Andy's attempt to create a reasonable descriptive model of ME.

No problems, again it's probably a sign that I didn't word things as clearly as I might have done.

For post duplication, it'll be easiest for the mods if you report the post that is the start of what you want and explain what you want.

 

Ok.

I was thinking of a thread that starts with post number 8 (your text) and includes the other posts until post 19 (which is where you suggest creating another thread). The title could be something like: "working out descriptions of PEM." Perhaps you, Andy could then indicate which posts you would like to keep on this discussion. Feel free to delete any of mine if you think they are derailing the discussion.

Thanks for your work on this.

 

This is a ll a very very good idea @Andy nice one

Actually I think it would be good to see, especially when held up against the other 2 (mild & moderate)

yes I have to agree 'over exerting' to 75%... 75%?! golly I don't know anyone who's moderate who could exert to 75% of 'normal/healthy' even once, never mind 2 days in a row.

I think all the SLEs & over exertion points are significantly too high.
I realise this point feeds into some differences of opinion in terms of what constitutes 'mild/mod/severe' but again I never heard of anyone mild who went to work full time & then only reduced their activities down to 75% at the weekend & avoided PEM, from what I've read most mild people spend their wk ends flat out on the sofa or bed if they work full time. Perhaps i'm wrong about that. But it would seem that the graph would be more accurate with the milds reducing down to 60 or even 50% at the wk ends, & the moderate 'overexertion' point showing at 60%.

Again only my pov …. maybe others will disagree.

Yes.... very important that the SLE moves down commensurately after the over exertion. And as the SLE moves downwards the sensitivity to things like sensory input goes up.
iyam this is part of why this condition is so hard for non sufferers to grasp.​

 

To my completely non-medical but engineering oriented brain, the common factor is energy draw - they all require energy. Physical exertion may be the obvious one, but processing sensory inputs does not happen by magic, every form of processing has to consume energy, physical, cognitive, signal processing, whatever.

 

Is PEM like DOMS? I'm not sure it is. One is the usual, expected soreness after exertion. Comparing the two might unintentionally mean lots of athletes think they have ME.

 

Well, to start, I say

So, for me, the elements that are shared are
1. delayed onset, both can occur hours or even days after exertion.
2. trigger, both are triggered by exertion.
3. some similar symptoms i.e. pain and soreness.

but I am not claiming that they are the same thing. You say that DOMS is the usual, expected soreness after exertion. Is it not reasonable to say that, for pwME, PEM is the usual, expected soreness, pain and exacerbation of other symptoms after exertion?

And as to swelling the ranks of pwME with "lots of athletes"? Sorry, I don't believe that this is a valid concern, given the additional criteria required for an ME diagnosis.

 

In my proposed model, or in the graphs I've used, or the descriptions of patients?

Well, currently many researchers, even ones who we rate the work of, still state in their papers that the primary issue for ME patients is unexplained fatigue that has lasted 6 months or more, so I'd like to suggest that my model is not an oversimplification compared to that, and helps by refocusing onto SEL/PEM. It is not my intention to deny any other symptom that anybody has but I'm focusing on SEL/PEM as it seems to be the central issue for the vast majority of patients.

My intention with the descriptions of the patients with mild and moderate ME is to demonstrate potentially what an individual might be able to do, given the restrictions placed on them by ME.

For the mild person, I say

and for the moderate person, I say

Additional description can definitely be added, and perhaps even additional graphs, to illustrate what is sustainable for patients, which is what I have attempted to do already, and what isn't.

 

My point was more that this downplays what PEM is. Everyone can get DOMS. Not everyone gets PEM. There are already lots of tired people who say they think they have ME because they work shifts or whatever. If PEM was likened to DOMS, then I could see people who overtrain and have poor sleep patterns thinking they have ME.

If I were to compare the two, I'd say something like 'PEM is more than DOMS because...' and explain the differences, I think.

This is all my opinion, of course.

 

Struggling to get my brain around this thread, each time I try to form a comment my thoughts fall apart.

However, I do think this is important, that we have a strong language to delimit the patient experience and a clear formulation of the concepts we see as most important.

Thank you to all who are contributing.

 

I too like SEL and want to add my own caveat. My suggestions are merely to help get this right. It's going to be hard to please everybody, though, because it will be difficult to describe PEM, or any of the symptoms really, in such a way as to include everyone all the time. That doesn't mean we shouldn't try, though.

 

Andy, without having read follow-up posts, I think you are off to a generally excellent start.

I do think that PEM should be defined when it is first mentioned (to help a general audience).

The one statement that was a clunker for me was: This suggests that the mechanism in the body that, in healthy people, leads to increased fitness is, in some way, broken in ME patients.

I understand what you are trying to say here, but the fact that increased activity and exercise generally makes a person in the healthy population feel better (both physically and mentally/emotionally) where exertion typically has the opposite effect in people with ME/CFS is a critical thing for people in the general population to understand. I think this point could be improved.

Quibble aside, good job!

Bill

 

About 70% of a human's total energy expenditure is due to the basal life processes taking place in the organs of the body (see table). About 20% of one's energy expenditure comes from physical activity and another 10% from thermogenesis, or digestion of food (postprandial thermogenesis).

I think Andy's proposal may not be too far off. The 70% figure is presumably typical of a normal lazy human. But Andy's SEL is,I think, the limit of what one can sustain. For Ranulph Fiennes in Antarctica this was 8000 calories a day. I suspect for an average adult it might be 4000-5000. I think the basal metabolic rate during sleep is about 60 Kcal/hr and the minimum during waking 90. That adds up to about 2000. Put another way a fit adult can use twice as much as their BMR and sustain it if they have to. Trebling it might be tough but my impression was that Andy was just choosing some illustrative figures. That would not worry me.

 

I agree, but it was you that was grumbling about the numbers not being precise!

I don't think the recommended intake for average males comes in to the equation if the level in question is sustainable limit. I agree that for PWME sustainable limit would seem to be way below that of normal.

I guess this one reason why I find a metabolic explanation implausible. If a metabolic capacity is reduced by more than half it should have been reasonably easy to identify in physiological studies.

 

Sustainable Exertion Limit (SEL) - I like it!

The word exertion may need some definition though. Healthy people tend to interpret exertion as being the same as physical exercise such as jogging. Whereas we think of it more as any energy-demanding process (physical or cognitive activity, infection, sensory processing, etc.).

Thought experiment - an attempt at combining:

• @Andy's model
• the observation by several others in this thread that SEL is not fixed
• the observation that sometimes some level of overexertion is temporarily possible
• the observation that sometimes, after a major crash, our functioning is permanently reduced

I propose that there are THREE thresholds:

1) a SEL threshold - exceeding this does not cause PEM but it lowers all thresholds

2) a fully symptomatic PEM threshold (fsPEM), higher than SEL - exceeding this does cause PEM and lowers all thresholds

3) a critical point threshold (CP), higher than fsPEM - exceeding this does cause PEM and lowers all thresholds and permanently lowers 'baseline'

Example (the numbers are just for illustration, they don't correspond to any specific severity; the word recover in the example means recover to pre-PEM state, not to healthy):

Starting SEL=40 & fsPEM=60 & CP=90 ---> PwME exerts at 50. This doesn't cause PEM but it lowers SEL & fsPEM.

New SEL=33 & fsPEM=53 & CP=83 ---> PwME exerts at 50 again. This still doesn't cause PEM but it lowers SEL and PEM further.

New(2) SEL=26 & fsPEM=46 & CP=76 ---> PwME exerts at 50 again. This now causes PEM because it exceeds the new(2) fsPEM=46.

PwME's reaction to PEM, option 1:

PwME reduces exertion to 30, thinking that is safe because starting SEL was 40. But because 30 is higher than the current SEL (26) the PwME remains in PEM (for recovery from PEM exertion needs to be below SEL, not just below fsPEM). Thresholds lower further.
New SEL=19 & fsPEM=39 & CP=69 --> The downhill trend continues.

OR

PwME's reaction to PEM, option 2:

PwME reduces exertion to 20. This is lower than current SEL (26) so PwME begins to recover. Thresholds begin to rise again (but only after several days because PEM, once started, doesn't go away overnight).

Other scenarios:

Starting SEL=40 & fsPEM=60 & CP=90 ---> PwME exerts at 70. Leads to immediate PEM. Eventual recovery to Starting SEL=40.

OR

Starting SEL=40 & fsPEM=60 & CP=90 ---> PwME exerts at 100. Leads to immediate PEM. Eventual recovery only to Below Starting SEL=35.

Severity in this model could be varied by higher or lower starting thresholds as well as by the magnitude/speed by which thresholds go down after overexertion, or recover after rest.

NB: The graphic doesn't follow the above scenarios exactly but tries to combine the various options. A bit messy, I admit, but haven't got the energy to try again right now.

 

If most of the body's energy production goes toward merely sustaining itself, then even a small decrease in ability to produce energy would mean a large drop in ability to function in daily life.

If for example 70% goes toward sustaining itself, and 30% towards daily activities, then even a 10% drop in total energy production would mean that only 20% can go towards daily activities. 20% instead of 30% should be quite noticable for the patient. In a study however that 10% could look like an insignificant change.

 

Exactly. This is the notion that has been discussed in another thread recently, with analogy to "disposable income". When you have very little to spare you only need quite small changes in the absolute values to have a dramatic effect on the margin left over - potentially going negative.