There has been a lot of talk about anaerobic thresholds but do we have any good evidence for people with ME/CFS going above their threshold or for it to have anything to do with symptoms?
Purely anecdotal but with enough strength to it that, combined with the fact that producing high quality evidence is extremely difficult, it should at least be respected, although it should not be taken as a firm thing, doing the same silly mistake of thinking that such thresholds have firm numerical values, such as POTS requiring 30 BPM and concluding that an increase of 29 is the same as 0.
It's more of a rule of thumb that mostly acts as a guide for what it means to pace. There is no exact science, not even an inexact one, no way to define it universally, and these things tend to fluctuate and vary over time anyway. Rules of thumb make are useful when they're the only available option, but they do require a lot of experience and very carefully tuned biases.
Given the tools and methods of medicine, given how there obviously is no firm quantity of something that can be measured here, I don't think it's possible to do this scientifically, and probably not yet, but ever. There are things where scientific certainty is simply not available, and where deciding to ignore it as it if doesn't matter is just as bad an option, and this is one of them.
Most likely at some point there will be treatments that simply make this problem not matter anymore because it will have been bypassed entirely, which is just about the only way we ever solve problems of this type. Nobody has to worry about the right level of sweetness in urine is concerning as possible diabetes, and that's just as well.
