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Empty Lungs STA

12.04.202001.11.2021sergeyvladivostok

Static Apnea (STA) is usually the first thing any Freediver learns, whether on a freediving course (learn about Freediving course) or while lying in a bed.

STA is the easiest way to learn all the steps – relaxation breathing, relaxation during breath-hold, recovery breathing. You even don’t need that much equipment – mask if you do it in the water, or nothing if do it “dry.”

It sounds like a perfect combination, right?

STA also helps gain confidence before moving to more advanced Freediving disciplines such as Dynamic Apnea (DYN) or even depth disciplines.

However, if your main goal is to dive into the Ocean, there is a better option.

But first, a little bit of theory. When you dive into the Ocean, there is no such feeling as extreme fullness in the lungs (which you have when you do a full inhale before normal STA). During the descent, your lungs get compressed quite quickly due to the increase of ambient pressure. As a result, the volume of any gas (including air in your lungs) will decrease accordingly.

How can we simulate it on land?

The answer is empty lungs STA training. Start with relaxation breathing as usual, but before breath-hold, instead of full inhale, you do full exhale. After that, do the same as with full lungs breath-hold – be as much relaxed as possible.

Since your goal is not absolute time but rather relaxation (get comfortable with the feeling of “smaller” lungs) – you don’t need to push yourself (at least no need to do it often).

Just be relaxed before contractions start and during the first few.

I like to do empty lungs STA in the form of an O2 table.

If you have never done such training before, here is an example (this is how we do it for the first time with our Advanced Freediver students)

RELAXATION BREATHING	BREATH HOLD
2 MINUTES	10 SECONDS
2 MINUTES	20 SECONDS
2 MINUTES	30 SECONDS
2 MINUTES	40 SECONDS
2 MINUTES	50 SECONDS

And keep in mind, if you are planning to do this training in the water, ALWAYS train with another Freediver, who knows how to do safety (video how to do Safety) and knows Rescue procedure (video how to do Rescue).

Looking for the best Freediving computer? Check out this link for Suunto D4

Are STA CO2 tables a waste of time?

06.09.201905.11.2021sergeyvladivostok

There are many debates whether CO2 tables are helpful or useless for Freedivers. And in reality, as always, truth is somewhere in the middle.

We are practicing CO2 tables, classical and modified on our Advanced Freediver and following courses.

STA breath hold

Freediving training

First, what is a STA CO2 table?

Take 50% from your current maximum STA and repeat it 6-8 times, every time decreasing rest time. If your current max, let’s say 2 minutes, this is how a classical CO2 table would look like for you.

REST	BREATH HOLD
2.00	1.00
1.45	1.00
1.30	1.00
1.15	1.00
1.00	1.00
0.45	1.00
0.30	1.00

Before you start doing this type of training or critique it, let’s ask the main question – what is your goal in this kind of training? Have a longer breath-hold?

Now let’s have a look at what happens during this table.

First, a Freediver who does this table, practicing relaxation breathing. Seven times from 2.00 to 0.30 practicing a critical skill. Calm down your mind and relax your muscles. Don’t underestimate this skill.

Next, the freediver trains how to relax while holding your breath. And this is a crucial skill for all levels and especially for beginners. Don’t try to be tough and “handle” contractions; learn how to hold your breath longer without them!

Probably the first 4-5 attempts will be pretty easy, and you won’t experience any urge to breathe symptoms – beautiful, coming out from your comfort zone is not your priority at this moment.

And it might be on the last 1-2 the Freediver going to have 1 or 2 contractions. So, in addition to previous goals, we train how to stay relaxed during these first couple of contractions for these two attempts.

If you don’t have any, increase each breath hold by 5 seconds on the next training.

My conclusion – if you are a beginner or intermediate Freediver and trying to build a foundation – this classical STA CO2 table is a legit way of training!

But then why do a lot of experienced Freedivers critique it? Because it is a waste of training time for THEM! They have already mastered how to do relaxation breathing or stay relaxed and not panic during first contractions. They passed this step. Now they have different goals.

And yes, a classical CO2 table is not the most effective way to train tolerance to a high level of CO2. But if your STA is less than 4 minutes, do you need to train it? Or your priority to learn basics, which is relaxation, not suffering?

Don’t blindly copy the way how champions are trained, when you are a beginner!

Get the Mares nose clip to improve your results in STA (Amazon affiliated link)

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 train DYN for beginner Freedivers

02.02.201917.11.2021sergeyvladivostok

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.

Freedivers

PADI Advanced Freediver

PADI 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!!

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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 book “Longer and Deeper”

17.12.201817.11.2021sergeyvladivostok

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!

Buy this book on the Amazon

Nose clip for Freediving

11.12.201803.11.2021sergeyvladivostok

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.

By Svitlana Gaidai

Lungs overexpansion in Freediving

08.12.2018sergeyvladivostok

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 lungs9 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.

lungs1 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
Unconsciousness
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.

lungs6 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 lungs7 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