CO2 Training revised

I have noticed I get two kinds of contractions--a lighter kind that is related to high CO2 levels, and a 'deeper' one that is closely related to dive response. The lighter kind, with CO2 training, became something I hardly even notice, and from a 'safety' perspective I don't consider them critically important. The deeper ones are going to happen to me when dive response starts happening very strongly, which can be if I am truly below normal O2 sat, or if I am swimming and conditions are right (some combination of cold water, flowing water, relaxation depth). Deep contractions while swimming can and do start when I still have loads of O2 left, so they are not always a bad thing from a safety perspective. I honestly don't consider 'contractions' to be a very good safety signal, or at least they are an extraordinarily conservative signal.

For me, very strong dive response also means I am going to be paying a big lactic penalty on the dive if I have to swim a long way to the surface, and it can also make it harder for me to see and hunt, and if I am wracked with huge contractions, it will also be hard to concentrate on fishing. In competition, I have a different mental focus and level of relaxation so contractions whether big or small are less of a bother. Honestly, the big ones feel kind of good but because of the lactic acid build-up that accompanies them there is a lot of muscle pain.

Not enough data for a detailed reply, but here are some thoughts.


Everybody's different on contractions, but strong ones that come on with little build up are often associated with some degree of hyperventilation. might be worth checking your breathup.

FRC is usually effective at reducing the severity of contractions, at least early in the dive. Try about 1/4 inhale and see if that results in less severe contractions. For me, at about 60 percent inhale, contractions used to come earlier, but much lighter than full lung and build up move slowly. After several years of doing pretty much all FRC, contraction come maybe a bit later than they used to full lung, but still start very low and build slowly. Dives are longer and more comfortable.

Since everybody is different, you need to identify why you are getting strong contractions to start with and a general training approach that works. Once there, fine tune it to your body.

Marciano said:

No Breath -up, I posted because my case is quite from everything that I have seen. Even if do lot's of warm up, they stay the same.
I just want to have more relaxed dives.
I think something genetic or biological gives me this hyper sensitivity to CO2. That is why I'm searching for alternative methods of training.
Normal one didn't worked, FRC delays a bit and give lighter contractions, but on full inhale they are really strong.

Click to expand...

I think heavy CO2 training helped with my contractions, not really sure. I have been mostly spearing and doing line dives recently but for CO2 training, any kind of dynamic apnea exercise with a very short rest interval or controlled number of recovery breaths, done for at least 20 mins per session, 3-4 times a week, is good and will give you gains in CO2 tolerance within 4-6 weeks. If you are an experienced diver already in pretty good shape, I don't really think you will get much out of static CO2 tables.

The deeper contractions (real dive response) I get do not seem to respond to CO2 training. I noticed that with training my tolerance to CO2 narcosis (that foggy/dizzy feeling) and CO2 headache went up noticeably. Those effects are probably only going to be noticed by aggressive serial divers/spearfishermen.

Like I said, I really wouldn't worry about the contractions if you are training/diving for performance and have proper safety. If you are worried about hypoxia, start experimenting with a pulse oxy meter. By using one of those (and doing countless tables and exercises) I began to realize that the very strong contractions are part of my dive response. In my case, fully warmed-up, doing dry statics, they may not come for at least 4-5 minutes (although I may get small contractions sooner), until my O2 sat is reading in the eighties (medically this would be considered very hypoxic although I am still at least a couple minutes away from samba). However, on full lung facial immersion, no warm-up, in very cold water, I will experience those type of contractions (and significant bradycardia/vasoconstriction) sometimes within 30-40 seconds while O2 sat is still at 98%. In a pool, doing DYN, they come usually a little bit past 50M; I just try to relax 'into' them as they are happening. Hard to describe, but with the 'big contractions' that I'm referring to I swear I can almost feel some kind of blood shift happening in my chest.

I have tried learn my body's sensations of actual hypoxia instead of just worrying about contractions. Again though, if you train very aggressive dynamic CO2 type stuff, the contractions you get during a relaxed wet static are not very bothersome (in my case at least).

Anyway, good luck with your training. stay safe.

3 big purge breaths before diving is a fair amount of hyperventilation, especially if they are long. You might try eliminating the purge breaths. That should reduce the severity of contractions, but also reduce your comfortable dive time.

What type of diving are you training for? Competition, spearfishing, general reef crawling, other? Sounds like you have a strong DR and good aquacity. You should be a strong candidate for FRC diving as a normal diving mode if that fits your type of diving. It sure works for me as a reefcrawler/spearo with very poor c02 tolerance. Definately easier longer dives, less severe contractions, and, if Seb is right, safer.

Fair warning, doing FRC all the time takes some getting used to. Among other things, it substantially restricts your depth, at first. Takes a while to get it back.

That's strange, I thought I had replied to this one already...