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Cool brains underwater

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I knew I shouldn't have bought a wetsuit with integrated hood.
 
This technique has circulated for years. Murat was a specialist in it. Several variants include:
- Breathing on your back to warm your face, then turning over into cold water
- Flooding the sinuses with cold water
- Diving without a hood in extremely cold water
etc...

I've only tried severe brain cooling once, it worked incredibly well, except for the very large side effect that once the brain is cooled dramatically, thinking slows down and it becomes very difficult to perform even simple tasks.
 
I would have thought that for depth disciplines, just doing a few warmup dives (or actually cool down dives) without the hood would be sufficient to cool you down, especially in cold water. Or perhaps even better you dive without a suit altogether, I'm guessing you'd get a bigger effect and also a lot of vasoconstriction.

Sounds like it would be more interesting for static/dynamic (just because it won't matter much if you can't think etc). In an older thread on here about the dive reflex someone suggested putting ice cubes under the swim cap.
 
Simos diving without a suit can cause you to tense up as a natural reaction to cold water, ultimately resulting in the opposite of what you wanted. Tense muscles lead to higher O2 consumption.
 
I dive without hood, here in BC. I don't know if it works, I am getting some good times if I manage to stay relaxed. After a few dives it doesn't feel as cold but I am getting verigo or loss of sense of balance and, like Eric says, mental slowdown which is hard to desrcibe. Sometimes if water is way cold, like early spring, I cannot overcome the pain from cold, it burns right round ears, and that makes me having to cut my diving short. And getting out of the water is difficult when your vestibular thing doesn't work, visual reference to horizon doesn't work for balance, better have your partner to hold you or crawl on your four.

Anyways, I am shopping for the hood now. I didn't know a thing about brain cooling and its effect on breath holding but even if there are any benefits, I would take some comfort instead.
 
mishu1984 said:
Simos diving without a suit can cause you to tense up as a natural reaction to cold water.
Click to expand...

when you go past certain point, hypothermia doesn't make you tense anymore, you just get numb. I often dive in a state of hypothermia beyond shievers. Beside vertigo which I described earlier, there are also losses of hearing and colour vision as core temperature continues dropping.

Doubt there are any benefits to it though, overall pleasure of diving becomes somewhat corrosive scary and god only know when light will go out because you are in an altered state of mind from magniutude of things that are wrong - high CO2, low O2 and low core temperature. Coupled with impaired judgement on top.
 

Sounds like one of The Worst freediving experience ever, imho of
course.
 
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I haven't tried diving without a suit in cold water, I don't imagine it'll be much fun and surely dangerous for the average diver because of everything mentioned + increased chance of lung squeeze.

I do like to swim in cold water without a suit whenever I get the chance - it's a unique feeling. Fully agree that after a few minutes you just go numb - vasocontriction kicks in really strongly and in fact you can literally feel the blood returning when you come out and start warming your body.

The main problem I found when swimming in cold water is in fact the head (no swimming cap) - if the water is cold enough you literally feel as if your head is freezing, it's painful and it's hard to even think. Unlike the rest of the body, I haven't found any way of making it feel better and it doesn't get numb in the same way. I definitely wouldn't like to dive like that.

Having said that, I find it challenging when diving without a suit in water which is mildly cold - you are ok on the surface but when you hit a thermocline it's challenging to keep relaxed and in fact a pretty good exercise for relaxation. It's the kind of thing that makes you work on decoupling your mind from your body sensations. In my opinion cold is one of these things that the more you fight it (instead of accepting it) the worse it gets...
 
If you practice, diving in cold water (8-10C) without a wetsuit can be extremely comfortable, even wonderful. In fact the best (most fun) dive of my life was an FRC dive in 10C water with no wetsuit lasting around 3'15" a few years ago. The already amazing experience of freediving is amplified by the strange, surreal feelings you get, feeling the water against your cold skin, while the core of the body feels strangely warm despite the cold. And the mind acts differently, almost as if on some type of drug. The body is totally relaxed, the dive time is enormous and much longer than with any wetsuit.

In 2005 I did an 80m constant weight dive without any wetsuit in very cold water (8C), and it felt incredibly awesome. But recreational dives are even better.

The problem is the adaptation. To feel comfortable in this style of diving requires around 5 practice sessions, and these training sessions are very unpleasant. But if you push through them, it becomes awesome. The pain in the head, on the ears, on the chest, goes away.
 
"However, swordfish keep their eyes and brain at higher temperatures while allowing the rest of their bodies temperature to be controlled by the ambient environment." from this tet zoo comment:

http://blogs.scientificamerican.com...iction-confirmed-plesiosaurs-were-viviparous/

Ranjit Suresh @ 6:51 pm 08/12/2011
" Bernard et al. 2010 provides evidence that plesiosaurs (ancient seal-like reptiles which gave livebirth, so not egg layers. DD) maintained relatively constant temperatures in the range of the high 30′s Celsius. But, it’s not clear to me if they were gigantotherms, had higher internal temperatures through vascular heat exchangers like some sharks, tuna, and swordfish, or were tachymetabolic like mammals and birds.

The scientists used oxygen isotopes in their teeth to determine these temperature ranges. However, swordfish keep their eyes and brain at higher temperatures while allowing the rest of their bodies temperature to be controlled by the ambient environment. "
 
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Well, swordfish does not dive in apnea, so does not need to go into any oxygen-saving mode, so there is no point in cooling the brain down.

Otherwise, I believe that having the brain cool is helpful at the intial phase of the apnea (to slow down the metabolism and reduce the oxygen consumption), while in the final hypoxic phase warm brain might be better - it improves the oxygen desaturation (Bohr effect - oxygen binds less to hemoglobin in acidic and warm environment), preventing so the blackout. Putting the hood on in the last phase may perhaps help a bit.
 
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Right, swordfish remain in apnea breathing with gills, are coldblooded but the brain/eyes are are secondarily warmed by the heat of constantly active muscles. Plesiosaurs were probably partially warm blooded reptiles, surface-air breathers like seals and humans.
 

WTF man???
Do you not read your own posts, ever?
For a start:
ap·ne·a also ap·noe·a ( p n - , p-n )
n. Temporary absence or cessation of breathing.

But you're telling us our friend the swordfish BREATHES in apnea?? Which is it, is he breathing or not?! It's like a static running race.

And now to further your debate you add in theories about the plesiosaur?

Don't worry about a static running race, "apnea breathing" is more like an opinion with a deliberate removal of logic..... Now where can we find one, or twenty, or those???
 

I am in serious doubt about the whole thing.

IMHO diving bare skin in such cold water results in such massive heat loss that cannot be "balanced out" by heat production.

Therefore, core temperature will continue dropping, eventually leading to the loss of consciousness. I have already descibed the feeling of degradation of sences (hearing, colour vision, motorics and sence of balance) that I experienced diving in such sub-cooled state.

This is not a "recreational" diving at all. This is more of a hard core experimental diving. I was blessed with waterfront cabin for a week, where I could interrupt my diving and with the help of a buddy to get back to the cabin and stay in a warm shower for a while. Even then recovery is slow and takes a while to get back to normal. Long term effects of such sub-cooling is not known, cannot be good anyway. We are talking sickening blow to our heat regulation process.
 
From post #13, correction:


(Apparently editing posts is not allowed after a certain time period, this corrected post replaces the earlier one.
 
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From Marc V. "IIRC, mammal mitochondria (I don't know about birds) produce much more heat (4 or 5 x "less efficient") than reptile etc mitochondria = "tachy-metabolic".

Tp gradients in the body AFAIK are always realised through CC heat
exchange, eg, muscles in tuna etc., and even lower Tps in (internal)
testes of dolphins!

Humans have no CC heat exchangers between heart & brain,..."
 
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