GUE Rec Ascent Profile

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David Novo

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Is the GUE recreational ascent profile of 9m/min during the first half of the ascent and 3m/min thereafter an implementation of Buhlmann with GFs (with a 0 stop length at any stop, including the point where GFlo is reached)?
 
GUE uses (also see SOP) GF20/85 for rec3 and technical dives. Since they were doing technical dives before even having a recreational program, it stands to reason they used Buhlmann to come up with (or validate) the MDL ascent protocol as well.
However, I have no idea if the protocol is actually based on a specific deco model with rec diving in mind or simply an ascent rate that works within the GUE rec envelop (including the standard gasses) that complements the tec training. Also don't forget about the 1m/min final bit.
Interesting question, makes me wonder where other agencies got the 3 min @ 5 meter safety stop from.
Obviously stopping shallow for a while helps offgassing, but it would be interesting to see why the specific methods were developed, and maybe even which method is best.
For what it's worth, since my fundies I have been doing extra slow ascents on every rec dive, and after a full day of diving I feel less tired compared to when I did a "safety stop - ascent to the surface" style dive day. Not really proof of anything, but it certainly made me a fan of the slower ascent profile.
 
Also don't forget about the 1m/min final bit.
Interesting question, makes me wonder where other agencies got the 3 min @ 5 meter safety stop from.
It may be the other way round, since the safety stop came from research in the mid 1970s.
 
It may be the other way round, since the safety stop came from research in the mid 1970s.
Yes, you are right. I guess I should have phrased it differently: by now, we know that doing a safety stop / really slow continues ascent works, it adds more conservatism to the profile. At the moment, there are several methods that achieve this ("traditional" safety stop / GUE style continues slow ascent). Does anybody know how these methods were developed / discovered?
- developed into standards simply because people discovered it works?
- developed into standards because a certain model said so?
- developed into standards because there was a different theoretic benefit?

And follow up:
Are there significant differences between the various methods with regards to safety?
I guess we could include all the deep stop arguments in the discussion as well (like time in the water etc etc) but since this is about rec ascents I would be content with an answer like "this works in real life, corresponds with model X and the deviations from that model that are made are done because of reason Y"
 
Also don't forget about the 1m/min final bit.

I did fundies last year and there was no reference to 1m/min for the last 3m. Even "Beginning with the End in Mind" states that one minute from 3m to the surface is desirable but not mandatory.

Yes, you are right. I guess I should have phrased it differently: by now, we know that doing a safety stop / really slow continues ascent works, it adds more conservatism to the profile. At the moment, there are several methods that achieve this ("traditional" safety stop / GUE style continues slow ascent). Does anybody know how these methods were developed / discovered?
- developed into standards simply because people discovered it works?
- developed into standards because a certain model said so?
- developed into standards because there was a different theoretic benefit?

And follow up:
Are there significant differences between the various methods with regards to safety?
I guess we could include all the deep stop arguments in the discussion as well (like time in the water etc etc) but since this is about rec ascents I would be content with an answer like "this works in real life, corresponds with model X and the deviations from that model that are made are done because of reason Y"

This would indeed be interesting to know.
 
I did fundies last year and there was no reference to 1m/min for the last 3m. Even "Beginning with the End in Mind" states that one minute from 3m to the surface is desirable but not mandatory.

I don't think the SOP is public domain, so I will not quote the entire thing, but if you did fundies you should be able to download the SOP 3.0 document. At the top, in the generic bit of the ascent profile, it mentions the last stop at 6 meter, with an ascent of 1 meter / minute to the surface. 2 lines after that is goes into the recreational specifics: last stop at 3 meter, followed by a slow ascent to the surface. So you are right, it is desirable but not mandatory. Same as a safety stop basically.
If you follow the desired / encouraged slow ascent, it will better match any theoretical model used to create the ascent protocol. After all, somebody somewhere thought it was a good idea to ascent like that.

quick edit: if an agency goes through the trouble of creating an ascent protocol that differs from most other agencies, they probably have their reasons. Following the recommendations of the protocol means you respect those reasons as much as possible, even if they are not mandatory.
 
I always thought the minimum deco ascent was a great way to prepare you for later technical training. Especially the 9m/min ascent to the first "stop", while keeping a team together.
 
I don't think the SOP is public domain, so I will not quote the entire thing, but if you did fundies you should be able to download the SOP 3.0 document. At the top, in the generic bit of the ascent profile, it mentions the last stop at 6 meter, with an ascent of 1 meter / minute to the surface. 2 lines after that is goes into the recreational specifics: last stop at 3 meter, followed by a slow ascent to the surface. So you are right, it is desirable but not mandatory. Same as a safety stop basically.
If you follow the desired / encouraged slow ascent, it will better match any theoretical model used to create the ascent protocol. After all, somebody somewhere thought it was a good idea to ascent like that.

quick edit: if an agency goes through the trouble of creating an ascent protocol that differs from most other agencies, they probably have their reasons. Following the recommendations of the protocol means you respect those reasons as much as possible, even if they are not mandatory.

I fully agree with you that the recommendation should be followed. However, GUE's Rec book "Beginning with the End in Mind" recommends a slow ascent taking 1 minute from 3m to the surface not 3...
 
GUE uses a MDL ascent profile which is different from what is being used for their technical diving and Rec 3 curriculum, which includes mandatory decompression stops.

For the minimum deco ascent, your first stop will be at half your bottom depth, and you will ascend from the bottom to that stop at 9m/min, afterwards you will ascend 3m/min, to be exact you will be ascending for like 30 seconds and stopping for like seconds.

The 1m/min from the last stop to the surface is only used in dives with a mandatory decompression stop, so it will normally be like 6,5,4,3,2,1 and surface, however if conditions are bad (choppy surface) one may choose to shorten/omit this.
 
I fully agree with you that the recommendation should be followed. However, GUE's Rec book "Beginning with the End in Mind" recommends 1 minute from 3m to the surface not 3...

That might be, but the book is quite old (or at least my version 1.0 is from 2008). The SOP document is revised more recently in the last few years, so the official current GUE thinking is best reflected in that document.

In any case, I just wanted to point out that you should consider the entire (recommended) ascent strategy if you want to compare it to any Buhlmann + GF / VPM / whatever model.
For me, this is a continuation of the question you asked in the OP: why? Why did somebody decide to go from 1 m / 3 minutes to 1 m / min? Why was that softened a bit for rec dives later?
Somebody made that decision. Could be because "slower is safer", could be "matches advanced training", could be "matches model better" or something else.
Would love to know the "why".
 
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