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The science behind the recovery breath

Jeroen Elout

New Member
Aug 29, 2017
6
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Philippines
The recovery breath razes a couple of questions for me:

1. What exact advantage does the recovery breath give versus the normal continuation of breathing when a diver comes up?
2. Is the little pressure we apply on the lungs supposed to push extra O2 in to the blood stream? If that is the case, could the recovery breath get used before the dive to put extra O2 in to the blood stream?
3. Would the recovery breath procedure use more muscle power (and there for O2) as normal breathing?
4. Who invented the Recovery breath? In what year became the recovery breath normal practice?
5. Are there any scientific studies on divers that return to the surface with and without recovery breath and the mental state they are in (Or PPO2 levels with or without recovery breath)
6. How come humans need so much time to recover while turtles only need two breath?
 
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japppo

Active Member
Jan 3, 2015
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Finland
www.youtube.com
Hi.
I don't have anything to say about recovery breaths, but your question 6 got my interest.

My understanding is that sea turtles have a larger lung volume in relation to oxygen carrying tissue. Two breaths are enough to ventilate the lungs and the lung capacity can ventilate the tissues during the dive.

This is just a rough example from the top of my head, but for example a human could have 5 liter lungs and 5 liters of blood, and a sea turtle could have also 5 liter lungs but only 1 liter of blood. Therefore in the turtle's case it is not so significant if the blood/tissues are fully ventilated on the surface or not. As a human I would like to see my blood oxygen level reach close to 100% before the next dive, regardless of recovery breathing technique.

I could be totally wrong here... just based on my understanding of a quick googling of couple e-books about sea turtles.

Of course there are many more differences between species in the lungs and their ability to exchange gas.
 
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SubSub

Well-Known Member
Aug 26, 2015
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Stockholm
Or more simply put on point 6.

Turtles are seacreatures where evolution has perfected them for aquatic life for millions of years, whereas we humans are a land living spieces whom have the possibility to explore the underwater life to some extent.
 

NoFair

Well-Known Member
Aug 18, 2014
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Sea turtles also have a slower metabolism and much lower oxygen needs than we do
 

cdavis

Well-Known Member
Jan 21, 2003
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Sarasota, Fla
Suggest you define what you mean by "recovery breath". To me they are simply the first few fast breaths to blow off enough c02 to become comfortable. If you mean hook breath, that's a different thing, designed to keep your blood pressure high until fresh 02 can get to the brain.
 

Nathan Vinski

Well-Known Member
Apr 19, 2015
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Canada
Answers for questions;

** just to be clear recovery breathing is the breathing performed at the end of a dive to recover from the dive itself. Blowing off CO2 is called hyperventilation.

1) The advantages of the recovery breaths (hook breaths: pressure applied by the lungs) are that it minimized the effects of slight hypoxia at the end of the dive. They give us the best chance to not have an LMC or a blackout.

2) The pressure actually increases blood pressure. At the end of a dive when we start breathing again our heart rates will increase quite a bit, this lowers blood pressure which could lead to a blackout. This is similar to feinting after standing up too quickly. The hook breaths keep the BP high and counteract this.

3) This one is very difficult to answer. The muscle contractions will use more O2 but keeping the higher blood pressure is probably more beneficial than relaxed breathing, considering that the breathing muscles don't use that much O2, even with the contraction.

4) The hook breath itself was invented by WW2 pilots counteracting high G-forces. The Higher blood pressure kept blood in the brain preventing pilots from feinting. This was the breathing part of something called the "Anti-G Straining Maneuver) Not quite sure who brought it into freediving

5) Don't think so

6) SubSub's answer is spot on. Unfortunately we're still land mammals and spend the vast majority of our time on land, unlike marine mammals, amphibians, or marine reptiles..
 

zazuge

Member
Jun 30, 2018
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ghardaia, Algeria
I think nathan already answered most points, but i'd like to add more
1) gas diffusion happens from higher to lower partial pressures, yes, high pressure in lungs leads to more diffusion of O2 in blood stream
"If that is the case, could the recovery breath get used before the dive to put extra O2 in to the blood stream?" <-- on normal relaxed breathing, your blood stream is already 95~99% saturated with O2, so it have no point to use it before a dive.
About the pressure in blood thing, i'd like to clarify it better by saying that avoiding active exhaling means you avoid the possibility of O2 partial pressure on O2 to go below the critical level, so, when you surface fast, your O2 partial pressure is blood is still above the BO level, but after 10~20seconds blood circulate around from your lungs (now at surface ATM pressure) and go to your brain and they might trigger a delayed BO,
So by pressurizing your lungs as soon as you reach the surface, you reduce that risk a bit.
There is something else others didn't mention though, and it's related to buoyancy, avoiding exhales and keeping your lungs full for a bit, gives you good buyancy, and it could help you in case of LMC or BO.
 
Mar 20, 2011
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Los Angeles
The hook breathe came into freediving in about 2000, the story goes, when Kirk Krack was traing Brett Lemaster for his CWT world record attempts (about 80M back then). Brett would surface just fine from his target dives, breathe and do a clear SP, and then they would see the color drain out of his face and he'd black out or samba. They tried introducing hook breathes and viola...

It is worth noting that Alexy has stopped hook breathing after his dives but it seems that while it works for Alexy it anecodotally does help plenty of other competitors who are diving at limit, and it is never detrimental.

Sent from my SM-G930T using Tapatalk
 

Nathan Vinski

Well-Known Member
Apr 19, 2015
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Canada
Thank you. But how do you DO a "hook" breath? Is it something i just have to be taught how to do?
Do a sharp big inhale, say "hook" as fast as you can, hold the "K" sound for 1-2 seconds, and release with a passive exhale.. repeat that 3+ times.

...Or take a course/get on YouTube.
 
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zazuge

Member
Jun 30, 2018
64
7
23
38
ghardaia, Algeria
hook breath isn't as complicated as equalization
you just have to use your IRV or inhale reserve volume
means you inhale above your nornal tidal volume and only exhale passively a little over your FRC
 
Apr 11, 2018
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New York
hook breath isn't as complicated as equalization
you just have to use your IRV or inhale reserve volume
means you inhale above your nornal tidal volume and only exhale passively a little over your FRC
Thank you; i will try to find out exactly what FRC means or how to tell if you are at Functional Reserve Capacity. i'm truly a novice
 

cdavis

Well-Known Member
Jan 21, 2003
3,961
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Sarasota, Fla
FRC: open your windpipe and relax for a few seconds. The amount of air left in your lungs is your FRC. It varies a lot between divers and conditions( in water or out, wetsuit on or off).

Nathan's description of a hook breath above is the best thing I've seen, really easy to understand and follow. I do mine with less than a full inhale and pressurize the chest while doing the "K"
 

noel.rivas

Member
Jul 27, 2017
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Mexico
Re #2a: If I'm getting things right, a hook type recovery breath will make air pressure in the lungs oscillate: pressure goes up on inhale, stays up a bit, then goes to 1 ATM —at sea level— on passive exhale; repeat.

If the goal is to increase air pressure (and with it, O2 partial pressure and blood pressure), why is packing not used as a recovery technique? I'm not sure how much additional pressure is created by packing, but I would assume that the combination of pressure and O2 volume would make it a good choice.
 
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