CO2 tolerance

[Kin]

I found recently my CO2 tolerance increasing rapidly and I have a question mostly medical - physiological in nature about this subject. When increasing the tolerance in carbon dioxide what exactly happens in the body? Blood gets more space to occupy gasses or you just you desensitize the CO2 receptors? I think I read somewhere that elite free divers that train to the limits of their CO2 tolerance often have blood with higher hematocrit levels and storage properties also it is more viscous than an untrained person.

I had the idea (probably false) than when you gain in CO2 tolerance (more space in blood to occupy the extra gases?) automatically you create more space for oxygen in it?
To put it simple: Is there any changes in how much O2 body uses-stores when gaining CO2 tolerance?

Thanks in advance for any answers.

 

[trux]

According to some studies, physiological CO2 tolerance is a myth. I am not sure whether it is right, and certainly not to 100%, but it is true that the ability to stand higher levels of CO2 is much more mental than physiological. And then it is also not so much a question of tolerance of high levels of CO2, but more of a better management of its production (or oxygen consumption management if you want). With some training you learn relaxing better, and may get earlier and stronger diving response, which both then contribute to lower oxygen consumption, and hence also lower CO2 production.

High hematocrit would help stocking more O2, and also more CO2, but since only about 5% of CO2 are bound to hemoglobin, it would not make much difference for the CO2 tolerance. Besides it, you'd really need to train very intensively to increase your hematocrit levels. I just compared mines from two years ago and now, at it did not move at all. Despite doubling my times and distances, and despite frequent trainings, my hematocrit remains pretty average.

So although I consider the claim that physiological CO2 tolerance adaptation does not exist for exaggerated, it is certain that to some extent it is true - most of the higher tolerance is simply mental training, and most of the rest is due to lower consumption (better relaxation, better diving response)

 

[Kin]

So I should take the 1min extra I gained in my breath hold in a week doing CO2 tolerance training mostly as a result of correct mentalism?

 

[trux]

One thing you can be pretty sure of: one week of doing CO2 tables has absolutely no impact on your physiological adaptation, and the less on your hematocrit level

 

[Kin]

Thanks for the explanation.
Anyone that doesn't agree with trux?

 

[cdavis]

Fundamentally, no. In a week, you might see some small adaption in terms of better relaxation, blood shift, that sort of thing, but most of the improvement is surely mental.

When you start training, there is a huge area of "low hanging fruit" where you get better very fast. In the area of C02 tolerance (and most of the rest), most of the "low fruit" is purely mental, just getting used to the feeling.

Connor

 

[efattah]

We know that huge amounts of CO2 tables will increase your blood bicarbonate levels, which are a major buffer of CO2. That's the only major physiological change in my opinion, although it takes a HUGE amount of extreme CO2 tables to accomplish it -- and the effect goes away in as little as 24-48 hours. This is further evidenced by people at altitude (where bicarbonate levels go DOWN), and upon returning to sea level, it only takes about 2 days for their bicarbonate level to return to normal. When their bicarbonate levels are down, they can't hold their breath for more than a few seconds.

On the same light, you can eat baking soda (sodium bicarbonate) or potassium bicarbonate to force your blood bicarbonate up, but this causes diarrhea in most people.

Taking citric acid and/or lemon juice which contains citric acid indirectly increases your blood bicarbonate, but to a much smaller effect.

 

[fpernett]

According to some studies, physiological CO2 tolerance is a myth. I am not sure whether it is right, and certainly not to 100%, but it is true that the ability to stand higher levels of CO2 is much more mental than physiological. And then it is also not so much a question of tolerance of high levels of CO2, but more of a better management of its production (or oxygen consumption management if you want). With some training you learn relaxing better, and may get earlier and stronger diving response, which both then contribute to lower oxygen consumption, and hence also lower CO2 production.

I' ll like to take a look at the studies where CO2 tolerance is considered a myth.
There is a lot of evidence, that if you expose your respiratory center to high levels of CO2 there is a saturation of the neurons and that affect the respiratory drive. The best example is the people suffering of Chronic Obstructive Pulmonary Disease (COPD) they have a high level of CO2, so with the time the respiratory drive is triggered mainly by levels of O2.
There is also an study with freedivers breathing a gas mix with increasing levels of CO2 and the highly trained athletes had a blunt respiratory response to High Levels of CO2.
And for the original question, as I mentioned, CO2 tolerance is due to a blunted response, and that will not affect O2 stores (in my opinion). Elite freedivers use different types of training so it's difficult to say what kind is helping them to increase Hb levels, but I think this more a result of hypoxic training

 

[Kin]

I' ll like to take a look at the studies where CO2 tolerance is considered a myth...............

That would be interesting. I like to see them too.

 

[trux]

I' ll like to take a look at the studies where CO2 tolerance is considered a myth.

If I only could find it again. I know about at least one specific study, and was searching the original reference already once, but cannot locate it. However, besides others, the study has tested several groups of subjects, including non-divers and elite freedivers (if I remember well the original source, Tom Sietas was one of them), slowly increasing the level of CO2 in the inhaled air. The breaking point was practically identical at all groups. Some later discussion (not the original one) about it can be found in this thread: http://forums.deeperblue.com/freediving-science/82096-freediving-leading-sleep-apnea.html

There are also some reasonable arguments against it, and that's why I wrote that I am not sure whether the studies are right or not.

However, I think it is apparent that the increase of the breath-hold time by one minute after a single week of training cannot be attributed to physiological adaptation, and certainly has nothing to do with hematocrit increase.

Another argument supporting the theory that the "CO2 tolerance" is to large extent mental, is the fact that if an experienced freediver comes back to training after a long period of rest (meaning several months or years), he will be often able holding the same time at the first try, as he did in the peak of his previous diving career. I experienced this with several friends, club colleagues, and even myself - I've been apneist and UW rugby player in the 80's, and came back to freediving 20 years later, where at the very first training I equaled my old PB rather easily. If I ever had any physiological adaptation in the 80's it was certainly long gone by then.

And finally the studies about blunted response to hypercapnia observed at divers (not only freedivers) support rather the theory that it is more a learned reaction than physiological adaptation. Some of the studies I reviewed about this topic compared groups of non-divers and divers with diverse level of experience, and although there were differences between non-divers and divers, they did not find any significant differences among the divers with different level of diving experience.

 

[Kin]

On the same light, you can eat baking soda (sodium bicarbonate) or potassium bicarbonate to force your blood bicarbonate up, but this causes diarrhea in most people.

Taking citric acid and/or lemon juice which contains citric acid indirectly increases your blood bicarbonate, but to a much smaller effect.

Interesting (not the diarrhea part) but is it safe to try?

 

[mystiach]

Interesting (not the diarrhea part) but is it safe to try?

If you are an adult with healthy kidneys it's unlikely that it would cause lasting harm. Your bowels would probably let you know of adverse effects long before other potentially serious symptoms come along. However, it is a bad idea to pump a lot of potassium or sodium into your body long term, your renal system won't thank you for it. It has also been suggested that KHCO3 (potassium bicarbonate, and therefore presumably sodium also) is carcinogenic for rats: "The feeding of KHCO(3) resulted in hyperplasia, papillomas and carcinomas of the urinary bladder."

This doc has sourced various articles about sodium bicarbonate toxicity. Hazardous Substances Data Bank, National Library of Medicine, Bethesda, MD. March 2003.

So I guess go for it and let us know eh? I guess chronic diarrhea is one thing that could give you major improvement in breathholding! rofl

 

[titan]

frank pernnet what a really great post but assuming your point of view who many time does the co2 tolerance lasts?!?!? can we make it last longer in a long term way?
I felt contractions comig later with time but I would like to build a whale like fitness in the long run
thank you guys

 

[fpernett]

@ Ivo I have experienced the same, but I don't think a maximal dive is the best way to test your CO2 tolerance. In fact I only train CO2 tolerance to avoid contractions at depth (I'm very prone to lung squeeze). In pool disciplines I don't think in contractions as a bad thing. I believe what you're talking is about the struggle phase in static apnea, where trained divers can hold for longer because they tolerate this phase much better than untrained people, and that is more a psychological adaptation. Natural CO2 tolerance is another story. Apnea time is not a good example of CO2 tolerance because of many factors. Respiratory rate and ventilation with increasing CO2 levels in a blind fashion.
@ Titan The only way, in my opinion, is to keep your training all year long. Even when you're training near to maximal you're training your CO2 tolerance too

 

[Kin]

Forgot to mention that all the CO2 tolerance training all week was FRC only. Not sure if this changes anything.

 

[Lil Dragonfly]

it is a bad idea to pump a lot of potassium or sodium into your body long term, your renal system won't thank you for it.

What if I always drink loads of water with it? Will that prevent the kidney damage?

 

[mystiach]

As I said before, excess sodium or potassium won't do much to a healthy individual short term. The whole point of the renal system is to get rid of the excess. So if you overload that for prolonged periods of time all that happens is that you end up with more K or Na in the body than you are supposed to have and your body is under stress from it.

Of course more water would be better for you and better equip your body to flush out the excess. But high levels of sodium can lead to high blood pressure (and other bad things, check out the link I posted before), that's well documented, and excess KHc03 can definitely lead to some nasties. It can also give you ("infrequently", but I would imagine the studies haven't looked at people scarfing down KHc03 on ceral) hyperkalemia. Hyperkalemia can cause (usually temporary) paralysis of vital organs.

It would also depend on how much you take and what your body can deal with. Also, if you're on any medications they may interact or impair your capacity to deal with high levels of salts, and that could be disastrous. I'd suggest asking a doctor about what levels are safe to take as I have no idea. But if you took it for years at some crazy dose I reckon you'd end up poisoning yourself.