Ascend drills - how many is too many?

[scubaozy]

We'll soon be doing some ascend drills from 25m (80ft). Alternative air ascend, normal ascend that sort of thing. We're planning three per dive, we will not (intentionally) exceed safe ascend rate and the ascends will all be performed at the beginning of the dive. Obviously, we will be regularly asking about sinus / ear discomfort, etc. And being at the beginning of the dive there should be very limited nitrogen tissue loading. But drills being drills, there's likely going to be points for improvement, and do-overs. My question is, is there any theory or practical guidance on how many of such drills can be fitted in one training dive? Can we do 1 extra? 2? Any input / experience is greatly appreciated!

Which course is this? P2? I have not heard of 25m as a requirement. Is this some arbitrary depth or are you following any standard?

 

[Wibble]

Find that doing ascents from shallow, 6m/20ft, can really play with my eustachian tubes.

As ever, should you get a block, deal with it in the normal way. If it's persistent, then you might need to give it a rest -- go and have a nice cup of tea.

Maybe it's just being in a shallow training lake that does it

 

[Vicko]

For AOWD my students are doing those ascents, sometimes deeper, once a dive, at the end.
Having a person be comforable with blue water ascents with or without a guideline makes them a better and safer diver.


On the other hand, getting me bent from 9 or more 25m ascents in quick succession does nothing for their training.

 

[Lorenzoid]

They can, but deeper ascents make it more realistic, forcing you to control your drysuit, the wing (and loop if on a rebreather). Forces you to think ahead and know how much to dump without dumping too much and descending.

Also handling a SMB at the same time.

Oh, and how can you learn what 9m/30ft a minute feels like if you're at 6m/20ft?

As I said, starting shallower sacrifices realism for the sake of safety. I'm not an instructor and admittedly only see this from an ordinary diver's point of view, but it seems to me that we can't train entirely realistically for every scenario. Some things may best be simulated for the sake of safety.

In my practice sessions, we would deploy an SMB from 30 or 40 ft and practice ascents with it, stopping every 10 ft., sometimes sharing air. Doing the same thing more times by starting deeper might be more realistic and provide more opportunities to stop, but a next-best alternative is to repeat the shallower ascent more times.

As for learning what 30ft/min feels like, why couldn't that be a separate exercise? It's not even much of an "exercise" because it's how we ascend from every dive. Does a diver at this level (I assume this is not for the basic OW course) not know what a 30ft/min ascent feels like? Again, I'm not an instructor and speak here only as an ordinary diver, but I think a diver could learn these skills in chunks, in each exercise practicing the bits that are then new to the diver. Eventually, put it all together and do an ascent from realistic depth, but at that point there shouldn't be any need to repeat it multiple times in the same day.

 

[Duke Dive Medicine]

We'll soon be doing some ascend drills from 25m (80ft). Alternative air ascend, normal ascend that sort of thing. We're planning three per dive, we will not (intentionally) exceed safe ascend rate and the ascends will all be performed at the beginning of the dive. Obviously, we will be regularly asking about sinus / ear discomfort, etc. And being at the beginning of the dive there should be very limited nitrogen tissue loading. But drills being drills, there's likely going to be points for improvement, and do-overs. My question is, is there any theory or practical guidance on how many of such drills can be fitted in one training dive? Can we do 1 extra? 2? Any input / experience is greatly appreciated!

This is a sawtooth dive profile, which can increase the risk for decompression sickness.

Best regards,
DDM

 

[R.Chisholm]

OK, some more background. I AM an instructor (albeit a fresh one - CMAS indeed), and I am asked to assist on this drill. And, clearly, I am having some concerns. I agree with @DiveProKoko that many lessons can be learned from 10m. Having said that, I also see the value of experiencing how loooong (2.5 min) a safe ascend from 25m really is. But three in one dive seems quite a lot, esp if the idea is that we need to repeat in case of 'beauty flaws'. Hence my question.

But what is the recommended max? Say we do it once, but there is room for improvement, does it make sense to do it a second time in the same dive? BTW: I am unaware of any (CMAS or otherwise) 'rule book' where it specifies that this is not 'allowed'. So any recommendation is greatly appreciated.

When I took a CMAS 3* course in Switzerland we typically did one rescue ascent from 130 ft/40m in the beginning of the training dive all the way to the surface. At the end of the the training dive there was usually an ascent from 130 ft/40m using buddy breathing all the way to 18 ft/6m (at which point after a minute of holding position the exercise is supposed to end).

Not sure I'd recommend this & I'm told most CMAS affiliates have dropped these exercises (at least from these depths) because they consider them too dangerous.

While I have no desire to teach this if I was a CMAS instructor I'd expect my students to demonstrate proficiency in shallower water say 12 ft/4m before this was done any deeper.

 

[boulderjohn]

At the end of the the training dive there was usually an ascent from 130 ft/40m using buddy breathing all the way to 18 ft/6m (at which point after a minute of holding position the exercise is supposed to end).

Back when buddy breathing was the norm for OOA training, Dr. Glen Egstrom's studies supporting its use determined that buddy breathing under stress could be performed successfully if that two diver team had successfully completed 17-21 practice sessions. They also had to practice together regularly to maintain those skills. If they did that, no problem! They could count on being able to buddy breathe in a real-life emergency. Otherwise....

Here is a quote:

I tend to regard buddy breathing as a skill which is presented early in the course and rehearsed during each training session. We have found that 17-21 trials will develop the ability to swim and share air at the same time.​

​

Here is an article from nearly 30 years ago arguing that the invention of the alternate air source meant that it was time to stop teaching buddy breathing because alternate air sources made the skill obsolete, and using it instead of an alternate air source was too likely to lead to a double fatality. If you don't do what Egstrom advised (17-21 practice sessions followed by regular practice), you could not count on being able to do it in real life. This is what happened in the only buddy breathing case I know of in relatively recent diving--a woman in Florida was given a rental regulator set with no alternate, and when another diver went OOA, they attempted to buddy breathe, and both drowned.

That is why almost all agencies have dropped buddy breathing. If you were to conduct a buddy breathing exercise from 130 feet, with or without the 17-21 previous practice sessions prescribed by the only study I know of, and if one or both students were to die, the lawsuit would not go well for you. I suspect that would be true even if your agency approved it, because in the trial the agency would have to explain why it still sanctions an exercise that has been discontinued by almost everyone else because it is considered too dangerous.

 

[jayknight]

Thanks all. Lots of food for thought and very sound advice, confirming a lot of my hesitation and concerns. Will adapt the plan accordingly.

 

[ofg-1]

Just remember, your number of ascents need to be greater than your number of descents.

 

[Wibble]

Just remember, your number of ascents need to be greater than your number of descents.

This is really playing with my OCD inner self that's screaming "equal to"!

Unless you're including submarine escape drills where there's no descent.