Open (Palmerston North, New Zealand) Effects of exercise at anaerobic threshold on post exertional malaise in individuals with ME/CFS

I may be wrong but my understanding of an anaerobic threshold is that it is the difference between running a 100 metre sprint and running a 1500 metre distance race. Running a 1500 metre race competitively, which most of us get nowhere near, is still under the anaerobic threshold, because you can only continue for five minutes if you are using aerobic metabolism. If you exceed your anaerobic threshold you get badly out of breath and there comes a point pretty quickly where you simply cannot continue. If I am ill I find it hard to do normal activities like going up one flight of stairs but I don't think that has anything to do with anaerobic threshold. I am not out of breath, I just cannot get my muscles to do what I want. I think that has more to do with cytokine signals.

 

I dare say they do that but it seems a disconnect. The anaerobic threshold is the top of aerobic. It sounds as if they believe in advising exercise that is below aerobic. They do not seem to be related. I have to say that even with the US studies I am a bit puzzled about the relevance of the anaerobic threshold findings to PEM. I think someone thought this might be a good way of showing PEM objectively but it does not seem to fit to me. PEM kicks in much earlier as I understand it.

 

Minor point but the link is to the ANZMES website. Having recently read the overview of a recent Australian conference provided by ANZMES where there are a number of spelling/grammar errors I'd imagine the error has been introduced by ANZMES, rather than the researchers themselves.

 

I am trying to get an idea of numbers here.

It seems that a standard cardio gym work out for 45 minutes involves a power output of about 50-150 Watts. That is all below anaerobic threshold for sustained exercise. Anaerobic threshold kicks in around 250 Watts. (Apparently Chris Hoy could produce 2400 Watts at peak power.) Someone with ME might have a usual threshold of 200 Watts and a 20% drop would be to 160 Watts.

But if PEM only occurred when people went to do a cardio workout in the gym - even a gentle 50 Watt version - then it would not be a problem. Most of my life I have not exercised to this extent except on ski-ing holidays. If the only problem for PWME was that they could not do cardio workouts then it would hardly be worth calling an illness. As I understand it people get PEM from long train journeys in which would probably involve increasing the 10 Watts we expend just sitting down to maybe 20 Watts at most. My guess is that people who can do 40 Watts without problems would not consider themselves unwell. So although anaerobic threshold measurements may tell us something interesting about the physiology I don't see they have much to do with management.

 

This is interesting. Does that mean that in your view PEM cannot be explained by deficiencies in aerobic capacity? And might this suggests that the drop on a second day CPET could be unrelated to most of the PEM ME/CFS patients experience in their day to day life? As far as I know, no study has compared second day CPET results with a PEM questionnaire.

 

Is there a repeat CPET study that controls for the effects of traveling?

ie. having patients come to the clinic and do everything except repeat CPET and comparing them to the patients that did repeat CPET.

 

I tend to think it is likely to be related, but indirectly. So it is not a 'measure of PEM' but an objective measure of a change in physiology that may accompany PEM.

 

An anecdote. I'm messed up today because I did some baking and cooking yesterday. Unfortunately the banana almond bread I made made my gut inflamed (non celiac gluten sensitivity strikes again?). Anyway, my ability to walk is affected. Anything higher than old man walking speed gives me a feeling of excessive exertion. It's one of these sensations that are difficult to describe. It's not being out of breath, but there is an element of not having enough oxygen and struggling with the effort.

My heart rate was too high this morning as well, it was immediately noticable upon awakening. The bread was eaten afterwards for breakfast, so it is not to blame for this.

I don't remember feeling anything like "hitting a wall" yesterday or doing anything particularly strenuous.

 

As I understand Workwell material they see two periods of anaerobic respiration during exertion/exercise. (Trying to explain simply here for benefit of all reading )

1st - On changing from resting state to exercising state. The muscles must tap into anaerobic respiration until such time as heart rate, breathing etc ramp up to supply the increased O2 demand.

Thus the first couple of minutes of exertion are anaerobic. Once more O2 is available, then aerobic respiration should go up and in normal people the real exercise can then begin.

If exertion is then ramped up beyond the individual’s ability to supply more O2 to the muscles (level of personal fitness applies here) then a 2nd phase of anaerobic respiration kicks in, and this is the one that is so difficult, because it cannot be relieved by further increased HR & breathing rate. Thus it is short lived.


Workwell say ME patients can’t ramp up aerobic respiration appropriately. So I think they are looking at the anaerobic threshold as if there was only one transition. Meaning our anaerobic thresholds appears almost as soon as we start to exert ourselves?

At least that is my interpretation of what they are saying.

 

I agree with you that I don't think the real problems lies with the anaerobic threshold, but I am sometimes out of breath. I think the problem actually lies in the aerobic part (could also be an indirect problem, I don't know).

My symptoms have fluctuated a lot in the last year, so I can compare well.
When I was in a really bad crash last year, I started wearing a heart rate monitor. I had the flu feeling and feeling of lead in your muscles, but when I wanted to go up the stairs in my house I was also out of breath and my heart rate shot up to 140.

I still have problems now, but they are mild. I can now easily get up the stairs, my heart rate is 80 and I am not out of breath, but my muscles still feel like lead.

I have found that when I got a lot better, I could more easily do short bursts of activity than maintain anything. That's still the thing that's keeping me from doing anything normal. I can clean in short bursts of 10 minutes, but then I have to lie down to not get PEM. I went to a restaurant, after two hours I can't sit up anymore, my muscles just give in and the next day I can hardly get out of bed for that "activity" of sitting up for two hours.

If there is actual activity (sport) involved, I can more easily keep going at that moment(probably because of the adrenaline), but the next day I have PEM off course and can't do anything.

 

It's VO2 peak and VO2 at AT that are indicative, usually: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6131594/

So I've seen CPETs where the VO2 peak drops from 21 to 14, and VO2 at AT that drops from 35 to 20. Everything else is usually okay.

The work rate/power in W is usually the same on both days, as this is used to show that 'effort' is the same on both attempts (along with rate of perceived exertion and other things).

 

From my position of medical ignorance, I'd assumed this was what happens with PwME anyway, on a routine basis. I remember reading maybe 10 years or so back, that a PwME effectively "hits the wall" much like a marathon runner does it, except that for the PwME it happens pretty much every day, maybe several times a day. Although, from reading your description, the badly out of breath bit is not the same. But symptom of muscles, brain, everything, rapidly draining of (what feels like) all energy, and feeling downright ill, certainly seems to match what my wife describes, and what I understand to be some aspects of hitting the wall. Or am I mistaken in thinking hitting the wall is the same as hitting one's anaerobic threshold?

 

@Barry Perhaps our aerobic systems just don’t properly turn on - so we are still deprived of O2, but don’t get the breathless bit so much?

 

It differs between studies. The large study by the workwell foundation actually found the greatest difference for workload at aerobic treshold.

See the table on MEpedia https://me-pedia.org/wiki/Two-day_cardiopulmonary_exercise_test

 

I've sent an email highlighting this thread to Dr Hodges and Miss Otte and inviting them to join in and address the questions that have been raised.