Just wanted to share a thought on the matter, which I'll get to towards the bottom of the post.
I personally think it's clear that UTD don't promote or use RD as an algorithm but rather a starting point from where to adapt - I know that's been said a thousand times, but I've brought it up as I think it's particularly relevant in the context of the Spisni-study, which I'll get back to that in the bottom of this post, after a quick discussion on the Spisni-study itself.
But first:
The setpoints no longer work for 60-120+min BTs
The "interrim" setpoints (1:1, 1:2, 1:3) aren't designed to do bottom times beyond 120min, "the book" is actually
perfectly clear about that.
Nor are the divers who learn those setpoints trained to do such dives - by the time you're doing those bottom times, you're in Cascade Deco-land (Tech Gold, i.e. Full Tech).
We can, and often do, talk about scenarios where adaptations to Ratio Deco (incl. Cascade) make sense, but I think that's a different thing from knocking on the interrim setpoints for not being something they're actually not even made out to be.
NEDU demonstrated that extra mid-deco-ascent was counter productive with such statistical power that they had to halt the study before all the dives were even done.
I think in order to draw NEDU into it in this fashion, we'll also need to be fair and point out how that statistical power (which is elaborated on in
this article) was derived;
In order to make a clear result, trial adaptations (mentioned below) were made, and I would argue to a degree that obscures the picture somewhat in relation to the questions we're asking the study.
For instance, the divers in that study were probably bordeline hypothermic (I can argue how that may very well have had an impact), they used air for the bottom portion of the dive, and more importantly, they used air for the
decompression portion of the dive.
These factors helped answer the questions which were being asked of the study, absolutely, and were probably necessary towards that goal - but in my opinion, they also mean that the study's potential limitations should be mentioned in this context.
Statistical footwork aside (everyone's a statistician!) NEDU did
prove that deep stops aren't the black-and-white, universal solution that they were - for lack of better phrasing -
generally thought to be, but must be seen in a context. I don't personally think there's anything novel in that, but it's worth reiterating and pointing out that NEDU proved it.
It also did show slow tissue on-gassing as a probable counterpoint to them (deep stops).
This is not to try and belittle the work;
However, I think there's more to it, and this is where Spisni comes into play, as mentioned above:
Spisi illustrated some of the metabolic impacts of that extra time.
Namely, CCL5-response.
If we assume that inflammation has a significant or determining role to play in this, then I would think it's reasonable to assume that it's by way of bubble-induced platelet aggregation (BIPA), and further by way of CCL5-activation.
I don't think there's anything radical in working on that hypothesis, at least.
As we recall, CCL5-response levels are genetically determined.
That is, in addition to slow tissue on-gassing (and more general factors that we can't say to have a different impact depending on choice of algorithm/deep stop emphasis, and therefore won't take into account here - such as hydration level, fatigue, fitness level, etc.), we might have an element of genetic disposition.
That is, in the same way as we know to have "CO2-retainers", we might have "deep stoppers".
If so, it should be possible to show in a trial a correlation across CCL5-response and VGE across two groups differing only in CCL5-response predisposition.
I think that's an interesting thought.
In either case, it would mean that one algorithm or deep stop emphasis cannot be universally optimal across persons, just like it wouldn't be across dive conditions.
I think that's worth keeping in mind in the debate.
