Deep stop

[Bubbletrubble]

This is s typical deep recreational profile in Cove 2 ... one of our popular dive sites ... I use this particular one as an example in my gas management seminar ...

Gas was EAN32

I don't use the dive computer to manage my NDL's ... I've done this dive so many times I often don't even look at my computer.

Max depth is at about 110 ... first stop is at some pilings at around 60 ... next stop is at some pilings around 40 ... after that, it's a shallow swim back to the entry.

This is a shore dive, and we pretty much just follow the bottom the whole way.

Since you responded, I'm going to assume that this is a typical profile for which deep stops help you feel "less tired."

Are you calling the stops at 60 fsw and 40 fsw "deep stops"? (I realize there's variation in what people consider "deep stops" and the pilings are probably convenient/interesting stopping points.)
You appear to be spending a lot longer at the stop depths than what is normally prescribed for a "deep stop" (if we accept as a definition a 1-3 minute stop at half-max depth).

I wonder how increasing the number of deep stops, lengthening the duration, or not performing them at half-max depth influences the diver's feeling of post-dive tiredness.

 

[scubadada]

I agree. Probably the only realistic way of doing a study where the subjects are "blinded" to the profile is to conduct it inside a dry chamber. It might be a good idea to give the subjects tasks to distract them and prohibit access to timing devices so that they are kept unaware of the profile. A set amount of physical activity (or not) could be incorporated into various stages during the dive (to simulate real-life workloads). Post-dive Doppler bubble score detection could then be conducted at pre-determined intervals. Afterward, subjects would self-report how tired they were and answer other questions regarding symptoms potentially associated with subclinical DCS. Such an experimental design might get pretty close to isolating the effect of deep stops. I'm somewhat surprised that Bennett's group hasn't done something like this yet.

You may be right.
The reason I was curious about all of this is that several participants in this thread were so emphatic about how much better they felt conducting deep stops.
My experience has been different. For the recreational diving that I typically do (a few square profiles but mostly multilevel, usually not getting into single digit NDLs with a conservative computer, fairly slow ascents upslope, extended safety stop), I felt no difference at all +/- deep stops.

As per my previous post, this is also my experience. As I would consider this a very safe intervention, I would encourage all to try it for themselves. As Bob (Grateful Diver) points out, it is your own head. I happen to be of the scientific bent in my own activities.

Best, Craig

 

[huwporter]

Although not directly related to the topic of adding deep stops to a recreational profile, I think this paper makes very interesting reading when thinking about how the body reacts in the real world vs. the entirely theoretical world of deco models:

Nitrogen elimination in man during decompression

(FTR, I also do deep stops on square or squarish recreational profiles, as 1 min stops at 3m intervals from half average depth. And my personal anecdotal belief is I feel better for them. I also have a hypothesis that people differ greatly in how 'sensitive' they are to microbubbles - which is why some people believe they feel much better from deep stops while others don't feel a difference.)

Cheers,
Huw

 

[MXGratefulDiver]

Since you responded, I'm going to assume that this is a typical profile for which deep stops help you feel "less tired."

Are you calling the stops at 60 fsw and 40 fsw "deep stops"? (I realize there's variation in what people consider "deep stops" and the pilings are probably convenient/interesting stopping points.)
You appear to be spending a lot longer at the stop depths than what is normally prescribed for a "deep stop" (if we accept as a definition a 1-3 minute stop at half-max depth).

I wonder how increasing the number of deep stops, lengthening the duration, or not performing them at half-max depth influences the diver's feeling of post-dive tiredness.

It's a pretty typical profile for that site ... other sites require a different profile. Keep in mind that the vast majority of my dives are shore dives, where I'm following the bottom down and up a slope. At some point along the way ... typically at about half my deepest depth ... I'll find a place to stop for a minute or two ... somtimes longer if there's something interesting to look at.

The whole point of deep stops is to give your faster tissues a chance to "catch up". I worry way less about the slow ones unless I'm either pushing NDL's or exceeding them ... in which case, I'll spend a longer time on the shallow stop once I get there.

"Feeling better" and "post-dive tiredness" are really subjective ... but I do believe that managing your ascent rate in a manner that makes for slower offgassing rates will affect how you feel after the dive. It works for me, at any rate ... which is why I do it.

... Bob (Grateful Diver)

 

[Dsix36]

I have done deep stops in both recreational and techinical depth dives in order to compare my deco profiles and after dive conditions to my normal deco stop dives. I have found that the only difference that is really of much notice is that my time to surface is increased (very slightly in recreational dives, but quite a bit in technical dives). I have never noticed any difference in the level of tiredness that I experience after the dives. I have intentionally modified my deco profile to get me as shallow as possible, as soon as possible, (basically the opposite of deep stops) in order to conserve gas in an emergency and with the exception of having some subclinical bends (very slight niggle in one of my knees) on each and every attempt, I have not been able to tell any other differences than with other deco profiles.

Disclaimer: I have been called an idiot by more than one person, so this post is worth absolutely nothing more than you paid for it !!!

 

[PfcAJ]

I agree. Probably the only realistic way of doing a study where the subjects are "blinded" to the profile is to conduct it inside a dry chamber. It might be a good idea to give the subjects tasks to distract them and prohibit access to timing devices so that they are kept unaware of the profile. A set amount of physical activity (or not) could be incorporated into various stages during the dive (to simulate real-life workloads). Post-dive Doppler bubble score detection could then be conducted at pre-determined intervals. Afterward, subjects would self-report how tired they were and answer other questions regarding symptoms potentially associated with subclinical DCS. Such an experimental design might get pretty close to isolating the effect of deep stops. I'm somewhat surprised that Bennett's group hasn't done something like this yet.

You may be right.
The reason I was curious about all of this is that several participants in this thread were so emphatic about how much better they felt conducting deep stops.
My experience has been different. For the recreational diving that I typically do (a few square profiles but mostly multilevel, usually not getting into single digit NDLs with a conservative computer, fairly slow ascents upslope, extended safety stop), I felt no difference at all +/- deep stops.

Doppler scores aren't great for predicting dcs. I think some sort of a fatigue inventory would be a better metric, but you'd have to be comfortable with a relatively weak statistics. Those things are never very strong, ESP not when compared to something like a Doppler score.

 

[MXGratefulDiver]

I have intentionally modified my deco profile to get me as shallow as possible, as soon as possible, (basically the opposite of deep stops) in order to conserve gas in an emergency and with the exception of having some subclinical bends (very slight niggle in one of my knees) on each and every attempt, I have not been able to tell any other differences than with other deco profiles.

... why don'tchya just bring more gas? That way you can skip the niggles ...

... Bob (Grateful Diver)

 

[Zeagle Eagle]

50% of your avg depth, no longer than a minute then move up. Personally, I ascend at 30fpm to 50%, then slow it down to 10fpm thereafter. Roughly the same total time as a traditional safety stop, but distributed over a more gentle ascent curve.

That's about how I do it now. I never intentionally exceed 30 fpm then slow down around 30-40' or so. I do a 5 min safety stop, my SAC is pretty good so I usually have more air than most (no point in getting back on the dive boat with a lot of air). Keep in mind I am strictly a recreational diver, old and out of shape now and rarely exceed 80-90' nor exert myself a lot. I am also one of those guys that feels better on nitrox. Whether it is in my head or not. I don't know. I am waiting for the smart guys to tell me if it is a placebo effect or not.

 

[Bubbletrubble]

Doppler scores aren't great for predicting dcs. I think some sort of a fatigue inventory would be a better metric, but you'd have to be comfortable with a relatively weak statistics. Those things are never very strong, ESP not when compared to something like a Doppler score.

Yeah, we don't really know what Doppler-detected bubbles really represent. After all, it's intravascular bubbles that we are looking at. They're probably just an indicator that some sort of decompression stress occurred fairly recently. Still, they are straightforward to measure and certainly quantitative.

I like the idea of a "fatigue inventory" in addition to simple self-reporting of how tired the subject is. Maybe some sort of video game could be designed or adapted which tests mental fatigue.

 

[Zeagle Eagle]

You know what, I think I am just going to follow my computer for the time being until you smart guys can figure out a definitive answer. A blind scientific study may be the best answer of all.