How "much" of air consumption is physiology? How to improve consumption?

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My average RMV is 0.6 psi per minute. That’s in a drysuit with doubles in cold water. The lowest it’s ever been was 0.54 on a very relaxed quarry dive, but still drysuit, doubles, and cold water.
Imagine how low it might be on a warm water, tropical dive with a single and no suit - you should try it ...sorry, couldn’t resist!:poke:
 
I almost quit diving shortly after being certified due to my terrible air consumption. Now my SAC is better then average. After 50 or so dives I started seeing quite a bit of improvement. I think the biggest deal is just getting used to breathing under water. When I first started I used to think about taking my next breath in while I was exhaling. Now while I exhale I just slowly let the bubble trickle out. From watching, or listening to, old Gopro videos my breaths taken per minute are about half of what they used to be. I am sure I will catch some crap for this but I don't think fitness is that big of a factor, unless you are fighting current or kicking hard.
 
Experience will make the most difference, but there are some lessons that you can learn and apply now.

  • What is your style of diving? Many new divers (I know I did) are excited and dart around the dive site like a puppy at a dog park. Most dives are better if you move slow, look around closely, and remember its not a race.
  • Control your depth. If you dive partner has better air consumption than you do, stay 5 feet shallower than they do. Eventually you will catch up.
  • Buoyancy matters. Have someone video you while diving. Chances are you are kicking, moving to stay buoyant, using arms and fins frequently. When you really have control you move less, breath less.
  • With experience you gain confidence, which means you relax. Diving can be like yoga or meditation, where you really relax, establish a slow, deep, continuous breathing cycle. Slow deliberate movements.
 
Keep diving , more bottom time equals better SAC.
This is a common attitude and true to a point. But lower SAC makes diving more fun. I believe it makes it safer as well because a relaxed, deep breathing diver is much further from panic than a tense, fast breathing one. It certainly reduces the tendency for divers to cut into their reserves. A good friend of mine actually ran OOA on a safety stop because he was too embarrassed to be the first to call the dive (he finished the dive on the guide's octo without problem).

I also believe that an improved SAC rate is a skill that can be taught. Just telling divers to consciously lengthen their exhales can result in real improvements in a single dive.

There's an exact parallel here in buoyancy control. The standard response to all but the most gross buoyancy problems in a new diver used to be "Don't worry about it. It gets better as you dive." Now, I think the attitude is shifting to where most people will agree that this is something that should be addressed immediately through directed practice or additional training.
 
Thanks for all the replies. Yesterday was a travel day so I didn't have access to check the thread.

I definitely do think I am excited/anxious on the very first dive of the day for the first 5 or so minutes until I relax.

I also know that I still am not 100% "comfortable" while diving in the sense that I am a bit nervous/anxious. I sometimes feel like I work myself up prior where I am anxious a day or so before, and then the morning of the dive I feel it too. I will even dream about it the night before sometimes. Typically though when I get in the water it goes away pretty quick, and my second dive I don't really feel it at all.

I do know that even though I am AOW and have done a deep dive to 100', and also a wreck dive at 70', I still have something mental about going deeper. This trip I didn't even tell them I was AOW because I didn't want to go deeper than 60' just because I want to get comfortable there before I start going deeper. And I will say I immediately felt SUPER comfortable with that and didn't even realize how quickly I got down to 65' on my first dive.

These two dives definitely helped work on my confidence and comfort going deeper so I think all of that, more experience, and continuing to try and concentrate on as minimal movement and slow breathing will help with all of it.
 
My wife and I have essentially the same SAC and are usually the last on the boat. She is 5'2" and 110....does not really do much threshold or anaroebic cardio. I'm 5'7", 150lbs and do tons of high end cardio 6 times a week (ultra endurance MTB, BC skiing, trail running). Even when I first started diving (she was an experienced diver when we met), we had a similar SAC.

I'm convinced fitness level had a big part in our similar rates as opposed to other factors. YMMV
 
My wife and I have essentially the same SAC and are usually the last on the boat. She is 5'2" and 110....does not really do much threshold or anaroebic cardio. I'm 5'7", 150lbs and do tons of high end cardio 6 times a week (ultra endurance MTB, BC skiing, trail running). Even when I first started diving (she was an experienced diver when we met), we had a similar SAC.

I'm convinced fitness level had a big part in our similar rates as opposed to other factors. YMMV
Curious - for reference, what is your SAC? I do absolutely agree that fitness (especially aerobic fitness) can play a big role for most (it has for me). However, based on the fitness of many divers I’ve seen with very low SAC’s, it’s clearly not the only factor.
 
Once I realized that it was okay to hover and not move the SAC came down exponentially. I also ride out every propulsion right to the end. Long glide phases reduce O2 conversion.
 
I also know that I still am not 100% "comfortable" while diving in the sense that I am a bit nervous/anxious. I sometimes feel like I work myself up prior where I am anxious a day or so before, and then the morning of the dive I feel it too. I will even dream about it the night before sometimes.

I have 250+ dives and I still get nervous before the first dive of a trip. I think it's my mammalian brain reminding me that I really can't breathe under water! So I have to remind myself that it's all good, and remember to exhale as I descend, and not take a big breath at the surface. (when you breathe in your systems interprets that as a cue to be prepared for action - and as you exhale your system takes that as a cue to relax. It works for me.)

I just looked at my log book (another reason to keep track) and found that I got to 100 feet on my 42nd dive. Up until that dive I was super nervous about going that deep, but I think I was narc'd because when I looked at my gauge and saw 100 ft it felt totally fine. I say this because I think that's when my SAC rate began to improve. I think I was anxious even when I thought I was calm. I learned, that day, that I could survive underwater and that in order to do so I needed to be intimately familiar with all of my equipment - so I began to feel more competent.

Btw, on that trip, the folks who were the last out of the water were an older couple (maybe in their 70's) who smoke and drank (heavily). I remember actually being a little irritated that we had to wait on the boat so long!! So in terms of physiology, I just don't know the answer.
 

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