For what it's worth, 70% of HRmax is a pretty decent pace and if they successfully matched the workloads for all intents and purposes HIIT should actually fare better if my personal experience is any guidance. Steady-state cardio triggers the worst symptoms in me (although it is very debatable at this point if I can actually reach the workload required to make the HighIntensity part of the intervals true, I have not tried that for a long time).
I cannot see, however, how they can possibly reach the conclusions they wrote unless there is more to it than what is posted in this thread. Did they mean the exacerbations in fatigue were not different from baseline or from each other? Because vs baseline it sounds reasonable that they either did not properly select the patient cohort (which would be weird given the first sentence under 'Purpose' - it would invalidate the entire thing) or did only look for changes instantly after the bout which are not necessarily meaningful (e.g., I usually cannot sleep for ~24 hours after exercising like that and have disabling pain all over my body for a week which is way worse than any tiredness I experience immediately after training). Vs each other is pretty meaningless unless you can show any benefit from exercise, so it really just supports that we can look at HIIT as well as steady state work but it obviously doesn't mean either is worth our time. Also, why does it have to be a graded exercise course? We already know that we don't do well on those, pretty much by definition. I would be much more interested to see if e.g. one regular bout of exercise without any forced progression that may give me short-term symptoms leads to less illness progression over the years.
More nitpicky, I do not think anyone who is as deconditioned as most people in a patient population should be will be able to do actual HIIT as it is defined. You almost have to be a regular trainee to be able to truly make it to high intensity (even if you reach your peak perceived intensiveness it might still not be close to high intensity iirc), so if you match workloads you will likely just have a mix of low-to-moderate and the high end of moderate vs steady state moderate. But maybe the use of the term has changed in the last ten years since I looked into this - if it has not, it might be somewhat relevant because it would invalidate some cases of cross-referencing literature in the future which is sort of annoying.
Edit: Glossing over the full text, I can see they changed the meaning of GET vs how it is used in e.g. PACE. See:
GET uses cautious increases in gentle aerobic exercise and is generally guided by the patient’s report of symptoms
..which is the opposite of PACE-GET which ignores exacerbation of symptoms and instructs to increase workload anyway. The go on to cite that walking is well tolerated which does not apply to me at all (exercise modality does not seem to matter for me personally).
On recruitment, they claim that this is were they got their n=15 from:
The clinic provides a specialized exercise physiology and clinical psychology intervention for patients with chronic fatigue states, as part of an integrated cognitive behavioral therapy and GET program.
A clinic that does this will almost by definition not select patients with ME, so it is important to keep in mind that we are dealing with a rather loosely defined 'CFS' cohort, whatever that may mean.
Adding some weight to my nitpicks:
The “high-capacity group” (n = 14) included those participants who were able to manage 20–30 min of walking. The capacity level was indicated by the patients’ treating exercise physiologist.
Again, it may be true that the way the term HIIT is used for people with coronary heart disease has a different definition of how it is used in training for sports, but as I said it is extremely unlikely that someone who can manage 30 min walks as the upper end of their limit is able to tap into their reserves enough to meet the required intensity. This is not that relevant if everyone is aware how the terminology is used, but in exercise science I assume we would talk of moderate intensity intervals if we wanted to be technically correct.
Another point on patient selection:
Eligible participants had to meet the international diagnostic criteria for CFS (
8); have their treating exercise physiologist and clinical psychologist resolve that they had a stable pattern of symptoms, including optimized sleep–wake patterns, and mood; and be regularly exercising approximately 10–15 or 20–30 min of walking at a gentle pace without producing a prolonged exacerbation of symptoms.
I'd be out because my symptoms fluctuate, including sleep/wake cycle and mood. I cannot exercise for 10 minutes without producing a prolonged exacerbation of symptoms. So while it is true that they were only looking at very moderate cases, we have to keep in mind how much preselection is going on here - essentially everyone who gets PEM from the intervention is out from the get-go. It is really only a study for people who actually do reasonably well on regular (albeit super low volume and intensity) exercise, which I imagine would preclude almost everyone who is a regular on this board. I would be happy if they made it more clear that they study their non-PEM-CFS so we can avoid any confusion. I would not have spent the last hour looking at this if that were more clear from the quoted parts... and subsequently I am not going to spend more time on this because this is obviously not applicable to me and I don't think I'm gonna find out anything that would help me here. I wish they were more upfront about that, but I suspected as much from the HI-IT part already so I guess the joke is on me. Yet again.
