blood centralisation? sign for coming blck out?

[marc25]

hi,

while doing dynamik i have a strange feeling.

at about 70-80 m (pb 105 m) it feels like the blood would "leave" the arms (and legs) and just circle in the core.
i know that this is part of the dive reflex.

but my questions are:
i was wondering that i could really feel this.
does anybody feel this too?
usually i get "afraid/annoid" and surface shortly after this. after surfacing i am not really exhausted and i dont really think that i would run out of breath or that i am close to my real max.
is the centralisation of the blood a sign of a black out to come soon or can i "ignore" this feeling?

sorry for my english,

marc

 

[trux]

Search the forum and the web for the term "blood shift" - it is a sign of the diving response kicking in, which (briefly told) is an "oxygen saving mode" and does not necessarily mean dangerous level of hypoxia, but rather a lower oxygen consumption. It does not mean you should ignore the feeling - you should watch all your body responses, but you need to have more experience to recognize when you are really hypoxic. You will want to avoid getting too hypoxic, but on the other hand you want to get strong diving response, including blood shift as soon as possible during the dive.

EDIT: Do not forget to enter "blood shift" into the search function - you will get much more detailed answers there. Also looking for the terms "diving response" and "diving reflex" will show you many interesting threads and documents. You can also check out some of the links listed here:
blood shift @ APNEA.cz
diving response @ APNEA.cz

 

[marc25]

hi trux,

i think blood shift is only in deep diving.
"pumping" blood between the lung and the ripcage to prevent a lung squeeze.

i am thinking about something different. i think it is called "vasoconstriction", but i dont know if it is the right english expression.

greetings
marc

 

[Mullins]

Vasoconstriction has the effect of shifting blood from the extremities to the core...

 

[trux]

Yes, as Dave tells, vasoconstriction (and also the constriction of the spleen) has the consequence that blood moves from extremities to the body core and to the brain, increasing so the blood pressure in that part. In depth, due to the gradient between the ambient pressure and the inner pressure in lungs, the higher blood pressure will cause swelling of blood vessels in lungs, hence reducing the lung inner volume and compensating the pressure difference. Although depth is one of the factors having influence on the strength of diving response, vasoconstriction and the consequent blood shift are definitely common also in shallow depth or even at dry apnea.

And as I wrote, they are not necessarily a sign of a dangerous level of hypoxemia, but rather they just mean the diving response kicked in to save oxygen. The sooner in dive the feeling comes, the better it is, and the less oxygen you consume. Early diving response is the exact reason why divers are able doing great performances on FRC dives (exhale dives).

To simulate early diving response, besides empty lung dives, you can try doing a 45s static apnea and then your usual dynamic length (without inhaling in between) - although paradoxical on the first look, you will be surprised how easily you can do a big distance after such relatively long static apnea where you would assume losing already an important part of your oxygen.

NOTE: never train alone, without close and uninterrupted surveillance of a person familiar with freediving safety and experienced with handling freediving blackouts and sambas! Never rely on pool life guards, or bystanders - their help will not come soon enough (if at all). That pays always, but if you are going to experiment with new techniques, where you do not yet know your body reactions, it is double important!

 

[Erik]

Vasoconstriction (and therefore shifting the concentration of blood- 'blood shift') can occur without diving. Obviously not pressure-induced, but it happens, especially if you get into a heavy training regimen. I got to the point where I could induce vasoconstriction within seconds by holding my breath, even without a breathe up.

 

[trux]

... I got to the point where I could induce vasoconstriction within seconds by holding my breath, even without a breathe up.

Yes, you actually indeed get vasoconstriction without the breathe up easier than with it, since an increased CO2 level is one of the more important factors of triggering the diving response.

 

[sanso]

Marc,
Don't be annoyed, blood shift is your friend.
And even if it isn't the blood shift You're feeling, happy thoughts are still better when in the water than unhappy ones.
I am quite certain that I can feel the active part of the blood shift kick in, and when I feel it, it always makes me think "Yeah, there we go! good, good, good,..." -
BTW: when this happens, and shortly afterwards you feel immersion diuresis putting some pressure on your bladder, then you know you're good. :t Nothing like peeing ones pants during a good dive. ;-)

 

[Erik]

Marc,
Don't be annoyed, blood shift is your friend.
;-)

Agreed, it's a good feeling- tells you that you're working properly.

 

[marc25]

thanks a lot

i didnt feel it that strong before.
the feeling startet a month ago
i knew the theory and that it is good, anyway it is a disturbing feeling the first time...
anyway, now i know for sure it is my friend and i will tell this to myself the next time

trux, dont worry, i never train alone. in our diving club we are usually 4-5 freediver training together. if we go close to our max, there are usually 2 savetyfreediver who know what they do and what they have to do..,

greeting,

marc

 

[sanso]

... in our diving club we are usually 4-5 freediver training together. ...

Now I'm curious. Where is your club?

 

[demasoni]

BTW: when this happens, and shortly afterwards you feel immersion diuresis putting some pressure on your bladder, then you know you're good. :t Nothing like peeing ones pants during a good dive. ;-)

I usually feel the need to relieve myself after a certain consistent point during a dive and always assumed it was time to come up, because shortly after the pee, contractions started.

I had a feeling that I could keep diving after peeing and that these contractions were a sign of DR, but I always came up because I was alone. Assuming I have a buddy under controlled conditions, I wonder how much longer I can stay down there?

 

[marc25]

sanso,

we are training in krefeld, which is close to düsseldorf,

marc