Physical activity measures in patients with myalgic encephalomyelitis/chronic fatigue syndrome [...], 2020, Rowe et al

cassava7

cassava7

Senior Member (Voting Rights)
Pre-print, not peer-reviewed.

Physical activity measures in patients with myalgic encephalomyelitis/chronic fatigue syndrome: correlations between peak oxygen consumption, the physical functioning scale of the SF-36 questionnaire, and the number of steps from an activity meter

Rowe PC, Campen C(Mv, Verheugt FW, Visser FC

Preprint from Research Square, 08 Apr 2020
DOI: 10.21203/rs.3.rs-21479/v1 PPR: PPR148584

Background: most studies to assess effort intolerance in patients with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) have used questionnaires. Few studies have compared questionnaires with objective measures like an actometer or an exercise test. Therefore three measures of physical activity in ME/CFS patients, being the physical functioning scale (PFS) of the SF-36, the number of steps/day (Steps) of an actometer and the %peak VO 2 of a cardiopulmonary stress test were compared.

Methods: female ME/CFS patients were selected from a clinical database if the three types of measurements were available, and the interval between measurements was ≤ three months. Data of the three measures were compared by linear regression.

Results: in 99 female patients the three different measures were linearly, significantly and positively correlated (PFS vs Steps, PFS vs %peak VO 2 and Steps vs %peak VO 2 : all P<0.001). Subgroup analysis showed that the relations between the three measures were not different in patients with versus without fibromyalgia and with versus without a maximal exercise effort (RER≥1.1). In 20 patients re-evaluated for symptom worsening, the mean of all three measures was significantly lower (P<0.0001), strengthening the observation of the relations between them. Despite the close correlation a large variation was observed between the three measures in individual patients.

Conclusions: given the large variation in ME/CFS patients, the use of only one type of measurement is inadequate. Integrating the three modalities may be useful for patient care by detecting overt discrepancies and may aid study designs aimed at improving exercise capacity.
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Link: https://europepmc.org/article/ppr/ppr148584
Article: https://assets.researchsquare.com/files/rs-21479/v1/manuscript.pdf
 
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So it's a retrospective study where patients who had a single score recorded for each of the three different measures within 3 months of each other were studied. And they found strong correlation between the 3 measures.

I guess it's mildly interesting but it tells us nothing about the effect of interventions on how people score themselves on questionnaires, which is our main concern with CBT/GET studies.

I like the fact that they conclude more than one measure should be used and possibly combined in some way to measure study outcomes, but I'm afraid it could be misused by the BPS people to claim questionnaires are fine because they correlate well with objective measures.
 
Trish said:
I like the fact that they conclude more than one measure should be used and possibly combined in some way to measure study outcomes, but I'm afraid it could be misused by the BPS people to claim questionnaires are fine because they correlate well with objective measures.
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I'm not sure I do like that. They have three different measures that correlate, though not fully, and it's unclear why or whether they should be given various weights or in what context one should be more important than another.

Not quite sure how to think about this.

What do you think, @Jonathan Edwards?
 
Sasha said:
What do you think, @Jonathan Edwards?
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I don't see much logic in the abstract. I have no idea what the correlations tell us - partly because there are no actual data, just p values. If the correlations were very close then there would been need for combining measures. They tell us there was a lot of variation so presumably they were not that close.

The talk about integrating measures but do not indicate why they think that helps. It sounds as if they think it will reduce the variability - but why would one want to do that if things really are variable?

I don't get the impression they have any insight into what it is they are wanting to achieve and how they might do it.
 
In my view the approach is leading to nowhere anyway. I think that they don´t have the right idea of the illness (I think also that some patients might not have the right idea, although it might be more than one disease, of course).

As far as I understood other patients from forums, the symptoms are ranging in a huge variability, and this already indicates that at least here no strict linear relationship takes place.

Well, they looked at physical symptoms, maybe here is one?? But whatfor then? One should better look at the junction where all symptoms could be generated. I think the ICC may give a good idea (even if they might be too restrictive).

One of their three measurements is VO2. Speaking for myself, having been especially mentally affected (still I am), I can say:I had some difficulties to go for a walk lasting longer than an hour, but I could ride a sporty bike all the day (though only two times a week if I din´t want to get worse). I do not see how the approach they take would measure this. I had no "energy" to do my beloved push ups or yoga, but I could work halftime effortless (if I only reach my bed timely).

I would recommend to think and ask more adroitly, albeit maybe the result will tell something interesting, someday.
 
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As Mezzani stated: “It must be borne in mind, however, that patients with severely impaired exercise tolerance can attain skeletal muscle strength exhaustion even earlier than central hemodynamic and ventilatory factors become limiting, interrupting exercise at peak respiratory exchange ratio values even lower than 1.00” [41]. Our data therefore suggest that an RER < 1.1 should not be used as an exclusion criterion for future studies of exercise performance in ME/CFS patients.
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The key point is that VO2Peak is not equal to VO2Max unless those central hemodynamic limits have been reached (lung capacity limits are far from being reached in CFS or ME patients, unless they also suffer from COPD or other lung condition).

It is indeed difficult for some patients to exercise to a true VO2Max, and I agree this should not be an exclusion criterion, but you have to ask the question as to why are these patients even doing a single maximal CPET in the first place?
 
On the topic of push ups and skeletal muscles.

A while ago I changed my physical activity from walking to push ups and pull ups. About 15 and 5 on most days, sometimes repeated later in the day. I clearly gained muscle strength and mass but my endurance has changed very little. My feeling is that the limitation in this kind of exercise is indeed the muscles, but if the muscles are being exhausted on a daily basis, even if just briefly, shouldn't endurance increase? Is it unusual that it's not increasing or does it take more for endurance to improve?
 
Despite the close correlation a large variation was observed between the three measures in individual patients.
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Hardly surprising. The three measurements were taken during a three month period.

From memory, my VO2max dropped by 20% from the first one to the second one taken 48 hours later (and I didn't have noticeable PEM symptoms during the second one). When you have a VO2max swinging around like that (and probably more than that) as a result of previous activity, what's the point in comparing it to any other measure taken at an equally random time? Same with the step count, and probably even for a questionnaire that asked you to say how things have been for the last 6 months (because one day you might think back positively and another day your evaluation might be coloured by how crap you feel in that moment, or what happened yesterday).

I reckon you would have to have a careful protocol of a defined sustained amount of activity for at least a week before the VO2max becomes a figure that you could reasonably compare with another measure. And the activity tracker measure needs to be an average over a considerable period of time. And I don't trust the questionnaire to give anything much of value, full stop.
 
strategist said:
A while ago I changed my physical activity from walking to push ups and pull ups. About 15 and 5 on most days, sometimes repeated later in the day. I clearly gained muscle strength and mass but my endurance has changed very little.
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I have a strange experience. In 2010 I heavily got worse after having changed my diet. For one week I could not lift up things (I had to occasionally lift up at work) of some weight. It felt as if the muscle would not be able to exert its strength.

After a week or so I still felt worse, but the muscles were fine again.

Snow Leopard said:
No.
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Yes.
 
Part of the picture of ME is that there is a certain level of overall function which can give a number on something like the SF 36 but it is far too blunt a tool to pick up anything much about the processes going wrong.

The original criteria included variability over minutes, hours, days and so on which CPET testing can pick up if done twice but results for any random day don't tell us anything.

Questionnaires only give the least interesting results for ME, like continually doing research which shows that blind people can't see. A waste of money and of little use to patients.

I wish papers like this were part of a move to ditch the questionnaire for proper tools of inquiry.
 
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