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blood shift the next day?

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Aug 17, 2002

does anyone know of any studies on how quickly blood is reabsorbed by the body after a bloodshift? what is the maximum amount of blood ever measured? and finally, is there some blood remaining in the lungs maybe a day or 2 later?

thanx for replies

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i haven't come across any studies myself. it must be difficult to quantify the amount of blood in this way. if you're asking how much blood has moved from the periphery to the core, then i suppose you have to define the limits of those areas - that's seems quite difficult to me.

i wonder whether there would be a correlation between blood shift and FEV. i think there might be, but i'm not certain about that.

i would be very surprised if the effects of blood shift lasted that long after leaving the water. i would have thought the effect would diminish exponentially over the course of a couple of hours at most - depending on your activity level and how quickly you warm-up. it seems that the shift can take place within minutes of immersion. so i don't see why it should take hours or days for the shift to reverse after leaving the water.

those are my thoughts...?

ps: see you in about 7 weeks!
pps: i'll notify Ben Gowland (physiology boffin) of this thread
My guess is that the effect is gone within 10-20 minutes.
This is how it feels at least.

One might be able to do spirometer tests on this.
Since I have one I might do that some day since it is an intresting question.

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yes, i think i would expect most of the effect to have gone within 30mins of leaving the water.

Roland - why do you think it might take 1-2 days?
Instinctively, one would assume the same as Alun mentioned, but I do recall a thread here where an Italian researcher found signs of blood shift a day or so after diving.

I agree with the FEV theory and it is certainly true to an extent as I know people have proven it (personally and publically). Whether the change in FEV is equal to blood shift is unclear.
hi everybody. thanks for your replies.

reason for my question was that my current warmup doesn't include negatives really, and i have the idea to include them more and more but want to do that slowly and gradually to not disrupt my current routine too much. i am very happy with my warmup at the moment but have the impression that i need to 'upgrade'.

please correct my understanding of FEV: functional exspiratory volume meaning the greatest amount of air one can exhale? that means air volume remaining in the body is residual volume, no?

that brings up another question:

when doing negatives after a full, forcefull exhale means i start my dive with RV. when diving deeper my ribcage and diaphragm flexibility will compress my RV further, still without any negative pressure in the lungs. only below the point where my flexibility ends will a negative pressure develop that leads to blood shifting into the lungs.
now when the ribcage/diaphragm are very flexible and there is a quick and strong response of bloodshift there will be no real pressure felt on the chest, because flexibility and bloodshift will at all times equalise the airpressure in the lungs.

my experience is that when i train empty lungs a lot my depth is limited by eq only while having no pressure feeling on my chest. is there any way to tell wether that is because of flexibility or bloodshift, or is it always a combination of both?

now i believe that doing negatives is very beneficial for various reasons, but isn't the flexibility benefit maybe greater than the actual bloodshift (unless you're diving wr-depths??)?

maybe all that doesn't make much of a difference when you reach your depths without a squeeze, but it is a topic that has been causing some discussions in my neighborhood.

thanks in advance for any responses.

I believe that the dive reflex, once strongly evoked, persists for many hours at least.

I have as a tentative hypothesis, for example, that the best way to warm up for a static apnea attempt is to evoke a strong dive reflex by effortless ( to the extent possible) exposure to apnea and hydrostatic pressure, say, by a series of relaxed 1 - 2 minute pulldowns to 30m, followed by a 2 - 3 hour rest (perhaps while riding to static attempt site).

Using myself as a highly subjective subject, I've observed that my static performance, in terms of time and comfort, has been much better than I had any right to expect when this program was followed.

It makes sense that the dive reflex, or the predisposition to it, would persist. Physiology is inherently conservative. It is a homeostatist, a status-quo preserver. That's how living things differ from rocks: they respond, and do so in the service of preserving a prioritized set of states. The dive reflex is associated with preserving the highest -level states in the hierarchy: brain functions, etc., and so it stands to reason that when the environment evokes it, it would remain 'on alert' , as it were, for a some time. It takes asphyxiation very seriously, and it makes sense to expend whatever costs are associate with this alert if the threat of sudden death by asphyxiation / drowning has been detected.
just a machine

I dont think the scientist would include bloodshift in what they call the "dive reflex" although it is a reflex when diving deep.


I dont see the bloodshift as any part of a mental effect or an effect that involves the brain.
I think it is quite physiological and even mechanical thing happening. It is a system of water and air in some hoses and ballons that is put under pressure.

I think it is more logical that the body adapts BACK to normal mode quite quickly. I can see no advantage for the human body to walk a round in a bloodshift state on land. The body is too smart to do that.

My body does not seem to be that smart.

As I go through a set of dives, it is plain to me that the blood shift becomes more and more pronounced as I go along. I feel it as numbness in the legs, and notice I've turned into a piss factory.

The diuretic effect persists for hours, definitely, after I've stopped diving. I am locally famous as the guy who has to make several desperate stops during the 90-minute drive back from the Keys, and who crashed through the doors of the house and the bathroom on arrival at home. This, hours after I've stopped drinking water.

In me, at least, the blood shift is definitely something that takes 20 minutes, at least, to "warm up" through apnea and increased hydrostatic pressure. As an enhanced predisposition, it does seem to me to linger, certainly for hours.

I, too, am a devotee of Occam's Razor and have been inclined for years to prefer the simple, physical/hydraulic model to the esoteric "mammalian dive reflex" with respect to peripheral vasoconstriction.

My problem is that it very definitely feels to me, and has for decades, as though the physical/hydraulic model is inadequate.
It does not incorporate one of the most striking features of organisms in general and the human organism in particular: learning.

But of course, not everything that feels like it is, is. That's how come we invented measurement and science.
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