Improving my SAC rate

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One thing that was suggested to me just after I started diving was to practice slow breathing. I started while lying in bed breathing in slowly and then exhaling even slower, trying to take twice as long to exhale as inhale. After a while, I noticed that while diving I was doing it without thinking about it. My air consumption dropped quite a bit.

Also, the more you dive, the better your SAC rate will be. It just comes naturally.

And, BTW, I'm 63 years old, 6 ft tall, and currently around 240 lbs (down from around 275 this past April.) My SAC rate has averaged between .45-.50 since before losing the weight. And while I'm not in the best of shape, I'm probably a lot better than average for my age.
 
Two things you can do to improve your SAC...

1). Dive a lot to get more comfortable/relaxed while underwater
2). Try to minimize your need for air by moving slowly and staying in trim.

I have observed that people who are moving around constantly run out of air sooner than people moving more conservatively. For example, why "swim" down or up when you can glide down or float up using your BCD?
 
A general fitness program that is balanced between cardio and strength training will benefit your well being and diving. All other things equal, two divers, one overweight, out of shape and sedentary and the other fit, on BMI and active, who do you really think will have the lower SAC? What if part of the dive requires swimming against a current or some other physical exertion? Do you think the sedentary and out of shape diver will cope as easily as the fit diver or recover from the exertion as quickly? What if you get into a situation that pushes your body to the aerobic limit, that is one of several instigating factors for panic. A fit diver will be able to sustain a much greater effort for a longer time without blowing up.

Swim, bike, run, strength. You can substitute elliptical, rowing machines, stair steppers, or other cross training but be sure to balance the workouts. Do not confuse "big" (muscles) with fitness, they are not entirely the same thing.

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Many divers have proudly taken advanced courses and feel with that certification they are slightly "Above" others they are diving with. The people in the dive industry have their hands full with these divers. The newer diver usually listen because they know there is a lot to learn about this sport. All of the advise on this trend is good but the most valuable is getting comfortable in the water and that takes a good trim and knowledgeable buoyancy. Practicing in the pool with a trained instructor to check your trim is the best solution to getting this in order. Check with your LDS for some certification courses. Neutral Buoyancy is the one to shoot for. Also, when you get to your dive destination inquire about water temperature and currant. (Lots of current means more weight and more wetsuit means more weight) If you feel it necessary to stare @ your gauges the entire dive make sure they are hooked on your body and not dragging along the bottom. Figure that out before you get in the water. If you need to show all of your past park entrance tags or your favorite squeaky toy, make sure they all are inside your jacket. Once you are trimmed well you will have better control and not damage the coral, etc. Also, I have noticed ones with lots of yoga are use to deep breathing and blow through the diving gasses. If you have had yoga that is good because you are probably fit - just be aware of your breathing. If you are relaxed in the water you will have shallow breathing and therefore breath less gas. Placing your tongue on the roof of your mouth while you breath makes one very aware of their breathing because it feels like you are swallowing your tongue. After awhile you become very mindful of each breath. Also, your body weight is important - less fat less added weight - just as less wetsuit - less added weight. Your extra muscle will weigh more but the extra added weight from adding for your extra body weight will be more and harder to trim. Believe me I am an expert on that subject!!!! When I first starting diving, I was told by experience divers that "Diving is the lazy mans sport". I was rather shocked - remembering my cert classes not long ago. What diving is every dive adds on to your experience. There are challenging dives and challenging places - don't get me wrong on that - I also know all about those places. What it takes is figuring it all out and most of all enjoying what you are doing. Respect those that are there for the same reasons you are and above all love and total respect of the precious diving environment. Getting your buoyancy down is the most important aspect of being a competent diver - everything else will follow. Being flexible, fit, and strong are all important also but as stated in other comments, being relaxed and well trimmed is something divers should be aware of @ all times.
 
@scubadada had it right: Trim, buoyancy and propulsion are very important. I am in horrible shape, especially since I broke my leg. I have stupid low SAC because of my exceptional trim, buoyancy, propulsion and three other factors. I don't use my hands (sculling), I move only when I have to and then it's dead slow.

Get someone to video you on your next dive. Examine it for trim, kick style and how you're using your hands. Post it, if you want feedback.

Swimming in a pool is great for cardio and if you have to battle currents, so do that. But real improvements in your SAC are a function of technique and slowing down. It's a big ocean. You're not going to see it all on one dive.
 
Thanks for the support, "Oh Snap" and happy fishes to scuba dada.
 
I've recently found that on relatively "slow" dives, I do alright. My first dive back in the water after >3 years, which is only my third dive in over a decade, I was <0.5cuft/min, and came out of the water with 750psi left in an Al80. The two much more experienced and active divers I was with, both petite women, were only 2-300psi ahead of me with Al63’s. I didn’t do the math to compare their consumptions and mine, clearly they were much better than mine, but I was shocked and excited that my first dive back didn’t wind up with me thumbing the dive because I sucked through my air long before anyone else. This was shallow, mellow, not a lot of ground covered. Spent a fair amount of time hanging out with fishes and anemones up close.

Next dive was relatively deep (115ft), with an instructor, a divemaster, and two other very active divers. All guys, all but one in excellent physical condition, and all much more aggressive than my two previous buddies. We swam at a moderate pace and covered a pretty fair amount of ground, and I absolutely HAMMERED my gas trying to hang with them. I let them all know I was low, and popped ~20ft above them to start my safety stop earlier than the rest. I hit the surface right on 500psi, while most of them were still 8-900+ on the same tanks, 2-3 minutes behind me.

I absolutely believe comfort in the water, and conservation of motion will help a lot, and every one of my buddies had those traits far more in hand than I currently do. However, I also believe fitness is critical. I’m extremely average in terms of fitness. Lots of room for improvement, but I’m “fit” enough to be healthy from a medical perspective – cholesterol, blood pressure, spirometry, etc. are all better than average, year after year. The reason fitness stood out to me, was the one “less fit” diver on my last dive was notably hanging out ~10ft shallower than anyone else for the entire duration of the dive, sometimes much shallower. On surfacing, he was right in the pack of average for pressure left in the tank – still ahead of me by a couple hundred PSI, but behind a couple of the others, and at no point prior to our safety stop did I see anyone within 10ft of his depth. If he spends the duration of the dive at 1/3ATM less than anyone else, is far more experienced than I am, and he certainly looked plenty relaxed and calm in the water…all I can come down to from there is general fitness.

Also, if there's no need to go deep, don't. Easiest way to improve your gas consumption is stay shallower. I was nose into the bottom, seeing the sights for most of our dive. That certainly didn't help my case.
 
I enjoy hearing what is important to a diver - I find most do not want to "rock the boat" and keeping up with the pack and/or being an above "average" diver of the pack is absolutely critical. I do stress the trim aspect is still critical. Unless you have serious current or you have mileage in mind for a dive, you will be miles ahead and use less gas if you concentrate on trim. Feet up you are out of trim and are fighting and using energy and diving gas to keep those feet level with your body. There is a VERY simple fix for this issue. Talk to your LDS and do a pool season and get that all straightened out before you go on your trip. Soon you will be able to totally chill on a dive and you will be listening to you're breathing and become very "zenned". That is when your gas consumption will drop and you will come up from a dive all peaceful, rested, and totally energized.
 
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