eth727
Guest
I passed the 1 breath swim test for NAUI ADV Rescue Diver but what is the best way to hold my breath longer to pass the DM test?
1 Breath swim for NAUI DM swim test
- Thread starter eth727
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How far and/or how long do you need to hold it for the DM test? How was that different than your Rescue Diver course?
ScubaFeenD
Contributor
So here is what I find works for me (I'm not a DM, but I do do breath hold swims for practice). You need to slow your breathing rate and try to calm down if you can. Then right before you go take a deep breath and go for it. Now here is the tricky part. Hold all of it in and when you start feeling the slightest like you need to take a breath start breathing out at a slow rate every few feet. What you want to achieve is maximal oxygen absorption while preventing hypercapnea (elevated CO2). By holding your breath right to the point you start to feel the desire to breath you are allowing the maximal time for oxygen absorption. Ten, by breathing out you are still allowing oxygen absorption while helping to prevent CO2 buildup. It's the CO2 buildup that drives your desire to breath, so as you let it leave your blood you help to repress the need to take a breath. Everything else is up to your fitness level; the more fit you are, the more efficiently you use O2 and the longer you can function with slightly lowered O@ in the blood).
NOTE!! Do not hyperventilate prior to doing this. You may drop your CO2 level low enough that during the swim you become hypoxic (too little O2) and you could pass out. Just breath naturally.
NOTE!! Do not hyperventilate prior to doing this. You may drop your CO2 level low enough that during the swim you become hypoxic (too little O2) and you could pass out. Just breath naturally.
PM SparticleBrane -- he's got some video of technique for breath-hold swimming. When I copied the model, I did MUCH better.
Mike Boswell
Contributor
Hi Drdrdiver,
This is what I have always done since I was a freediver, but I don't know why the slow exhale works. I always supposed that the slow exhale just relieved the urge to breathe.
The reason you give puzzles me because I would have guessed that the CO2 offgassing would be a function of the partial pressures in the blood and in the alveoli, and those wouldn't change by exhaling - would they?
J receptors are the usual explanation for stretch-induced dyspnea....
In fact, exhaling in the absence of inhaling new gas does nothing about your blood CO2 levels (nor the levels in the lungs). What it does is "fool" your brain into thinking you are breathing, so you can defeat the urge to inhale a little longer. It does work, though.
The biggest trick to doing a long breath-hold swim is to minimize the amount of muscle activity required to get the distance done, while also minimizing the time -- in other words, efficient propulsion. That's what the video I told you to ask for demonstrates.
When I did Fundies, I had HUGE trouble doing a 50 foot breath-hold swim. I thought I would fail the class because of it. When I did Cave 1, I did my 75 foot breath-hold swim, surfaced for one breath, and turned around and did it back again. The difference wasn't fitness, it was efficiency.
The biggest trick to doing a long breath-hold swim is to minimize the amount of muscle activity required to get the distance done, while also minimizing the time -- in other words, efficient propulsion. That's what the video I told you to ask for demonstrates.
When I did Fundies, I had HUGE trouble doing a 50 foot breath-hold swim. I thought I would fail the class because of it. When I did Cave 1, I did my 75 foot breath-hold swim, surfaced for one breath, and turned around and did it back again. The difference wasn't fitness, it was efficiency.
ScubaFeenD
Contributor
First a few disclaimers. 1.) when i said every few feet, i meant horizontally, as I use this technique while doing a subsurface swim. 2.) I have never been taught diving physiology formally (its not part of medical curriculum, at least not until fellowships) so much of this is not based on primary scientific literature but is a hodge-podge of normal physiology and extrapolating based on my understanding of water pressures and diving. 3.) it is a quick and dirty way to explain my method, which may not work for others; it was just a suggestion based on what has worked for me.
That being said, I will explain what I envision happening a little more
You are absolutely right, partial pressures reach equilibrium in the alveoli and blood. However, based on pressure and gravity differences not all of the lung is perfused equally all the time. Im not sure how this would work horizontally in the water, but when i initially thought about it I wasn't too concerned with minutia such as that. As you breathe out slowly some mixing is probably occurring where air in poorly perfused areas is getting to areas of better perfusion, thereby letting more CO2 out of the blood. Additionally, there is communication between chest wall stretch receptors (from what i remember) and the J receptors gsk3 mentioned and the brain that also has some control of breathing. The interplay of this all is how I envisioned it working.
I could be wrong about the CO2 concept altogether, or it might play a much smaller role than I initially led you to believe. I may have just thought about it too much as well.
Regardless, I was really getting at the maneuver to help you hold your breath a little longer while trying prevent passing out.
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