Buoyancy and Breathing

[aquaregia]

Stop thinking about how you're breathing, you'll be much better off.

I've spent ten years studying academic (read: fake) engineering. I'm no longer any good at doing things, only at analyzing how badly they get done.

More seriously though, I am breathing a fair bit slower than usual, and my resting rate is a bit under 6 seconds/cycle (which I know is at the low end). I'm probably doing 8 seconds or so underwater. I thought I'd heard somewhere that breathing longer and deeper would decrease my SAC -- am I backwards?

 

[LeadTurn_SD]

I've spent ten years studying academic (read: fake) engineering. I'm no longer any good at doing things, only at analyzing how badly they get done.

More seriously though, I am breathing a fair bit slower than usual, and my resting rate is a bit under 6 seconds/cycle (which I know is at the low end). I'm probably doing 8 seconds or so underwater. I thought I'd heard somewhere that breathing longer and deeper would decrease my SAC -- am I backwards?

No, you are not backwards. But slowing your breathing rate too much puts you into the realm of "skip breathing", CO2 retention, etc. You probably are not there, but that is certainly a place to avoid.

It is good to be aware of how you are breathing, and to "check-in" with yourself frequently, and to keep your exertion level as low as possible during the dive so you can easily maintain a slow steady breathing rate.

Each dive as I make my initial descent I remind myself to relax and breath deeply, and periodically remind myself through the dive.... but I'm not actively controlling the pace... I think as RJP said, when you stop thinking about your breathing (other than to take full breaths), everything else will sort itself out.

Best wishes.

 

[Straegen]

I like humming actually. Any suggestions for good songs that will creep out my buddy? I'm hoping to exploit the lack of directionality to make my buddies think they're losing it.

Don't think it will work but the theme to jaws or the shining pop into mind.

 

[devilkitty]

I've been steadily decreasing my weight since my OW, and I've also been decreasing my SAC. I'm noticing now that I'm having some trouble keeping level while I breathe, however. My position is fluctuating perhaps as much as 2' every time I breathe. I suspect this is because the air in my lungs is a larger proportion of my buoyancy now that I have less weight and thus less air in my BC, and also I'm breathing slower and deeper. I did some quick back-of-the-napkin calculations as a sanity check, and they seem to indicate that my lungs could make a buoyancy difference of between 3# and 14#, although the extremes would be fairly unlikely. I'm guessing 5# is closer to it (based on spirometry, SAC and breathing rate estimates). It seems like I have a three way tradeoff between weight, SAC and vertical constancy.

My SAC is still quite high (0.85ish) so I'd rather not sacrifice that. Should I wear more weight and keep more air in my BC? Or should I just get used to the positioning issues?

SAC is a good thing to keep in mind, but a great SAC won't do you a lick of good if your buoyancy is way out of whack. Work on the buoyancy first; improving your SAC can come later.

Go out and do some diving where there's something else to hold most of your attention: poke around the outside of a wreck; go looking for the elusive Man-Eating Lake Perch; see how many beer bottles you can find at the bottom of the local pond; whatever. (That's not to say you should ignore buoyancy completely -- obviously you'll do what it takes to stay safe.)

You'll be surprised how much better your buoyancy control is once you stop over-thinking it. Once that sinks in (no pun intended), the "Aha! moment" won't be far away; then it's just a matter of polish and trim.

 

[fnfalman]

Like others have said, don't fully fill your lungs. Just breath normally and don't use your lungs (i.e. holding breath for too long) for buoyancy control. If you do that, you will end up with a nasty, blinding headache that is the result of CO2 build-up.

 

[MattV]

As an engineer, think about the timing. You have something close to 2 periodic signals. One, your current 'momentum' based on past buoyancy and the other the instantaneous force generated by your current lung volume/buoyancy.

If you put these two forces out of phase, you won't move.

 

[TSandM]

Rick Murchison has a THREAD on this topic that is better than anything I could come up with, but MattV has really nailed it as well. It is an issue of timing and rhythm, and is the only purpose I could ever intuit for the fin pivot.

 

[ajduplessis]

I've been steadily decreasing my weight since my OW, and I've also been decreasing my SAC. I'm noticing now that I'm having some trouble keeping level while I breathe, however.......

Try to breath with your diaphragm (yoga/martial arts style). Generally divers to try to expand their chest with "deep" breathing leading to big fluctuation in buoyancy. When using the diaphragm (breathing with the stomach) the lungs “expand” into the abdominal cavity, resulting in more controlled breathing and better buoyancy. I hope this explanation made any sense.

 

[spectrum]

I've spent ten years studying academic (read: fake) engineering. I'm no longer any good at doing things, only at analyzing how badly they get done.

More seriously though, I am breathing a fair bit slower than usual, and my resting rate is a bit under 6 seconds/cycle (which I know is at the low end). I'm probably doing 8 seconds or so underwater. I thought I'd heard somewhere that breathing longer and deeper would decrease my SAC -- am I backwards?

Thinking is good but don't overthink or fixate. It sounds like you have a lot of things going in the right direction. The next building block is timing. The 5 pound swing you estimate is a good number but the solution isn't really about math.

Remember that changes in buoyancy do not change your depth instantly. The goal is to begin to exhale just before you begin to rise. Couple that with inhaling just before you drop. This will level thngs out quite a bit and with practice become second nature. Now that you have a nice deep slow breathing cycle you will probably porpoise a little and in general that's OK.

You will find that in tight quarters where you need pinpoint control you will need to breathe to suit the control need. This may mean modifying timing and depth of breaths.

As you dive more and more you will become more in tune to your state of buoyancy and the reactions become more natural.

Keep up the good work.

Pete

 

[herman]

Like others have said, don't fully fill your lungs. Just breath normally and don't use your lungs (i.e. holding breath for too long) for buoyancy control. If you do that, you will end up with a nasty, blinding headache that is the result of CO2 build-up.

I suspect this is a mis type but your lungs are what you use for buoyancy control once you are properly weighted and you have the required amount of gas in your BC/dry suit. Some air in your BC/dry suit may be needed for gross adjustments but breathing rate and lung volume are what you use for fine control of your buoyancy. Keeping BC/drysuit air to the minimum necessary helps SAC in several ways, not the least of which is to improve stream lining- an inflated bladder means more drag.

aquaregia, from the research I have done on the subject, the average buoyancy swing of an adult male is somewhere in the 10 to 12lb (total) range so your 5lb is about right- assuming that is +/- mid lung volume. If you are bobbing 2 ft my guess is you are breathing very deeply with a very slow rate. As you do, you are setting up a small buoyancy cycle that tends to feed on itself, getting bigger and bigger with each breath. By breathing a little less deeply, a little faster and breaking up the rhythm you can put a stop to it. It might help your SAC a little but it's not worth the loss of precision in buoyancy control it causes. Breathing a little deeper and slower than surface resting normal is good but you may be carrying it a little too far. Save the deep breaths and modified breathing rates for purposeful depth adjustments during the dive - ascending a few feet to go over an object and to returning to depth.
Over the last couple of years I have been working a lot on buoyancy control due to an interest in vintage diving. Back in the day, BCs did not exist so quite often we do not use them when diving the old gear, diving re-enactors if you will. It has opened my eyes to what true buoyancy control is and has made all the rest of the diving I do a lot easier.