SWB: Reducing the Risk

[sebastien murat]

Here's a free tip without all the physiological mumbo-jumbo:

If you think/sense you're not going to make it simply remove you mask, pull your hood back somewhat, take off any nose-plug, or whatever is covering your face, upon initiating your ascent. This simple act will magnify your O2-conserving dive response when you most need it, on the way up reducing the risk of a BO.

Seb

 

[sebastien murat]

PS: this technique can also be used to minimize the risk of a BO in the latter part of any static or dynamic dive, by the way.

Seb

 

[dannybuoy]

It also would make the surface protocol 1 step easier, and you'd have more time to do it. And, in case something does go wrong, it makes it easier for the safety divers to do what they have to do.

But the main idea is that the added stress and discomfort of diving without a mask, plus the greater exposure to water on areas crucial to dive response, causes the body to conserve oxygen better?

Oh wait, mumbo jumbo territory.

 

[sebastien murat]

In short: yes

Seb

 

[BennyB]

Seb - brilliant stuff, exactly the kind of information we need to know.

I'm all for it and I love science, but damned if I can understand it all.

Cheers,
Ben

ps Completely unrelated - was talking to a friend the other day about freediving who said that a mate of hers used to live with you in Cairns?

Unrelated again - another aussie friend up the road here in London heard me talk about freediving and said that when she was younger, at the pool in Cairns a guy used to ask her to keep an eye on him, she said he just used to lie on the bottom for a while then start swimming for ages. Small world hey?

I'll get the names and email you.

 

[dannybuoy]

Thank you sir,

One day i hope to understand why it is that stress in a dive is good; to experience it is something i hope to postpone till necessary.

When would you suggest ditching the mask/noseclip during dynamics and statics? (when in the dive, not when are you going to make that suggestion -if ever)

Daan

 

[sebastien murat]

Am no sir!

You wrote: "...to experience [stress] .... is something I hope to postpone till necessary".

Otherwise its not really stress, rather a controlled (semi-stressful) condition.

In dynamic and static: my recommendation is to not dive with anything on the face, but most can't handle that. So, my suggestion would be just before you're about to surface from any taxing dive, i.e. at least a good 5-10" before.

Seb

 

[Fondueset]

Thanks Sebastian.

I wonder what the impact of this technique will be at the current water temps here - 3-4C!!

I do love the feeling of diving without a mask. I'm not aware of any really good vision solutions though.

 

[naiad]

Thanks for the tip. I don't mind doing static with nothing on the face, but I wonder what the rules would be in competition? Taking the mask off on the surface is part of the surface protocol.

 

[sebastien murat]

By the way, if any of you regularly subscibe to other forums, particularly foreign spearfishing sites, I might suggest you consider passing on this tit-bit of info, with or without referral, because if it prevents one BO and saves just one lone diver, then it's absolutely worth it.

I'll have more info on countermeasures against BOs out soon, as well as on deep-diving safety, in the aftermath of Loic's passing.

Cheers
S

 

[sebastien murat]

3-4 degrees...serious O2 conservation, but you'll also get a cold shock response => swallowing (neural) response, which one might interpret as urge to breathe, but it is has no metabolic effect on O2 consumption, unlike the dive response which conserves O2, especially if the water is particularly cold and flowing over the face.

 

[sebastien murat]

What of those who dive without a mask in comps?

 

[Fondueset]

Last year I had a problem with Nausea from the initial cold-water face hit - so I used an ice mask - which does keep you very much warmer but I'm not crazy about the insulated-from-the-environment feeling.
This year my new suit is cut closer on the forhead - which keeps the water off the stomach meridian points there - so no nausea - no ice mask. A full face hit is still pretty challenging though - because of the nerves in the eyebrows.

Sebastien - I've been reading some of your stuff lately. Quite awhile ago I noticed my peak breathholds happen when I'm just starting to get a chill going and it's been cool to see your findings. At current temps this is only a couple of dives before the chill itself becomes an issue - but in spring/summer/fall when I'm moving in and out of thermalclines and the surface is 10c and above it works out nicely. I'm not touching the depths/times you do - but it is quite interesting.

 

[sebastien murat]

I guess a little pain in the eyebrows is still better than a BO

S

 

[Fondueset]

No question there! - I was just debating with myself about diving without a mask in really cold water to see how it affects my times - sorry for not being clearer.

 

[sebastien murat]

Without doing a max dive, but using an O2 sensor and a bucket of icy water, you can do that quite easily. You'd be surprised what you'd learn about cold water and the difference between having the urge to breathe and simply needing to swallow.

Seb

 

[Fondueset]

This stuff is hugely helpful
A question - when I experience sudden leg fatigue toward the end of a dive - not normal fatigue from kicking, but a sudden burn - is that pretty much an indication of DR kick in? I am not too concerned with pushing the envelope - but safety is definitely primary.
(I'm passing on your mask suggestion to the extremely small freediving contingent here)

 

[sebastien murat]

Firstly, I'll assume you're not sprinting at the end of the dive because sprinting whether breathing or not => switch to anerobic metabolism = muscle 'burn.'

A couple of things:
- Except in the most extreme cases, no 'burn' at the end of a taxing dive => beware: BO could be around the corner. Exception = increase in Mb stores and anaerobic fitness will delay burn.
- 'burn' = good sign of peripheral vasoconstriction of locomotors even under exercise conditions. Most certainly due to central hypoxia-induced peripheral vasoconstriction, but also apnea/cold-water induced vasoconntriction.
-if you have a poor DR, because of excessively elevated metabolic rate, warm muscles, genetics, training, etc => little to no burn => bad news => risk of BO inversley related to DR, i.e., strong DR => reduced risk of BO.

This means one should opt for strategies that magnify the DR to reduce BO; strategies like minimizing the work rate in the first part of dive, etc.

For sub-max effort dives (i.e., serial dives) a 'burn' is no good.

It all seems complicated but its not. Best way to think of it is like navigating through a mine field: its ok if you know where the mines are! There aren't too many mines.

S

S

 

[Fondueset]

Thanks!

The burn phenomenon occurs usually during ascent - and definitely not sprinting. I pretty much allways get it if I push the dive - which I rarely do. The only other thing that happens at the end of dives - after surfacing/breathing - is a feeling of heat in the face - like blood is rushing to my head (BP spike probably).

Thanks so much for posting here! I want to optimize safety but still have decent bottom time. I'm really still feeling out my own limitations.

'minefield' - what a soothing metaphor

 

[dannybuoy]

Hey, what's mines is yours! My mines are your mines. Really, you can have them.

That's why i call you 'sir', sir; huge respect for the way you think. My equations go not much further than hunger => food = hmmm. I'd never have thought of exhaling before a dive, or exposing myself to any form of cold. Now that i've tried, and wimped out on most occasions, i might start deliberating entering your minefield, say in 2012-ish.