freediving course koh tao Archives

Basic respiration control for Freedivers (part 1)

12.03.201913.03.2019sergeyvladivostok

In the last couple of months, I noticed that even some Freediving professionals are not completely understanding how breathing control in humans happens. And be honest, while I was writing this article I found out that I was not 100 % correct as well.

Hopefully, this article helps you to understand better what exactly happens with your respiratory system when you hold your breath. And if you find any mistake here – feel free to correct me – I am still learning as well!

As any other Freediving school, we are teaching about breathing control on our Freediving courses, but here I tried to put a little bit more details.

To start with – we have two different types of chemoreceptors which are detecting chemical changes in our body and sending signals to our respiratory center within Pons and Medulla Oblongata (both located in the brainstem), from where impulses send to our external intercostal muscles and diaphragm, to change the volume and frequency of our breathing (or cause “urge to breath” if you are holding your breath).

We can divide these receptors into 2 categories

Central chemoreceptors. Why “central”? Because these receptors are part of our central nervous system and literally part of our brain (located inside Pons and Medulla Oblongata). Since these receptors are not inside blood vessels, they are responding to high CO2/H+ not within the blood, but within cerebrospinal fluid (CSF), which separated from the blood vessels by the blood-brain barrier (BBB).

Let’s make an example. You hold your breath for a few minutes. Amount of CO2 increases in your blood, the amount of H+ also increase creating low pH (respiratory acidosis). H+ doesn’t diffuse through BBB, but CO2 does. This CO2 bonds with water inside CSF and produce H+, an increased amount of which is going to be detected by central chemoreceptors.

CO2+H20↔H2CO3↔HCO3+H+

Recently I learned that lactate has an impact on this process as well. Lactate, which is produced during anaerobic energy production, in a form of lactic acid, can go through BBB where it brakes down to lactate and H+, which eventually lead to the activation of central chemoreceptors.

Eventually, central receptors can desensitize and this is why we have the potential to become less sensitive to high H+ over some period of training with exposure to a high CO2 (whether it is a breath hold training or some form of HIIT).

Peripheral chemoreceptors. They are not part of the central nervous system (instead, they are an extension of the peripheral nervous system) and located inside aorta (largest artery of the human body). More specifically – inside the aortic and carotid body. Interesting fact – here we have one of the highest blood flow in a human body.

Chemoreceptors inside aortic body sensitive to the change of partial pressure of CO2 and O2. If there is a change – they send the signal to Medulla Oblangata via Vagus nerve.

Chemoreceptors inside carotid body sensitive to change of partial pressure of CO2/O2 and change of pH (metabolic change, due to high lactate production for example). And if there is a significant change – send the signal to the respiratory center via Glossopharyngeal nerve.

The main function of peripheral chemoreceptors (glomus cells) is control of pO2 (in contrast with central chemoreceptors, where the main trigger is a change of pCO2/H+). As I said early, they also sensitive to the change of pCO2/H+ but secondary. It means that the sensitivity of these receptors to the low pO2 is greater when pCO2/H+ is high.

Activation of peripheral chemoreceptors are low when the partial pressure of O2 is close to the normal (100 mmHg), but when it is going below 60 mmHg the activity increases rapidly due to a decrease of hemoglobin-oxygen saturation.

Peripheral receptors are not desensitized over time.

Two common hypoxic ventilation responses (CO2/pH can stay at the normal level) – reaction to high altitude or high concentration of carbon monoxide in breathing air.

How all of this can be useful for us Freedivers? In the middle part of the breath hold, when your contractions start, it is a reaction to a high CO2/H+ sensed by central chemoreceptors. Peripheral chemoreceptors are not playing an important role at this moment since the partial pressure of O2 is close to normal. But close to the end of your MAX attempt, when pO2is going to be close to 60 mmHg and low, a reaction from them will contribute to your urge to breathe.

For further reading

Useful videos to watch

How to prepare for a Freediving course. (Swimming)

10.02.201911.02.2019sergeyvladivostok

As the Freediving Instructor I was asked many times – do you need to be a professional swimmer to become a Freediver? And the answer is no, you don’t to be a pro. But there are no doubts that swimming helps a lot in learning Freediving, especially in the beginning.

So, if you are planning to do a Freediving course (find more information about Freediving courses) in the near future and want to be better prepared for it here are a few things which I recommend you to do in the pool

Swimming with a mask and snorkel. Any style – breaststroke or freestyle – doesn’t matter. Benefits – you get used to breathing from a snorkel (and clean it from water), becoming comfortable with a mask and not stressed out when there is a bit of water inside
Swimming with fins, mask and snorkel. Face down, not too fast, not too slow. Same benefits as above, plus you are working on kicking (not bending knees too much, correct rhythm etc.)
Swimming with fins on the back. Improving the kicking technique and body position control. Make sure that your knee not coming up above the surface.
Swimming with fins on both sides. Further improving your kicking style and body position control. Keep your body as horizontal as possible.
Alternating swimming on one side, with swimming on your back. General body control.
Vertical kicking (if your pool is deep enough). This style is close to what you are going to do in the open water

These exercises not going to make you an incredible Freediver, but they will boost your confidence in the water and improve your kicking technique. Here is a short video about the importance of swimming for a beginner Freediver.

How to prepare for a Freediving course

16.01.201916.01.2019sergeyvladivostok

Quite often future students ask, how they can prepare for freediving course, which they would like to start in a couple of weeks (or even months).

Of course, if you just heard that freediving exists and you want to try it immediately – just sign up for a course. During the course, the instructor will explain everything you need to know and help you to do all the requirements.

Check out which requirements you need to pass to become a PADI Freediver

But some people always prefer to be one step ahead and well prepared before they start something.

For them, number 1 recommendation – spend some time in advance training your swimming skills. Yes, we have fitness requirements in PADI freediving course. But no worries, it is just basic swimming (200 meters without fins or 300 with fins) and can be performed in any style (also without time limit). If you know, that you cannot meet this requirement, then it is 100% better to train swimming skills before. In some organizations, though there are no requirements for swimming at all. Which seems extremely strange.

But even if you know that you are pretty good at swimming, it would be better if you go to the local pool, or even better the sea, to practice. Because more time future freedivers spend in water before the course, the more confidence they gain. Thus in such simple cases as leaking mask or water coming into snorkel students feel less stress. The whole course will be more smooth and you may feel more relaxed if such small details will not disturb you. So the 1^st thing you can do before freediving course – remove stress by regular swimming (with fins even better).

The next thing which we recommend to work on is Frenzel equalization. If you tried scuba or freediving before, you know how and why to equalize. If you are looking for some explanation on how to work on equalization, check this youtube video. Besides, let me know in comments if you have some questions about it.

Indeed equalization in freediving is probably the key point. Even scuba instructors sometimes are facing challenges with Frenzel equalization, because diving head first in vertical position differs a lot from diving feet first. In this concern, it would be useful to spend some time practicing it in advance.

What else can be done if you have a few months ahead before the freediving course? You can do some stretching exercises. Stretching is beneficial for freediving, however, it is easy to pass the 1^st level without any stretching at all. But if you are going to do advanced or master course, stretching will be super valuable and will help to make the course much safer and enjoyable.

The 4^th thing on which it is better to focus is relaxation breathing. There are plenty of breathing technics for different purposes. You need to focus on relaxation breathing for freediving (here is the link on basic relaxation breathing routine).

Also, so many people ask what they can read before starting freediving. My answer is always the same – just read a freediving manual. I don’t know about other organizations but in PADI we can provide students with the freediving manual in advance, where you can find theoretical aspects and practical advice.

I hope this information was useful.

And if you have further questions, or maybe, want me to cover some precise topics in next articles – feel free to let me know in comments.

How to start training STA breath hold

30.12.2018sergeyvladivostok

First Freediving course is over (if you haven’t done it yet – check here for more details), you are happy and willing to train more to become a better Freediver. The big question – how to train?

If you are lucky, and there is a Freediving club nearby – then just join it. You will find support and motivation there. But what to do if there is no Freediving club nearby? How to progress? Well, this is what we are going to discuss here

First of all – if you are planning to train in the water, you HAVE TO have a Freediving buddy. No exception. What about easy breath holds? Still no, you have to have a buddy in any case! If no – train STA dry (less fun, but safer!).

Before you start – refresh your knowledge about Breathing process in general (at least a part that it is CO2 which caused the desire to breathe, not O2). Don’t know where? Check out our video about it here

The worse what you can do in the beginning – is to start pushing your limits too hard! Why does it? Impressed someone? Because your friend can hold breathe longer? Or is it because 3 minutes sound impressive? Whatever reason you have – don’t do it.

Remember, a huge part of Freediving is relaxation, so, start with it.

But let’s be more specific. Let’s say your breath hold on the course was about 2 minutes. And you want to reach 3 minutes within 3-4 months. Here is your plan (train 2-3 times per week). Choose only one of these exercises for a session

Do 5-7 breath holds, without checking the time at all. Finish every attempt as soon as you feel uncomfortable (urge to breath). Your goal is relaxed breath holds
Do 5-7 breath holds, with start timing only after you start feeling uncomfortable. For example, your safety buddy can count to 10 (or less) after you have your first contraction. The goal is still to stay relaxed even after you have an urge to breathe.
Do easy CO2 tables (more details in the video here). Increase your breath hold time very gradually (only last 1-2 breath holds should be challengeable). The goal is slowly to accumulate CO2 and still be relaxed
Practice relaxation breathing (as meditation, pranayama breathing, and three section breathing). The goal is not to fall asleep.

Have you noticed “PUSH HARDER” advice? No? This is because there is no such advice here! You don’t have to push harder to reach 3 minutes static breath hold!

Stay safe and progress slowly!

Freediving problems. Part 1 (LMC/BO/SWB)

26.09.201826.09.2018sergeyvladivostok

I usually ask my students, what do they think, is Freediving dangerous sport or not? And

if it is a PADI Freediver course (first level in Freediving), more likely the answer is yes.

What do you think about it? Stop reading for a second and let me know your opinion in the comments section at the end of this article!

Done? Good!

Ok, let’s start with it – any activity is potentially dangerous. And I am not even talking about such activities as a base jumping or rock climbing. Walking on the busy street can be extremely dangerous, right?

However, if you follow the rules of this particular activity – risks can be dramatically minimized (don’t walk on a highway for example). And Freediving is not an exception. Follow simple safety rules and Freediving would be the safest water based activity!

But I would lie to you by saying that there are no risks in Freediving. Are they big? Let’s have a look.

It is going to be two parts about most common problems in Freediving.

First one about – LMC/BO/SWB

And second is going to be about lung squeeze, DCS/lung overexpansion/gas narcosis

Before we start – it is very unlikely that you are going to experience it on your Freediving course (especially on the first level – chances close to zero). But with the experience, you are going to be not that much distracted with a high level of CO2 (you still have contractions, but you are going to be more ok with them) and able to hold your breath longer and longer. And longer your breath hold is, less O2 it is going to be at the end of it. And less O2 you have more likely problems can happen.

Let’s say a Freediver decide to do his PB (personal best attempt). He is relaxed and enjoys his breath hold. At some point, contractions (involuntary movement of respiration muscles) will start. But he is still relaxed. He has them before and he is not freaked out, everything is under control. Contractions become harder and harder, but he is still holding his breath. At some moment, contractions became unbearable and Freediver comes up. But because the level of O2 reached the critical level, there is a chance of LMC (loss of motor control). What happens with this Freediver if he has an LMC?

He is still conscious; the heart is working, blood still circulating through the body. But the partial pressure of O2 is too low for normal functioning. He is not fainting, but close to it. Signs can be small (blue lips, light uncontrolled eyes or head movement), or big (body shaking and losing coordination). What happens when a freediver lose coordination while he is in the pool? Big problem…

And this is why your buddy is very important! Safety buddy is going to grab the Freediver, provide support, remove a mask from the face (or nose clip) and encourage him to breathe!

HOW TO AVOID LMC?

No hyperventilation before any breath hold
Don’t push too much (be moderate with your progress and don’t do big jumps in it)
Secure support (float, pool’s edge, your buddy arm) after surfacing
Proper recover breathing after stop holding.
Don’t do PB’s if you are dehydrated, too tired, you haven’t slept well, it is your second training per day etc

AND NEVER FREEDIVE ALONE!

HOW TO DEAL WITH LMC?

Support your buddy, making sure airways about the surface
Remove mask/nose clip
Encourage to do recovery breathing
Be ready to deal with BO

If you have an LMC, take it as a lesson, stop training for at least a day, analyze why it happened and don’t repeat the same mistake ;-)

What is BO? In Freediving we call it a situation when Freediver lost his conscious due to hypoxia (insufficient supply of O2) during the long breath hold. There is a difference between hypoxia and anoxia – complete deprivation of O2 supply. Why it is important to understand this difference?

Anoxia is extremely dangerous because some of our tissues could not survive without O2 supply even a couple of minutes (brain as an example). During hypoxia there is still available O2, but not enough for normal body function. And the protective mechanism launched – Freediver experience blackout.

HOW TO AVOID BO?

Don’t do hyperventilation
Do recovery breathing after any breath hold
Avoid pushing too much your limits (especially if you are a beginner)
Don’t depend on the watch, if you feel that you need to stop – stop!
Have enough time to recover between Freediving sessions
Don’t train when you dehydrated

AND NEVER FREEDIVE ALONE!

HOW TO DEAL WITH BO?

Learn rescue skills under professional supervision
Practice these skills
If your buddy has a BO – don’t panic, you can easily recover him
If you have a BO – stop your training for today
If there is a chance that you inhale water – look for a medical checkup

As you know, BO happens when there is not enough O2 for normal buddy’s function (when a partial pressure of O2 below a certain level).

When we are diving, pressure changes very fast, compared to the surface. When we are only 10 meters deep, pressure increase twice (2 atm), 20 meters – three-time (3 atm) and so on. Same happens with the pressure of any gases in your body, include O2.

Deeper you go higher partial pressure of O2 you have.

But now you turned 😉 And while you are ascending, you are still burning down O2, but now also pressure decreasing. And on the last 10 meters, it is going down twice. And this is where the majority of SWB happens (some of them even on the surface).

swb2 It is almost the same recommendations which I wrote about how to avoid BO! let’s repeat

Don’t do hyperventilation
Do recovery breathing after any breath hold
Avoid pushing too much your limits (especially if you are a beginner), in case of SWB – don’t progress with depth too fast
Don’t depend on the watch/depth, if you feel that you need to turn – turn!
Have enough time to recover between Freedives (apply the rule, surface interval 3-4 longer then dive time or more conservative time)
Limit the number of deep dives per session
Don’t train when you dehydrated

AND AGAIN – NEVER FREEDIVE ALONE!

Rescue skills in open water

What to do if your buddy has SWB

Reach the diver
Grab him
Bring to the surface
Remove the weight belt if necessary
Blow-tap-talk for 10 seconds
2 rescue breath and ask for help
Start moving the diver to the boat/shore, providing 1 rescue breath every 5 seconds
Remove from the water and start CPR

Everything that you need to know about MDR (Mammalian Dive Reflex) in Freediving

23.08.201824.08.2018sergeyvladivostok

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:

Apnea
Bradycardia
Peripheral vasoconstriction and blood shift
Spleen contraction

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!

Learn how to hold your breath longer!

08.08.201809.08.2018sergeyvladivostok

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!

Here at Crystal Freedivng we are going into more details of relaxation breathing on PADI Advanced Freediver course and PADI Master Freediver course.

Now, let’s talk about breath hold itself.

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!

Stay safe!

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!

Decompression sickness in Freediving

27.07.201805.01.2019sergeyvladivostok

Is it possible to have DCS for Freediver? Unfortunately yes…But at the same time, it is quite easy to put the risk at the minimum. At our school, we normally discuss in details this topic at PADI Master Freediver course, so here are our thoughts on this subject…

In scuba diving, when you are breathing compressed air underwater, your body is saturated more and more with Nitrogen (79% of the air is Nitrogen). The chain looks like this – you breathe in the compressed air from a scuba tank and now the pressure of N(Nitrogen) in your lungs more than in your blood, so, it going to your blood. And now in your blood pressure of N is higher than in your tissues, so, it is going to your tissues. Until you have an equal pressure of N everywhere (this is what we call saturation). And when you start coming up, opposite happens. Now pressure of N is smaller in your lungs, so the reverse process is happening – from your tissues N going to the blood and then to your lungs and then you exhale it. But it doesn’t happen that quickly. In some tissues, this process is slower than in others.

So, this is why when scuba divers coming up, they need to do it slowly (in this case N slowly coming from your body with every exhale) and they also need to have a long surface interval between dives (to release as much N from their body as possible before the next dive). And why they can spend the only a certain amount of time on certain depth (not to get too much N to their tissues).

dcs2 If they violate these rules, they have a very good chance to have DCS! Without making it too complicated, DCS is when molecules of N combined in your blood (or tissues) in the form of a bubble and can cause very serious damage!

But why it can be an issue for Freediver?
Among the first, spearfishers who were shooting fish relatively deep (around 20 meters) noticed that after the long session they have symptoms which are commonly associated with “bends” (another word for DCS). So, imagine you dive to 20 meters. On the surface, you did big inhale and bring this air (and around 79% of it is nitrogen) to 20 meters, where the pressure is 3 times higher. So, the pressure of any gases inside your lungs (we call it partial pressure) going to be also 3 times higher. If the pressure is going to be higher in the lungs, then it will go to your blood and further to your tissues in the attempt to reach equilibrium. When you start your ascend, the reverse process will take place. But not 100% (some of our tissue need time to release N2). Some N2 will still be in your tissues. Very very small amount. Not a dangerous amount. But then you are going to do 50 dives more to this depth. And now you have much more N2 in your blood. And on your next ascent, it can forms bubbles and this is DCS….

There are also some predisposing factors which can increase the risk of DCS. Let’s name a few

Dehydration
Exercises
High level of CO2
Cold
Not enough surface time

As you can see, spearfisher who is doing a long session with relatively deep dives and small recovery time has a very good chance to get DCS….What to do, if you are spearfisher? Limit duration of your spearfishing session, have enough rest between dives, use appropriate thermal protection, stay hydrated!

Ok, what about DCS for Deep Freedivers?

Let’s say you are one of the most famous Freediver of all time, Herbert Nitsh, and diving not to 20 meters but to 214 meters!! You make a big inhale as possible (don’t forget, around 79% of inhaling air is N2) and put it under a huuuuuge pressure of 21 atm (this is what you have at 200 meters). During your descent, this N2 from your lungs will come into your bloodstream and from there to your tissues.
And now you will start your ascent. It would be No Limit discipline and you are not going to use your muscles for going up (which is very good to reduce the risk of DCS), you are probably also not dehydrate it nor cold (which is also very good)
But you are quite fast for this huge amount of N2, dissolved into your tissues. The bubbles will form. But not big in the beginning. But when you ascent with the constant speed, they are going to increase in size (because the pressure is decreasing). How to prevent it? You need to slow down…And this is what Herbert did – he dramatically decreased his ascent rate after 50 meters (from 3 m/s to about 1 m/s). He also did some safety stop at 10 meters to make it even safer. And this is how he became The Deepest Man on Earth by making a dive to 214 meters!!
But later, when he was trying to beat his own record he lost his conscious on his way up and failed to do all of the above (safety stops and slow down his speed). As a result, massive DCS….Luckily (actually his story of recovery is almost like a miracle) he survived and recovered from it!

But if you are diving not that deep, let’s say to 40 meters; is it possible to have DCS? And the answer is yes… Last year Freediving legend William Trubridge got DCS during his routine training. I mean routine for him but crazy for all of us! Let’s have a look at it

William did 5 dives to 40 meters with “hangs”. Time of each dive was about 1.50, the surface time between dives only 2.15. As a result, after his 5^th dive, William felt one of the symptoms of DCS – numbness in his leg. He went to a hospital and took special treatment for DCS there (pretty expensive!). This story has a lucky end as well, William completely recovered and competing again!

According to him, he done this type of training before (even harder) and never had any problem.

So, what is the problem here and how to avoid it? The dives were not too deep and not too long (especially if you are World Champion). But the recovery time was quite short.

So, if you are just starting freediving – this is a basic advice – DO have long surface intervals. How long? Here a couple of ways how to count it

The time between your dives should be 3-4 times longer than your dive time. For example, if your dive time 30 secs, then have a rest for at least 2 mins
Divide dive time by 5 and the result is a time in minutes. If you dive to 40 meters, have a rest for at least 8 mins.

And be even more conservative – have even longer rest!

A few things which I would you to remember

dcs3 First of all – symptoms of DCS. Type 1 DCS – skin rash on shoulders and upper chest, joint and limb pain. Type 2 DCS – peripheral tingling and numbness, unconsciousness, respiratory arrest and paralysis, coughing, feeling of air-starving.

Second – predisposing factors. Obesity, intense exercise less than 12 hrs before diving, age, fitness level, dehydration, injury and illness, alcohol, carbon dioxide, cold. Obviously, scuba diving before freediving is absolutely no-no!

Treatment for DCS – the patient should lay down and breath 100% O2. Transportation to a recompression chamber should be organized as quickly as possible. dcs4

And one more times how to avoid DCS

Don’t freedive after scuba diving
Have enough surface interval
Don’t ascent very fast from the deep dive
Reduce the number of deep dives in one session
Limit the duration of the dive session
Stay hydrated and use an appropriate wetsuit
Don’t consume alcohol and don’t do intense exercise before a session

Stay safe, enjoy Freediving and educate yourself about the activity which you love!

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If you have any question, feel free to ask in comments below!

Breathing for Freediving (part 1)

12.07.201825.07.2018sergeyvladivostok

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 lungs (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.

alvioli 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).