Huge air consumption even after +200 dives

[Tycksel]

I'm about your same height and weight. Like you, I've optimized my weighting, my technique, streamlining, and keep my SAC rate down. Trouble is, due to our size, we have proportionally larger muscles, larger lungs, and higher O2 consumption as a result. If you workout regularly -- particularly strength training -- it's even worse!

Simplest solution: bigger tank (100cf or 120cf). It will be proportional to your size. My friends like to joke that I carry a water heater on my back, but it's honestly not a hindrance given my size. I just make sure to bring a bungee or ratchet strap to keep it rolling around the boat since the larger diameters don't usually fit in the tank racks.

Yeah we used to have 15L (or 13,2L precise) tanks on our boat too, but because they didn't fit to racks, they removed those.

 

[Blackcrusader]

Yeah they have filmed me many times. My trim is totally horizontal and I'm also diving with wing, so that makes horizontal trim quite easy. Not using hands at all when I dive. I usually kick, glide for 5 seconds and then they still for around 5 seconds.

I always go up a little when I inhale and go down a little when I exhale, so that's why I think that my buoyancy is just ok.

I'm using 3mm vest with hood and 3mm full wetsuit. Water temperature is 28-29c. I'm quite happy with that and don't feel cold.

I am 185cm and weigh 130kg.

You say you breathe every few seconds. I generally breathe in every 15 second and then exhale... My sac rac is less than 10l/min often 8l/min or less depending on conditions.

This video of me taken by a dive buddy. I breathe every 15 - 20 seconds or so Just been in Maldives. One German chap was telling me he breathes three times to every time I breathe.


This though was nuts even for me. I think my brain must have shut down. AL80

 

[Blackcrusader]

Part of the issue is simply that you are a big guy. A larger body is going to consume more oxygen, it's just physiology.

This is not true for all large guys. In Maldives the biggest guide who is pretty fat along with me were the better divers on gas consumption. This 93 minute dive to a wreck at 34m depth then along a wall at 15m depth. Ended with 50 bar.

 

[Blackcrusader]

Yeah we used to have 15L (or 13,2L precise) tanks on our boat too, but because they didn't fit to racks, they removed those.

A guide took this video of me. Some divers behind to compare breathing you can see how many times they bubble to me.

One thing is go slow, very slow. Lots more to see and it's not a race to go from A to B.

 

[nippurmagnum]

did few dives with 15L tank last winter, but it gave me maybe 5min more divetime. I only use 800g weight with 12L tank and with 15L tank I'm maybe 4-5kg overweighted.

Wait, are these steel tanks we are talking about? Which you're using without a wetsuit? And is your body fat percentage 3 percent? And when you dove the 15L, did you go 10 meters deeper than normal on average? Otherwise that doesn't compute.

 

[schuylerclark]

I'm always the one to run out of air first cause my wife's almost a foot shorter than me. My experience with larger tanks is that they lower my RMV/SAC rate in addition to having more air. Best I can figure is that it clears my mind of the concern of running low on air, relaxing me, and improving my breathing rate/volume. If I'm on an 80 cu ft, she usually takes a 60, or if she's on an 80 I'll use a 100. This matches us up and knowing I won't run short on air before others makes the experience more enjoyable for me.

 

[stepfen]

Haven't gone trough all the messages, but here is my case: I just did my 500th dive. Started diving ~9 years ago. I’m 46 years old, 1.9m , ~95kg. Started with SAC of 20+lt/min back then. Over the years I dropped to my minimum ~11lt/min (about 5 years ago) but that's absolutely minimum with absolutely ideal conditions (warm calm water, solo at my pace). I've noticed that every "disturbance" adds about 2lt/min to my SAC. So, buddy diving in ideal conditions? SAC jumps to ~13lt/min. Group following a guide? 15lt/min. Guide in rush or current 17lt/min. Guide in rush and current 19lt/min. Cold water, drysuit, not good sleep, etc each adds about 2lt/min and so on. BTW those are the minimums expected values. Usually they are higher than that. I can't even imagine if I had to lead a group myself. So I think we are in similar situation.

Another thing. When I started I was about 120kg with practically no exercise (other than some trekking now and then). Then lost weight down to about 88kg minimum. Then started exercising (and gained some weight up to my current 95kg). Now I exercise about 3 times a week and regularly run 5k (in about 30mins). To be honest I didn’t see much difference in SAC as my fit level increased. Of course I can move much more comfortable all the gear before, during and after diving now, but SAC reduction over the years seems to not have much to do with my fit level as my minimum SAC was achieved before I started exercising and now that I am fitter I can’t really reach that low SACs any more.

Not a pro but I understand your frastration.

 

[grantmac]

I'm around 100kg with similar dive numbers.

Going to doubles dropped my SAC way down. Like 12l/min in drysuit and heavy undergarments.
Also I'm a huge proponent of a natural inhale followed by a lengthened exhale. It takes time for gas exchange to happen.

 

[autrichon gris]

Another thing: diving is absolutly not a contest of which breath the less ! Apnea while diving will cause you probably headache, stress and questions upon "why do i breath this much, i need to breath less"...
Learn to NOT think about your breathing while diving, add some meditation/relax mind, and you will see that your SAC will decrease.

 

[CG43]

So far there have been many good and very good proposals and the videos of Blackcrusader .
On these videos we see a diver who exhales a good amount of bubbles in a short time after a long breathold . We do not hear the inhalation, but it will probably be as long (or short) as the exhalation.
This is anything but like " first rule of scubs diving is never hold your breath " but there are good reasons why this way of breathing is so effective .

Let's assume that : 1.) the strongest respiratory stimulus is the PPCO2 in the body and thus also in the lungs.
2.) Our body body produces a constant rate of CO2 .

The PPCO2 in the lungs depends only on the total pressure and CO2 concentration, not on the amount of air in the lungs.
When we start exhaling depends on the CO2 concentration, no matter how full or empty the lungs are.
Exhalation changes the total amount of CO2 in the lungs, but not the CO2 concentration.
In order to effectively reduce CO2 concentration, the residual air remaining after exhalation must be diluted by the amount of inhaled air.
After inhalation (CO2 dilution), the greater the volume of air in the lungs, the slower the CO2 concentration will increase.
If you now bring all the influences together, the most effective breathing consists of deep exhalation, deep inhalation , breathold deep exhalation ........
The average CO2 level is medium, because it is approximately in the middle between the lowest possible value and the respiratory stimulus threshold.

Unfortunately, there are problems to realize this breathing in practice,
because the human being is not a machine.
Being able to breathe deeply with perseverance requires practice and relaxation at the same time. You can also practice this on land.
Nevertheless, when diving, you should only breathe as deeply as is comfortable and relaxed.
A bigger problem is the inhaled breath holding .
When the airway is blocked, anything that compresses the diver can create pressure in the chest cavity, thus disturbing blood circulation and the diver's relaxation. This can be a tense respiratory muscles, a tight diving suit, straps or a BCD. It may be enough to breathe in a little less deeply. If you don't feel comfortable with the breathold, then insted exhale slowly. A diver who does not feel comfortable will never breathe effectively.
The most important thing is whether you like these breathing pauses or not.
There are pictures of the happy submerged breathold babies. Are you such a baby ?
What is predisposition and what can you train? Everyone will have to try that out for themselves, and my recommendation as usual is freediving.