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The Best of Freediving Tips - Techniques

The following tips and articles were extracted from various posts to DeeperBlue and individual contributions.

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Mouthfill Techniques


Umberto uses Frenzel to equalise to 120m (inverted, Variable) and then a Valsalva at about 135 which takes him to 150 (No Limits). He has very little trouble equalising CW, due to incredible diaphragm control, and I suspect he is mouthfilling as well.

I don't think Pelo even packs when he goes on holiday...


Back in 1998, I had spoken with several divers who had competed in Sardinia. I was asking about deep equalizing techniques. Several divers used a 'mouthfill' method which involved filling the mouth up each time you tried to equalize. Among those divers was Australian Tony Heugh, who explained to me how he would fill his mouth up with air each time he tried to equalize.

I was doing a chi-gong standing meditation around October of '98 when an idea popped in my mind. All of my ideas come to me during chi-gong standing meditation (the fluid goggle idea came during such a meditation).

It occurred to me that one might benefit by filling the mouth only ONCE, at the maximum depth which one could fill the cheeks completely. When this idea came to me, it was not at all obvious that a single mouthfill method would have any advantage over current techniques, including the 'repeated mouthfill' method. I tried to do many calculations but at the time I didn't understand enough about the various airspaces to conclusively decide whether or not the technique would be helpful.

Further, I was uncertain if it was even possible to trap air in the mouth and equalize with the throat still closed (epiglottis closed). I didn't understand enough about the anatomy of the nose and throat to figure that out.

Eventually I began doing experiments, and at first it seemed that it was impossible to do the standard frenzel with the throat closed. However, after many hours of practice, I found that it was in fact possible, but it was simply a reflex to raise the soft palate whenever you close your epiglottis. Eventually I 'de-trained' that reflex after many hours of practice. At the time I had never heard of anyone else spending 3+ hours a day on the couch trying to detrain a throat reflex, so I began to wonder if anyone had done this before. I thought that if this technique really did offer an advantage, then surely someone must have thought of it before. The fact that I had never heard of anyone doing a single mouthfill made me think that the technique could not possibly offer any advantage over existing techniques.

Mayol himself described the extreme effort it would take to 'force' air into his ears while trying to equalize head-down on his 80m+ dives. This alone told me that he had not used a single-mouthfill technique.

Anyway, it was not until early 1999 that I took a trip to Alouette lake to test out the technique for real. At first I tried filling my mouth at the surface and then doing negatives. I quickly found out that performing the technique in the water, with so many other things to think about, was not easy, and I kept losing my mouthfill or my soft palate would lock up. Eventually I managed to do it on negative dives.

Then I tried a dive where I filled my mouth up at about 10m and continued down to 22m. I was amazed that when I got to the bottom, my mouth was still full of air. I sensed that the technique might actually have some merit after all. This confused me even more, because by now (several months later) I had spoken to many more divers about equalizing techniques and still none had ever mentioned a 'single-mouthfill' technique although many had spoken about repeated mouthfills or reverse packing, diaphragmatic frenzel, continuous valsalva, saline equalizing, etc...

I competed in Nice, France in 2000 and did several 67m dives, but I didn't feel the need to do the mouthfill and instead relied on the diaphragmatic frenzel, which I found I could still do with little difficulty at 65m+. After the competition was over I had a long talk with Herbert Nitsch about equalizing techniques. I explained my 'single-mouthfill' technique to him, even though I didn't actually use it at the competition. He told me that he had tried the repeated mouthfill and reverse packing methods before, but he had not heard of the single mouthfill -- and like most people, the idea that a single mouthfill at 30m could last you until 100m+ seemed ridiculous.

It was not until I was training for the CW record in 2001 that I found out how much energy I saved by filling my mouth at 30m and then never doing any effort until the bottom. It allowed me to sleep during the descent, and I saved a ton of energy. The descent became a joke. The ascent was the whole dive.

It was during that time, June 2001, that Herbert was training for the CW record in the Austrian lake. I had been chatting over e-mail about how much energy I was saving by doing the single-mouthfill. Unfortunately it is so hard to learn that Herbert hadn't been able to do it yet. Equalizing was his limit and although he was aiming for 82m, he ended up with a 72m record.

Two months later I did my personal best of 88m and found that even after equalizing at the bottom I found that my mouth still had air left for more equalizations, ultimate proof, for me, that this technique did offer an advantage.

I did the 82m record and then eventually decided not to go to Ibiza. However, when Herbert congratulated me on my 82m record I spent some more time chatting with him about the single-mouthfill method, and I told Herbert not to give up. During training in Ibiza he finally figured it out and did 89m, followed by 86m during the competition, breaking my short-lived 82m dive which had only passed 'official' ratification the night before.

At that point I had some mixed emotions. I wondered about my philosophy of sharing techniques. The selfish part of me said that if I never shared techniques, perhaps I would still hold the record! Then, I figured that I would get good karma by sharing and good things would happen eventually.

I had also been chatting with Patrick Musimu. Early the next year (2002) he was trying for the CW record with the IAFD. He had a personal best of 79m and was limited by equalizing. Pipin was trying to teach Patrick the sinus flooding technique, which Patrick tried, but he found he got very dizzy and disoriented, since he was not on a sled. I kept e-mailing Patrick during the days before the record, offering more detailed explanations than are given in the document on my website. Patrick then did his 87m record with ease, and told me that three days before, he had gone out into shallow water with Isabel and finally figured out how to do the single-mouthfill.

So, when faced with the question, was anyone doing the single-mouthfill technique before 1998? I suppose we can never say for sure. Unfortunately when people say 'mouthfill' technique, almost everyone thinks of the 'repeated mouthfill' technique, and people like Dieter Baumann say 'oh, I've been filling my mouth since the 70's.' Unfortunately it isn't the same technique. Dieter was Herbert's coach during his 72m lake record where Herbert missed his target of 82m due to equalizing. I felt like asking Dieter why he didn't teach Herbert the 'mouthfill' technique back then.

What I can say is that so far, of the people who are currently doing the single-mouthfill technique, none are doing it very efficiently. Herbert still broke his eardrum in Cyprus despite the mouthfill technique. Musimu himself said he thought he could maybe make 95m with the mouthfill. However, if done properly it will get you far, far deeper.

Currently my personal best for a negative dive, filling my mouth at the surface, using a sphera mask, is 32.8m. With a full pack, I can get a full mouthfill at 35m with great effort.

Doing the math:

negative dive:

0m to 32.8m = 1atm to 4.28m = 4.28x

Mouthfill @ 35m = 4.5atm

4.5atm * 4.28 = 19.26atm = 182.6m

So, if I were to fill my mouth at 35m with the same efficiency as I did on the 32.8m negative dive, using the sphera mask, I would reach 182.6m, head-down, equalizing with a mask. Now THAT is an example of an efficient mouthfill.

If someone like Hubert Maier with 14L lungs did it that efficiently, he could probably get to 200m+ with a mask!

Eric's Frezel-Fattah

Extension of Eric's work

Hands-free Equalization

Hands-free Equalization


This may really be helpful, I have been practicing this for decades!

It takes a few careful tries until You get the feeling.

Starting from the surface going down, I allow a little pressure to build up in my mask very carefully. While I compensate my mask, moving my jaw a little bit, I take advantage of the pressurized air that is now escaping into my tubes (moving of the jaws facilitates the opening of the tubes). If You can equalize very easy by pinching Your nose You should not have any problems with the "mask-technique". As I continue to equalize, the mask is kept away from squeezing my face and at the same time the tube is acting like a valve, opening up at every blow into the mask.

I am not sure if the connection between mouth and lungs (epiglotis) has to be shut while You do it (I will check it out next time when I go diving). This technique as helped me to go -30m/plus in unassisted constant ballast (constant weight without fins) and added a lot of joy in freediving. However I am limited to a maximum of -40mt that way (with the last equalization around -36mt).

For maximum dives I have to resort to the newly acquired frenzel/fattah method. How I was able to apply this technique successfully, even though I failed in some of the exercises prescribed in effatah's famous document,


Same way I discovered I could do it. I was priming my throat muscles to do a Frenzel, and it just happened. I felt like I won the lottery . Best way I can recommend to get hold of those hard-to-reach muscles is to pretend your listening to the mother-in-law go on about her new plans to decorate her house. In other words, practice yawning while keeping your mouth closed . Next time you feel a yawn, listen to the 'rumbling', [sometimes] followed by the gentle pop in your ears. That's the sound of success. When you can access these muscles, and make that same sound at will, you're on your way. To finally make it work for you underwater may require a tongue thrust, jaw wiggle, or stronger muscles. Everyone is different. That's the best I know how to teach this esoteric technique.


You can try -SBT- "skindiver's back-pressure technique"

You simply use the back pressure / ( high pressure) of the mask and equalise against that. Push it against your face to help it to seal whils't learning if you must and strap it quite tightly. You will learn how loose you can make it before leaking air foils your SBT attempt.

1 ) Simulate the clicking that you hear in your ears when you yawn.

2) Hold the tubes open. *

3) Breathe out into your mask.

4) Do not not not close your throat.

5) Allow the air to enter the tubes whilst breathing out into the mask.

*You can practice holding the tubes open on land without mask by :

1) clicking ( opening up the tube)

2) holding the click ( ie do not relax the muscle once clicked)

3) Listening for your fairly hard nasal breathing in your head.**

**You will know that you are successful if you hold the click and breathe in and out through your nose and hear the air rush inside your head via your inner ear instead of outside. It sounds like a regulator delivering air on scuba.

With some observation you will find that you can actually feel your drums flex in and out with fairly exaggerated nasal breathing.

Tip: if your tubes wont open or only one opens ( common) then do a normal frenzel and then release the pressure in the ears with one click.. but hold the click and breathe in and out through your nose listening for your inner breathing.

(IIf you hear your breathing via the outside ear only, your tubes are still shut.

f you cannot get to hear your breathing in your head then you will prolly never get this right.)

Then try it in the water. Your can learn to do it on scuba much easier since the air is being delivered at ambient pressure, there is lots of it, and if your mask leaks it doesnt matter.

Then try apply what you have learned on a freedive.


What you are doing when equalizing hand free, is flexing your tensor palatini and levator palatini muscles. The only good picture of the tensor palatine muscle I have seen was at an ear specialist office. It actually wraps around the eustachian for the lower length of it. The Eustachian tube normally is closed in the lower 1/3 of its length. One of its functions is to open and allow air into the middle ear, to increase the pressure in middle ear to that of the outer ear (ear drum in the middle). The tube them closes to hold the increase air volume and pressure in the middle ear.

On your ascent the increase pressure from the middle ear is usually all that is needed to open the Eustachian tubes to let air out of the middle ear and into the thorax. The idea that it would be great to have your Eustachian tubes open all the time is a myth. This happens to some people and it is called PET. I forgot what the letters stands for, but it’s a problem that really messes up some people’s lives. The main symptom is hearings one breath in the ears. Also holding them open for a whole length of a descent is not good either, because you can over inflate your middle ear and put to much pressure on the eardrum. The best is quick and short equalizations. That way any excess air pressure will bleed out the Eustachian tube quickly and the ear will quickly equalized.

Scuba diving has two big advantages to hand free equalization. First is that the diver is usually not inverted (makes a big difference for some people). The second is that a scuba regulator, regulates the air pressure in the breathing cavities to the ambient pressure on the out side of the eardrum. All you have to do is open the eushachian tube for a split second and presto, they’re equalized!

Now in freediving, you get less than ambient, or negative pressure in the breathing cavities when at depth. This is why at extreme depths diver’s lungs actually fill with fluid and blood. This is also why it’s much harder to equalize hands free in freediving. It becomes harder and harder to push air into the eushachian tubes and middle ear without holding the nose and doing a frenzel or other technique.

I learned all this stuff by, well frankly I had too. I had a bad inverted equalization problem, although I had no problem upright and could even do it hand free. I researched it for months and purchased and practiced on an inversion machine. It took me about 8 months to master and I still have to practice twice a week. The moment I think I have it, I will have problems again.

For me the trick was to learn to flex the muscles and open the tubes before I put any air pressure on them. Any air pressure first, and they wouldn’t open when I was inverted. I learned to flex the muscles by employing the theory that if a muscle flexes, even if not by its self (firing muscle tissue) it still send signals to the brain that it is moving and you can learn that feeling and use it to learn to flex the muscle. Basic physical therapy stuff. You know were they retrain someone to use their muscles by manually moving it for them at first?

To do this I stood in front of the mirror and did the Frenzel technique several times, really concentrating on the feeling around the tubes open. Then I kept decreasing the pressure. If I lost the feeling I increased the pressure to regain it. In a few days I was able to fire the muscles and open them without any pressure. Then for inversion it was a quick mater of learning to fire and immediately pressure.

For what its worth, that’s my story. Oh I have found that packing will allow me to equalize hand free a little further down, but for me its like what jvoets said. It takes more time than just pinching the nose and going down fast. Although if I thought it was possible for me to learn to equalize hand free well enough to descend at top speed, I would certainly work on it.


It's not the 'yawning' that opens the tubes. It's after the 'yawn' that they pop. If you're keeping 'tension' on your neck, they probably won't go. It's the split second after you release the tension that the eq takes place. Practice doing that yawn technique in front of the mirror. If your doing it right, your adams apple should be pulled up. If it' not, try doing the same technique, only this time, with your tongue smashed to the top of your mouth. Now, right when you relax the muscles that are making the rumbling sound, thrust your tongue backward into your soft pallate. At this time, your adams apple will drop back to its original position, and your ears should have [simultaneously] produced a cracking sound.

If you want to simulate a dive. Pinch your nose, and suck in, until you de-equalize your ears (making the pressure lower within your eustation tubes). Then practice equalizing. Using this, you'll know for sure if your going to get it underwater. Don't do it too much though, or it can make ya dizzy with a headache.

Depth Effects

Residual Volume Measurement Ideas




Sunday I tried to measure residual volume. On a dive to 10 meters, I exhaled completely for over 10 seconds, emptied my mouth and pinched my nose to close off the expanding mask. When I got to the surface, I measured the air that I could exhale in 10 seconds and it was 1.1 liters. Given the method used, it should be read 1.0-1.3, I think. Head down or head up didn't seem to make any difference. Does that sound like a measurement of residual?

Since my vital capacity measures 5.2-5.8 (the higher number is immediately after stretching), I can leave the surface with a total air volume of 6.4 to almost 8 and should reach residual at 43 to 56 meters with the Beuchat mask or get a complete mouthful of air at 36 to 46 meters. When I tried, the 35 meters (no packing) worked OK, but at 45, I couldn't fill my mouth. Carlos, who patiently supervised all this, commented that I lost some air on the deeper dive.

Since a full exhale plus mouth full dive to 10 meters is possible, the lungs must be able to squeeze down to about half a litre. Just thought that I would share and find out if my logic will pass review.


At 10m, once you exhale, the air which volume which remains is RV @ 2atm, so you have a total of 2RV at 1atm.

When you get to the surface, you have 2RV total in your lungs. When you exhale to the max, you exhale down to 1RV, so the amount exhale would be 1RV, so yes, it seems your method should work. Quite ingenious!

It doesn't take into account the volume of your sinuses though. If you closed your epiglottis on the descent and allowed air from the mask to fill the sinuses, it would work better. Also, it doesn't take into account blood shift, which should be quite weak for a 10m dive.

I have an additional idea.

Try this:

Do the test at 5m:

@ 5m, you exhale to RV @ 1.5atm, then upon ascending you have 1.5RV. Once you exhale down to RV, you must have exhaled 0.5RV. So double the amount you exhaled.

Do the test at 10m.

Do the test at 15m: RV @ 2.5atm, then at the surface you have 2.5RV, exhaled to 1RV, meaning you exhaled 1.5RV, so divide the amount you exhaled by 1.5.

Do the test at 20m, dividing the result by 2.

Interestingly, we see a trend:

For depth X, divide the exhaled air by X, then multiply by 10:

@ 5m: RV = ( Exhaled volume / 5 ) * 10

@ 10m: RV = ( Exhaled volume / 10 ) * 10

@ 15m: RV = ( Exhaled volume / 15 ) * 10


Then, you can graph the results, and any errors should show up in the graph.


There is another method too, but more complicated.

This method can measure both total lung capacity (TLC) and residual volume (RV), with no equipment needed!

The method is as follows:

- Get in the water with no wetsuit, and fully wet your hair

- Inhale to the max (and/or pack)

- See how much weight you need to become exactly neutrally buoyant

- Next, at the surface, inhale to the max (and/or pack)

- Go to 10m

- See how much weight you need (or how much buoyancy) you need to become totally neutral

- For exhales, same thing, exhale at the surface, see how much buoyancy you need to become neutral

- Do the same at 5m or 10m

To get an accuracy of 0.1L, you would need 0.1kg weights, and pellets with 0.1kg of buoyancy, all of which would need to be figured out before hand. However, it would be quite accurate, the only inaccuracy is the definition of 'neutral buoyancy.' The surface part should actually be done at 5m, to eliminate parts of your body breaking the surface.

You could make it even more accurate by not using neutral buoyancy, but by weighing yourself with a scale, via a cable to the surface.


- Inhale to the max, wearing a 15lb belt

- Go to 5m, have the surface operator 'weigh' you via a cable to the surface

- Go to 10m, weigh yourself again

- Go to 15m, weigh yourself again

Same for exhales.

This would be EXTREMELY accurate if the scale on the surface is accurate. You could figure out the total volume of compressible airspace in your body to within grams.


What is the need for a depth correction depending on salinity, water temperature etc. considering the following:

You probably measure all the deapths with the same deapth gauge/ computer. These machines normally use a fixed water density to calculate deapth (in the manual it mostly says that they are calibrated for salt or seawater use). Normally deapth calculation is not temperature corrected (no corrections are made in water density/ displayed deapth based on different temperatures). If you know what water density the deapth gauge/ computer uses for its calculations there is no need to do corrections for this RV calculation. For the calculation you want to know what water pressure you are at and you do not need to know the exact corrected deapth so you can skip a lot and calculate the water pressure directly. Displayed deapth * water density used by the computer model = water pressure you are at.

If you use lead to do the measurements:

I think that the lead if measured in sweet or saltwater makes no huge difference in the end result of the whole calculation due to small differences and other inaccuracies in other measurements. Just weigh what the lead that you use weighs in the water, which is less than on land, and also depends on things like if it is coated or not.

Great ideas to measure RV. Would be wonderfull to see some more experiences with the various measurements and methods.

Another idea: does the small error that the volume of the sinusses or mask make matter if you equalize them anyway? This could make these methods even more valuable than the (expensive) medical tests.


To Kars and all others who would like to measure the volume of the ears, sinuses or even the mask that needs to be equalized.

How about the following method:

Use the method of full exhale on different depths and measure the volume you can exhale again at the surface. Calculate the residual volume in the following cases:

1 when ascending close off the lungs with your epiglottis and let the air in the sinuses, mask etc escape into the water.

2 when ascending suck back into the lungs the expanding air from sinuses, mask etc. so it does not escape and can be measured.

3 dive with a noseclip or close the nose and suck the expanding air from the sinuses etc. back into the lungs so it does not escape and can be measured.

1= residual volume of the lungs

2-1= volume of the equalized sinuses+ ears+ mask

3-1= volume of the equalized sinuses+ ears

2-3= volume of the equalized mask space

I have no spirometer and therefore cannot do the measurements but am very curious what numbers anyone gets and if the volumes differ enough to be able to do the calculations.



Static Relaxation


About the relaxation, I didn't give him any really specific instructions, but just described what I feel and do during a static. You sort of have to go for it on a "feeling level".

When I close my eyes I settle down inside, finding a quiet calmness, enjoyable, sometimes blissful. But the essence of it is that it's quiet and one has a feeling of sinking inside, of peace.

Try to locate that "zone" or place or feeling inside and just let it lead you deeper into more quietness. Don't try to push away thoughts that come as that will raise your level of mental activity and consequently your metabolism will also rise, burning more O2. So if thoughts, distractions or contractions (that ugly word ) come up and have a tendency to take you away from that state, don't fight them but just gently get back to that feeling. Softly drift back. Don't worry about how many times you have to get back, contractions may throw you way off. Just always gently drift back. In time the quietness will predominate and the contractions will be somewhere in the distance.

At first contractions will probably overshadow the quietness but with practice one should be able to experience the contractions while not losing that quietness, as if the two states could coexist simultaneously.

The point is that the quietness or peace or being in the "zone" is a more direct experience of our own inner awareness, and that is not limited by anything, being unbounded in nature. In theory contractions should not eclipse this experience but in actuality being a subtle and delicate perception it gets knocked around a bit because the nervous system has to be trained to experience it more directly and permanently - at least for the majority of us.

And this is one more interesting benefit of freediving: By diving into the depths, whether static or dynamics or constant, we also end up diving into our inner nature as the result of a search for more quietness and therefore less consumption of O2. If focused in this way, freediving is a very powerful spiritual technology, where "spirituality" is defined as the experience of our deeper levels of awareness or perception.

Co2 Compartment Hypothesis


Suddenly, it dawned upon me. I'd like to introduce a concept for breath-holding which really isn't new, but should explain a lot of weird mysteries many of us have noticed while doing apnea.

Let's start with some physiology review:

- O2 has almost no solubility in water

- CO2 is very soluble in water

Because of that,

- Most of your oxygen must be stored in hemoglobin and myoglobin, and lungs

- CO2 can be dissolved in the blood plasma (i.e. blood water), as well as the rest of the water in the body

The 'bohr' effect states that the hemoglobin will only release oxygen in the presence of adequate acidity.

When CO2 dissolves in water, it creates carbonic acid, and thus acidity.

[this is all old news, just bear with me]

Thus, when you overbreathe, your CO2 level goes down, and your blood becomes very alkaline, preventing hemoglobin from releasing O2.

Further, low CO2 causes blood vessels to vasoconstrict. Vasoconstriction prevents blood flow, and thus prevents oxygen flow to vasoconstricted areas. The result is tingling fingers, fading vision, and finally hypocapnic blackout.

However, all of those effects are caused primarily by the acidity (or alkalinity) of the blood itself. By rapidly hyperventilating, you will rapidly change the acid-base balance of your blood. However, in the short term, the remaining 50kg of water in your body will not be affected. This is a huge point.

Let's divide your body water into two compartments:

- Water in the blood (i.e. blood plasma) = about 5L

- Water in the rest of the body (body water) = about 50L

As you hyperventilate, your blood water rapidly becomes alkaline, and can cause a hypocapnic blackout. This could occur even if your BODY WATER were still very acidic, and laced with CO2.

For example, suppose you finished a CO2 table and were laced with CO2. Now, you hyperventilate until your vision fades. You conclude that you have blown off all the CO2 from the CO2 table -- incorrect. Your blood is now alkaline, but your body water is still very acidic, because it takes a long time for acidity to 'diffuse' from your body water into your blood, and vice-versa.

The same effect can be seen by watching your exhaled CO2% during a CO2 table. If you do a pattern of 1'30" hold, one breath, 1'30" hold, one breath, etc., and you measure your expired CO2% on each exhale, it will quickly rise to around 7.5%, and remain there for many cycles. You assume that you are in a steady state, blowing off the same amount of CO2 that you are accumulating. In fact, the CO2 is diffusing into the body water. If you keep it up for at least 10 minutes, then, still doing the same pattern, suddenly your expired CO2 will soar to 8.0%, 8.5%, 9.0%, and 9.5% and 10% -- because now your body water is saturated with CO2 and there is no where else for the CO2 to go.

For a long time I did the following static pattern [note; hyperventilation in this context means fire breathing]

- two breaths, then inhale+pack, 3'30" static

- short recovery

- two breaths, then inhale+pack, 5'00" static

- 2'00" of hyperventilating

- Full exhale, 2'00" static

- 2'00" of hyperventilating

- Full exhale, 2'00" static

- 2'00" hyperventilating

- Full pack, 6'00" static

- 2'00" hyperventilating

- Full pack, max static, 6'30"+

The contractions would come the latest on the last breath-hold. I would feel heavily depleted from the exhale statics, and too many statics in general. However, for a reason which I didn't understand, I needed this long pattern in order to delay the contractions long enough to hit a huge time. I could only hyperventilate for 2 minutes -- no more -- otherwise I would black out during packing (not to mention feel awful).

I assumed that 2 minutes of hyperventilation would 'blow off' all my CO2 (since I would get all light-headed). If that were so, then it seems that a 2-minute hyperventilation on only the 2nd or 3rd breath-hold should do it, and delay the contractions as much as I needed -- but it wouldn't work. Why did I need so many cycles?

In fact, if you look at the above pattern, there is a total of 8 minutes of hyperventilation. The exhale statics are so short they don't result in CO2 accumulation. Even the 6'00" inhale static did not accumulate much CO2, as evidenced by my CO2 monitor upon exhaling.

What was really happening was that I needed 8 minutes of hyperventilation to 'blow off' the CO2 stored in my body water. Because of slow diffusion, it is impossible to blow off the body water CO2 in only 2 minutes of hyperventilation, even though those same 2 minutes caused me to nearly black out from hypocapnia.

So, this would explain why some people have great success by doing 8-minute breathe-ups, doing relatively slow, deep breathing. The breathing rate is not enough to over-alkalinize the blood (i.e. no hypocapnia blackout), but, by maintaining the blood generally alkaline, it allows a gradual blow off of the CO2 stored in the giant 50L body water supply.

So, if my hypothesis is correct, then a slow, 8 or 10 minute breathe-up, should delay the contractions far more than 2 or 3 minutes of hyperventilation to the point of dizziness.

So, to summarize:


"CO2 Compartment Hypothesis":

- Rapid hyperventilation changes the blood acidity rapidly, and does not allow the body water to equalize with the blood. Rapid hyperventilation will cause light-headedness and hypocapnia symptoms long before the body water is alkaline. In order to alkalinize the body water, the blood must be kept alkaline for a long time (10 minutes+). In order to acidify the body water, the blood must be kept acidic for a long time (10min+). Using this methodology, the athlete can choose to begin his apnea in any one of four configurations:

1. Acidic blood, alkaline body water

2. Acidic blood, acidic body water

3. Alkaline blood, alkaline body water

4. Alkaline blood, acidic body water

Each state would be reached by approximately the following pattern:

1. Acidic blood/alkaline body water = 10 minutes of slow deep breathing, followed by a 5-minute CO2 table

2. Acidic blood/acidic body water = 20-minute CO2 table

3. Alkaline blood, alkaline body water = 10 minutes of slow deep breathing

4. Alkaline blood, acidic body water = 20-minute CO2 table followed by 2 minutes of rapid hyperventilation


Application to the Real World

Given that blacking out from packing, and all hypocapnic blackouts are caused by alkaline blood, then in theory the diver could reach a very low state of total CO2 without suffering from hypocapnic problems by choosing state #1 = acidic blood, alkaline body water. In fact, the blood would not need to be acidic, just neutral. So, 10 minutes of slow deep breathing, followed by a 2 minute breath-hold, should allow the diver to inhale and pack to the max without hypocapnic symptoms. At the same time, the alkalinity of the body water would be so high that the diver would have a huge CO2 buffering capacity.


Great thinking and I'm sure you've just discovered something significant here, thanks for sharing it with us. The challenge now will be how to test and verify your thinking. I have a couple of related questions.

1. Is partial pressure differences the primary mechanisim for moving CO2 from body water->blood->lungs. With the PH of the blood simply providing a favourable/unfavourable enviroment for this transfer?

2. Does the level of O2 in the blood bonded or dissolved(I'll come back to this point) have any impact on the bodies ability to move the CO2 from body water->blood->lungs

3. In moving to a slow 10min breathe up what type of breathing pattern do you think would be optimal

FROM MY POST ABOVE - O2 in the blood bonded or dissolved

From my tech diving days we did some long deco on 50% O2 at 18m to open the "oxygen window" which allowed a secondary pathway for off gassing nitrogen. This mechanism assumed dissolved blood oxygen as well as bonded oxygen. Is a similar situation possibly relevant here. I recognise that we aren't breathing the benefits of 50% O2 but neither are we facing the nitrogen saturation levels of tech divers. .....just some thoughts

Ben Gowland

A few points:

1) CO2 is not just dissolved in blood but is also bonded to the Haemoglobin. It bonds to the outside of each of the four protein molecules in the Haemoglobin. This means that the blood store of CO2 is greater than just the plasm and cytoplasm content. I don't think this impacts your thinking much, but it means the difference between blood and body CO2 carrying capacity is not quite as big as first thought.

2) I disagree that you should be able to get the acid blood/alkaline body scenario. I agree with the other 3. With the 10 mins of deep breathing, you would of course get rid of lots of CO2, but in your mini-CO2 table, the CO2 would build up in the 'bodywater' just as much as it would in the blood. Then you would breathe off some blood CO2, gain a bit of O2 and do your breathold. This means you would end up with slightly alkaline blood and 'bodywater'.

Anyway - great stuff as always. I am sure you are on to something here. In some ways it is looking full circle - i.e. we are back to the 'breathe deeply' prep that was the done thing 10 years ago. I will defintely be thinking of how to apply this thought to my diving. I may even do a dreaded static or two.....


One thing I would note: it seems to me that the time to resaturate the body tissues back to their normal "resting state" CO2 levels would be much shorter than the initial breathing required to lower it. The circulation of the blood through the body combined with the atmospheric partial pressures of surrounding CO2 provides a really good diffusion rate to force the CO2 back into the tissues. The 5 minute CO2 tables may be too much. You may need to cut back to 3 minutes to get the optimal. This is only a thought, but I am wary to think that the time to release the CO2 is at a 1:1 ratio with the time to reabsorb it into body tissues.

I think of it this way. The removing of CO2 from the tissues through deep breathing techniques is like doing work to move a rock uphill. You are adding enough energy to the system to not only move the rock, but to overcome gravity. However, moving the rock to the bottom of the hill much less energy/time is required as gravity is adding to the movement.


Some points:

I neglected the bonding of CO2 to hemoglobin. If I'm not mistaken, only deoxygenated hemoglobin can bind CO2? Correct me if I'm wrong. Anyway, I think the total CO2 binding capacity of the hemoglobin is small compared to the body water.

Second, I'm certain that it is possible to reach acidic blood and alkaline body water. Keep in mind that when I do the 1'30"/one-breath/1'30" style CO2 table, my etCO2 is level around 7.5% for 15 minutes, before suddenly soaring to over 10% in the next five minutes -- why would it take so long? I'm getting contractions from the first few holds -- my O2 is still high, so the contractions are caused by acidic blood (and not low O2) -- yet, although my blood is acidic enough to cause contractions even at the start, it takes 15 minutes of steady state acidic to cause my etCO2 to soar.

I think it is true that the rates of diffusion differ: CO2 in the body water can only be removed by diffusion into the blood and then removal by the lungs. However, CO2 accumulates 'on-site' in the tissues/water itself. However, as long as the blood is pumping, the blood wipes away the CO2 which is produced in the tissue/water. If the blood did not pump, or if the lungs are empty, then the CO2 in the body water would accumulate extremely rapidly. However, inhale apnea causes CO2 accumulation in the body water only very slowly, because the lungs and blood can store significant CO2 (combined), and the constant flow of blood prevents accumulation of CO2 in the tissues, unless the blood itself is acidic.

This is why I think that during inhale apnea, CO2 accumulation in the body water is slow. So, if we alkaline all the fluids by 10-minutes of breathing, then do one apnea to contractions, I strongly doubt that in those 3 minutes the entire body water has been saturated with CO2. This means that the blood must be acidic while the body water is (relatively) alkaline.

Once again, the main idea is that it takes a 20-min+ CO2 table to cause etCO2 to soar.

Here is a question for the geniuses:

- We know that hyperventilating increases the total O2 store by increasing the hemoglobin oxygen saturation of VENOUS blood (i.e. from 60% to 80%) while the arterial O2 saturation remains > 98% (i.e. see Lindholm's thesis)

- The disadvantage is hypocapnia (or so we thought)

So, would it then be possible to make the body water acidic, then do rapid hyperventilation in order to increase the O2 store? If so, then the acidity of the body water would prevent hypocapnia in the later stages of the breath-hold, thus giving you the 'best of both worlds' : good CO2 level to ensure O2 release, and high O2 to start the breath-hold.

This method mimics what I currently use for deep diving; something I call the 'acidic system of diving.' The idea is to use an acid other than carbonic acid (CO2) to supply the acidity to release oxygen from the blood. By eating a diet high in acid forming foods (mainly meat / protein), the body becomes acidic (mostly from uric acid I think). In this acidic state, I can hyperventilate for a long time, pack without dizziness, and thus start with high O2, but not suffer over-alkaline blood, because even with the lack of CO2 for acid, the uric acid takes its place, keeping the blood pH in the useful zone to retain consciousness at the end of the dive. This has worked wonders in constant weight, but it sucks for static (at least for me).

Jersey Jim

Interesting you mentioned the diet to replace the carbonic acid with another form for your "acid system of diving". On the 25 minute ride home from work last night I began back on the 1-breath static pracice that I mentioned in the spring training thread. I usually forget about all statics for the 3 months between Nov. & January. What was surprising, was that I didn't get around to eating my afternoon pink grapefruit until shortly before leaving work. I was worried it would negatively affect the static. The pattern of 1:30, 1-breath, 1:30, etc., was noticably easier than last year. I feel I can progress this year to 1:35-1:40. I wonder if the ascorbic acid from the grapefruit had an impact in the manner you mentioned? As I always peel away the secondary skin & pectin, there was very little "bulk" that would require blood diversion for digestion. Although I did, and always do take vitamin E with my grapefruit, in the form of almonds. This also probably resulted in very little fiber bulk to divert blood. I found this to be surprising because my best static practices occur on an empty stomach, and this one was pretty comfortable.


This Eric theory make a lot of sense to me.

I decide to listen my brother, on how to make the beath-up for a max static, this is the pattern:

  • 6 min breath-up
  • Doing some packs every minute or 30 secs (for me 6-10)
  • Stop packing for the last 2 min of breath-up
  • Maximal performance (without packing) no special numbers, just until you can hold it anymore.
  • 8 min breathe-up (without packing)
  • Final attempt after full packing

With this method I could get my PB in the first attempt and improve it in the final.

I think this is related not only with pH but also with O2 stores.

In the CO2 movement we have to take into account that after a extreme breath-hold the venous CO2 is very low, the build-up during the apnea remain local (cell), after some minutes it start to be released to the circulation. If we remember and old study in AMA divers, the etCO2 was very low inmediatly after the dive.

I think we are still far to found "the key" but I love to see people like Eric, that is always looking for answers.

Ben Gowland

CO2 binds to haemoglobin irrespective of O2 as the sites are remote from each other, however, I do seem to remember that this is one of the mechanisms by which the bhor shift occurs. Thus the bound CO2 affects the binding site of the O2 and reduces the bond strength.

Frank's post stirred up some thoughts in my head about the time it takes to get CO2 from the body to the lungs. If memory serves (which it may not ) then it takes 5-10 minutes for a red blood cell to make a return trip from the lungs to the legs and back when at rest. This figure is more like 1 minute to the brain and back. This means that any build up of CO2 in the body would still take 2.5-5 mins to get from the legs to the lungs and once the lungs are resisting the offload of CO2 from the blood, the CO2 in the arterial blood will increase and trigger the chemoreceptors in the aorta, carotid sinuses and the medulla. I think that some simple modelling of blood flow and chemistry would go nicely here - although I don't have the time at the moment. I will certainly give it a go soon.

The thing that has been bugging me for some time about all our theories of blood acidity and O2 saturation etc is that we seem to be relying on qualitative concepts i.e. acidic blood offloads O2 better (and is worse at picking it up, don't forget). The problem with that is that it isn't refernced to the actual figures that the effect curve gives and relating these to the figures that is seen in the blood during a breathold. I know Eric and others have done some great stuff with a lot of instruments (oximeters etc) and gained some proper data. I think we could use that data more effectively if we feed it into some model.

I think this idea of Eric's is great, but I'm still not convinced that we are applying the concept correctly to human physiology. A spot of modelling might go nicely here. I don't have time to do it at present, but may well do so in a week or two. I think we could have much to gain.

bevan dewar

hi. the 4 configurations eric describes seem to make sense, but i dont know what take from it. it will help with formulating hypothises and designing experiments which could be carried out in water, but there in lies the problem for me. i wouldnt want to change my breathup routine for reasons purely academic, so i would want some empiracle evidence that one of these configurations works better for me than another. but as i see it the only way to decide this would be to try all four breathups decribed before attempting dives to progressively deeper depths, until i had reached a depth where three of the breathups had resulted in a samba. only then would i have a winner.(c.w i'm talking about). difficult to do in practice because you cant have 3 sambas in a row and expect the fourth dive to be a true reflection of anything. and if you do one of these configuration dives per day you have the problem of unknown variables entering the experiment from one day to the next. also, i think my instincts of self preservation would object to two minutes of hyperventilation before a very deep dive. do these experiments need to be done? and like this? what do you all think? short of sifting through 5000 posts of anecdotal evidance i dont see any other way. i'm thinking as i write, so i hope this makes some sence.


CONTINUE ON TO PAGE 2+ ***********




Blackout Avoidance : ATRC Test


There is a great tool for SWB prevention: I call it the ATRC test = ability to retain consciousness test. I thought I 'invented it' in early 2001, but it turns out a few other people have been using vaguely similar techniques.


Chances are that the first few times you try this you will almost certainly black out (on dry land) and crash on any nearby objects (possibly injuring yourself -- it happened to a guy here), so you must have a buddy ready to catch you when you fall!!!

Crouch down (buddy beside you), exhale fully, then RAPIDLY stand up while inhaling RAPIDLY. Continue inhaling to the max, then begin packing your lungs as fast as humanly possible. Count your packs, and pick a number that puts you within a few packs of totally full, and when repeating the test in the coming days and months, always use the same number of packs for consistency.

Once you have finished packing, remain standing (if possible), for about 15 seconds. Then, assuming you were able to remain standing, SLOWLY (!!!) exhale, SLOWLY!, through pursued lips (if you exhale rapidly you'll get a pounding headache).

If you are packing and start feeling light-headed, you may have to crouch down to avoid a blackout.

If your body is in a state which favors retention of consciousness, you should be able to do the test and remain standing, without the slightest bit of light-headedness.

A 'pass' is defined as performing the test and being able to remain standing. A 'B-type failure' is defined as having to bend over to stay conscious, but with no shaking or loss of motor control (B stands for 'blackout' type failure). An 'S-type failure' implies bending over and losing motor control and having a samba.

Here is the scale I use:

  • 10 / 10 = pass with no light-headedness
  • 9 / 10 = pass with slight light-headedness
  • 8 / 10 = pass, significant light-headedness but no danger of having to bend over
  • 7 / 10 = barely pass, vision & hearing fading, almost had to bend over
  • 6 / 10 = finished packing fully, waited several seconds, then had to bend over
  • 5 / 10 = finished packing fully, immediately had to bend over
  • 4 / 10 = half way through packing, had to bend over
  • 3 / 10 = didn't even start packing, had to bend over
  • 2 / 10 = could barely even stand up without fainting
  • 1 or less, fainted from just standing up

This test is the most remarkably accurate way to predict what will happen to you during a hypoxic (borderline) dive. If you fail (6/10 or less), then you shouldn't be getting in the water; you'll be risking your life, because you could blackout from a conservative dive, without warning.

Of course, even if you get 10/10, it doesn't mean that you can dive alone or push it, it just gives you a relative indication that you are in better shape than on days when you scored less than 10.

You'll find that adequate sleep, hydration & electrolyte balance are the most important factors to pass the test.

I have used the test almost daily for one and a half years, observing how I pass and fail based on what I eat, how I exercise etc., and I have developed special routines that put me in a 9/10 or 10/10. I have tried doing deep dives after failing the test, and during those dives I either BO'd, samba'd or had tunnel vision upon surfacing. It has been very accurate for me.

I usually do the test in the morning before going to the dive site, then again before putting my suit on.

Please remember that you must have a buddy watching you or else you could seriously injure yourself! Even with a buddy, do the test away from objects that might hurt you if you fall.

This test measures a huge number of physiological parameters, including adrenal gland function, blood pressure, hydration, cerebral hypoxia tolerance, high energy phosphate stores, nervous system excitability, etc. It is difficult to analyze them all; but the bottom line is that if you fail the test, you're in bad shape for diving.


Please be careful with this test. Do not over-pack. I didn't warm up, and packed slightly more than I usually do -- hoping to get the full effect of the test. I ended up injuring my chest which put me out for a few weeks, and I had to get chest X-rays done (for pneumothorax and pneumomediastinum). So, I strongly recommend that you pack-stretch before (gradually) and then don't over-pack!


Counter-weight System


Fin Swimming (Monofin technique)

Dolphin Swimming Techniques



Peeing in the wetsuit

URL [05/27]

I just flush my suit with lake water before I exit- that way I know it's water spilling on the boat deck when I take my suit off and nothing else.

As soon as you hit the water the pressure on you kidneys cause immersion diarrhesis ( Sven, spelling on that one?) and give you the urge to go.

I always make sure to tie a water bottle to my float so that I have plenty of fuel for my hotwater suit system.


[Why you should...]

The cells that line your bladder are called transitional epithelium cells (your eustation tubes are probably lined with pseudostratified columnar epithelium; that's the stuff of the respiratory system). They start out all bunched together when the bladder is empty, and are stretch thin when the bladder is full (kind of like an accordion). Although they can handle quite a stretch, with too much stress, they will be damaged and lose their ability to recoil. Overstretching can make you feel like you still need to go, even after you're empty. Better to listen to your body on this one.


There's only two types of wetsuits, those that have been peed in and those that will be. There's only two types of divers, those that pee in their wetsuits and those who lie about it. In over 20 years of diving, I have never peed in my wetsuit(!), but if I ever did, I'd probably pump seawater through by pulling the collar in and out from my neck, and the arms and legs of my shorty. Or getting upside down, and blowing bubbles into my collar (wetsuit neck-hole), making the bubbles come out the legs.

If I ever peed in my wetsuit.


I never do it myself but, I have a few observations.

Standing on the swim step it will run down and out the slit in the toe of your bootie that lets the air bubbles out on the first few dives.

If you pull your weight belt down to the hips, you won't pee in your ear (works best if your dimendions are 40" 40" 40" like me).

When you take your suit off, you'll be glad that the nylon is on the outside and you don't wear a bathing suit.

Some very good spear fishermen can load their gun while 'heating up' the suit.


How to make air-rings




Reader's Comments:

Please leave your comments or suggestions below!
 Im very intuiged by free diving and have found this website very useful. i have never done it before but i have been doing swimming for over 15years and i am only. i have a good ability to hold my breath but i cant seem to reach any where near the times iv read in this. what techniques or training do you part take in to achieve these extraordinary breath holds. please reply as soon as possible,
thank ben
2006-03-28Ben Darby
 Im very intuiged by free diving and have found this website very useful. i have never done it before but i have been doing swimming for over 15years and i am only 17 now. i have a good ability to hold my breath but i cant seem to reach any where near the times iv read in this. what techniques or training do you part take in to achieve these extraordinary breath holds. please reply as soon as possible,
thank ben
2006-03-14robert o'neill
 Hi, I'm interested in freediving but have questions/concerns I need your help with first.
1. what are the principal body structures/components limiting the compression of the lungs during a dive.
2. what are the primary cardiovascular dangers that freedivers encounter when decending to great depths?
3. what was Tanya's TLC at 160m if it was 5 litres at the surface.
4.what are the advantages & disadvantages of hyperventilating before diving.
Your help & advice would be appreciated.
Thanks in advance.
 I have been planning on putting up a writeup of my recent tour of the local recompression chamber (not for me!), which provided a great overview of some of the risks inherent in the freediving. I'll update this once it's online.

As with all of this, I have no medical training so you should ask these questions of a trained instructor. Nonetheless, here is what I have understood (offered purely for entertainment value only :).

As for Tanya's TLC, my understanding is that lung volume won't reduce much further past your residual volume. At that point further compression increases cause thoracic filling (blood plasma into lungs) and shunting of blood into your chest cavity, enabling you to become essentially incompressible (ie. not an airspace any longer).

Hyperventilating can be extremely dangerous for freedivers. While it might reduce the discomfort and urge to breathe in one's dive, it can delay your hypercapnic breaking point (urge to breathe due to CO2 buildup) until after your hypoxic limit (where you will blackout). Limited purge breathing seems to add value in one's target (not during warmups), but again, like packing, it has the potential to be very dangerous and must be taught by a proper instructor. Be safe!


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