"skip breathing" and tri-mix question

[freedivernd]

I haven't done any homework on this but was wondering if someone here could answer a question for me. I came across something while reading today about dangers when "skip breathing" while using mixed gas at depth. I don't think I've ever heard of that - can someone explain. I notice when I scuba dive that, probably due to all the free diving I do, I catch myself holding my breath all the time. Is that what they were referring too as far as "skip breathing"?<br><br>Fred

[nomads]

Fred, My understanding of skip breathing is that it is a technique of holding ones breath unnaturally to possibly get better air consumption with scuba. It seems to me a number of problems could arise particularily co2. There are a lot of better ways to increase air consumption than skip breathing. I don't know how this would apply to freediving. I've only read about skip breathing in the context of scuba. Paul

[tbrown]

That is exactly what skip breathing is, holding your breath while scuba diving. There are 2 problems with doing this. The first is that you may ascend with your breath held and suffer an overexpansion injury. The second problem is that eventually you will have an increase in your CO2 levels, which can lead to an actual increase in breathing rate, which will make you use even more air than breathing normally. You can also get toxic effects from CO2 levels being too high. That is why people that skip breathe report headaches and sometimes nausea upon surfacing... higher CO2. I believe, and this part I'm not sure of so take it with a grain of salt, that it is possible to get toxic effects from CO2, which when combined with deep profiles, could be amplified on ascent. Short of shallow water blackout except with CO2 instead of O2. But then again that is just speculation as I am not a tech diver. At least not yet. I would think that in your case, the effects might be less than for the average diver (with your higher tolerance of CO2 due to freediving), but I don't think that a higher tolerance would provide complete immunity.

[wazeediver]

May I just add one little tid bit

Co2 excess (hypercapnia) increases brain blood flow,and that increases the "dose" of oxygen to the brain.

Just my 2 cents

Al

[beeger]

CO2 retention has been shown to increase susceptibility to nitrogen narcosis.

[freedivernd]

Another thing.. after too long of a holiday break I was back in the water and did a 90 yd underwater swim w/fins - my legs got the lactic acid hit before my lungs gave out but I still ended up with one splitting headache for the rest of the day. Apparently it's easy to lose some of the co2 tolerance.

Fred

[wazeediver]

Fred
Where can I find info on " lactic acid hit"

Thanks
Al

[freedivernd]

Al,
I'll try to find some specific info on it for you and will post links here when I find them. I just know it as a real burn in my leg muscles, always the last stretch before I surface from a good, near my limits, dynamic (swimming while holding my breath). I should learn more about it too as it's a real pain.

Fred

[freedivernd]

I cut and copied this from a post by E.Fattah, Canadian superman of freediving... I don't think he'll mind the reprint. Also, here's a link that has good info on the ins and outs of lactic acid:

I thought the following was interesting read so am posting it in it's entirety. There were lots of references to lactic acid when I did a search at deeperblue in the "articles" section and a few references to them in the "forums" section.

The following was in reference to a "coast and kick" style of diving.

Fred

The dreaded leg fatigue

What you are describing is not deliberately stopping, but stopping because you have no choice. This is very common, especially during deep dives, especially in cold water. In July 2001, when I started diving over 70m in the cold vancouver water, the leg problems started hitting me. I would need to stop several times on the ascent; I simply couldn't kick anymore. The problems gets worse and worse with depth & cold, because the blood gets sucked out of the legs during the blood shift, and the deeper you go, the longer you sink. This culminated in the worst nightmare of my freediving career, when I nearly died during the 88m dive (!) I had started sinking at 30m. I filled my mouth at 35m, and sank into the 5C water with my 2mm orca suit. By the time I reached 88m, had been sinking for 58 seconds (58m @ 1m/s), and the narcosis was extremely severe. My friend Peter was waiting for me at 25m. But, when I turned around, my legs became extremely tired after the FIRST monofin stroke! There was no blood in my legs!! My arms were numb. I managed to kick to about 68m, then I stopped; my whole body was weak and I was overwhelmed with narcosis. After a few seconds I started kicking again, until I reached 53m: at 53m it was totally black (out of range of the bottom light). My whole body was so weak I could not move any muscle. My arms were too weak to grab the line. There was no weight belt to ditch. My mind was in a strange dream land. I forgot about everything. I couldn't move. I was so cold. There was one thought in my mind only; Peter is at 25m waiting for me, but this is almost 30m away. I'm going to die now, I thought. I started sinking again, into the blackness, unable to move. Then, a contraction woke me up. I suddenly realized I was sinking into death, when I decided to try kicking again. I thought, try again, maybe the legs will move, and they did move, but it was pain & lactic acid. I managed maybe 5 strokes before I stopped again, now fighting for my life. A few more strokes, another rest, and another rest, and another. Eventually I saw Peter in front of me. I wasn't sure who he was or what he was doing there, but something told me that this was a good sign. I stopped in front of him for several seconds, as the clock passed 3'00. I eventually made it to the surface, clean, and I raised my arm in triumph--not because I made the depth, but because I survived.

That was, of course, the last time I dove deep in Vancouver without scuba divers or a DRUM system to save my life. That was July 27, 2001, and I have not even tried to break the depth since then. Instead, I spent the whole year practicing to 70m, trying to make 70m without any narcosis or leg problems.

I discovered many things. The main problems were caused by:
1. Extremely tight orca wetsuit sucked the blood out of my legs
2. Insufficient glycogen stores
3. Accumulated lactic acid from the previous day of diving
4. Improper warm-up routine; I didn't move my legs at all in my warm up.
5. Diving too heavy; this resulted in too much effort to get back up
6. Wrong monofin style; relying too much on the quadriceps
7. Lack of any deep warm ups didn't provide any narcotic preconditioning

#4 is the most important. You can control the blood flow to the legs, and the degree of blood shift out of the legs, by controlling your warm up. However, if you have trained properly, you should have huge stores of high energy phosphates in your legs, and in that case, you don't want much blood flowing to your legs, because the more blood flows to your legs, the more oxygen your legs consume.

Having a higher proportion of fast-twitch muscle fibers will drastically improve your leg power in the deep phase, because the fast-twitch fibers don't need oxygen, so for them it doesn't matter if there is no blood in your legs.

There were other issues too, but those are the main ones.

Eric Fattah
BC, Canada

[wazeediver]

Thanks fred

the more I read,the less I know...........

Al