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Exhale Diving

Thread Status: Hello , There was no answer in this thread for more than 60 days.
It can take a long time to get an up-to-date response or contact with relevant users.
Seb, I apologise for my last post. It was 2.30am in the morning and I was angry and tired and did indeed not spend enough time trying to read what you had to say. I should have also waited until I calmed down before replying, and therefore may actually had something a little more constructive to say. Anyway, thank you for your explanation I do understand it a little better now. Brett sorry for jumping to the wrong conclusion earlier from what you were saying. I think Ben may have started to realise what I was getting at. I should also not have attacked the concepts and techniques of FRC diving itself as I do not understand enough about it to make judgements and it may indeed provide benefits to others. If people wish to use it that’s their own choice. I do not have problem with exhale diving, as I said it’s something I do myself. I will say for the record that I do feel uneasy that it be used by recreational divers but that is something I may have to get used to and is only my own opinion. Again it’s up to personal choice.

I would like to calmly attempt to explain why I got so wound up over this whole topic, and what may help in future to avoid other people doing the same. What got me upset started with the original post when Brett mentioned he wanted to change to exhale diving to reduce the chance of Samba or Blackout. To me this made no sense because I was comparing what would happen on a single dive ie same depth & duration inhale vs exhale. Ben then mentioned that with FRC there is a whole change in style and approach in technique. Again I had no idea what he was talking about. It wasn’t until several posts later that Ben finally mentioned that he does actually reduce both his depth on time on any single FRC dive. (I do see now that Seb did indeed mention this in his post.) To Ben and Brett they already knew this and probably thought it was implied. As an outsider I was missing this extremely vital piece of information ?!
Did I wildly jump to a conclusion ?
Well can anyone on this forum seriously tell me that as a beginner they did not want to be able to dive longer and deeper ? (and hopefully safer)
Sure with any new technique there is a learning phase and people shouldn’t always try and set PB’s straight away. But what seems to be unusual in this case is that a newcomer must make significant reductions, and possibly even never increase their max depth/time whilst on FRC vs inhale when you are talking about any single dive. In any case this is the very thing that got me so upset, specially in Brett’s case where he would definitely have to reduce both his depth & time on a single dive whilst being in the learning/adapting phase. If not he would have been greatly increasing his chance of blackout. So as you can see when I saw a discussion of exhale diving, and people mentioning that it is safer, in my mind when comparing identical dives it was the complete opposite……..

To help break down what I believe is one of the biggest confusions on this subject I would just like some honest opinions now. Eric mentioned that with FRC it slightly decreases your max dive compared to inhale. Wouldn’t that only be the case for advanced divers ?
So for most people wouldn’t they have to make a significant reduction in both depth & time on any single dive?
(I’m not sure if someone has already done a poll on this on DB, the stats may be useful for future discussions.) I’m not asking this to payout on FRC diving. As Seb and Eric mentioned this trade off may be greatly outweighed by other advantages such as much shorter rest intervals and therefore with FRC the overall bottom time can be increased in any one diving session. This along with other examples such as the one Eric pointed out where he was able to do more dives at a specific depth because of the reduced risk of DCS.

As for my suggestions of discussing this technique in future:-
I am sincerely asking everyone, please don’t use short statements on exhale/FRC diving such as “exhale diving may reduce the chance of Samba or Blackout.” I believe that most people without knowledge of FRC diving will interpret this to mean they can dive to the same depth and or time on a single dive and do this safer. (People other then myself have definitely made this very interpretation before). To me Ben was little more correct with the statement:-

exhale diving doesn't remove the risks of blackout - it shifts them 'sideways'. The likelihood of the classic SWB from rexpanding lungs is considerably reduced, but the likelihood of BO is not reduced overall - unless you change the way in which you 'approach' the dive which you could do with either technique.

My own thoughts are, if you wish to explain that this whole style of diving may help reduce BO, then please also include something along the lines of – “ in most cases both the depth and duration of any single dive is reduced, but rest intervals are greatly reduced therefore the net result will be an increased bottom time in any single dive session……..”
Clearly mentioning that depths & times on any single FRC dive will be reduced in most cases may help others with diving experience but not FRC theory from getting overexcited and people getting angry at each other. Not to mention reduce the chance of a possibly dangerous misinterpretation. I see this as no different to when talking to beginners about static technique. If you don’t know the person I think it’s often courteous to include a quick “please don’t do a static in pool without a buddy”. They may probably know this already but it doesn’t hurt to make sure. It doesn’t take a lot of effort and may help increase the safety of others. While we are all enthusiastic to point the advantages of our favourite technique to others I think it’s responsible to also point out any potential risks.

Thanks a lot,

P.S. Seb regarding your theory of me seeing you as a competitive threat - this is not the case. When you did your dynamic record attempt in Brisbane I sent you an email to congratulate you. I also asked you and was hoping you wanted to compete in the AIDA cup in Hawaii (2002). You told me then you were not interested in competition. Up until recently I have always thought it was a pity you do not compete because someone at your level would have given an Australia team a really good chance of placing well in a freediving team competition.
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HI, Water Rat here,

I didn't understand all the terms, either. For me, simple lack of experience, with the sport. I have 12 FEET--not METERS--to work with in a swimming pool. I'd like to know more about depth--WHY I AM HERE ON THIS THREAD--*Learning*
I've decided WRs are too much of a Head Trip for me, too. Don't have any--don't need any. PB's will do nicely.
I'm with Tyler, don't shut this down--some of us want to learn more. I'm also with Seb--do it for FUN--not for an EGO TRIP--I made that mistake, and it made me miserable--no performance, however good--even a GIRL 6:40--done in 1976--when the Official Men's record was 6:29.8--Hyperventilating with O2, it was 13:42.5--It STILL wasn't good enough--even though it wasn't in competition--so that tiny breath in near the end wouldn't make any difference--it was dry. It was practice! Goodnighty--why did I make such a Big Deal outta it?
So yeah--I'm now doin' it for fun--and maybe I'll even do 7--for fun--as a PB!

2.30am is never a good time for much of anything except sleep!

Awfully big of you…..apology accepted and no grudges held.

In some ways I was being overly detailed and descriptive to satisfy the likes of people such as Dr. Simon Mitchell who was also unfamiliar with the terminology and language many of us are employing.

Eric wrote: “FRC slightly decreases your max dive compared to inhale.” To which you replied, “wouldn’t that only be the case for advanced divers?” We don’t have enough divers doing this sort of diving to know but considering the time it’s taken me, it’s a fair bet that’s probably the case. No doubt one would have to adapt to the considerable hydrostatic pressures on the body, acquire the technical skill and experience of knowing where and when to use it. There are, however a small cadre of divers who’ve I’ve recently taught that have equaled and even surpassed their pb’s on inhale on their first attempt and without any prior experience with this strategy. One noteable case involves an ex-water-polo player who with no prior warm-up carried out a static of some 50” at which time he proceeded to swim some 90m in distance with a pair of fins, for a total time of 2’40. Although impressive to say the least he suffered a blackout as a result of a grossly disproportionate inbalance in his static:dynamic ratio; I suspect he swam way before reaching his PBP.

Moreover, for the ‘racers’ (Claude Chapuis’ term) who are impatient for quick fixes and results then this type of diving I would suggest is not for them and certainly I have no qualms about turning people away if I think that they’re psychologically immature or unbalanced even if it come at some financial loss. Certainly, I spent enough years working in the scuba diving industry to see it’s considerable shortfalls in safety.

There is presently no place for this type of diving for those training to set personal bests in dynamic or static in the pool except perhaps as a long-term training aid for inhales; which remains questionable.

It is IMPERATIVE that exhale dives in the pool are done in the following way, if pushing oneself to one’s limits:

STATIC phase first, followed by a DYNAMIC phase

If done properly, the timewise ratio should, in my experience, be 1:1

Only in this way can the negative effects of the ‘exercise response’, i.e., rapid blood oxygen desaturation, be slowed. This is achieved by allowing the peripheral vasoconstrictive effects of the ‘dive response’ to become adequately manifest. The vasoconstrictive effects are not only caused by apnea but in this case also largely potentiated by central hypercapnea, i.e., a build-up of CO2.

At what point should we switch from static to dynamic? If one begins the dynamic phase too early, i.e., before the physiological break-point occurs (PBP)* then it is unlikely that the peripheral blood vessels will be maximally contracted. That being the case, any muscles that are activated at this time will result in a more rapid blood oxygen desaturation because active muscles are a strong stimulus to maintaining the blood vessels that feed them, less vasoconstricted. Moreover, the larger the muscle mass activated, e.g., the muscles employed in swimming, the faster the desaturation and the more likely the potential for loss of control/consciousness. In a warm-water environment where peripheral vasodilation is likely to be elevated this desaturation effect is likely to be aggrevated; all the more reason not to swim from the onset.

There is a trade-off: if you swim before the PBP you may swim a little further but not much more. Once again, the reason being that well perfused and active muscles will ‘rob’ you of your oxygen stores very rapidly. Indeed, you may well feel like your muscles are not very fatigued at all but, loss of control is just around the corner! Unfatigued muscles, on the other hand, are the ideal state of being for repetitive, bout diving which by its very nature involves relatively shallow, short and frequent diving. That is, it should not be extreme except in the sense that dive sessions may be quite prolonged, e.g., several hours.

You may well find that, timewise, there is very little, if any measurable difference, between a pure ‘exhale’ static and an exhale static immediately followed by a dynamic. This is because unperfused or grossly underperfused muscles, i.e., ones that have had their blood flow and hence oxygen removed, cannot rob your more vital organs of any oxygen. That’s not strictly true, in the sense that it still requires extra oxygen to activate the peripheral nervous system to make them contract but for our purposes that’s insignificant as evidenced by very similar bottom times between the various dive modes of static and static + dynamic.

Having said all that, it would be pointless to overextend the static phase much beyond the PBP as no benefits will be gained in terms of distance. In fact, once the PBP is reached one has a fixed bottom time irrespective of whether one could sprint swim the dynamic phase or inch ahead at a slugs pace. You can try this yourself by varying swimming speed in the dynamic phase and measuring heart rate. There should be no increase in heart rate. On the other hand, if you leave before the PBP there’s a strong likelihood that your heart rate may even increase for some time before hypoxic effects kick-in.

The PBP is that point at which there is dyspnea (subjective urge to breathe or ‘air-hunger’) coupled with contractions from the inspiratory muscles, e.g., the diaphragm.


PS: On the issue of comps: competition rules and comp. safety measures, as they are currently laid out by the associations unfortunately prevent me in practice and on principle from partaking . The comps this summer in Jervis Bay and NZ will be something altogether different, I hope.
Question: do you have another alias by which you have contacted me in the past?
Hi Seb,
Sorry haven't been posting my full name - Walter Steyn I live in ACT. (Wal is short for Walter.. not Walrus :D)
Don't have any other Alias that I remember. When I sent the emails, I was working at CSIRO so should have just been my name at something like @csiro.au or @cmis.csiro.au. Oh yeh I was also in a finswimming club with Henry and Sandra Hatch(Ozfin) that came out to time you for a 50m sprint. ( I remember they thought it was very odd that you sprinted with arms by your side :D )

Seb you were saying the bottom time of the dynamic phase (when done correctly) being fixed regardles of the speed ?
I take it then that to achieve a maximum depth or distance a max sprint effort with a monofin would be the way to go?

I often thought it would be nice if there was a way that we could fool the body into thinking it's hypoxic the start of the dive even with a full lungfull. Like with Eric's little exercise - start on exhale, then pack small amounts over time until full. Because of the increased dive reflex at the start the total time is much greater then a normal static, but you have still only used the same amount of air. Would be great if there was a way to do that on a breathold. (Perhaps we should carry and breathe from a plastic air bladder ? :duh :D )
I guess perhaps that is in some ways similar to what you are doing with the FRC technique.

P.S. What comp in Jervis Bay ?!


Great to see you posting on this forum and I hope to see you passing on your thoughts and knowledge regularly. Equally good is to get a clearer balanced view on the pros and cons of exhales as there does seem to have been some confusion on this approach amongst the Aussie spearos & freedivers based on the Oz press. As a humble suggestion it would be great if you could use the next press opportunity to set the record straight for the good of safe diving practices.....just a suggestion. ;)

You mentioned a comp in Jervis Bay, did I miss the details for this in an earlier post or could you point me in the right direction?

As a Sydney based freediver, I have (as far as I'm aware) the only boat in Sydney set up for freedivers and it would be great to do some diving with you if/when you are down our way. It's only a small runabout, but it gets from A to B and has dive lines, safety gear including oxygen etc. Wal(Walrus) is a regular at my house and on the boat and it would be great to get you guys together for some dive time (there is an offer in there for you for a place to stay while in Sydney as well).

PM me if you want some contact details.


I just went to your website and noticed you are running a course in Sydney 9/10 october (only 12 sleeps away!). If there is space still available please let me know and I'll hit paypal. Also if you need somewhere to stay (and you don't mind mid home renos and a 2 year old noise machine - named jack) let me know.


I attended the clinic with one of the guys I go spearfishing with and I have noticed that he seems to be adapting faster to the technique than I am. Admittedly he is a better diver than me and has been hunting for about 12 years now I have been only doing it for 3 years, however I am much fitter I run about 4 times a week and weight train about 3 or 4 times a week plus whatever diving we do when my sinus lets me. He is lean in appearance while I am more muscular with broader shoulders.

My question is are some people better physically suited to the style than others as appears to be adapting faster than I?

Also we have noticed that if we follow 3 or 4 exhales with an inhale, the inhale appears to be much longer not only longer than the exhales but longer than we would normally expect, yet if we do another inhale again it is much shorter. What is happening here?
I suppose it is because the blood concentrates to the thorax (bloodshift), and the blood is therefor available in large amounts, during breathup, to take up oxygen. In the same time the tissues in the legs etc. consumes less oxygene because there is less blood available to "rob" oxygene from. This phenomen is very strong when doing exhales.

When you start doing full inhales, the blood will be "pushed away" from the thorax region and the benefit from strong bloodshift will dissapear.

Maybe there is more / other explanations.
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that's pretty much why most competition divers use at least 1 exhale dive to warmup for their max dive (inhale). The exhale dive kicks in a strong dive reflex. I wouldn't have thought it wears off that quickly though, ie the dive following. Perhaps is has to do with your recovery?
From what I understand the rests between exhale dives are quite short? If you then switch back to inhale you would need to go back your normal rest times.

Been following this very interesting thread and I've got two questions:
1. FRC diving is [functual risidual capacity] or passive exhale diving as some call it, is the exact ammount of Air important? I mean, what's the importance of passive exhale, why not passive exhale and a little more or less? On the same note why not empty, obviously you won't be able to go as deep but apart from this reason is there another?

2. Assuming I start my dive with L litres of air and O oxygen molecules, when I deepen and say reach L/4 volume of air I still have O molecules (theoretical descent rate of INF). However, I've noticed that holding my breath at depth is much more difficult than on surface and it's harder the deeper you are. Why is that, since I have the same ammount of O2 to work with. (it might be due to lung's surface area and O2 saturation taking longer?)

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To point #2, I experience the opposite. The deeper I go, the less I feel the need to breath. I noticed this from my first days of training until now.
Frox, I think Eric pretty much covered this already in this thread:

Originally posted by efattah

Case 2: Inhale dives. Here, the lungs compress at depth. Without some sort of aggressive ventilation at the surface, your CO2 level at the bottom would be insanely high. So, 99.99% of divers take at least a couple of deep breaths before they go down, to counter the pressure-CO2 effect. Beginners often get confused at the bottom, because the urge to breathe may be high; then, during the last part of the ascent, the urge to breathe might decrease, as the CO2 level decreases (with lung expansion). Expert divers, with higher CO2 tolerance, aren't fooled by that phenomenon.
jome, would that mean that my theoretical diver that descended in no time would be able to hold his breath as long as he does statics (assuming he has limitless CO2 tolerance)?

tylerz: does that mean that you can do your static PB (or almost the same time) at depth (if you descend using a rope and leave a little to ascend)?
Originally posted by Brett Craik
My question is are some people better physically suited to the style than others as appears to be adapting faster than I?
I'm not sure about this, but I think some people are better physically suited to the style than others. Some people adapt to it very quickly, while others, like myself, find it almost impossible because of the effect of pressure and the lack of air. This is partly why I complained about it so much - maybe it was not fair of me to do so, because it seems to work so well for some people.

does that mean that you can do your static PB at depth
Frox, I have never attempted underwater statics and rarely even surface level statics. I am just referring to the discomfort experienced when hanging at various depths. The longest dive I have ever done is around 2:40.
Frox, I have never attempted underwater statics and rarely even surface level statics. I am just referring to the discomfort experienced when hanging at various depths. The longest dive I have ever done is around 2:40.
Well, that's exactly what I meant, my longest dive was prolly around 2:15 and I was returning to the surface because I needed to breath, and when I did attempt 'hangs' then @10m I could do ~3:10 and it dropped pretty drastically when I tried doing deeper hangs. And I'm not entirely convinced that the only difference is CO2 pressure...
My experience is that the air hunger is definately bigger at depth at a given pre dive ventilation and a given time.
As a beginner I had BIG problems with this and it totally limited my diving for ~1 year back in 1997-1998.

There are some things that made me get rid of the problem:
-Relaxation during surface intervals, decreased tissue output (CO2)
-I can totally relax the diaphragm at depth which is hard for the beginner when the strange feeling of the lungs goes below FRC at depth. The right feeling at a deep dive is depending on the feeling in the stomach, TOTALLY RELAXED.
-Optimized breathup for max possible O2 and optimized CO2 level.

One thing I noticed is (on a deep constant weight dive) that when I pass the depth where lung volume is close to RV (30-35m) the feeling of need to breath fades and it feels like I could be there forever. The range 30-35+ to turn around point is the most relaxing and comfortable phase of a dive.
After the turn at a dive to for ex. 60m the airhunger starts slightly and the first contraction at maybe 35m.
-Maybe narcosis plays a part in decreasing air hunger at bigger depths???
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"Holding my breath." I recognize THAT PHRASE! (LOL!)
Still a newbie...Question for y'all: How do you tell the after-effects of hypoxia? (Not enough O2, I presume?)
I did plenty of depth exercises today. When the bod said, "I'm tired," I rested for awhile, then went back. All short dives.
Have a slight head-ache, it was worse--but I DO have bad sinus problems.
Is squeezing all the air out you can in the 3-foot of the pool and going down for a brief dive safe?? (I took 3 deep breaths in and out first)
Water Rat--hoping she doesn't drown herself, she's gotta novel to write, and doesn't believe in suicide. She's gotta swim alone, most of the time...nobody around here seems to care a thing about freediving! ('Cept ME!)