But I think that just illustrates how many different usages there are.

There may be a lot of confusion over ME symptoms but for both patients and doctors fatigue is a symptom, not a process that explains the symptom. 'Central fatigue' IS a process that might explain a symptom but again that just shows how comp[lex the language is.

But I don't think complexity of language of this sort need be problem. We cope with all the time in natural language. We understand context sensitivity of words.

 

[DigitalDrifter]

We would be served better by giving up the term and trying to find words that are more specific because as it stands the patient means one thing and the doctor another

I feel the same way about the term ME. When you say "ME", patients think serious physical disease characterized by an adverse reaction to exertion but doctors hear delusional hypochondriac.

We need a new term, preferably one protected by law. The IOM could have gave us it with SEID but they screwed up by conflating it with CFS, the Wikipedia article for SEID was soon vandalized and made to redirect to CFS so we were back to hypochondria.

 

[CRG]

We understand context sensitivity of words.

That really needs some qualification: "Humans have a variable capacity to apprehend the context sensitivity of words and apply such apprehension relative to cultural, social, political, financial and other interests, prejudices and advantages."

Yes in most (all ?) human languages context sensitivity is a work a day feature, but there are grades of ability in appreciation of it and of course ignorance of a particular language handicaps understanding of context sensitivity, even when provided with a translation.

The ME/CFS patient experience is heavily coloured by hasty, lazy judgements and at times outright cynical sophistry in the ascription of meaning that medics and others make of patient description of symptoms, it is not surprising then that patients, for whom language is often a challenge, are motivated to seek to place limits on Humpty Dumpty's rule :

When I use a word,’ Humpty Dumpty said in rather a scornful tone, ‘it means just what I choose it to mean — neither more nor less.’

’The question is,’ said Alice, ‘whether you can make words mean so many different things.’

’The question is,’ said Humpty Dumpty, ‘which is to be master — that’s all.”

Almost all academic study uses common words in 'special meaning', and academic phrases find their way into common usage where they take on non academic senses, so insisting that ME/CFS has to have inviolate special meanings all to itself is probably a lost cause - however that shouldn't mean that there's no rigour in the specificity of terms as they are applied to what patients describe. For example if patients (or a notable fraction of patients) describe different experiences of/as fatigue (tiredness*, exhaustion, weakness, sleepiness etc) then the words used need to be properly interrogated, and that applies in research, in treatment and support, and benefit claims.

* To me tiredness implies something normal - it's what one experiences after 16 hours or so without sleep, which might be accelerated by a range of environmental conditions, unusual exertion etc. What I associate with ME/CFS is exhaustion, reduced reaction times, loss of muscle power, loss of ability to concentrate, uncontrollable sleepiness separate from any diurnal process or prior exertion, fuzziness of vision and other sensory reduction. Pre ME/CFS I associated these things with, variously, the effects of exceptional physical effort, heavy alcohol consumption, significant lack of sleep over days, night shifts and viral illness.

 

[Mithriel]

Moved posts

Medical Express Study finds association between long COVID symptoms and altered oral microbiome

quotes:

Study co-author Dr. Bradley ... Myalgic encephalomyelitis/chronic fatigue syndrome is a condition characterized by chronic fatigue, lasting at least six months, that impairs one's ability to perform daily activities and typically has additional impairments in memory and concentration. This syndrome is also linked closely to chronic inflammation as the driver of these patients' symptoms.

Slightly off topic, but this definition of ME is the cause of a lot of our problems. It is not fatigue that impairs our ability to perform daily activities. The disease makes normal daily activities cause fatigue. Until that is understood it will be hard to move forward.

 

[Sean]

Slightly off topic, but this definition of ME is the cause of a lot of our problems. It is not fatigue that impairs our ability to perform daily activities. The disease makes normal daily activities cause fatigue. Until that is understood it will be hard to move forward.

This.

It is not fatigue in any normal sense. It is an extremely high cost to physiological activity of any kind, including base metabolism. We are starting from way below par before we even exceed base metabolism.

It is a pathological load of some kind on the body. I suspect almost everything we have seen so far is just the consequences of the otherwise normal physiology trying to adapt to that.

I am not convinced the primary answer lies in the energy systems of the body, except maybe as clues to further back up the causal chain.

 

[Haveyoutriedyoga]

On the NHS page for Addisons it says "You may experience: lack of energy or motivation (fatigue)".

So fatigue can be lack of motivation, according to this page. Or energy is equal to motivation. Note that it does not say "lack of motivation [COMMA], or energy (fatigue)".

The ME/CFS page it doesn't mention lack of motivation.

Same word, different definitions.

 

[poetinsf]

So fatigue can be lack of motivation, according to this page. Or energy is equal to motivation. Note that it does not say "lack of motivation [COMMA], or energy (fatigue)".

The ME/CFS page it doesn't mention lack of motivation.

Same word, different definitions.

But it does mention fatigue, and that "fatigue" could encompass "lack of motivation". To me, fatigue is something other than pain or injury that stops you from doing what you need to do. Attempting to qualify or classify fatigue based on the sensation seems rather useless and futile.

My PEM feels more like depression lately. Getting myself at the desk to solve an intellectual problem becomes an impossibly herculean task. Yet, I can force myself to get up and do something physical, like doing dishes or cleaning the bathroom. That would've been impossible when I was in the deeper end of ME/CFS and fatigue felt like a complete physical exhaustion with gravity 10 times stronger. I still spend 5 hours lying down when in PEM, but I'm now affected mentally more than physically.

 

[SunnyK]

But it does mention fatigue, and that "fatigue" could encompass "lack of motivation". To me, fatigue is something other than pain or injury that stops you from doing what you need to do. Attempting to qualify or classify fatigue based on the sensation seems rather useless and futile.

My PEM feels more like depression lately. Getting myself at the desk to solve an intellectual problem becomes an impossibly herculean task. Yet, I can force myself to get up and do something physical, like doing dishes or cleaning the bathroom. That would've been impossible when I was in the deeper end of ME/CFS and fatigue felt like a complete physical exhaustion with gravity 10 times stronger. I still spend 5 hours lying down when in PEM, but I'm now affected mentally more than physically.

When I was mild, I was exactly this way. And unfortunately that meant that I overexerted by doing things like laundry and grocery shopping-- this was before I had the diagnosis so I didn't realize I needed to be more careful about pacing-- instead of doing some of the brain activities that would not have involved physical exertion.

 

[Daisybell]

Apologies if this is not relevant - but fatigue is my main issue. I now eventually have a muscular dystrophy diagnosis and ME has been taken off my list of medical issues. I still feel that fatigue is my biggest problem, and it’s not well recognized by the neurologists. They look for a muscle that is atrophied, or strength that is significantly reduced in a 5 second assessment. I am still able to be strong(ish) for most muscle groups but I spend nearly all my time feeling exhausted. And if I do too much one day I am much worse for a few days afterwards. Recent MRI scans for FSH dystrophy have shown that for most (possibly all?) patients, every muscle is actually affected even if it doesn’t feel subjectively weak. I am aware of some of my muscles being worse than others, but the overall feeling is fatigue and then fatigueability on top of that. I feel that is like ME - but perhaps without the PEM - although if I really overdo things, I do feel dreadful.
I don’t know if that adds anything useful to this discussion!