For quite a while I have had this sneaking suspicion that the mammalian dive reflex in humans is more/equally attributable to a reaction
against colder temperature than the actual water. I just found out that that suspicion is justified: The reflex only works when water
temeprature is under 21C. The face is much more suspeptible/sensitive to temperature changes then the rest of the body and so it seems
triggers the reaction as a means of preparing the body for cold, and not exclusively for diving.

A long time ago I posted saying that "colder water would 'theoretically' permit you to hold your breath logner" and got shot down a little for being too 'theoretical', it seems that that idea was on the right track after all: If you are diving in tropical waters you will not stay down as long as in temperate waters if the fact is that a reflex only works under 21C. When I posted that I should have specified water which was 'cool' but not
cold and therefore leading to shivers which would increase/maintain normal heart rate.

It could be that the reaction of the dive reflext and against the cold is one and the same, but I wander how it is differnt from other mammals, whether theirs is the same double reaction or is more specific.

There is an experiment I thought of to test this:

1. Blowing cold air in the subjects face and seeing wether this triggers the reflex.

If any of you guys are keen would you perform this experiment on yourselves? If yes, run it as so:

-Do a hold without cold air exposure and test for how long you hold your breath. Take a break. Then do another after exposing your face
to air con, or maybe the freezer for a minute or so and then doing the a hold again. Repeat this as many times as you want logging your time.

Can't find wether this has been done or not, but I a have a feeling this could have an interesting result.

(Please don't take this too seriously, although I have a feeling I may be onto something)

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"o o o ooo o oo o o o 0000o0o 0 oo000 OOo O0O o 0o0 o0o0O"

Mate I dont know if I want my missus to find me blacked out with a frozen head and my ass sticking out of the freezer

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Taking the fight to the fish!

the mammalian dive reflex is the slowing of the heart rate right?? if so why don't you just measure heart rate after exposure to coldness. surely a breath hold varies from one time to the next depending on your preparation. measuring heart rate would take out some of the variables in the experiment....

leigh

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Do you know what really makes me smile? Facial muscles.

The samba video mentioned something about this, the euro guy was saying that some pro divers pull their hood off their chin and take out their snorkel before diving down, that exposes the face to coldness, therefore slowing the heart rate down.

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Taking the fight to the fish!

Thats the thing: the mammalian dive reflex does not stop at just "getting your face cold", the theory/prinicple is touted as more than that. It is
the idea that we as mammals have a biological disposition to diving underwater. This has more profound implications.

You would hold your breath to simulate a real dive like other mammals: seals, whales, dolphins. If there is a mammalian dive reflex it would have
to have something to do with holding your breath, if it doesn't then why call it that?

Re: Leigh's comment ...

Could do two tests: the one I mentioned and the one you mentioned and see what the difference/similarity is. I imagine you would get a better picture of it.

I am going to try to do some more research on this before I say anything else.

... Jaws, or maybe she would!

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"o o o ooo o oo o o o 0000o0o 0 oo000 OOo O0O o 0o0 o0o0O"

will your findings come under "the mammalian head in freezer reflex"

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Do you know what really makes me smile? Facial muscles.

If I have enough evidence to support the theory, then yes! (Just think of the the headlines!)


Funny shit...

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"o o o ooo o oo o o o 0000o0o 0 oo000 OOo O0O o 0o0 o0o0O"

Have a read of 'Manual of Freediving' by Umberto Perlizzari and Stefano Tovaglieri. It goes into the mammalian dive reflex in some detail including blood shift and the likes, there is a lot more to it than just a cold face.

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That's where I saw the leprechaun. He tells me to burn things...

Yes, there is apparently definately more going on there then merely cold on the face, apparently. But I have a strong that what happens is not a single process but a few different processes that may serve other functions as well and are not specific to the mammalian dive reflex. If that is so then the so called "mammalian dive reflex" is more a non-definitive concept than a strict/total account of what is actually happening. As stated, it only works when the water is under 21C. Obviously mammals live places where water is over 21C. I am trying to disprove the idea (that is the job of being "scientific" about things) although am very fond of it. I'll be definitely looking at that book.

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"o o o ooo o oo o o o 0000o0o 0 oo000 OOo O0O o 0o0 o0o0O"

yeah on one hand you have a longer bottom time and a headache from the cold water and on the other hand you have a lesser time but no headache!

so really its either man up or stay nice and toastie.

hmm hard decision

All your doing is slowing the metabolism down, cooling blood and slowing heartbeat, that's why trout fishermen put there mudeye in the fridge, keeps them from turning to dragonfly... same principal...different application.

but wouldnt there be significant differences as we are mammals and they are insects that breed, develope etc depending on the water temp

Interesting that we develop in fluid in the womb, though are fed gasses through the umbilical cord. Cold water and pressure effect us when looking into dive reflexes, though we come from a stable temperature and pressure in the womb.
Would the dive reflex be more accurately studied when the entire body is in contact with the water?
With dolphins their abilities underwater are linked with a double blood warming system (cycling blood through warmer tissues twice) as well as the position of the fatty tissue in specific areas of the body and where its in contact with the water. Their heart rates and blood/oxygen/CO2 holding capacities therefore influenced by the changes on the entire body...?

Its pretty complex stuff there, main thing that is the issue for me is why should the collected effects be known as a mammalian reflex if they function in isolation for different reasons?
And, why does it only work in water under 21c? Cold triggers it rather than the water. Still researching ...

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"o o o ooo o oo o o o 0000o0o 0 oo000 OOo O0O o 0o0 o0o0O"

Who cares?