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Get high and get on down: a response

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.
Day 4 today of my IHT sessions on the homemade Hypoxicator. I've built an oxygen analyser as well now as I was getting annoyed with referring to conversion charts with the millivolt meter. With my newly aquired 3900P oximeter measuring SaO2 and the analyser measuring FO2 I'm having a whole lot of fun training "hard" in front of the TV (Faulty Towers this morning). With a rebreather style unit that has no bottom limit I have to keep an eye on things to stay at 10% FO2 which currently relates to about 81% SaO2. The unit allows me to maintain anything from 0-21% which is remarkable for 1/2 a days work in the workshop!

I'm not entirely convinced that I'll see any improvement in my apnea limits but it is fun nevertheless.

More accurate lowest SaO2 reading?

I remember Eric Fattah saying how the blood in an artery maintains its O2% regardless how far along its path it is from the heart. The reason, if I remember correctly, is O2 is not draw from the blood until the blood exits the arteries into the capillaries. In the capillaries 02 is draw out and CO2 is put in. The blood exits the capillaries into the veins. Blood pressure and volume maybe lower in an artery the further away from the heart it is, because it has been diverted in so many places, but the blood that makes it to a particular point, has the same SaO2% as it did when it first left the heart.

So if there is a large lag time with a finger probe then would a more accurate reading of the lowest SaO2% obtained be after the hold ended? The lowest SaO2% at the main artery leaving the heart will eventually make its way to finger, even if its 25 seconds after the breathold ceased, won’t it? Withstanding machine problems from too low of perfusion, algorithms, reading frequencies, etc. the pulse/oximeter should eventually read the true SaO2% obtained at the end of the breathold and it should approximate the lowest reading obtained 20+ seconds after the hold ceased, shouldn’t it?
I don't recommend you trying this. This is for informational purposes, and without consideration of dangers and a safe environment to practice, this can lead to serious injury.

I managed to work out a sequence that one can do without any equipment which should simulate the IHT conditions as described in the article, as it did for me while exercising and analyzing with a pulse oximeter. Much less precision towards maintaining a specific SaO2 unless you have an oximeter on hand, but the results due to this inaccuracy are most likely to induce a greater adaptation.

This was created because my father is going to hike to base camp at Everest and he was looking for something to help with acclimatization. The values are tailored for him, having no freediving related adaptations currently, but after the steps I will put the variables I used to reach the IHT equivalent.

1. begin exercise until relaxed, continuing to exercise for the rest of the steps.
2. hyperventilate (quick inhales and exhales; inhaling 3/4 amount of a normal breath; 2 inhales per second).
3. exhale fully.
4. hold your breath.
5. when it begins to feel a little uncomfortable, repeat from step 2, but this time on step 2 only perform 3-6 hyperventilations.
6. continue the cycle for 5 min of exercise.
7. continue exercising normally for 5 min.
8. repeat from step 2.
9. continue full cycle 3 times in total.

Notes (remember these are written to a non-freediver):

Step #2: Every person is different when it comes to hyperventilating. We have different abilities to remove CO2 and this ability improves with practice. So, I think you will probably need to start with 20 hyperventilations on the first cycle and on every cycle after that, 6. The less the better. Also, hyperventilating assists at making your body more suceptible to fainting, therefore you need to closely listen to the sensations of your body for over-doing it. The first cycle requires more hyperventilating than the rest of the cycles to allow you to hold your breath longer on the first hold until your oxygen levels have depleted to a level that you intend to maintain throughout the exercise. (note: for myself I did about 15 hyperventilations for the first instance, and 3-5 for each cycle after that)

If you find you are becomming dizzier with each cycle after holding your breath, then perform less hyperventilation and this will induce a shorter breath hold, if you cycle when the same level of discomfort occurs.

Step #3: Remember we are trying to maintain as little time as possible with oxygen in the lungs, therefore perform these exhalations and inhalations with focus on haste.

Step #4: Holding your breath, especially on exhale is a little disconcerting and awkward. Just relax and don't push anything. There is no success or failure here, so don't worry about a thing. Don't struggle too much and don't give up. Just find the balance. You will probably find you can hold your breath while exercising for only 8-15 seconds. IMPORTANT: It does not really matter how long you hold your breath for, instead all we are interested in, is maintaining a lower level of oxygen in the blood. You will need to experience a subtle discomfort at the end of each breath-hold, but not much more than that. (note: on the pulse oximeter my SaO2 level would drop to low 70s by the end of my breath hold and during the hyperventilations, would rise to high 70s/low 80s. I could have easily adjusted the range higher similar to the IHT)

Step #5 (same as Step #2 but modified): When finishing step #4 DO NOT take a large inhale, or breathe normally, or hold your breath. You must hyperventilate immediately otherwise the CO2 buildup will become intolerable and you will end up becoming replenished with oxygen to normal levels. You now don't hyperventilate as much as the first time, since you are not just trying to satisfy your body's need to stop the build-up of CO2 and maintain the level of O2. By hyperventilating quickly a few times, you can get rid of the nasty CO2 and only replenish a slight amount of O2.


1. If you have any history or are unaware of blood pressure troubles, heart conditions, etc... your should consult your doctor regarding your trip and intentions, and therefore the same applies to this type of training. The adaptations can thicken your blood, put stress on your heart, increase blood pressue, etc... all of which under normal circumstances your body has other factors to balance out those adaptations, allowing the body to be healthy and generally even healthier than previously. However, maybe there are conditions where this training would be too sudden or stressful.

2. Easy does it! The steps are the model, but you must be aware that your current body condition may require easing into certain things. Instead of performing this for 5min the first few sessions, maybe only do 2-3min and 6 cycles instead. Maybe hyperventilate a little more at first (say 10 times on each cycle) and if you can perform the full exercise a few sessions, then lessen the amount of hyperventilating to the suggested 5-6 times.

3. Hyperventilating can seriously make you faint, so no sudden movements especially in the vertical direction while performing these exercises. Get to know your body and hyperventilating. Only do 6 times the first time you try hyperventilating and do it laying down or sitting safely in the MIDDLE of your bed. Get to know what it feels like. If safely laying down or sitting in the MIDDLE of your bed, keep increasing how many times you hyperventilate, to find when/if you start getting light headed. Under these same conditions practice some breath holding after hypervenitlating. Just until you are uncomfortable to get a sense of your body. If you determine that you feel light headed after 20 hyperventilations then start with 1/4 of the number of times and slowly increase to see when you start feeling a little light headed. After holding your breath while exercising, and suddenly breathing, you will most likely feel a sudden wave of light-headedness. Note how severe it is and back off on the length of the breath-hold as well as derease the hyperventilating. It should be ok to feel a subtle wave of light-headedness. Just be careful. I felt it every time as I was working this out.

4. This practice is considerably stressful on the body overall. Low-oxygen conditions allow the build up of free-radicals, of which I know little about other than anti-oxidants are essential and vitamins to maintain a healthy body under these types of stresses. Take extra vitamin C and eat lots of vegetables and fruits, preferrably organic. This is of utmost importance. You can become very ill if you allow your body to be stressed in this form without adjusting your diet to the new demands. As well the adaptations often have to do with generating haemoglobin, which requires iron, therefore a good source of iron or iron suppliments is important.

Interesting to note, is that the same effect could not be achieved while remaining motionless. But then we need the exercise and it probably induces more adaptation than at rest. Remaining motionless if I hyperventilated as little as possible to allow me to hold my breath longer, the oxygen requirements would be replenished even if I held my breath to very low levels. Since the metabolism is very low at rest, the returning veinous blood was not depleted significantly, therefore the blood could be replenished quite easily.

Thoughts? Questions? Corrections? Mud-slinging? ;)


Hi Tyler,

Can you tell me what your saturations looked like during this as I have been unable to come up with an approach that allows me to do 5mins on 5 mins off for 90mins and in the "on" maintain Sa02 between 70%-80%.....for us mere mortals it's just too draining/fatiguing for that length of time(single session) and over 15-20 consecutive days.


oops - I just reread it and noticed this is only a 30min session of three "on" phases of 5mins. 3 "on" phases is about my limit and doesn't compare to the 9 on my homebuilt unit. Additionally I'm almost through 20 consecutive days, which there is no way I could do using breath hold....this is not a mud slinging attempt as I wish there was a simpler way that worked for the majority of freedivers.

Hey Andy,

For what I was doing, it really was not a struggle at all and does not require any significant tolerance if one juggles the variables. It went something like this:

Jogging on the spot for a minute, SaO2=95% breathing normally. Not an all out max jog but not slow either. I could have easily increased the intensity. Hyperventilated 15-20 times, exhale, hold breath, SaO2 dropped to < 83% in less than a minute (if I remember correctly), discomfort came at nearly the same time, hyperventilated 5 times, exhale, hold breath, SaO2 bottomed at ~78%, rises to 82%, rapidly about faces and drops to 75% by which time I am beginning to feel discomfort, hyperventilate 4-5 times, exhale, hold breath, and repeated the same, SaO2 would drop to ~70% just after hyperventilating (due to lag in blood supply) then rise to ~78%, then drop rather quickly to ~70%. These cycles would probably take 20seconds in total.

Remember the key is that there is never a hold while the lungs have air in them, other than residual. Every hold is done on an exhale as much as can be ventilated without using special techniques. The inhales are only part of hyperventilation cycles. The CO2 ventilated removes the discomfort, so it should not be difficult to hold until O2 returns to lower end of threshold (if you worked it out with the delay factored in; the actual reading of the oximeter shows you roughly mid way in the drop when you probably feel the need to breath again).

Hope that helps.

ADR said:
...which there is no way I could do using breath hold....this is not a mud slinging attempt as I wish there was a simpler way that worked for the majority of freedivers.


I don't quite follow your reasoning that there is no way you could do this under the conditions you have stated and why you don't think it would work for the majority of freedivers? It seems to me that your understanding of the breath hold cycle is that one is holding their breath in a manner that is extremely strenuous?

The breath hold section is just a cycle to limit the amount of oxygen to the blood, not a breath hold to push one's limits or endure any amount of CO2. Therefore I don't understand where the difficulty factors in?

As well, doing it for 30min or 90min, I don't think would be any more strenuous other than the normal strain of adding another 60min on. And why are you doing 90min anyhow? That seems like huge overkill. What type of exercise(s) are you doing for 90min?


I just completed a 5 min cycle, with extremely moderate jogging, no effort on breath holds, and the results had a consistent range SaO2 of 78%-83%. I just ate earlier, maybe making it that much easier to have a lowered SaO2. I hyperventilated 3 times half the time and 5 times the rest. I could have gone on all day performing that routine, only limited by physical exhaustion that would have set upon me as normal. To clarify the breath holds were not as long as I mentioned in previous posts. They were only 12seconds max. With the odd bit longer after a 5 breath ventilation. Variations in the depth of ventilations based on feeling.

I will try a similar routine but this time with an intense exercise.


Ok now for the intense workout,
I am sweating, feel like coughing up my dinner, but all in the name of science ;). Exercise sprinting on the spot, heart rate 160bpm+. No effort on breath holds, and the results had a consistent range SaO2 of 78%-83%. I hyperventilated 3 times half the time and 5 times the rest. Although I did find I could change the 3 breaths to 1/sec instead of 2/sec. Which was much more comfortable at that rate of exercise I found. Once again, I could have gone on all day performing that routine, only limited by physical exhaustion that would have set upon me as normal. The breath holds were only 6 seconds max.

I doubt anybody would have any difficulty with these routines.


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In the name of science, I tried the breath hold exercise. It works. I only tried one cycle, but got my SpO2 down to 81%. I may go to the gym and try a full set.

In Sport, when the heart rate monitor first came out I heard a story of a coach who remarked to his student "why are you bothering with that thing, it is a waste of time". We all know how popular heart rate monitors are in sport today. I think with more research exercise with different breathing techniques used in conjunction with pulse oximetery will provide a new modality in fitness training. Current research seems to suggest that light exercise whilst brething hypoxic air produces the greatest up-regulation of mitochondrial activity and stimulated human growth hormones to a level that can not be achieved with exercise in ambient (room) air.
I think there could be other, perhaps more pertinent, issues than the upregulation of mitochondrial activity and obtaining increases in Hb during exercise. Most elite athletes have in fact a reduced haematocrit but elevated blood volume. This is necessary to better circulate large cardiac outputs during intense exercise. I think Mb is very important, since Mb increases muscle waste product buffering capacity -> increased aerobic endurance and delay the predominant switch to anaerobiosis.

However, to stimulate significant increases in [Mb] requires one to reach quite an elevated level of hypoxemia (hypoxia of the blood), since Mb does not desaturate very well at all, unlike Hb. Indeed, one would have to be quite unconscious or very "high" indeed to induce significant growth. Most studies of altitude acclimatization show no such increases. This could be achieved, however, through the application of apnea + cold (periphery) + exercise.

Taking it to the extreme, it could be argued that without a dive response (DR) the muscles aren't effectively able to use the oxygen bound to Mb. This is probably the reason why the DR even exists in the first place, to use otherwise unavailbale MbO2 stores.

Food for thought
Tyler's method raises an interesting question that I have wondered about since this thread began. Is there a difference between the type and magnitude of adaptations one would expect from: (1) moderate levels of oxygen desaturation maintained over longer intervals, verses (2) more intense desaturation but maintained over shorter intervals?

Tyler's method seems to be a way of maintaining desaturation in low 80s high 70s for several minutes while exercising. While, the IHT program that Mark Harris followed, it seemed like he reached low 80s desaturation for only 20-30 seconds. At the further extreme, most trained freedivers could reach, with empty lung statics, saturation in the 60s and even 50s, but only for a short period.

So do we think it's better to reach really low saturation (60s and 50s) for short interval repeats, or more moderate desaturation maintained for longer periods? Or, perhaps a combination of both.
I believe more profound hypoxia for shorter periods is better. The reason is that studies have shown that HIF-1 alpha levels increase exponentially during profound hypoxia, even if the desaturation only lasts for seconds. HIF-1 alpha is the hormonal 'trigger' for hypoxia adaptations. Further, we already known that hypoxia/reoxygenation cycles are more important than continuous hypoxia.
efattah said:
I believe more profound hypoxia for shorter periods is better. The reason is that studies have shown that HIF-1 alpha levels increase exponentially during profound hypoxia, even if the desaturation only lasts for seconds. HIF-1 alpha is the hormonal 'trigger' for hypoxia adaptations. Further, we already known that hypoxia/reoxygenation cycles are more important than continuous hypoxia.
Then apnea is the best way to train?

One more quick follow up:

Today I attempted to see, while performing medium exercise, what would be the lowest range I could stabilize my SaO2 using the technique I described recently. I managed to hold it in the 60%-70% range for a 5 minute exercise, without any significant difference in effort in terms of the breath-hold. However, as much effort as I was to induce on top of that via attempts to hold my breath longer and ventilate more, only caused me great discomfort and loss of stability in the range, including feeling on the edge of fainting. I performed this twice in seperate session attempts to get lower, but to no avail. Although I did not increase the exercise intensity.


Thanks to Tyler for a great idea. This is MUCH less uncomfortable than empty lung statics or apnea walking.

I tried this last night and it seems to work for me. Using fast walking as the exercise, I found I could maintain the process with a 20 second hold and 3-4 hyperventilations. I don't have an oxymeter, but the feeling I was getting was the same as at the end of half lung apnea walks, which I'm pretty sure is low o2. The difference is the feeling (and probably the o2 saturation) is more intense but much shorter in apnea walking.
Free time is often a limiting factor; I don't have a free hour a night to devote to this. Just an idea, would it be useful to combine this technque with a series of very low saturation events? For example, 15 mintes of the above with another 5 minutes of half lung apnea walks? That way, you get both and don't spend quite as much time.

Hey Connor,

Thanks for the acknowledgment! I as well found it was quite easy for the legs to produce feelings in the same vein as when I would do apnea walks. As well the sensation increased while I did the more extreme 60%-70% exercise and also seperately increasing the exercise intensity did the same. Somebody else mentioned the 1 hour+ routine, however my expectation is that the largest benefit would come somewhere between 15-30min of performing this 3 times a week. 15min might be a 4min holding cycle with 1min regular exercise cycle repeated 3 times, with increased intensity and the lower range of SaO2.

Of course all speculation but relating to experiences with other exercise stress adaptations such as incurred from weight lifting, hiking and jogging for me personally.

Yet, I am not suggesting that diversifying by combining with another form of apnea, would not be a potential max benefit. I would expect that to be best.

tylerz said:
It seems to me that your understanding of the breath hold cycle is that one is holding their breath in a manner that is extremely strenuous?


When I said "which there is no way I could do using breath hold" I wasn't meaning the breath hold itself was the hard part but rather using a breath hold technique to do this instead of a hypoxicator is difficult. To clarify what I'm doing (now complete) is a 20 day cycle of 90mins per day(5mins on/5mins off repeats) without exercise. The point I was trying to make is that if you are doing 90mins without exercise (standard Russian style IHT schedule) it is difficult to replicate this using a breathhold approach. The exhausting part about it is the hyperventilation and breathold repetition not the breath hold itself. Ventilating hard to reduce CO2 enough for that period of time is very exhausting....for me anyhow :) If you can do this session without effort then that's great, all I was saying is that I can't (20 days in a row) and I doubt most people could.

While questioning the value of 90min sessions and 20 consecutive days of sessions is fair it's not very relevant when what I was doing was comparing my sessions with the hypoxicator to equivalent sessions without one using breath hold. If someone WITH a pulse oximeter wants to try and replicate it then I'd be really keen to hear their results. 20 consecutive days of sessions on the hypoxicator sitting on the coach was actually really draining and I'm glad it's over :) .....now for the follow up blood work!!

Hey Andy,

Thanks for clarifying!

Your statement regarding, ventilating CO2 being difficult for a broken up 45min, is possible since we all have differing abilities to ventilate CO2. But more important is your statement of not performing any physical activity, which as I stated as well, I could not get this technique to work under those conditions. That was the first thing I attempted. ;)

I was responding to what seemed like your interest in finding a suitable technique towards adaptation for people in general, which I (mistakenly?) gathered from your statements, "...as I wish there was a simpler way that worked for the majority of freedivers." and "...for us mere mortals it's just too draining/fatiguing for that length of time(single session) and over 15-20 consecutive days." Therefore my response was targetted and attempting to be "relevant" not only towards you but to the general audience of "the majority of freedivers" and "mere mortals" as well, with that as the focus.

Can't wait to see your blood results!

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Thanks for the explanation and I think your exercise approach is great and perhaps better for the majority of freedivers if it does actually produce adaptations, as IHT equipment and time commitments are a significant barrier to most. It will be the next thing I'll try if my coach potato approach shows up as being a red herring.

Your comments on CO2 venting are interesting as I hadn't thought of the potential double negative you have highlighted. My CO2 tolerance despite trying every training mechanism in the book continues to be terrible and this coupled with a potentially poor ability to vent CO2 could explain some training observations I've made. Can you shed any more light on "differing abilities to ventilate CO2"?


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