I don't understand: breathing deeply and using breathing for buoyancy control seem to contradict each other

[KatieMac]

I heard that too in the beginning. I don't think anybody actually breathes like that when they are diving. But I understand they likely say that so you aren't doing shallow breathes.

I think about it like this - I'm breathing 1/2 way each time. But which half?

If I want to remain at the same depth, I use the middle half - breathe in to 3/4 and out to 1/4. This is very much like your normal breathing.

If I want to descend, I use the top half - breathe in to 1/2, breathe out completely.
If I want to ascend, I use the bottom half - breathe in full and breath out to 1/2.

 

[iliketopetsharks]

I think this video explains it quite well

 

[Still Kicking]

Breathe the same way at 60' as you do walking from the couch to the kitchen. That's the goal. Natural as can be.

If you want to use your breathing to control buoyancy you can retain more or less air in your lungs at the end of a breathing cycle but you keep breathing. As long as there is an open airway, you don't have to worry about overexpansion.

 

[scubadada]

For those of us with a lot of diving, breathing has become automatic. Within bounds, it is easy to control your depth by breathing higher or lower with your lung tidal volume within your total lung volume. If this is insufficient, you add or detract from your BC gas volume.

 

[therookie]

I thought the ideal is to go from close to 0% to 100%? Is that wrong?

I took it this way too, initially. Maybe not 0% to 100% and back but 20% to 80% and back. And I had the same sensation you describe - bobbing up and down in the water column like a yo-yo. And if I did it when I was closer to the surface towards the end of a dive, I would wind up losing control of my buoyancy and popping up to the surface. I actually now think I had a mild case of skin DCS during one trip, specifically as a result of that - ascending too quickly close to the surface. So personally, yes, I would say it is wrong.

So I had to break that habit, train my brain first to breathe normally underwater (which it didn't want to do naturally, because it "knows" humans can't breathe underwater), and then train it further to breathe more efficiently underwater. And after a while, you start thinking about it less and less because the brain just starts taking over the same way it has topside since shortly after birth, and diving just gets better and better. Learning how to breathe sounds funny because we have done it literally all our lives, but learning how to breathe underwater is definitely an acquired skill.

Practice, practice and more practice. It seems to be the key to almost everything about this hobby.

 

[happyharris]

Thanks for all your input everyone. This has been a revelation. Key takeaways are

1. Breathing should be normal tidal volume, not anywhere near maximum forced in/out.
2. PHASE!!!

With hindsight it is obvious, but there are 5 variables in breathing and buoyancy, not 4. We can think of graphing our breathing as a sine wave (like this). There will be quite a number of variables we can change about our breathing, but nobody has talked about phase.

Average volume and initial vertical motion will affect overall depth, not the yoyo-ing of depth. Deepness of breath, length of breathing cycle and PHASE of breathing cycle each interact together to to vary to speed and amount of the yoyo-ing. That leaves:

1. Deepness of breath - this will affect the size of change in buoyancy, and therefore, all other things being equal, the size of the yoyo-ing. Lower is better for stable buoyancy, but going too low means inefficient use of oxygen.
2. Length of breathing cycle - to a first approximation won't actually change the amount of the yoyo-ing, just how quickly it happens. Viscosity means a really short cycle will probably reduce the size of the yoyo-ing. So lower is better for stable buoyancy, but going too low means inefficient use of oxygen.
3. PHASE. This is the key. I think it's the thing that experienced divers have learned to do sub-consciously through practice, and don't know to describe to people because they don't know they are doing it. If we breathe in while we are going up, and breath out while we are going down, we will actually end up in a positive feedback situation, and never stabilize. However, breathing out when we are going up and in when we are going down might not be right either. It might be that the right thing to do is breathe in at the maximum downward speed, not as soon as we start going down. Or something else.

With practice, and experience diver learns to gradually adjust the phase of breath cycle to produce a stable depth with a small change, and an acceptable length and deepness of breath cycle.

Now I just have to go off and do it.

 

[johndiver999]

Thanks for all your input everyone. This has been a revelation. Key takeaways are

1. Breathing should be normal tidal volume, not anywhere near maximum forced in/out.
2. PHASE!!!

With hindsight it is obvious, but there are 5 variables in breathing and buoyancy, not 4. We can think of graphing our breathing as a sine wave (like this). There will be quite a number of variables we can change about our breathing, but nobody has talked about phase.

Average volume and initial vertical motion will affect overall depth, not the yoyo-ing of depth. Deepness of breath, length of breathing cycle and PHASE of breathing cycle each interact together to to vary to speed and amount of the yoyo-ing. That leaves:

1. Deepness of breath - this will affect the size of change in buoyancy, and therefore, all other things being equal, the size of the yoyo-ing. Lower is better for stable buoyancy, but going too low means inefficient use of oxygen.
2. Length of breathing cycle - to a first approximation won't actually change the amount of the yoyo-ing, just how quickly it happens. Viscosity means a really short cycle will probably reduce the size of the yoyo-ing. So lower is better for stable buoyancy, but going too low means inefficient use of oxygen.
3. PHASE. This is the key. I think it's the thing that experienced divers have learned to do sub-consciously through practice, and don't know to describe to people because they don't know they are doing it. If we breathe in while we are going up, and breath out while we are going down, we will actually end up in a positive feedback situation, and never stabilize. However, breathing out when we are going up and in when we are going down might not be right either. It might be that the right thing to do is breathe in at the maximum downward speed, not as soon as we start going down. Or something else.

With practice, and experience diver learns to gradually adjust the phase of breath cycle to produce a stable depth with a small change, and an acceptable length and deepness of breath cycle.

Now I just have to go off and do it.

You are missing something important. All other things are not equal. Of course you are going to oscillate in buoyancy in association with respiration. This is simple physics.

What you really have is an unstable equilibrium. If you start at "neutral", when you exhale you will begin to sink and when you inhale you begin to rise. You are always going to oscillate around a theoretical neutral point.

If you have a thick wetsuit, and/or a lot of air in the BC, then any vertical deviation from the neutral depth will cause the wetsuit and BC air to either expand or shrink. This can make a big difference.

So the LESS "compressible stuff" you have on your body (to affect the buoyancy) the easier it is. Of course the depth you are diving is also hugely important in this regard because when you are deep, these external airspaces change just a little and when shallow they will change much more. But understand that it is just much easier to control things in a dive skin compared to a thick wetsuit with a bubble of air in the BC.

If you maintain a decent horizontal trim, the normal buoyancy swings will cause less changes in depth, because you present a maximum amount of drag. If you position yourself in a more vertical position, you present much less drag - (but you can cheat by holding one leg back at a 90 degree angle and the other fin (thigh) held forward to make a lot of drag). Anyway, proper body position ameliorates a consider amount of the "problem" - simply by physics.

I strongly believe that it is more important to breathe in the most efficient manner and not worry about a little vertical oscillation.

In what diving situation does it matter, if you rise and fall 6-8 inches back and forth? Maybe some technical diving and maybe trying to shoot macro video? - but otherwise what difference does it make?

As others have said, once you do several hundred dives, these issues just evaporate and you deal with it unconsciously, but until then, don't sacrifice your metabolic efficiency to chase a superfluous made up goal - of trying to be completely stationary.

If you dive in any type of dynamic situation, you are not going to be still anyway. If there is any surge or any current, the presence of nearby obstacles (rocks, wreck, reef) is going to throw up some turbulence (eddies) and your body is going to be affected by them as well, so the theoretical goal of perfect stability becomes even less attainable or practical.

I manipulate my buoyancy all the time by artificially changing my breathing cycle, but it is only for a short term goal, like maybe rising 6-8 feet over an obstacle or trying to become heavy (exhaling fully) so I can slam down on a lobster and instantly grab it, pinning it to the bottom. But as soon as that activity is over (maybe 10-30 seconds), I will resume a normal comfortable respiration.

Trying too hard to suppress your normal breathing demands is a great way to get a killer co2 headache, work yourself into a panic and otherwise have an unpleasant time. You will also probably use (waste) more gas because you are not allowing yourself to make the most efficient use of your gas supply.

 

[BRT]

Great question. It does seem contradictory, doesn't it?

A thought experiment: If you were neutrally buoyant at a certain depth and tapped the inflator on your LPG with your thumb, what would you expect to happen? You expect to go up (a little), right? And then if you tap the deflator with your index finger, what would you expect to happen? You expect to go down a little.

So the "yo-yoing" you describe is exactly that, but in your lungs instead if in your BCD. It's just physics - you breathe in (or put air in your BCD), you and your gear now displace more water so you become more buoyant and up you go (a little). Breathe out (or expel air from the BCD) and the opposite happens.

As mentioned above, a large part of the trick to this is in figuring out the timing. Our OW instructor explained this (and demonstrated it) very, very well, but it still took me a LOT of practice to get the hang of it. I still do not pretend even yet to be close to really good at it, but I have at least managed on several occasions to avoid crashing into the reef just with breath control.

I don't know if this is really valid (the more experienced here that read this please correct me if it's incorrect advice) but what helped me was to learn to breathe s-l-o-w-l-y under water, and to train my brain to make that my natural breathing pattern underwater. That lessened the feeling of "yo-yoing", especially at shallower depths (like near the safety stop when your AL80 tank that is seemingly used everywhere in the Caribbean is getting close to empty, a topic for another thread) and also improved my gas consumption.

Bottom line is that you need to get into the water. My personal prediction? You will just finally feel that you are starting to get the hang this on the last dive at the end of your trip to Barbados, leaving you begging for "c'mon, just one more day!". Replace Barbados with Roatan, and that's exactly what happened to me .

Tap your inflator and you will go up a little, then more and then a lot. Same deflating.

 

[hammet]

Not deeper breaths.
Slower breaths.

 

[justinthedeeps]

It seems like the only way this can work while breathing adequately is when the rhythm of breathing is 180° out of phase with the rising sinking.

We probably unconsciously breathe out, sink a bit, then breathe back in to stall the sink.

I know I have given myself CO2 headaches in the past from too much creative yoga breathing at depth..

Definitely recommend trying a rebreather if you like to breathe completely freely and deeply with few caveats!