Air Consumption

[Riger]

Emperor Divers, MY Tranquility, 7 whole Days, Just Wifey and me....

8 Days . 9 Hours 52 Minutes and [-]35[/-] [-]34[/-] [-]33[/-] [-]32[/-] 31

Hmm

 

[TSandM]

Getting fitter increases your basal metabolic rate (the obligatory consumption of oxygen, just by being alive and sitting still). This is because fat has a lower metabolic rate than muscle, and you are replacing one by the other. However, when muscles are larger and stronger, they need to use less of their substance to achieve the same force (muscle cells don't propagate when you get stronger, they just get bigger and more powerful). So the oxygen used for a given amount of effort decreases. In general, fitness will allow you to achieve more for the same oxygen consumption.

 

[emttim]

Hello all,

(btw: 9 Days before Wifey and I leave on a Red Sea Liveaboard !!)

Back to the matter at hand, 2 things;

1. I was never taught about SAC rates on OW course, of course I soon realised what they are and that they have a valuable role in your planning ...

2. Someone in this thread mentioned that being fit increases your air consumption. I am presently a little chunky and not too fit, but I have recently started a fitness program and am choosing healthier culinary options, if this is going to be a disadvantage for my SAC rate, then ... ? I thought fit body = lower heart rate and therefore more efficient use of 02 therefore ..... you see where I am going. Anyone care to enlighten (ha ha see the pun) me?

Did I mention that its 9 Days before Wifey and I leave on a Red Sea Liveaboard !! Yaay

Regards
Richard

Even outside of scuba, every person should try to stay in shape and/or be in good physical shape to include doing cardio at the gym for the health benefits. Either way, you're benefiting yourself by exercising regularly since at a minimum it will allow you to stay healthy enough to dive for a longer amount of time in your life by reducing the chance of stroke, heart attack, etc.

Getting fitter increases your basal metabolic rate (the obligatory consumption of oxygen, just by being alive and sitting still). This is because fat has a lower metabolic rate than muscle, and you are replacing one by the other. However, when muscles are larger and stronger, they need to use less of their substance to achieve the same force (muscle cells don't propagate when you get stronger, they just get bigger and more powerful). So the oxygen used for a given amount of effort decreases. In general, fitness will allow you to achieve more for the same oxygen consumption.

Hits the nail on the head. Plus you won't hate the surface swims as much if you're not so winded at the end of them. Although I'll personally always hate surface swims with a passion.

 

[prskate2]

I am also a pretty new diver. But I took to it quick. You just need to find the perfect weight for yourself. Relax as much as possible. Maybe you even want to fill up your BC without using the power inflater. I always have more air then everyone else. It all depends on the person.

 

[johnatabc]

All very interesting for a new diver who has always been the first person to notify the Divemaster leading the group that he is down to 100 bar - thank you.

But in practical terms how do you actually measure your SAC rate

 

[scubamickey]

I wasn't meaning, don't know your consumption rate. I wasn't meaning, don't plan your dive based on gas consumption. I was meaning, that whatever it is, don't focus on improving it. Focus on improving your skills and the consumption rate will take care of itself.

I can see how the way I phrased it would be confusing. So yeah, ya gotta know your sac.

Thanks for the clarification.

Whew! You had me scared there for a minute.

 

[Jim Lapenta]

All very interesting for a new diver who has always been the first person to notify the Divemaster leading the group that he is down to 100 bar - thank you.

But in practical terms how do you actually measure your SAC rate

first you need to determine How much air you are using at a given depth. The easiest way I've found is to do a dive to 1 atm (33ft) and swim as you normally would for 10 minutes. Note how many psi you used for that.Then use the equation that trixxie gave. This will give you your sac. for swimming. I will also do the same exercise but perhaps swimming a little faster or in cold water with my drysuit(takes a little more effort) and then do it also while resting at a deco stop or just hanging out on the platform if there is one. I then take the three -working, swimming easy, and resting to get an average.

And yes I do include this info in BOW. We may not actually get to do it during checkouts but the info is there along with calculating deco stops should you exceed your NDL's which is part of the YMCA course. SAC is not but as instructors we are allowed to add to the course if we feel our students will benefit from it.

 

[emttim]

first you need to determine How much air you are using at a given depth. The easiest way I've found is to do a dive to 1 atm (33ft) and swim as you normally would for 10 minutes. Note how many psi you used for that.Then use the equation that trixxie gave. This will give you your sac. for swimming. I will also do the same exercise but perhaps swimming a little faster or in cold water with my drysuit(takes a little more effort) and then do it also while resting at a deco stop or just hanging out on the platform if there is one. I then take the three -working, swimming easy, and resting to get an average.

And yes I do include this info in BOW. We may not actually get to do it during checkouts but the info is there along with calculating deco stops should you exceed your NDL's which is part of the YMCA course. SAC is not but as instructors we are allowed to add to the course if we feel our students will benefit from it.

Not a bad idea. I calculate a SAC rate for every dive but I just use the maximum depth as the average depth and then use this: SAC Calculator

I played with the calculator a little...using the max depth as avg depth doesn't seem to be too inaccurate, about a .1 margin of error at the most. Guess I need to get the download cable for my VEO-250 so I can get my actual average depths.

 

[Squishy]

When you are a new diver, the very mechanics of being underwater and managing your buoyancy, navigation, and all your equipment use up a lot of bandwidth, and very new divers are rarely completely relaxed.

But a major thing that contributes to tension, and massively contributes to gas utilization, is inefficiency.

To begin with, they often do not have their equipment properly balanced. Especially when diving in cold water, where a lot of weight is necessary, it's important to distribute that weight so that the diver in a horizontal position will tend to REMAIN in a horizontal position.

In addition, because of the lack of balance, new divers often swim with their hands. The hands are not an efficient means of propulsion underwater, especially not compared with fins, so again, this is largely wasted motion.

When you are not balanced so that you can remain still, you must swim constantly. I can remember my own beginning days -- it irritated the daylights out of me that my buddies could simply STOP and look at something, when I would have to swim circles around them, because I simply couldn't be still.

Achieving good buoyancy control, which includes getting properly weighted, helps with gas consumption as well.

It would be absolutely counterproductive for him to work on his gas consumption as an end in itself; we simply dive different sized tanks, and life is good for both of us.

Have fun with this, and don't get anxious about it. Do, if you can, spend some time in a pool working with the trim pockets on your BC,

Thank you all for your responses... I have been very impressed with this forum because everyone seems to be willing to help others. The responses I receive are always helpful and considerate.

That said... I thought the (excerpted) post above really identified some of my issues. First, I know I need to work on this. On a few dives, I really nailed my buoyancy and they are my most fun and memorable dives. I can definitely see how that can make a big difference.

I have 6 pounds of weight in the shoulders of my BCD and the rest in pouches. I think the distribution is pretty good, but I am still trying to find the correct weight.

I don't swim with my hands, but I have been known to use them to help me steer a little. Usually when I am coming up on something too fast and need to turn quickly. It is interesting that you mentioned how other divers swim slowly, because I noticed that when I had to turn abruptly it was usually when I was coming up too fast on another diver and was going to swim into his fins. He was an extremely skilled diver and swam slow and steady.

Your comment about having to keep swimming when others could just stop describes me perfectly. I find myself swimming in circles when others stop. Glad to know it is not just me. Also glad to hear that it is something that you can overcome.

Finally I am 6' 2" so I suppose my lungs are bigger than the people I dive with because they were all smaller.

Thanks again for all the advice (everyone). You've give me a lot to think about to improve my diving.

-Mike-

 

[prskate2]

There is no need to swim fast. Just swim at a pace that is comfortable for you. (As long as you aren't being left behind) You will notice a major improvement when you get your weight right and your buoyancy better. All it takes is practice, practice. Stop checking Scubaboard and go DIVE!