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Effects of CO2 tolerance training

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Oz freediver
Oct 3, 2001
Hi All,

I'm wondering what if any are the Physiological training effects of doing CO2 tables?
How is your CO2 tolerance actually increased ?

I'm sure that a big part of it is mental, and getting used to handling more contractions, and staying more relaxed during them.

Eric Fattah mentioned that straight after doing an hour or so of CO2 tables that the bicarbonate/ buffers in your blood get extremely elevated. Is this part of the training effect ?
Does your body then learn to release the bicarbonate/ buffers earlier then before on a normal static, or are your resting levels higher ? Does this then delay contractions ?

Also does this have anything to do with when doing a normal static series that your contractions come later after a couple of warm ups ?
I realize that the spleen contraction is the important part of the diving reflex and will give you more available blood oxygen after doing a few warmups. Wondering if the warm ups also give you better CO2 tolerance for the last static ?
If not then doing exhale statics to warm up should have the same effect. ie Spleen contraction but little CO2 build up.

I think you're right on -- exhale statics give you splenic contraction, but not much CO2 tolerance. After inhale statics, your bicarbonate level will be elevated (which is in part why contractions come later and later), and then, once you stop the statics, your kidneys will gradually re-assimilate the bicarbonate over the next 48 hours. However, I would guess that doing a CO2 table every 48 hours might produce a prolonged elevation of bicarbonate levels.

However, even though it takes 48 hours for the kidneys to renormalize the bicarbonate level, most of the reassimilation happens in the first 24 hours. That is why, if I'm going diving, I do CO2 tables the day before. I also do one (dry) exhale static to samba (the day before), but I don't necessarily recommend doing that.

Eric Fattah
BC, Canada
Thanks Eric,

that would partly explain why I noticed an immediate effect after only doing CO2 tables for a short time. That would give another good reason to practice statics daily specially before a comp, or alternate every day between doing tables and max statics.

Wonder if there is any long term training effect ie months to years of doing CO2 tables ?
Or would it go away quite quickly after stopping for only a few weeks ?

It would seem like from what you said the most benefit would be gained from daily or more intense training over a shorter period of time, ie 1 or 2 months in a row.

I know for me personally I noticed an increase in my diving reflex/ overall abilities within a few weeks of a lot of deep diving- just before a competition. I actually didn’t get a chance to practice statics much, then after a couple of weeks of deep diving, my statics were better then before ??
That wasn't so much to do with CO2 tolerance but may be another reason to do more intense training before a comp. Of course you have to eat right and get enough sleep to recover. :)

A beginner question


What exactly is the benefit of CO2-tolerance training?
Does it only extend the length of time you feel comfortable in the beginning of a static, before contractions etc.? Or does it also increase your max breath-hold time? If the latter is true, how does this happen?
Does anyone have a good guide to increasing your CO2 tolerance, besides doing dry statics and things like walking apnea.
Hi Cheese, hey cool logon name :)

CO2-tolerance training can help delay contractions, and/or make them smaller & easier to deal with. This should make it easier to relax on your static conserve O2 and can extend your max static.

If look on the freediver website there are tables you can download. CO2 tables are usually a series of statics, same length but rests get shorter & shorter. The table that I use is a bit shorter then the one on the UK site. A 2 minute table would look like :- 2 minute Static, 2 minute rest, 2 min Static, 1 min rest, 2 min static, 30 sec rest, 2 min static, 15 sec rest, 2 min static.

Do to CO2 tolerance training with things like apnea walking or dynamics you want to keep the rests very small. ie do repetitive 25m dynamics with 15-30 second in between. The idea is your body recovers some of it's O2 but doesn't get enough time to reduce the high CO2 levels. You will usually get a lot of contractions but don't get very hypoxic, depends on what you do of course. So in general you do statics or dynamics, much less then normal, but keep the rests short.

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Thanx walrus. I already use those tables and find them a very good tool for improving my statics.
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