It wouldn’t be a surprise if I say that it is not that many available Freediving books around. The last one which I read was “Oxygen” by William Trubridge. And I am also in the middle of “Manual of Freediving” by Umberto Pelizzari.
So, it was a pleasant surprise when the book “Longer and Deeper” by Jaap Verbaas was published a couple of months ago.
I don’t know the author personally, but I read a couple of his articles on the website Freedive Wire and also saw a couple of thoughtful comments here and there on different social media.
So, I was pretty excited to get his book. Is it worth to get it?
My opinion – 300% yes. First of all, it is not a “beginner level” manual, where an author explaining MDR or hyperventilation and you are skipping it because there is nothing new there. It is also not complicated medical research where you should Google every second word to understand what the article is about. It is somewhere in the middle.
But what is it exactly about? The book is mostly about how and why to train “dry”. There are exercises with explanations on how to do them and what exactly you will get from it.
I am not telling that these exercises are unique and you couldn’t find them somewhere else. But I was hooked by simple explanations about how exactly they work as a cross training for a Freediver. I haven’t met such detailed explanations before.
For whom this book will be useful? If you are a highly experienced Freediver with an academic background in the human physiology – then probably you will not find anything new. For anyone else – give it a try. Especially if you are not simply trying to increase your PB’s, but also want to understand deeply processes in the body during apnea training.
For example for me, none of the exercises was new (ok, I never tried apnea squads), but an explanation of how it works boosts my interest to understand more about certain parts of human physiology. So, because of it, I spent the last month trying deeply understanding different processes in a human body during apnea.
Overall this book is definitely in the TOP list of Freediving books for me at the moment and I definitely recommend reading it. And also I hope the author is not going to stop and will continue his researches and we can expect the second edition in the near future!
First of all the term, Mammalian Dive Reflex is a little bit misleading term since not only mammals have it. So, let’s call it Dive Reflex or Dive Response or just DR 😉
Doesn’t matter, you are complete beginners or you already Freediving Instructor, Dive Reflex is your best friend!
A bit of history. Many years ago one French doctor made a statement that man could not dive deeper than 50 meters because the thoracic cavity is going to be crushed (some sources say 30-40 meters). Why? Because every 10 meters pressure increasing with 1 atm and when you are 50 meters surrounding pressure already 6 atm. And it is huge. But back to those time, no one was even trying to do it (ok, there a couple of exceptions). But in 1961 Enzo Maiorca dived to this depth and survive! Why? Because of the blood shift! And blood shift is a part of DR!
DR is activated when our face is cooled (by cold water for example) or when we hold our breath. When we do both – even better!
This reflex helps us to hold our breath longer and dive deeper! How? By:
Peripheral vasoconstriction and blood shift
1. DR is responsible for spontaneous activation of Apnea. If we place infant underwater (don’t ask me why) their windpipe would spontaneously close (by vocal cords) and this prevents water from entering the lungs. This reflex quite strong upon 6 months and then start to disappear. My assumption – around this age baby start learning how to crawl and probably decide that Dive Reflex is not that important for them! Does it happen because of our genetic memories of our aquatic past or because nine months before birth our natural environment is liquid? Who knows 😉
2. DR causing bradycardia – slowing your heart rate (HR). Quite common is 10-30 % reduction of HR for Freedivers (up to 50% or more in highly trained athletes). There are stories with even more impressive results, but let’s skip them now. Sounds impressive? How about this – laboratory rats have 80% decreases in HR while submerged underwater!!
Bradycardia is usually followed by tachycardia (increase in HR) after breath hold is over.
Why bradycardia is important for Freediver? Well, it is a protective mechanism of our body, it decreases O2 consumption, which means we can hold our breath hold longer without risk of losing the conscious! It also compensates the result of peripheral vasoconstriction effect (which cause increased blood pressure)
3. Next benefit of DR is a peripheral vasoconstriction and blood shift
Back to 1974 study showed that during dives to 40-60 meters, the amount of blood in the thorax (chest cavity) increased more than twice! And this reflex was called (pretty obviously) blood shift.
Peripheral vasoconstriction (PV) is a narrowing of the blood vessels to reduce blood flow to non-vital organs (such as skin or inactive muscles, for example) ensuring that oxygen-sensitive organs like the brain or heart receive enough O2 for normal function. In another word PV is a redistribution of blood to vital organs from peripheral organs. PV also induces anaerobic metabolism, with an increase in lactic acid as a by-product. Interesting that the release of lactic acid into the bloodstream doesn’t occur (or at least significantly reduced) until Freediver resurface (at least this is what experiments on laboratory rats show).
For all of the above, you can say that blood shift (BS) happens (blood moves from non-vital organs to vital organs) when PV happens, but quite common Freedivers are using the term BS when describing the movement of the blood to the chest cavity to protect it from increasing pressure while diving deep.
Due to PV certain amount of blood pushed to the lungs, the capillaries in the lungs receive a greater blood flow and increase in size, compensating for space lost in the lungs due to increasing of ambient pressure. The lungs become filled up with the blood, which is reabsorbed when Freediver ascending.
IMPORTANT! Blood shift not pushing the blood into alveoli! It pushes it into capillaries around alveoli!
Why PV is very important for Freedivers? Well, it helps to move O2 from organs which can survive longer without it, to organs which are in constant demand of O2. So, it helps us to hold our breath longer and dive deeper (by moving blood to the chest cavity).
4. And the last but not least benefit of DR is the spleen contraction. Spleen in the human body has two main functions – mechanical filtration of red blood cells (RBC) and as a part of the immune system. We are interested in the first function. About 240 ml of RBC’s can be held in the spleen and released when needed (due to hypoxia for example). When the contraction of the spleen happens oxygen-rich RBC’s gradually start their journey to circulatory system increasing O2 carry capacity of our blood (and helping us to hold our breath longer).
Interesting that spleen not recovering fast, even after an hour it is only partially recovered (however there are studies which show that spleen can be fully recovered in size in less than 20 minutes).
5. This is not a benefit, but still part of DR. Immersion diuresis. Yes, this is an explanation why while Freediving you want to pee much often! As you know part of DR is PV and it causes increased blood flow to the torso area and increased blood pressure as a result. Our body detects it and releases a specific hormone responsible for liquid regulations, which increase urine production. Don’t be embarrassed because of it! But make sure that this reflex doesn’t make you dyhadrated (drink enough before and after Freediving session).
6. Another side effect of DR is faster muscles fatigue. And again you can blame PV. When PV happens and blood moves away from your muscles, they start to work in an anaerobic way and produce more lactic. And even after you finish apnea, the effect does not disappear quickly (depends how long and intense your apnea was). Do you need proof? Try to do DYN bi fins 100 meters and 100 meters surface swim (with the same fins) and compare how do you feel.
If you have any question about Freediving, let me know in comments below!
What is the best way to learn how to hold your breath? Of course, it is signing up for Freediving course 😉 But if you couldn’t do it at this moment (or did it and forgot), here is a small review about it!
If you haven’t read my previous post about breathing in general – check it out here
So, any breath hold has 3 parts – preparation, breath hold itself and proper recovery after it.
So, the first part is relaxation breathing.
We can say there are two main types of relaxation breathing
First one, let’s call it “old school” relaxation breathing is when you are trying to slow down breathing rate by extending your inhale and especially exhale part. There is even recommendation – exhale twice longer than inhale (not sure why twice). Let’s be honest – it is a mild version of hyperventilation (if you extend your exhale over a period of time, you removing extra CO2 from your body). I think Goran Ccolak said in his interview to Freediving Café, that every breathing, which differs from tidal breathing is hyperventilation. The question is how big ;-).
Yes, you are going to feel that you need to breathe less and less. But if you remember, your respiration rate regulated by the amount of CO2, reduction of CO2 will cause a reduction in the breathing rate. But do you want to reduce your CO2 level? Just quick reminder – if your CO2 level is low then O2 delivery going to be not that effective (Bohr effect).
You also creating some resistance for your respiratory muscles, right? And it potentially won’t allow you to completely relax (this is my opinion).
The second type of relaxation breathing is a relatively new way of warm up. Instead of extending the duration of your exhale, do tidal breathing and then just 1-2 big breath in (with passive exhale) before actual breath hold. Same breathing what you have before you fall asleep. Still better to use diaphragm breathing for it though (it means that you still want to learn and practice it). Let’s say for two minutes you are doing tidal breathing. You relax your muscles and mind. Your heart rate will go down since you are more and more relaxed. And your CO2 level not going to be high as well. But at the same time, it is not going to be below the normal level for this particular level of activity.
I remember first time read about it on William Trubridge FB page (hope I am not wrong here) and then Alexey Molchanov said the same on a Deep Week in Amed, about his breathing routine before a dive.
And lastly, another Freediving champ Adam Stern was talking about this type of Breathing on one of his last video!
Questions are – what to do while you are holding your breath and what happens in your body?
The answer is – try to become as much relaxing as possible. Easy to say, hard to do. What I recommend for my beginner students is to “scan” their body during breath hold and check if their muscles relax or not.
Face muscles (especially around eyes and jaw), neck, shoulders, arms, belly area, hips, ankles. And then do it again and again. Sooner or later you can relax without such “scanning”, but in the beginning, it is VERY useful!
If you are a beginner, not tolerance for a high level of CO2 or low level O2 important. It would be later. Now, you need to learn one of the most important parts of Freediving – how to relax!
So, you finished your relaxation breathing, made a big breath in and start holding. You managed your relaxation and completely relaxed. But all functions of the body are still working. So, you are still producing energy and as a byproduct, producing CO2. At some point, the CO2 level reaches a certain level and your respiratory center (RC) will send your muscles to remove this CO2 from your body. And you have the first contraction (movement of your respiratory muscles).
And what happens at this moment with your O2 level? It is going low for sure, but you still have plenty of O2. Enough for every body’s cells. And you know that and this is why you are keep holding.
Another contraction, a little bit stronger. But you are a Freediver and RC not dictated you what to do anymore. So, you are keeping holding. RC disagrees with you and sending you another command to breathe. Another contraction. And another. And they become a bit tougher.
Ok, you decide to finally follow this command and finish your breath hold! How? By start doing recovery breathing!
Ok, last part, recovery breathing. Why do it? During your breath hold (static, dynamic or depth) you use some O2. Longer you hold your breath, more O2 you use. Less O2 you have, higher chance of LMC/BO/SWB.
But as you remember, you start feeling discomfort, not because of low O2, but because of high CO2. So, when you stop holding your breath, what is your main goal – reduce the level of CO2 or increase O2?
The second option is correct. During your recovery, you don’t care about the level of discomfort (level of CO2), you care about not to lose your conscious!
First, exhale doesn’t have to be full (passive exhale more than enough) followed by full quick inhale. And you repeat it 3-6 times (or longer if you need it). Some Freedivers also do a “hook” breath – it is when after full and quick inhale, you keep this air for a second before exhaling.
And don’t forget while you are doing recovery breathing it is much safer if you have a support – float, side of the pool or anything else.
Another important rule – do recovery breathe every single time, not only when it was “hard” dive. Even after very easy dive you need to do it – it will help you to create a very useful habit and put it on a subconscious level!
Thank you for reading! If you have Freediving friends, who might find this article helpful – feel free to share! And if you have any question about Freediving – please let me know in comments below!
Let’s start with understanding why we (as humans) breathing. Yes, we all know that we need O2 (oxygen) for our life and this is one of the main functions of our respiratory system – bring O2 to our tissues.
But do you know that our breathing rate is mainly regulated by the amount of CO2 (partial pressure of CO2) in the blood, not O2. We even have a specific part of our brain responsible for this regulation. It has a very difficult name – Medulla Oblongata. This “thing” is responsible for such automatic functions as breathing, heart and blood vessels function, swallowing, digestion.
Why is it important to know, especially for beginner Freedivers?
Well, we all know that some of our tissues couldn’t operate without O2 even a short amount of time. For example – our brain. And when beginners hold their breath and feel the desire to breathe, they start to be nervous because they are thinking the level of O2 critically low! And it is becoming dangerous!
And – if not, why they feel uncomfortable?
Let’s say you are holding your breath for a minute.
Even if you are relaxed as much as possible, you still produce some energy. And as a result, produce some CO2. And when your CO2 reaches a certain level you want to breathe (actually you want to remove excess CO2 level). In Freediving quite often we use the term “urge to breathe”. So, how are going to bring new air to your lungs? What is the process looks like?
Our main respiratory muscle is our diaphragm. It is a big muscle between your chest (thoracic) cavity and abdominal cavity. When you need to inhale – your diaphragm going down (contraction of the diaphragm), chest volume increase and the air suck in. Reverse process happens when you exhale – you relax your diaphragm and it is coming to its normal position, pushing the air out of your lungs. Intercostal muscles (muscles between your ribs) involved as well, helping you make a bigger inhale or exhale.
And now let’s come back to urge to breath. When you are holding your breath and have an urge to breathe – it is simple contractions of your respiratory muscles (diaphragm for example), which are trying to remove CO2 from your body.
As a beginner, you want to stop holding your breath after you have a contraction, or a few seconds later (5-15 is a good start). But with the practice, you can hold your contractions much longer. And let me remind you, that contractions are not connected with the level of O2, it is a simple response of your respiratory system for a high level of CO2. So, you are safe when you have them, don’t be scared.
But what exactly happens with the air, when it comes to our lungs? You inhale fresh air (only 21% is O2, 78,96% N and 0.04 is CO2) and it starts its journey into your circulatory system! There is a natural dead space (no one dies, there is just no gas exchange) on its way (nose/mouth + trachea + bronchi + bronchial), so when air reach your alveoli, it has less O2 than you when you inhale.
Your alveoli are tiny compartments where gas exchange happens between your lungs and your blood (capillaries). The wall of alveoli is thin enough for gas (gas traveling both directions, from alveoli to blood vessels and back) and not thin enough for liquid (this is why blood normally couldn’t penetrate into your respiratory system).
So, from alveoli, O2 moves into your blood, where most of it binds with the hemoglobin and use it as a taxi to get to different tissues (your muscles for example) through arteries.
And within your tissues, cells use O2 for producing energy and also creating CO2 as a byproduct (as well as water). After CO2 produced, it goes to your blood (partially connected with hemoglobin, but mostly dissolved into the plasma – bicarbonate) and then going through veins to your lungs. Then again, through gas exchange, CO2 penetrates to your alveoli, going all the way up to your mouth and then you remove it through exhaling! This how we are breathing!
Pretty simple, right?
A few words about the importance of CO2 in our body.
If CO2 is just a byproduct of producing energy and our “urge to breath” depends on it, might be we need to remove it from our system before a breath hold activity? And then can stay underwater longer?
Probably same thought had freediving pioneers when they were doing hyperventilation (which is a big no-no nowadays). Basically, hyperventilation (or over breathing) is the process when you ventilate your lungs too fast.
What happens when you do hyperventilation – you reduce the level of CO2 in your body, which cause increasing pH of your blood (blood become more alkaline – respiratory alkalosis) and it triggers Bohr effect – now a connection between hemoglobin and O2 becomes stronger and exchange between capillaries and tissues becomes harder. In simple words – even if enough O2 present in the blood, it is much harder to deliver it to tissues. Since the human brain is very sensitive to the lack of O2, as a result of hyperventilation we have symptoms – dizziness, tingling in the lips, hands or feet, headache, weakness. Or in a worst case scenario – unconsciousness (our brain simple protect us from further depleting of O2).
So, CO2 playing an important part in keeping pH of our blood constant (7.34-7.45), so-called acid-base homeostasis
Thank you for reading! hope you found some useful information here 😉
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