Physiological measures in participants with chronic fatigue syndrome, multiple sclerosis and healthy

[Hutan]

So I participated in the followup study.
..................................................................Day 1.......Day 2 (48 hours later)
VO2 max Absolute (L/min)...........................1.71........1.27
Relative to bodyweight (ml.kg.min)..............23.97......17.81
Maximum Heart Rate(bpm)...........................177.........172
Maximum Workload (Watts)..........................105.........105
Normative VO2 max for my age range (relative to body weight)......Fair 22.8 to 26.9
..........................................................................................................Poor 20.2 to 22.7
..........................................................................................................Very poor <20.2

VO2 at anaerobic threshold
........................................Day 1....Day 2..........Normative for age range
Workload (Watts)...............90..........75
Heart rate (bpm)...............165.........148
Vo2 (ml/kg/min).................19.5........14.7.....................17.8
% of Vo2 max....................81%..........82%

So I'm confused. It looks like I did a VO2 max study - but it wasn't that hard and it didn't take that long. For sure, I could have gone on much longer/cycled with greater resistance.

I need to understand this more, but right now I'm not thinking well. I can't catch my thoughts and get them to sit in an orderly way, they just skitter away and hide. If anyone can formulate a question on this, I can ask the researchers.

ETA: My impression was that the researchers thought that they had found that VO2 at anaerobic threshold did drop in CFS patients in that preliminary study and that my results were consistent with what they expected.

ETA: reading the preliminary study, I now realise that it must have been the 'workload at anaerobic threshold/RER' variable that they found decreased upon re-testing in people with CFS. My results were consistent with that expectation.

 

[Hutan]

From the paper on the pilot study:

Starting at 15 W, the intensity was increased at a rate of 15 W/min. The test was terminated vol- untarily by the participant or when they were unable to main- tain a pedal frequency of 50 rpm, or the ACSM termination criteria were met (Medicine, 2014).

Given that I got to a 105 watts power level, that would mean I was only cycling for 7 minutes, which could well be right, with a few minutes of that time being very easy cycling (little resistance). I was able to maintain a steady 60 rpm as instructed and didn't voluntarily stop. I don't understand yet how the researchers knew when the VO2 max was reached (did the VO2 actually plateau or did the researchers decide to stop the test due to my heart rate?).

 

[Hutan]

From the paper on the pilot study:

It is clear that those with CFS/ME are frightened to exercise, due to the symptoms of postexertional malaise that may manifest after this and as a result can be unfit.

This seems a bit unfair. If I know that a jog around the block will mean that I can't function tomorrow and that I will be miserable with pain, it's not necessarily fear that is stopping me from jogging. I'd rather keep my limited energy for the things I have to do and do those things in a way that ensures that I can do them again tomorrow. That seems like a rational choice to me.

I also think that some of us have read things about the two day CPET testing that make it sound very difficult and likely to have serious consequences. So, any fear that the CFS participants expressed to the researchers may well have related specifically to the CPET test rather than, say, a brisk walk (or the 7 minutes of cycling that my CPET involved).

 

[Hutan]

(And I'm sorry if this point has already been made. I have read this thread and forgotten things - and will re-read it. I'm just working my way through the paper and trying to understand.)

The current study observed a reduction in workload at RER on day 2 in CFS/ME participants (12 W), compared to an increase in healthy controls (+13.5 W). This finding is consis- tent with those in similar studies to date. Snell, Stevens, Davenport and Ness employed a protocol almost identical to the current study, with 51 CFS participants and observed a significant decrease of 27.31 W at RER on day 2 of their study. They concluded that of all variables tested across peak and RER data, the difference in work at RER was the most sig- nificant variable (Snell et al., 2013). Keller, Pryor and Gilo- teaux studied the responses of 22 participants diagnosed with CFS and had similar findings to our study, with a decrease of 10 W at RER on day 2 (Keller et al., 2014). An earlier study by Vermeulen et al. (2010) also looked into this response across 15 female-only CFS patients versus controls, revealing a decrease of 41 W at RER in CFS compared to an increase of 10 W in healthy controls (Vermeulen et al., 2010).

So this reduction in workload (measured in watts) at anaerobic threshold/RER seems to be the difference to focus on.

My workload at RER decreased 15 watts over the two tests, so that looks to be consistent (although the interval between my tests was 48 hours not 24 hours). It should be noted that the power on the cycle went up in steps of 15 watts so the measurement of difference isn't very precise.

ETA: To clarify, the researchers are using 'anaerobic threshold (AT)' and 'RER' as meaning the same thing. Presumably it's actually when the respiratory exchange ratio = 1 that AT=RER.

 

[Valentijn]

I don't understand yet how the researchers knew when the VO2 max was reached (did the VO2 actually plateau or did the researchers decide to stop the test due to my heart rate?).

Your respiratory exchange rate (RER) was likely showing up in real time on a computer monitor that they were watching during the tests. So they could stop everyone when they hit 1.1 or 1.15, instead of waiting for people to basically fall off the bikes.

I went to 1.23 voluntarily on mine in Belgium, and was collapsed on the floor struggling to catch my breath for 15 minutes Stopping at 1.15 might spare patients a bit of that.

 

[Snow Leopard]

Given that I got to a 105 watts power level, that would mean I was only cycling for 7 minutes, which could well be right, with a few minutes of that time being very easy cycling (little resistance). I was able to maintain a steady 60 rpm as instructed and didn't voluntarily stop. I don't understand yet how the researchers knew when the VO2 max was reached (did the VO2 actually plateau or did the researchers decide to stop the test due to my heart rate?).

If you didn't stop because you felt like you're about to pass out, or your legs simply can't put out the power, no matter how hard you try, then you didn't do a maximal exertion test.

Peak RER is not the ventilatory or anerobic thresholds. The ventilatory threshold is when ventilation starts to increase at a faster rate than VO2.

 

[Valentijn]

If you didn't stop because you felt like you're about to pass out, or your legs simply can't put out the power, no matter how hard you try, then you didn't do a maximal exertion test.

No, RER is used as an endpoint for determining VO2max. The "max" is for maximal oxygen consumption, not maximal effort. Which is a good thing, because oxygen consumption is measured objectively, and maximal effort is subjective.

 

[Snow Leopard]

No, RER is used as an endpoint for determining VO2max. The "max" is for maximal oxygen consumption, not maximal effort. Which is a good thing, because oxygen consumption is measured objectively, and maximal effort is subjective.

Hutan was implying that (peak) respiratory exchange ratio (RER) was equivalent to the anaerobic or ventilatory thresholds, which they are not.

RER can plateau a bit before peaking, my VO2Peak was about 1.5-2 minutes after my RER plateaued on the first day. But the authors of this study have provided no data on the RER and they did not state that an RER of 1.15 or similar was a designated endpoint, so I remain sceptical.

 

[Hutan]

Hutan was implying that (peak) respiratory exchange ratio (RER) was equivalent to the anaerobic or ventilatory thresholds, which they are not.

I wasn't. I'm saying the researchers are using the terms RER and AT as synonymous, both in this published paper on their pilot trial and the report they sent me with my results. That only makes sense if they are meaning that an RER of 1 is equal to (or a reasonable proxy for), the anaerobic threshold.

See for example
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1980-00372017000100108

In conclusion, iRER1.0 can be used as an alternative method to detect AT in long distance runners.

RER's can obviously be greater than 1 - so a peak RER will be greater than 1 and isn't synonymous with AT.

I will ask the researchers how they determined when to stop my test (eg, were they using a specific RER like 1.15 as a cutoff).

 

[Snow Leopard]

I wasn't. I'm saying the researchers are using the terms RER and AT as synonymous, both in this published paper on their pilot trial and the report they sent me with my results. That only makes sense if they are meaning that an RER of 1 is equal to (or a reasonable proxy for), the anaerobic threshold.

I apologise for the miscommunication, I should have said you were pointing out the authors were making this (mistaken) comparison.

It's a really sloppy use of language by the authors as it makes no sense RER is a ratio and it is also a bad idea to assume RER=1 to be equivalent to the AT, in a nonhomogenous group (in terms of fitness). The paper should not have passed peer review as it is currently written...