In one of the last post, we discussed how you can train static (in case if you missed it, read here). And what about dynamic?
If for static you can do dry static apnea, then for dynamic you obviously need a pool.
Normally you can learn DYN on any PADI Freediving courses, but if you haven’t done any dynamic on your course, might be this video can help.
When you do static apnea – it is complete relaxation. The same principle can be applied for DYN – relaxation is the key. But in dynamic obviously you couldn’t relax all your muscles (since you need to move forward), but you should relax all the muscles not involved in this movement (neck, shoulders, etc). And even muscles which involved in the movement should be relaxed at the moment when you finish the kick (gliding phase).
Hopefully, it doesn’t sound too complicated.
How often do you need to train DYN? I think 2-3 times per week is enough for beginner Freediver. How intense? Not intense at all! Progress will come naturally.
There are few things about your technique, you want to be focused on. Choose one of them for a session and work only on it (let’s say be focused on your shoulders relaxation
the whole session).
How do you know your mistakes? Ask your buddy to film you (GoPro does the excellent job)!
Head position (should be neutral)
Relaxation in the shoulder area (quite often too tense)
Buoyancy (the first thing which you have to fix!)
Kicking both directions
Start kicking from your hips
Not bending knees too much
And here a couple of examples of DYN training
Main training – do short laps with 100% concentration on technique (mentioned above) and relaxation. If you current MAX less than 50-70 meters, do ONLY this training. Approximate distance 40-50% from your MAX. Amount of repetitions 5-10
Easy classic CO2 training. Let’s say 25 meters with 30-60 seconds rest. 10 repetitions. A bit harder than the previous exercise.
Over-under. Swim short distance (less than 40-50% MAX) underwater and without rest, swim same distance on the surface. Repeat 5-10 times. Can make it a bit harder if decrease surface distance.
PADI Advanced Freediver
Sorry to repeat one more time – focus on the technique and relaxation.
Do it for a month and then can try to increase your PB by 5-10 meters.
All the training should be done ONLY with another Freediver!!
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 1st 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 1st 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 4th 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.
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!
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!
When you start freediving it seems, that only equipment you need is a pair of fins and mask with a snorkel.
But after a while, you discover that there is so much stuff can be additionally used. You can easily live without it, but freediving training is going to be much more effective and fun with it
Today we are going to talk about one of these freediver’s toys – a nose clip.
As soon as you get the nose clip, probably static breath hold in a pool with it will be your first choice. At least this is what we are doing on a PADI Advanced Freediver course
What is the difference between using a mask and a nose clip – with the nose clip you have your whole face contacting with the water, which will help to trigger mammalian diving reflex (MDR). And it is strongly important for freediving as MDR influences blood shift, decrease heart rate and force your spleen to contract.
Some freedivers prefer to combine nose clip with another useful toy – swimming goggles. It is a kind of compromise between a mask and a “naked” face. It depends on your personal preference to wear goggles for static apnea or not. But keep in mind how sensitive your eyes are to pool water and chemicals in it. If you feel comfortable to stay in water without goggles – you are more than welcomed to do it. Just try and you will see the difference.
Another case where you can use your new nose clip in a pool is dynamic apnea. You will see how completely different your feeling going to be. And you will realize it, not when you replace mask with nose clip and goggles, but let’s say when you wear the mask again. This is quite similar to feel the difference in diving in a wetsuit and in a swimsuit.
And the last step for you in getting closer with a nose clip will be diving in the open water, where hands-free equalization provides you with a lot of opportunities to evolve as a freediver. Free Immersion and No fins are probably two main disciplines were you can improve technique efficiency without a need to pinch your nose every meter.
Monofin and bi fins dive also will become more streamlined and hydrodynamic if you don’t need to bring your hand to the nose for equalization. It will allow you to glide in water more smooth and effortless.
The same as in a pool, in open water it is completely up to you to use goggles or not. Of course, for depth trainings, you cannot use swimming goggles, which you use in a pool. In this concern, we are coming to another not compulsory but such a lovely accessory for freediving as goggles for deep diving. Nowadays such goggles can be two types – membrane lenses goggles (equalize automatically) and fluid lenses goggles (do not require equalization). But as I have mentioned above – there is no strong need in this. And probably one of the best proof that nose clip only diving works effective – it is extremely popular among high-level athletes at the competition.
First of all, lung overexpansion (LO) injury is very rarely in Freediving. So, don’t be scared. But since it can be a serious trauma better to have a solid understanding of what it is and how to avoid it.
First, let’s have a talk about the structure of the lungs.
Our lungs are sponge-like air-filled organs that transfer air molecules to and from blood cells. The trachea (windpipe) conducts inhaled air into the lungs through bronchi, which then dived into smaller branches (bronchioles), finally becoming microscopic.
The bronchioles eventually end in clusters of very small air sacs called alveoli. In the alveoli, O2 from the air is absorbed into the blood and CO2 (a waste product of metabolism) moves from the blood to the alveoli (and eventually exhaled). This process in the alveoli calls gas exchange.
Lungs are major airspace in our body. We have actually two lungs – a right and left lungs. They are situated within the thoracic cavity of the chest. The right lung is bigger than the left, which shares space in the chest with the heart.
Lungs are delicate tissues, and can easily be ruptured. If the air flow inside our lungs becomes restricted as you ascend, the expanding air can rapture the delicate alveoli inside the lungs. This can happen without any warning sensations (since the lungs do not sense pain). Chest congestion, scar tissue, lung disease, and damage from smoking can also create air flow restriction and contribute to LO.
When you do a scuba course, your instructor going to repeat many times that the main rule of Scuba Diving – never to hold your breath. Why?
When you do scuba diving you breathe compressed air from scuba tanks and your lungs have the same volume at any given depth. This is why if you are even 10 meters deep and make a rapid ascent with breath hold (due to a panic let’s say) your lungs will expand twice from the normal size! Lung tissue can stretch out a little bit, but not twice from its normal size. Which is easy can bring a scuba diver to the risk of lungs barotrauma.
Lungs barotrauma (LB) can be in a few basic forms
Arterial gas embolism – gas from the lungs escapes into the bloodstream (which can form bubbles and block blood circulation)
Pneumothorax – air enters the space between the lungs, expands and cause lungs to collapse
Mediastinal emphysema – air enters the space between the chest and the lungs, expands and put the pressure on the lung, heart, or blood vessels.
Subcutaneous emphysema – air escapes from the lungs and travels underneath of the skin (most often around the neck), which can result in voice changing, difficulties swallowing
Common symptoms of LB are
Paralyze, especially on one side of the body
Dizziness and confusion
Coughing up blood
Loss of vision
Change in voice
Heavy chest pain and difficulties in breathing
Is lung overexpansion can be a problem for Freedivers? Normally it is not. When you freedive, lungs compressed on your way down and re-expand on your way up to the original volume. So, there is no overexpansion.
But let’s have a look at two situations which can have a potential risk of lungs overexpansion injury
BREATHING FROM SCUBA TANK UNDERWATER. Imagine, a Freediver makes a dive to 10 meters. His lungs compressed at this depth almost twice. When he ascends, lungs come back to their normal shape. But what happened if Freediver takes a breath from scuba tank underwater and then ascent? After inhale from scuba tank lungs will expand to its normal size (sea level), but then, on the way up the lungs will expand twice. What about exhaling on the way up? It will defiantly reduce the risk, but not illuminate it (you also have to keep the ascend speed as slow as you can). But to remove the risk – DON’T TAKE AIR FROM SCUBA DIVER UNDERWATER!
By doing packing Freediver will over expand the lungs on the surface (lungs volume is going to be higher than Total Lungs Capacity). Then Freediver dive to the planned depth. During the dive he is going to have MDR (blood shift in particular) which moves a certain amount of blood into the lungs (causing blood vessels around alveoli to expand in size), preventing from crushing. On the way up air starts to expand, and blood vessels still bigger in size. This theoretically can increase the risk of lung overexpansion. The risk is not huge, but do exist. To minimize it, Freedivers who are packing exhale before they reach the surface (which also decrease the risk of BO). So, before you start practicing packing, please ask your self – DO YOU REALLY NEED TO DO IT? Please, keep in mind that packing is a highly advanced technique and should be practiced only by experienced athletes. Are you high experienced Freediver?
Treating lung overexpansion injury.
Symptoms of LO occur immediately and can include difficulty breathing, chest pain, crackling under the skin, unconsciousness or death. First aid must begin immediately while transportation to a medical facility is arranged. 100% O2 should be provided as soon as possible and CPR started if necessary. Ask yourself, do you have CPR skills?
The victim will need treatment in a hyperbaric (pressurized) chamber as soon as possible to shrink the air bubbles, and then slowly decompressed to allow the air to pass out of the body before it expands and interferes with respiration and circulation.
Suspected tension pneumothorax is treated with needle decompression followed by tube thoracostomy (at the hospital of course). If a smaller pneumothorax is present and there is no sign of hemodynamic or respiratory instability, the pneumothorax may resolve when high-flow 100% O2 is given for 24-48 hrs. If this treatment is ineffective or if a large pneumothorax is present, tube thoracostomy is done.
Computed tomography of the chest is recommending in any case of suspected pulmonary barotrauma in order predicting future fitness to dive
Probably the 1st thing your personal freediving equipment starts with is a mask and a snorkel.
This step is easy to explain: rental masks might not fit you well and can constantly leak. Besides, it’s always more pleasant to be the only one who wears the mask which touches your face. Also, you don’t depend on rental shops operation hours and with your own mask, you can go snorkeling or freediving wherever and whenever you want. And the last reason – it’s super easy to travel with a little mask in a bag. Way easier, than with a pair of freediving fins.
So how to pick up the decent mask? If you are already a certified Freediver, probably you know the answer. If not, let me explain
Remember one thing – the best mask for you is the mask, which fits you independently on cost and brand.
Let me give you a couple of advice on how to pick up the perfect mask.
It is always better to try the mask first. Ideally in the water, but at least in a shop.
And there are two main things you ’d better pay attention to mask shouldn’t hurt you and you should be able to equalize in it.
If you put the mask on your face and press on the top of the nose bridge and if you feel little pain, this mask is not for you. As little pain can become a terrible headache after 1-hour freediving or snorkeling session.
Another important thing – equalization. Be sure that you can pinch your nose to equalize. Some masks have extremely huge nose pocket, like Omer Zero, and it’s a real challenge to find the nose in such a mask.
Let’s talk about the features, which mask should have to be suitable for freediving.
So, in freediving unlike to scuba diving to equalize the mask we are using our air from the lungs, which is limited and which we actually need to dive deeper. That is why for freediving mask it is extremely important to be as low in volume as possible. And single lens mask has always more volume then double lens one. In this concern, you need to look for a double lens mask. Soft silicone skirt is important as it seals better around the face. And except that it is much easier to pinch the nose for equalization. In this concern, PVC skirt masks are not a smart choice at all.
Let’s take a look at one example of the mask.
You might have seen many freedivers diving in Sphera mask by Aqualung. It’s a gorgeous not expensive and unique mask due to its bent lenses, which allows the mask to follow the shape of the face. This provides super low volume and high side vision. But to make the lenses curve manufacturer had to use plastic instead of glass. And plastic is much less resistant to the scratches. That is not a problem at all if you care your equipment well. In case, you have a habit to drop your mask anywhere but not in the box, probably you have to check for another option.
And the last thing which I would like to cover is the difference between brand and noname masks. Brands usually provide good warranty conditions and in case your mask is broken due to manufacturing failure, you can apply for warranty repair or replacement. But be sure you have saved the receipt to confirm your purchase. The best way is to take photos of all your receipts and keep the digital copies in case you lose a paper bill.
I hope all these tips will be useful for you when you come to the shop for your 1st Freediving mask.
And if you have any questions, please don’t hesitate to ask in comments below.
Freediving, as a recreational water-based activity (as well as a sport), getting more and more popular. But still, it is far away from other water activities, like for example scuba diving.
There are a lot of myths around Freediving, which stopping people to try it. Or at least confusing.
Let’s try to find out which one is true and which one is not. So, let’s start!
Freedivers can come much closer to the marine life. NOT TRUE. Well, actually it depends. If you compare an experienced Freediver and a beginner level Scuba Diver, then it is true 100%. But if we compare both an experience Scuba Diver and a Freediver, then it is not that simple. As a former scuba instructor, I had a few thousands of dives and I can say that majority of the marine life can come very close to you (reef fish, turtles, stingrays, sharks etc). Less than a half meter. Some people are saying that fish afraid of the bubbles. But why should they be? Fish are afraid of their natural predators and they don’t make bubbles. Fish afraid if you make too much movement and if you are rapidly closing the distance. However, I am willing to accept that some marine life can come close to a Freediver (at least I was told so by other Freedivers).
Freediving is more environments friendly. TRUE. Freediving boat is usually much smaller and requires a smaller engine. And they don’t have compressors. It reduces air and water pollution (as well as noise pollution). All of this makes a difference on our impact on Nature. Also, Freedivers are usually not that close to the corals (especially beginner level), so, fewer chances to damage fragile corals. We are also diving on the reefs less often (mainly we are diving just in the blue).
Freedivers have less equipment. ALMOST TRUE. If you compare Freediving vs Scuba Diving – you will probably think – oh, this is 100% true, but it is not that simple again. If we are talking about starting – then for sure it is true! As soon as you have a mask, you can be a Freediver 😉 For scuba, even for absolute beginner level, there is a standard set – BCD, regulator, fins, scuba tank etc. Coming back to Freediving, like I said, in the beginning, you can just invest in the mask and snorkel. But then it will probably be more equipment – weight belt, neck weight, wetsuit, nose clip, safety lanyard, goggles for the swimming pool, float and rope if you want to train with your buddy independently, etc.
Freedivers are leading a healthier lifestyle. TRUE. Some people like to call Scuba Diving sport, which always confuses me. Obviously, it is not. But freediving is. Even if you are not very serious about results. Freediving training combines correct breathing, different relaxation techniques, different physical exercises (in open water, pool, gym etc), as well as mental training. So, yes, if you like to be connected with Nature and stay healthy – Freediving should be your choice.
Freediving is more dangerous. ABSOLUTELY NOT TRUE. Let’s make a line between Freedivers who are properly educated and follow safety rules and someone who has no idea about basic safety rules and just decided that he/she needs to dive deeper or hold the breath longer. Among the first groups, some problems occur, but they are not fatal. The second group is just playing Russian roulette. But the same is true for any other activity in our life – you have to follow safety rules. Even for walking. Disagree? Try to walk across a high way! When someone tells that Freedivers are dying regularly, I am always asking where this information is coming from. And there is no answer. Simple because it is not true. So, the bottom line here – follow safety rules and Freediving would be the safest water based activity!
Freediving is a more natural way to be underwater. Well, of course, it is TRUE. We don’t create with the scuba tanks on our back. But we have reflexes which help us to stay underwater longer and dive deeper. Holding the breath for a certain time is natural for us, as well to the other marine mammals.
So, what would be your choice? Ideally, try both freediving and scuba diving! In my opinion, if you want to explore reef up to 15 meters deep – Freediving is a much better choice. But if you are planning to explore a dive site 25-30 meter deep, then it is easy to do with a scuba tank. If you are interested in underwater photography or videography, then again, having scuba tanks make your life easier. On the other hand, if you want to enjoy to be underwater and also combine it with a healthy lifestyle – Freediving is a better choice.
If you are interested in proper Freediving education click HERE 😉
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!
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).
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
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
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!