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Apnea Carp
Oct 11, 2003
London, UK
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Very interesting discussion, not that I understand all of it. :)

I wonder if the presence/absence of the dive reflex makes a difference? I don't think I have a dive reflex, even without any hyperventilation or breathe-up, and I have never managed the no warm-up no breathe-up method with any success.


Dec 9, 2005
F:Lyon / CZ:Prague
I do not think it is possible not to have any diving response at all. It may be stronger or weaker; faster or longer to kick in; individual effects may occur with variable intensity; but I do not think it is possible that the body does not react at all.

The question in such case is rather why the diving response at such individual does not occur with expected force. There are external factors (i.e. water temperature), individual predisposition or experience/training (studies show higher diving response at regular freedivers, though it might be also the consequence of natural selection), and physiological aspects having impact on the DR. And one of the most important factors is the CO2 level, and consequent blood pH. So of course, the more you hyperventilate, the lower chance for an early and deep DR. And the lower DR, the less the DR will compensate the negative effects of hyperventilation.

One could tell, if there is no diving response, hence no trade-off between hyperventilation and the DR, then deep hyperventilation would be the best way. However, I believe it is wrong anyway - first, as I wrote, there is always some DR (even if quite weak), and second, some of the negative effects of hyperventilation are so significant that they impact the maximal performance anyway. Most importantly it is probably the decreased hypoxemia tolerance, which then leads to a premature blackout.

When comparing maximal attempts with and without hyperventilation, we have to differ between physiological and psychological maximum. Physiologically taken, as explained earlier in this thread, the theoretical maximum is a trade-off between the advantages and disadvantages of hyperventilation, and also its influence on the DR. But the real performance is more often interrupted because of the psychological barrier, especially if done under high CO2, hence you then do not really compare the maximal physiologically possible times.

Perhaps, in your case, the weak DR is influenced by subconscious hyperventilation even when you think you do not hyperventilate at all. But of course, there may be also other physiological conditions suppressing the DR. Perhaps frequent training in conditions improving the DR (cold water, no thermal protection on extremities, no mask, high CO2, stress, ...) may help waking it up better, and perhaps it will then kick in easier in more comfortable conditions too. Also frequent deep diving may help training the DR - the fact that until recently you only knew the pool and did not dive in open water, may be a reason for the weak DR.


51% freediver 49% spearo
Jan 31, 2007
Central Coast, Chile
naiad, I agree with trux, it is probably impossible not to have some form of DR.

If you dive in open water try this simple test:
Day 1. Note your given comfort level/dive time on the first dive. Note your maximum dive time for same comfort level in same conditions. It will probably be 3/4 way through your session. (say, in a 2 hour session, your best dives will be at 1:00 to 1:30?)
Day 2. In same depth, water temp, conditions. Enter the water, arrive at dive position and take your mask off, snorkel in, face down and let the cold water flood over your face, let cold water flood into your wetsuit. Keep your face in for at least 5 mins, occasionally "fanning" cold water over it. Then dive. I will bet that first dive will be near your max dive on Day 1 for the same given comfort level. That is some DR factors working for you.

At the beginning, add a dive, say to 10M, and hold on to something until your first contraction, then pop up, and the DR should be enhanced more again.

I was skeptical too, but the above works every time for me.
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New Member
Apr 8, 2008
Durham, NC, USA
more reading...

Sorry I have not been around in a while but while reading the back log I thought it might be worth adding to the reading some:

Lindholm, P and Lundgren, CEG. Alveolar gas composition before and after maximal breath-holds in competitive divers. Undersea Hyperb Med. 2006 Nov-Dec;33(6):463-7. RRR ID: 5053

NW Pollock, RD Vann, ED Thalmann and CE Lundgren. Oxygen-Enhanced Breath-hold Diving, Phase I: Hyperventilation and Carbon Dioxide Elimination. In: EJ Maney, Jr and CH Ellis, Jr (Eds.) The Diving for Science…1997, Proceedings of the American Academy of Underwater Sciences (AAUS), Seventeenth annual Scientific Diving Symposium, Northeastern University, Boston, MA. RRR ID: 4647

Phases 2 through 4 are being written for publication now, we have not had time to get back to it (though I agree, 8 years is excessive). If it takes too much longer, I'll post the grant report we turned in to the Office of Naval Research. Abstract we presented are available though:

Phase II abstract - RRR ID: 648
Phase III not reported
Phase IV abstract - RRR ID's: 6730, 6739

--Please use this link and not links directly to the pdf's in our database, it eats more bandwidth and gets expensive with the traffic we receive lately.


Well-Known Member
Jun 8, 2007
Phuket, Thailand
What matters is the % O2 increase over normal useable O2, not the % total volume increase. If the O2 in my lungs increases by 8% then I have 108% of my normal supply of O2 in the lungs. If I can normally deplete about 50% of the O2 in my lungs then my extra 8% would be 16% of my normal useful O2.

The period of time that my lungs effeciently move O2 to my blood increases by 16% too since that is all bonus O2. For most, that time when the SAO2 starts dropping rapidly is in the 3-5 minute range for a corresponding increase of about 30-50 seconds based just on the lung O2 increase alone. Assuming you get a significant venous saturation increase, let's say 10%, for an average increase of 5% for the entire blood supply. Let's also assume you have a 10%/min O2 depletion rate at the end of your holds. That 5% would give you about 30 seconds extra, best case. Your total benefit would be about 1:00-1:20 seconds, best case, except...

Now the negative effects. All that extra breathing introduces significant O2 debt at the beginning of your hold, so let's deduct 45 seconds from the benefit. Lots of CO2 got blown off, so at the end of your hold when you need to be able to consume O2 and your SAO2 is 75%, there is not enough CO2 in your blood at the tissue level to knock the O2 molecules loose from the hemoglobin, so lets give the Bohr effect another 45 seconds for a net loss of 10 seconds. You didn't feel hypoxic symptoms so you continued the dive too long, and at best, failed surface protocol, or at worst, passed out at 10 meters and had to be dragged out of the water by your buddies. Too bad their CPR was rusty. You didn't make it alive to the hospital. The good news is that you felt great until you passed out, so you died happy, and your corpse will have a smile on its face.

So in the end it is probably a wash or a net loss of a few seconds or maybe your life if you hyperventillate. Of course everyone is different.

So where do we go from here? A few purge breaths before a hold to maximize O2 in your lungs might be beneficial in terms of increasing useable O2 in the lungs. If you look at the mathematics of it, 5 purge breaths gets you about all the benefit you can get in that regard, because you will never get 100% new air into your lungs. Sustained hyperventillation has too many risks and negative effects and probably negates the benefit of a few purge breaths. Everyone has to define for themselves the limits of what they are willing to do, so educate yourself and make good decisions. Your life, and the lives of the people who will learn from you, may depend on it.
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Vladimir Tsyglian

New Member
Jun 16, 2017
Toronto, Canada
Very, very interesting thread. Obviously, any kind of HV has negative aspects associated with it. So as someone relatively new to this art my question is this:
From what I understand(I'm no scientist, so correct me if I'm wrong), hyperventilation has to do with the physical quantity of gas exchanged over a duration of time leading to a drop in C02 levels. This essentially means that most "Breathe Ups" are to a certain degree engaging in HV, correct? As they deviate from the body's natural breath flow. i.e. 1/2/3 mins of 5 second inhale/10 second exhale, etc.

So, would it be safer to simply breathe calmly for 2 or 3 mins(not forcing anything) and take 3 quick/deep breaths and then hold(someone stated earlier that some cultures do that traditionally)?
Surely there would be less c02 decrease in those 3 "purge" breaths than in a breathe up of 2/3 minutes of 5s inhales/10s exhales?

Sorry if my question is redundant and thanks in advance for the answers.


J Campbell

Well-Known Member
Sep 17, 2001
Annapolis, MD, USA
For me deep breathing puts me in a good psychological state -relaxes me. I'm not talking about rapid and forced inhales/exhales - but slow easy inhales not to max and passive exhales where the elasticity of my chest just naturally pushes the air out. The last 3 or 4 breaths I inhale deeper but still controlled and do a gentle abdominal squeeze to force the air out - but again got harsh. The final inhale is a full lung but not so much that I feel uncomfortable. This relaxes me and I feel good after such a breathe up and have pleasant dives
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