Skeletal muscle properties in long COVID and ME/CFS differ from those induced by bed rest (Charlton et al., Preprint, May 2025)

[bad1080]

Abstract​

Patients with long COVID and myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) suffer from a reduced exercise capacity, skeletal muscle abnormalities and post-exertional malaise (PEM), where symptoms worsen with cognitive or physical exertion. PEM often results in avoidance of physical activity, resulting in a lower aerobic fitness, which may contribute to skeletal muscle abnormalities. Here, we compared whole-body exercise responses and skeletal muscle adaptations after strict 60-day bed rest in healthy people with those in patients with long COVID and ME/CFS, and healthy age- and sex-matched controls. Bed rest altered the respiratory and cardiovascular responses to (sub)maximal exercise, while patients exhibited respiratory alterations only at submaximal exercise. Bed rest caused muscle atrophy, and the reduced oxidative phosphorylation related to reductions in maximal oxygen uptake. Patients with long COVID and ME/CFS did not have muscle atrophy, but had less capillaries and a more glycolytic fibers, none of which were associated with maximal oxygen uptake. While the whole-body aerobic capacity is similar following bed rest compared to patients, the skeletal muscle characteristics differed, suggesting that physical inactivity alone does not explain the lower exercise capacity in long COVID and ME/CFS

https://www.medrxiv.org/content/10.1101/2025.05.02.25326885v1.full.pdf

 

[Wishful]

The two groups differ in more than inactivity, which complicates comparison. They have quite different mindsets: agreeing to be inactive vs prevented from being active. The subjects with ME are probably much more stressed too, worrying about triggering PEM, money, etc.

For a followup, they should study the muscle tissue of other people who are inactive for different reasons, such as being in a body cast, paralyzed, severe depression, etc.

 

[cfs since 1998]

The two groups differ in more than inactivity, which complicates comparison. They have quite different mindsets: agreeing to be inactive vs prevented from being active. The subjects with ME are probably much more stressed too, worrying about triggering PEM, money, etc.

It's almost like you favor the psychosomatic view of ME/CFS.

 

[Rufous McKinney]

agreeing to be inactive

A normal person would become very stressed from being inactive to that degree, even if they volunteered willingly. In my opinion.

 

[Rufous McKinney]

That abstract is rather poorly written, I see the researchers are mostly from the Netherlands.

HERE: I don't know what this is saying, and would need to read the paper.

.." but had less capillaries and a more glycolytic fibers, none of which were associated with maximal oxygen uptake"

___
So do capillaries disappear if tissue is underused?
What are glycolytic fibers?

Assuming a lower density of capillaries per unit area, that would suggest reduced oxygen will be available and maybe more toxins and wastes build up from this reduced blood flow.

And glycolytic fibers- Sound like stuff that can gunk up the works.

 

[Rufous McKinney]

Google AI Says:

Glycolytic fibers, also known as Type II or fast-twitch fibers, are skeletal muscle fibers that primarily rely on anaerobic glycolysis for energy production. This means they use glucose without oxygen to quickly generate ATP, leading to rapid but short-lived muscle contractions. They are characterized by their large diameter, high glycogen content, and ability to produce powerful, rapid contractions, making them suited for activities like sprinting and weightlifting.



Maybe those fibers are not GUNK.

Wonder what other types of conditions result in an increase in glycolytic fibers?

 

[Rufous McKinney]

Glycolytic fibers, continued:

Fatigue:
Due to the less efficient energy production and the buildup of byproducts like lactic acid, glycolytic fibers fatigue more quickly than oxidative fibers.


Well well. Now we see how our muscles fatigue so much more quickly, this may help account for that.

Next I read this:

"Several health conditions are associated with an increase in glycolytic muscle fibers, often accompanied by a decrease in oxidative fibers. These include aging, obesity, and type 2 diabetes. These changes are thought to contribute to muscle atrophy and insulin resistance. "

Oh boy! Blood sugar is not good, in my case. Gets much worse when I'm in PEM Or more run down. I think alot of ME folks have issues with blood sugar.

 

[bad1080]

What are glycolytic fibers?

https://open.oregonstate.education/aandp/chapter/10-5-types-of-muscle-fibers/

 

[Rufous McKinney]

https://open.oregonstate.education/aandp/chapter/10-5-types-of-muscle-fibers/

I almost got all the questions right. Without reading the paragraphs. I sort of glanced over it, and seeing test questions got excited about tests.

 

[Wishful]

It's almost like you favor the psychosomatic view of ME/CFS.

Not at all. I'm saying that state of mind can affect various body functions in various ways, so the study in question isn't as simple as differences caused by ME, since the two groups differ in many other ways. That's why I suggested the followup, to see whether the changes in muscle tissue were specific to PWME, or were common in other causes for reduced activity.

 

[Hufsamor]

Agreed.
To compare forced bed bound with forced bed bound makes a lot of sense.

(I also think it’s rather terrible to make healthy people stay in bed over a long time. Research have shown a long time ago that a healthy man takes a long time and hard work to get back to his former health after a prolonged time of inactivity)

 

[Wishful]

I also think it’s rather terrible to make healthy people stay in bed over a long time.

It would be wrong to force them, but if those people volunteer because they believe it will help people, I don't see that as wrong. We can't create useful models of how the human body responds to certain situations without having some experiments done. Mouse experiments might give the wrong results. However, mouse experiments might be useful for maximizing results and minimizing harm from human experiments.

 

[Mary]

I'm saying that state of mind can affect various body functions in various ways, so the study in question isn't as simple as differences caused by ME,

This makes me nervous. The BPS crowd says we need to stop paying attention to how our bodies feel - just ignore symptoms - and we'll get better. I tried their technique and just crashed when I tried to ignore how I felt. I have crashed after being in a very good mood, having had a rare good day - and i have crashed after being in a crappy mood. My mood or what i thought had nothing to do with whether or not I crashed. The deciding factor was how much exertion I spent spread over how much time - it could be an equation! E/T = crash or not crash.

So I think you have to be very careful when you start talking about state of mind influencing bodily functions. yes, someone who is always catastrophizing might have higher blood pressure than otherwise, etc. But no matter how positive I try to be, it has never prevented a crash or made a crash resolve more quickly than it would otherwise. Imagine we all have broken legs - I don't think one's frame of mind would make a significant difference in the rate of healing.

 

[bad1080]

The BPS crowd

what's that? like body positivity?

 

[Mary]

what's that? like body positivity?

It means "biopsychosocial" - from AI:

The biopsychosocial model is a holistic approach to understanding health and illness that considers the interplay of biological, psychological, and social factors. It emphasizes that these factors are interconnected and influence each other, rather than being separate entities.

Although I think "body positivity" conveys the same thing!

 

[Rufous McKinney]

British Psychological Society

like body positivity?

edited: this acronym is very popular world wide.

 

[Mary]

The two groups differ in more than inactivity, which complicates comparison. They have quite different mindsets: agreeing to be inactive vs prevented from being active. The subjects with ME are probably much more stressed too, worrying about triggering PEM, money, etc.

For a followup, they should study the muscle tissue of other people who are inactive for different reasons, such as being in a body cast, paralyzed, severe depression, etc.

All clinical trials involve people who have different mindsets because we are all different, we all have different things going on in our lives, etc. However, clinical trials don't factor in the mindsets of the people participating. This would make research incredibly subjective and would obviate the whole point of a clinical trial. The researchers measure bloodwork and other quantifiable things. They don't ask, "how do you feel about participating in this trial" as some kind of quantifiable thing.

And how do you know what the healthy people were thinking? Maybe some of the healthy volunteers were in the middle of awful divorces or lost their job, etc. But that's not in the purview of the study. You can't assume the people with ME/CFS were more or less stressed than the others.

 

[bad1080]

It means "biopsychosocial"

yes, the idea the brain (the part that is impacted the most by me-cfs) can somehow think itself healthy is a wild concept and it doesn't seem to be far off of ideologies such as flat earth.

 

[kushami]

I read an article years ago about college students in the US volunteering to be on bedrest for studies. It was written by a journalist, not one of the researchers in the program, so I hope it was unbiased. The students were perfectly happy to do it to earn some extra cash and said at the end that they found it quite an interesting experience.

The logistics, e.g. waste excretion, were quite something. I believe the students were able to read, listen to the radio and perhaps watch TV. If I remember rightly, the journalist was surprised at how relaxed they were and that several had participated more than once.

Also – free food and being paid for doing nothing (from their perspective) might be quite attractive occasionally for a young, broke student.

I wish I could remember where I read it as it was a good article. Possibly Scientific American or New Scientist, as that was my science reading back then, but it might have been in the newspaper.

 

[Rufous McKinney]

might be quite attractive occasionally for a young, broke student.

You could teach yourself a foreign language while confined. Or, actually study for your Graduate Records Exam. I could see students doing that. And they tend to be optimistic and likely just figure they will rebound from this experiment, at a later date.

(see movie stars who gain 150 pounds, or lose 80, etc etc etc)