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

[happyharris]

I am confused about how using breathing for buoyancy control interacts with breathing deeply to be efficient with air usage.

In my training dives I found that I was eventually able to stay in a relatively still horizontal position, without flapping my arms and legs around. However, when I took a deep breath in, I would go up, and when I breathed out again, I would go down. The only way for me to stop yoyo-ing up and down was to take small breaths in and out. The problem with that, of course is that it's a really inefficient use of air, due to dead space. The advice I see is to take deep breaths in and out (4, 5, 6 seconds each).

Could people help me see what I am missing here? How do I breath in and out deeply, without yoyo-ing up and down?

 

[sea_ledford]

Sounds about right. What you are missing is some depth. The deeper you go, the less immediate effect of a breath has on your buoyancy. Figuring out neutral buoyancy control is hardest in a pool for the exact reason you state.

One thing that you can work on is to think about breathing around a midpoint. That mid point is where you should set your neural buoyancy with your BC, then you'll be taking half of a breath deeper than the mid point and half a breath shallower than the mid point. You'll still move up and down, but once you get the timing figured out, you'll end up using momentum to counteract the buoyancy shifts. So starting from the mid point, you breathe in, making you positively buoyant. But because you have some mass, it doesn't make you go up immediately. Once you feel yourself starting to rise, you will already be exhaling to the shallow side of the mid point. That will counteract your upward momentum and you'll only go up a couple inches before you start to sink again. But by that point, you are inhaling again, counteracting THAT momentum, and ultimately end up being stable. Particularly at very shallow depths like a pool, 4-6 seconds per breath is going to be way too slow. Don't worry about breathing to increase air efficiency, worry about your movement and positioning to increase air efficiency.

Then you can change where the mid point is. If you are a little overweighted temporarily (picked something up, or descended, but haven't added air to your bc yet, etc), you can shift the midpoint of your breathing cycle to the "top of your lungs" so you have more inherent buoyancy in your lungs, but are still breathing like normal.

So using stupid easy example numbers, at neutral buoyancy your lungs are at 50% full. At a regular inhale your lungs are at 60% full and regular exhale they are at 40% full.
If you are negative, you shift the midpoint to 75% lung capacity, so inhale is at 85%, exhale is at 65%.
If you are positively buoyant, you shift the midpoint to 25% lung capacity, so inhale is at 35% and exhale is at 15%

 

[Badger7]

A couple thoughts and this is a very relevant question. I'm sure others will have thoughts to share too.

1) Inertia, when you fill your lungs with air you become more bouyant, but it takes time for your body to start ascending. Breathing back out then counteracts that motion, but you don't start descending immediately afterwards either. If you're diving with a steel tank and any amount of lead, you're not going to be yo-yoing up and down unless you take big breath, hold it till you start really moving up, then exhale fully and keep empty lungs when you're already moving down. Nice easy breaths in and out counteract each other as the bouyancy change overlaps the change in depth.

2) Using breath for bouyancy - when you want to raise up n the water column without touching your inflator, its not so much take a breath and hold it, its more like breath from 50% lung capacity at the lowest to full lungs at the top of the breath. If you want to descend in the water column, breath from completely empty lungs up to about 50% capacity. This isn't the most efficient use of gas, breath-by-breath, but is extremely gas efficient when practiced as you're lessening adding and removing gas from your BC, suit, and/or wing. Once you're at your target depth, adjusting your BC or wing for neutral bouyancy and you can stay there with nice even breathing.

 

[Lorenzoid]

The advice I see is to take deep breaths in and out (4, 5, 6 seconds each).

I have long believed that the often-heard advice to new divers to breathe "deeply" does them a disservice. The advice stems from the observation that many divers tend to breathe too shallowly, which is generally worse than breathing too deeply, as shallow breathing can lead to CO2 buildup, which can manifest as headaches, narcosis and other bad things. So it makes some sense that instilling in a new diver the idea that they should breathe "deeply" might counteract their tendency to breathe shallowly. But the problem is that we have divers taking "deep" too literally, as you have.

In my mind, "full" breaths is more accurate. Focus on inhaling about as much as you would if you were breathing normally on dry land--that is, take a full but not exaggerated breath. Then exhale the same amount as you inhaled, inhaling and exhaling at a constant rate. In other words, I think the better way to think of it is to breathe normally, not in an exaggerated way.

If you breathe normally (when not swimming) you will rise and fall only a small amount--perhaps a couple of inches--with each inhalation and exhalation, not enough to perceive as "yo yo-ing."

 

[therookie]

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 .

 

[boulderjohn]

I have long believed that the often-heard advice to new divers to breathe "deeply" does them a disservice.

I agree. Yes, inhaling and exhaling will affect buoyancy, but if it is affecting it to the degree you describe, you are overdoing it. I told my students to focus more on the speed of breathing. A long, slow, comfortable breath is what you need, followed by a long, slow comfortable exhale.

In my last years of instruction, I started doing something on the first pool dive, before any skills were done, that seemed to take care of the breathing issues. I had them facing me in horizontal trim, fins and possibly lower legs touching the floor, with enough air in the BCD to have them just off the floor. I faced them and used my fingers to to make it clear when I was inhaling and exhaling. I had them match my breathing. When the whole group was comfortably breathing with me, rising and falling only a matter of inches (I didn't care if they touched the floor), we would stand up, and I would begin briefing the first skill.

 

[therookie]

I have long believed that the often-heard advice to new divers to breathe "deeply" does them a disservice.

As a new diver, I also agree. I don't remember if our OW instructor said it that way, but I've read and heard it elsewhere for sure and started breathing "deeply" in my post-certification dives, and had to "unlearn" it as part of the process of getting a better grip on my buoyancy control.

 

[boulderjohn]

As a new diver, I also agree. I don't remember if our OW instructor said it that way, but I've read and heard it elsewhere for sure and started breathing "deeply" in my post-certification dives, and had to "unlearn" it as part of the process of getting a better grip on my buoyancy control.

I was a PADI instructor, and the language used in that OW class materials did indeed say to breathe deep. I learned that I had to explain that carefully.

 

[rick00001967]

agencies may tend to emphasize "deep breathing" to promote healthy gas exchange and avoid co2 build up.
but for buoyancy control it absolutely can be a disadvantage.
the key is to breathe normally while being as relaxed as possible.
when relaxed you will naturally only need infrequent shallow breathes.
but if you are over exerting yourself, uncomfortable, very cold, nervous, or are just one of those divers who just wants to go go go, you dont wanna be forcing yourself to breath less.

 

[happyharris]

Sounds about right. What you are missing is some depth. The deeper you go, the less immediate effect of a breath has on your buoyancy. Figuring out neutral buoyancy control is hardest in a pool for the exact reason you state.

Thanks for this. I didn't specify but I was actually talking about my open water dives and 40-60 feet, not my pool dives (which were a waste of time, being in 4 feet but that's another story.

So using stupid easy example numbers, at neutral buoyancy your lungs are at 50% full. At a regular inhale your lungs are at 60% full and regular exhale they are at 40% full.
If you are negative, you shift the midpoint to 75% lung capacity, so inhale is at 85%, exhale is at 65%.
If you are positively buoyant, you shift the midpoint to 25% lung capacity, so inhale is at 35% and exhale is at 15%

So this means I should not be breathing full lungfuls in and out but rather only 20% - going from 40%-60% or 65%-85%? That is not what I thought. I thought the ideal is to go from close to 0% to 100%? Is that wrong?

Look at random search result I now understand a bit more about the difference between the lung capacity after forcefully breaking in/out compared to normal in out. Given that, it looks like you are saying that I should be breathing a normal tidal volume, not deeper in or out than that? Maybe that is my misunderstanding.