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CO2 Tolerance training for spearos? Y or N?

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Just visiting...
Aug 26, 2001
Hey everyone,

Just wanted to post my concerns on people who train for spearfishing by doing statics and other CO2 tolerance activities. (not that all statics are CO2 tolerance based)

I STRONGLY believe that CO2 tolerance training should NEVER be performed as a spearfisher. I invite everyone to bring in their thoughts/opinions in on this because I think it is a huge and very important issue to be considered.


My thoughts are as follows:

- Our "natural" warning sign that heeds us to breath comes from the receptors in our body that detect high levels of CO2. O2 detection is only present in certain disorders(pulmonary, cardiac).

- CO2 tolerance training, IMO, alters the intensity of our warning signs and/or raises the threshold of our CO2 detection.


SWB can occur at any depth. There are many opinions as to why SWB occurs, but the simple fact is that your body's O2 has dropped below a specific partial pressure that is the threshold in maintaining consciousness. Your warning signs that signal low O2 is just an estimate. I believe your body "assumes" you have a certain level of O2 just by the amount of CO2 detected. Obviously, your body has been given "margins" for error, so it assumes you have less O2 than you actually do.

The problem I see is that CO2 tolerance training is narrowing that margin of error. If you have built up an increased tolerance to accumulated CO2, the amount of O2 left in your system should be lower than what the body will now assume.

I know "contractions" and lung burning are painful and uncomfortable, but these are just our body's natural mechanisms for keeping us alive. I think the more you focus on altering these mechanisms, the more you are setting yourself up for a serious problem.

I could go on for quite a bit on this, but I'll stop here to see what everyone has to say.

Im no scientist by any means but what you are saying makes sense to me...

a good freediver isnt necissarily a good spearo and vice-versa. Like Bill Delabar told me on my first bluewater hunt..."Anyone can learn to dive, but not everyone can learn to hunt..."
that sounded a litle off...no offense to you competitive freedivers. What you do is unbelievable...
IMO, when freedive spearfishing you are participating/training in a CO2 tolerance activity. Unless of course you strive to never stay down longer or go deeper than you did the very 1st time you ever entered the water, then maybe you are not CO2 tolerance training. As far as making a spearfisherman more susceptible to blacking out by doing alternative breathhold activities, maybe just the opposite is true. I've seen 3 spearfisherman black out and had 1 friend die, none of whom had ever done any training other than diving. I've yet to see a trained freediver blackout while spearfishing.

Scott T.
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Andrsn, youre not the only one with that concern.
I'm surprised this issue hasn't been raised and discussed in these forums befre, not to my knowledge at least.
I have also been questioning the need for CO2 tolerance for constant weight competition dives. Maybe it would reduce the likelyhood of CO2 narcosis on very deep dives, but for dives of more modest depths the fact that (for me atleast) it is easy to push to the point of samba or blackout with little discomfort (even with a gentle breathup) makes me wonder the point of CO2 tables.

Something slightly off the point: why, if pCO2 is also increasing at depth(along with pO2), is the need to breath suppressed? Does not the relitive preportion of O2/CO2 stay the same as we decend? Also, by the time we are just about to break the surface on 30m dive, aren't the gass levels within our system the same as if we were at the end of a 60m dynamic? why does it feel easier to overdo it on a CW dive as apposed to a dynamic? Something I've never understood properly. cheers
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kook, welcome and thanks for your comments. I think there's a lot of information out there that I'd like to get cleared up in my head, too. :)

Scott, I think there's a thought outside the box that you may want to ponder. Losing a friend to SWB is tragic, I'm sorry you've had to experience this. I too have dealt with these issues personally and this is why I've been researching this stuff so intensely.

... Learning to cope with CO2 is not the only way to develop longer bottom times. I never push myself and never will. I never want to be coming up to the surface w/ no reserves left in me. I don't think it's safe for the recreative spearo. My training only consists of slowing myself down in dynamic exercises to where I cover more distance w/ less effort and less stress on my lungs. This has pushed me into a whole new world when I'm out in the water now. And, I don't feel like I'm jeapordizing my safety with how I'm doing it.

The reason why I started this thread was because I know there are others out there, both freedivers and breathhold spearos, that can add to this by either agreeing/supporting or disagreeing. But, if disagreeing, hopefully with just cause and supportive facts because I have put a few years into these thoughts of mine.

Thanks Andy nice & usefull thread....

I have something to ask. When you dive down how do you know when you should leave the bottom?. I mean do you surface at the first signal that comes from brain or you wait for secon, third etc...

I found that when i dive deeper up to 15 meter my brain send the give up signal later may be i am more concentrated and move less effortlessly but when i saw the fish i loose the control of heart beat and consume more air reserve. Anyway what homework do you suggest to do for new spero in order to increase bottom time?
This is a good one. I can see where both Anderson and Scott are coming from. Having experienced one blackout myself (one too many) and just last week having a friend of mine realate a samba experience I have mixed feelings. My blackout happened after the deepest dive I ever attempted. I am not sure of how deep but after doing a 100 foot then a 120, I can say that this one was around 140 feet. I hit the surface, took one breath then went down shaking. My spotter quickly grabbed me and pulled my head out of the water. The lights came back on immediately. My friend is an awesome diver having average bottom times of 2-2:30 while spearfishing. He said that after a 50 foot dive, he was creating lots of commotion on the bottom to bring fish in. Too much movement by his own admission. After about a minute he decided to head up. 10 feet off the bottom an Uku (jobfish) comes rocketing in straight at him. He levels off and fires. The fish wasn't big, maybe 5 pounds but started fighting like crazy. The diver had no reel or floatline so he tried to fight the fish up. Not really paying attention he kicked casually only to see the surface 30 feet away. At this point he says he started getting worried and started kicking hard. Progress was made pretty fast but he said he started convulsing underwater. Next thing he knows he is looking at the sky still shaking. His girlfriend and dive partner (lucky guy) is swimming toward him thinking he is playing around. He calls for her help but his speech is slurred and not coherent. He recovers from the samba, finds his gun and goes home a little more educated.

These are two completely different dives with similar results. My dive was a pure freedive with no gun and a touch and go at the bottom. My friend's was a hunting situation where a lot of O2 was burned on the bottom and extra effort was needed to haul a fish up. Would CO2 training have helped in either situation? I am not sure. Both dives were probably about the same in terms of bottom time (2:00), and significnat O2 was burned on ascent. As far as static times go, a 2 minute hold is nothing for both of us but given the situation it was much to long. Again I don't know if CO2 training would have helped.

Since that incident I am a much more careful diver. I received a D3 as a gift and it has really helped. I set the alarm to go off at 1:30 just to let me know how long I am down. There are dives where after a minute under my lungs are burning and I head up. There are other times that the alarm goes off and I feel no burn or have not had any breathing contractions yet so I stay down a little while longer. The alarm tells me that I should start thinking about heading up soon. It is not an indicator of when I should head up. My body tells me when I should head up regadless of how short a bottom time I have had. The depth guage lets me know how deep I am and I have a feel of how long and how much O2 I am going to burn on the way up. I am not sure if I want to alter my body's CO2 tollerance through tollerance training. Yes my CO2 tollerance will increase the more I dive but conversely my O2 consumption should drop as well. Again this is an excellent subject and I really want to hear what other divers (apnea and spearo) have to say.


Glad to see you're still with us! Please be careful. Congrats on the depth though.

Scott T.
Thanks for the thread Andersn,

I've never experienced anything even close to blackout or samba, but I've lost a friend this summer, who I unfortunately introduced to spearfishing competitions 2 seasons ago. There's still a photo on my site. He drowned due to not really clear reasons while training for one of our International events.
He told me this summer that he's working hard to increase his statics. Several days vefore the accident he did a dry static of over 5'30". Maybe I am absolutely wrong here, but I think that his increased confidence in his own abilities and his amazing drive contributed for the tragic events.
I've always shared with him and his dive buddy what many veterans consider a safety formula (which is probably true only for the Black sea) - If you don't see a fish after 40-50 seconds at the bottom, it's dangerous and pointless to stay there. I haven't followed this advice very close though - at the end of the competitions season I was doing bottom times of 2:30 to over 3 minutes. And maybe that contributed to the incident I personally had a year go.
So if you ask me now - I am strongly against anything that pushes your body to the limits. Scott is right that we are actually training while spearfishing, but that is a normal, slow and natural process I think. It has nothing to do with the heavy training you do for competitions.


P.S. Scott, how do you train for competitions?
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Give and take...

Brad, I would imagine that maybe a better tolerance to CO2 may relieve some of the anxiety that would occur when your body starts giving off all these signals. I can see how this would be fine for Freediving, but I can't really see it helping for spearos. If your friend had more tolerance, he may have been down on the bottom longer before he felt the urge to go up, but I would deduce that his O2 would have been exhausted a bit deeper on his return to the surface. :confused:

Like I said, I welcome ALL thoughts and opinions because I can't see a better way than to have your ideas crosschecked by people who are actually experiencing both sides of this.

Yeah, it's good to be alive. An experience like that puts things more in perspective.

I am not sure at what depth my friend started to Samba but on a 50 foot dive he must have used a lot of energy fighting the fish. I haven't been able to try that pool training regime you sent. I am not sure if any of the local pools would let me in with my blades.

Sorry to hear about your friend. It is definitely a tragedy when someone dies from SWB. My dive partner and I both agree with your friends. If on the bottom (actually laying or hiding on the bottom) for a minute and the fish don't appear or aren't coming in, we usually abort and head up. If the fish are still around we will breathe up and try again. On our last trip this idea worked like a charm. I was working some Mu (porgy) at around 45-50 feet. One in praticular approached twice at the end of my hold. I made three dives and on the third dive he came straight in to gun range after a few seconds on the bottom. I guess not getting aggressive toward it and constantly playing with the bottom made him curious.

My thoughts on this remind me of a pastor friend’s story. Don’t worry I’m not pushing any religion here. Anyway he said he had this atheist who came to him several times and argue with him about if there was a God and especially heaven and hell. One day my friend said to him, “If you’re so sure there is no God and heaven and hell, why are you coming here to argue with me”? The Atheist said, “just incase I am wrong! I want to give you ever chance to convince me”.

So Anderson, bring it all on. I would rather be alive than right.

My view, until Anderson shook my world in a concerned PM, was that by pushing the limits of CO2 tolerance, it would give me the ability to react accordingly if something went wrong that caused me to stay longer than planned.

This happened once to me. I became entangled and got scared. In the slight losing it I accidentally let some air out. Luckily I got untangled and I was relieved to see my buddy directly above me paying close attention on my ascent. I let him do all the diving for the next 30 minutes until I calmed down and was able to short through what had happened and what I should have done different.

I like Brad’s idea about the watch alarm and Anderson, didn’t you say once you used an alarm too. Also what do you mean by slowing yourself down with dynamic exercises? What exercises? I thought apnea walking would fit into this category nicely since its less intense than dynamic swimming.
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I understand that blood O2 tracks the partial pressure of lung O2 and the deeper you are, the more O2 you can use. If CO2 follows the same rules of exchange, the deeper you are, the more CO2 stays in the blood. Why then is the need to breath near normal at 10 meters and absent, for me, at 20 meters? I've even tried a few relaxed 4+ minute dives to 25 meters and have been able to feel the 'urge' kick in about 15 meters. Part of the mammalian reflex, I guess.
It is very important to understand this because we lose too many divers this way. As you progress, there comes a depth where there is a big change in the way the body works and it's very easy to lose track of time. Maybe that's why some of the best are using alarms, they received another kind of warning.
Hi Guy's

I think what wishbone has said hit the nail on the head. If I have seen nothing interesting after 40 to 50 seconds, I'm usually outta there. I do not understand enough to know whether training allows your body to ignore / tolerate the warning signs, or whether training allows your body to last longer in a 'safe-zone' until those warning signs begin.
So as I train, am I staying down longer because my body is better conditioned, and when I need air it will tell me...or am I staying down longer because my body needs air, but is better conditioned in hiding the signs ?? I do'nt know the answer to this yet, but with a 5 year old son waiting on shore, I am not searching too hard for it ! What I do know, is that my 'longest' dives have been in a zone which has not come from concious training, but from a situation where I am mentally at peace with everything...the day, the conditions, myself, my loved ones,those days where the silence and 'world' of the freedive just seems to be perfect. It's pie in the sky stuff maybe, but I would rather spend my time trying to understand what gets me into that zone, than learning to tolerate an urge to breathe. This thread has got me to think about my training from scratch, great one Anderson, awesome !
Maybe I'll have to make public my training routine. I didn't know how many people were conscious of this issue. :)

Bill, great points. I'm wondering if it would be possible to take vitals in a compression chamber? :confused: It just seems that there could be a lot more research done on this.

Don, I think the goals for apnea walking are to push through the urge to breath. The goals for dynamic(for me) is to cover the same distance with less effort. That training you know of has you come up at the first sign of discomfort, so minimal CO2 effects exists compared to CO2 tol training. And yes, I had my Stinger set at 1:30, but it's batteries are dead and it now costs over $70 to get them replaced(incl shipping). The alarm started to scare me because sometimes I'd wait for it instead of listening to my body. I'm glad I haven't replaced my batteries. :)

Bluecape, I think you've said it perfectly. I think we all have the same idea as to what's going on, we've just all come to it from different directions.
I still haven't made up my mind on this subject since I really like Co2 training for hockey and freediving, but also like to spearfish when the lakes are clear enough for it.

Anderson, I have been using the program you sent me for a couple of months now, although I have been out of the pool for the past two weeks due to an ear infection.:( I have to say that your program is much more enjoyable than Co2 training, but I only do it two days a week and switch off with Co2 training on other days to "cover all the bases".

I find that I never really push myself to the limits of anything since I have too much to live for. I know that I could go deeper, and longer, than I do but I come up early on both. IF I could get a few regular training partners together, and make a diver retrieval system, I might be tempted to push things a little further. Without all of those things in place I have no desire to.

Hi Anderson,

Great thread, a subject of real importance. I too like my safety margin and am very leary of increasing performance at the price of decreased reserves. I've tried to tailor my workouts toward increasing 02 tolerance, aerobic ability and lactic acid tolerance, but almost anything I know to do, dynamics, apnea walking, or just diving must, by their nature, increase CO2 tolerance. The only thing I've found that really makes a big difference and doesn't seem to reduce my margin is doing a few negative dives as a warm up and a breathup that slows my heart beat way down, complements of a PF clinic. I'd be real interested in what you are doing Anderson. If it results in things like your rig diving trip I'm REAL interested.

I read a lot of EricF's posts on related subjects (there are a whole bunch). If I understand him correctly, C02 tolerance reduction is good in the context of a doing several types of training. It still concerns me. EricF how about your opinion?

Thanks for the thread


After I won the Nationals in 2001 and qualified for the 2002 USA World Team, I decided I needed to become a better diver. I wanted to be the diver I should have been in the 1st place to be National Champion (at the time I considered myself a very mediocre diver in the grand scheme of things). So, I started apnea training for the first time in my career. I trained hard 3-4 days a week with an Italian freediver named Peppo Biscarini. We did statics, dynamics, freestyle swimming, kicking, under/overs, set training on reps, kicking no fins, with fins, underwater breast stroke, and just about anything and everything you could do to improve freediving abilities. I saw my abilities in the pool increase dramatically but there was a problem, my diving abilities in the ocean were staying the same. Then I went to Brazil and dove better in very shitty conditions than I do here in warm, clear Florida waters so I started to wonder why this was. Then I figured it out. In Brazil I had no anticipation, I didn't know where I was and most of the time I didn't care. My mind would relax and pretty much go to sleep until I hit bottom and then I'd start to hunt. So, when I came back to Florida I tried to reproduce that same mental state and found I was able to do it and it changed my diving ability by more than I had ever seen before. I’ve since realized that diving for me seems to be more mental than physical. So, now all I do is dive every weekend and play underwater hockey once a week. In less than a year I've gone from being a 60 foot diver to hunting upwards of 90 feet comfortably. At this point, I am ready to re-investigate apnea training and am registered for the Performance Freediving clinic in 2 weeks. I'll let everybody know how it turns out. BTW, I've yet to black out or samba yet. Maybe in 2 weeks.

And Brad,

What the hell was your buddy doing hunting in 50 ft with no line or reel. I don't care how good you are that’s dangerous. What would happen if that 100 Ulua came through and he shot it. Kick him in the ass for me!

Scott T.
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