• Welcome to the DeeperBlue.com Forums, the largest online community dedicated to Freediving, Scuba Diving and Spearfishing. To gain full access to the DeeperBlue.com Forums you must register for a free account. As a registered member you will be able to:

    • Join over 44,280+ fellow diving enthusiasts from around the world on this forum
    • Participate in and browse from over 516,210+ posts.
    • Communicate privately with other divers from around the world.
    • Post your own photos or view from 7,441+ user submitted images.
    • All this and much more...

    You can gain access to all this absolutely free when you register for an account, so sign up today!


Thread Status: Hello , There was no answer in this thread for more than 60 days.
It can take a long time to get an up-to-date response or contact with relevant users.


New Member
Jan 17, 2002
A theory for thought. (safety issues aside)

Most, when asked reply that hyperventilation is dangerous ( couldnt agree more ) and ineffective.

This theory proposes that hyperventilation is very effective (and dangerous.)

Hyperventilation by rapid and deep breathing ie a breath a second for a minute will extend a breath hold performance by up to 100%. This is achieved by making the limit of loss of consciousness more approachable but not by moving the limit of loss of consciousness.
Mechanically the need to breathe is caused by Co2 Build-up. This need to breathe stumulus can be depressed by blowing off much Co2. O2 loading is insignificant ? during hyperventilation.

Danger is when the Oxygen level reaches a too low level and the brain switches off before the rising Co2 level makes it intolerable to continue breath- hold.

Fear of not being able to make the return trip from the depths and the 'pain' of oxygen hunger is usually what mentally and physically limits a apnea performance. Equalisation problems aside.

Few divers continiously press right up to the limit of loss of consciousness. It stands to reason that reducing a need to breathe will extend the depth and time performance of most divers by reducing fear and pain, by extending comfort during the performance.

Yes, overcoming those mental blocks is much of what freediving is about but can hyperventilation be denied as an effective, and i will say again, but dangerous tool ?

Hyperventilation in itself is not dangerous but seeing as how by extending the comfort of the apnea period one may stray over the low oxygen shutdown limit, its practice is dangerous.

Hyperventilation will not speed the onset of Blackout nor will it delay it. It will however make the journey there more comfortable and participants with fluke good timing will enjoy generally greater successes. Those with inevitable bad timing will inevitably die.
What about in competition where safety is at its best and death unlikely ? Surely hyperventilation will provide good results amongst the increase in SWB ?

Is the accepted ' breathing- up' as practiced by most, not just an extended / mild form of hyperventilation?

Does anyone dispute the effectiveness aspect of this theory?

Having raised some curiosities.. please dont ever hyperventilate. It will kill you.
To do or not to do?

As you said, the high levels of CO2 trigger the respiratory centre to breath, also the low levels of CO2. But the respiratory centre is more sensitive to high CO2 levels (fortunatelly).
When a freediver hyperventilate he lowers the CO2 levels, but the O2 levels are the same, and also drives his blood pH to alkalosis. I think that the low levels of CO2 and high levels of pH make the apnea more comfortable.
The risk is that you lose that physiologic warning to breath. How do you know, how far is a dangerous low O2 level?. The alcalosis also induces vasoconstriction (narrowing of arteries) compromising the blood flow to the tissues.
On the other hand, if you know very exactly your performance so, you can use it to enlarge the 'easy part' of the apnea, but under high security measures. I don´t recommend it for constant weight. I only use it to static apnea.
So, to make a point, I agree partially with the theory but don´t recommend widely that practice.


Frank Pernett
Not correct!

Hyperventilation does change the stimulus to breathe, but it ALSO changes the point at which consciousness is lost. Hyperventilating reduces the bohr effect -- acidity in the blood is needed to release oxygen, with alkaline blood, the blood does not release oxygen as easily, and blackout will occur sooner.

However, insufficient breathing will also cause premature blackout, because then the diver will actually black-out from too much CO2.

Eric Fattah
BC, Canada
i have 2 questions..

1.how conservative is the formula.
i.e. i will use it in reverse. to find CW depth
DYNAMIC = (4/3)*CW + 22
50 = (4/3)*CW + 22
28 = (1.33)*CW
1.33*28 = CW
CW = 21

if my math is correct (probably not)

2. Eric, do you have a PH.D. in freediving? (does a record count?)


The dynamic - constant weight formula is not conservative at all, it is designed to precisely show your limit in one event vs. your limit in another.

Your math was correct, i.e. 50m dynamic = 21m constant, according to the formula.

Eric Fattah
BC, Canada
  • Like
Reactions: fpernett
Other effects

In addition to what Eric properly said, the respiratory alcalosis also reduces the brain blood flow, reducing further the O2 content on it. Other effects of respiratory alcalosis are the cardiac arrhytmias and the lower free Ca++ levels (which is basic for muscle contraction).

The 'reverse' formula is incorrect, but the result is right:

CW=DYN-22/1.33 = 28/1.33 = 21


Frank Pernett
I have read somewhere before that a US Navy dive manual says that taking four fast deep breathes rather than repetative shallow breathes over and extended period of time is safer. Whats the deal with this? Both methods are going to decrease the amount of Co2 and results in a longer breath hold because it will be more comfortable, so both should be just as dangerous. Admittatly I do use the the four breath technique simply because I feel like it is safer because there is little chance of over hyperveltilating. Is this four breath technique "breathing up"?

I do the same as what frank said, for constant I dont hyperventilate because there is already enough risks and I am not as experienced in knowing my limits for constant yet. And you cant just take a breath like in static and dynamic, if you feel like you' ve stuffed up then you still have to keep going towards the surface.

With static its totally different I know my limits even when I hyperventilate extensively and if your pushing to hard you can just take a breath and its over. I believe hyperventilation is good for statics.

today I was hyerventilating taking fast deep breathes i did this for 15 seconds and when i held my breath i instantly good very dizzy and my vision almost completely went, i felt like i was blacking out, what happened, and what would happen if i did it again and did black out?

mate that dizziness always happens to me at the start of statics for up to 30sec I think it is simply from the effects of hyperventilation. These are good effects to have in my opinion cos you are so dizy that you forget about time and the urge to breathe.


Hyperventilation does change the stimulus to breathe, but it ALSO changes the point at which consciousness is lost. Hyperventilating reduces the bohr effect -- acidity in the blood is needed to release oxygen, with alkaline blood, the blood does not release oxygen as easily, and blackout will occur sooner.

This is the long and the short of it.

Co2 is acidic. Blowing too much off turns the blood too alkaline. Alkaline blood is stingy with oxygen refusing to give it to the brain and the brain does not have a C02 stimulus to open the vessels to increase bloodflow to it to receive more oxygen anyway. Bang! your out !

Hyperventilation will reduce your performance in terms of maximum breathhold time. If you do it agressively you will most likely not give up when needing to breathe becomes crucial, rather you will pass out - just like falling asleep at night. You cannot pinpoint the moment it happens.

P.s. Terry Maas defines hyperventilation as deep or fast breathing to the point that your fingers begin to tingle.

Trust me.
The sensation you were feeling was due to hypocapnia-or low CO2. It can cause your blood vessels to constrict and reduce blood flow to your brain, causing dizziness and even blackout.
This is typically more of a problem when performed dry, and your body's sensitivity to this can reduce over time.


Skindiver I believe that hyperventilation extends breathold time by lots even though it has all those risks It is the best way to get a max performance.

Originally posted by MANTA99
. Is this four breath technique "breathing up"?

I believe that any breathing at all between dives must be classified as a "breathe up", so you can't escape it, really!
The function of a breathe up is to retain as much O2 as possible in your body before the dive, so in a sense we all "hyperventilate" when we make a conscious attempt to achieve that goal, yes? If we look at the actual meaning of the word hyper ("increase" in our case) and ventilate ("supply air" in our case), then we can't just assign the word to fast-breathing techniques.
A few quick and deep breaths before any dive will help to clear the CO2 from the air that is in your lungs, giving a better PO2 (closer to ambient) for the final breath you take before the dive.
Erik Y.
  • Like
Reactions: MANTA99
hi Erik

As Sebastien Murat says in his interview any breathing that is more forced than normal breathing is hyperventilation I totally agree except I hyperventilate properly Ie deep and quick so you get dizzy.

So how do you define "Normal" Breathing ?

It really doesn't matter anyway. I'm sure that for some people, with very high CO2 tolerance (Seb or Martin S), "normal" breathing may give maximum times/depths. But I think the majority still need to blow off some CO2 for better performance.

Having been and competed in an International freediving competition, I can tell you that pretty much everyone there hyperventilates to some degree.

I also go along with what Erik said, and pretty much everyone I know, spearos included always take some quick deep breaths before you dive. You want to get rid of that stale air right ?

Breathe up

I think breathing up has two purposes.

Psychologically ( and prolly most importantly) we all develop a pattern ( mantra ) upon which we build a repeatable performance and gain confidence. I call this grooving.

Physically increased breathing decreases Co2 increasing the comfort zone. O2 increase is negligible. Most of the SA team could not really increase their O2 saturation measured with an oximeter at the thumb, at rest, of 98% to 99% even after a big breathe-up.

We know that if you blow off too much Co2 you turn the blood alkaline and if you hold your breath too long you pass out without too much discomfort or warning. You also pass out earlier than you would have than if you had higher CO2.
This is why i breath more agressively for Constant and Dynamic than for Static. Those disciplines are more physical and the Co2 i breath off will build more quickly, hopefully giving a balance and staving off Blackout. In static, C02 builds much more slowly and here is a real danger of blowing off too much.

Hyperventilation is a general term and there are degrees of it, but perhaps is taken by most to mean increased ventilation to the point of dizziness. Increased ventilation to any point less than this i would call 'increased ventilation'.

The amount that one engages in increased and hyperventilation is the name of the game. Those that can work out a balance are the successful divers.
The balancing act is dependant on factors such as depth required. Time required at depth. Work to be performed at depth. Temperature. Darkness of the water. All these factors would be calculated ( instinctively by some and scientifically by others ) and the correct amount of ventilation applied.


I hyperventilate like hell intentionally between points during a u/w hockey match. My Co2 is so high constantly that i will never blackout. Your bodies response to hard work is heavy breathing. I maintain it at the same high rate even after it would have begun to slow naturally and i recover much quicker and am fresher for the next point.

Typically for constant i ventilate slowly until i just reach the hyperventilated ( by my definintion) plateau ( tingles ) just for a reference purpose, so i know where i am in the scheme of things.
Then during my two minutes countdown i back off and maintain a state i feel appropriate by reducing my breathing even to 3 breaths a minute or increasing my Co2 by wriggling, and pumping my fists or clenching my major muscles as i feel appropriate.

There are probably better ways to do this than my backwards approach, but i'm still learning to be better at this..

Last edited:

Wal normal breathing would be how you are breathing now at rest I guess.

DeeperBlue.com - The Worlds Largest Community Dedicated To Freediving, Scuba Diving and Spearfishing


ISSN 1469-865X | Copyright © 1996 - 2024 deeperblue.net limited.

DeeperBlue.com is the World's Largest Community dedicated to Freediving, Scuba Diving, Ocean Advocacy and Diving Travel.

We've been dedicated to bringing you the freshest news, features and discussions from around the underwater world since 1996.