Air consumption

[Nemrod]

You know, this gets touchy but you asked for help but then stated all was essentially perfect. Obviously something is not if you have a SAC of near 1.0.

I am also 5-10 but quite a bit less weight and I work out every day and my SAC is, well, it can be very low. Your being able to run five miles in an hour and swim 400 yards in 10 minutes is not a bad beginning point. But you need to perform exercise designed to keep your heart rate in the target (for your age) zone for at least 30 minutes. I recommend you do this three times a week and do strength exercises (weights/machines) twice a week. You have to make time for yourself. You may not live a lot longer if you are fit, that is a different argument, but it will be a higher quality life and that is hard to argue against. You are an adult now, you really do not need three square meals per day. I have three pieces of dry toast and orange juice in the morning, for lunch I have a granola bar and maybe an apple. For dinner my wife tries to do healthy proportions. (but sometimes I just cannot resist peanut butter and jelly ). You are what you eat and the vast majority of people eat to much and the wrong kind of too much. And you only need to look around to see that people have become prisoners in their bodies.

Here is from the BMI calculator using your stated weight and height:
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Height: 5 feet, 10 inches
Weight: 215 pounds
Your BMI is 30.8, indicating your weight is in the Obese category for adults of your height.
For your height, a normal weight range would be from 129 to 174 pounds.
People who are overweight or obese are at higher risk for chronic conditions such as high blood pressure, diabetes, and high cholesterol.
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Observe what your dive buddies do differently from you that you are first out. Do not worry so much over your air consumption, just have fun. I am recommending a fitness regimen so you can keep on having fun. But I betcha if you weighed 185 your SAC would be cut significantly and it would surprise you.

N

 

[lv2dive]

Diving at the GA Aquarium, the OP has to dive the tank they give him. Also, truth be told, there can be some exertion required, if one scrubs those rocks hard, or tries to do a very good good job on the windows. Not to mention the work required running the machines (I can't remember their names). I noticed during my tenure as a volunteer diver that some people worked harder than others... And those that did, especially bigger guys, could easily burn through more air than others.

Also, another consideration at the aquarium is that more seasoned divers do a great job of timing it so that they clean the big picture window from the top down rather than the bottom up.... To the OP, have you noticed this? This can be almost five-ten minutes where you are starting out at a disadvantage of almost one ATA [emoji6].

As a slight aside I would note that I never felt like I had to be vertical except in the surface-supplied exhibits. But then again, for the most part, I was also the only person who WAS horizontal the entire dive, so I don't know that I was more efficient/effective in that position, either! [emoji6]

 

[boulderjohn]

I just looked at the Denver Broncos roster, and here are the first two names:

OFFENSE POS. W H
C.J. Anderson Running Back 224 5-8
Montee Ball Running Back 217 5-10

Those guys are pretty fit, but the BMI says they are obese.

A number of years ago DAN wrote an article about dive fitness and how it can be measured. The conclusion was that the BMI was the worst possible way to measure fitness in an individual. It is only useful in dealing with averages in large populations. I remember the article well because it was written in response to a letter to the editor I had written about a previous article which used the BMI as a measure of fitness.

At that time I was reasonably fit, but nothing remotely near what you see in the professional athletes listed above. I had just completed a hydrostatic body fat test, which is the very best way to determine body composition. In that test, your weight is measured both in and out of water to create a comparison. It had me at 16% body fat, which was pretty good for a guy my age. The BMI had me as nearly obese. The analysis I received included a chart that showed what my body fat composition would be if I were to lose different amounts of weight solely through the loss of fat. In order for me to get down to the weight at which the BMI would say I was no longer overweight, I would have had to get down to BELOW 0% body fat. In other words, the only way I could get out of the overweight category on the BMI would have been to stop exercising so that I would lose muscle mass.

Now, I don't know how that pertains to the OP in this thread. I just wanted to point out that you really can't tell ANYTHING by the BMI alone.

 

[RDRINK25]

I just looked at the Denver Broncos roster, and here are the first two names:

OFFENSE POS. W H
C.J. Anderson Running Back 224 5-8
Montee Ball Running Back 217 5-10

Those guys are pretty fit, but the BMI says they are obese.

A number of years ago DAN wrote an article about dive fitness and how it can be measured. The conclusion was that the BMI was the worst possible way to measure fitness in an individual. It is only useful in dealing with averages in large populations. I remember the article well because it was written in response to a letter to the editor I had written about a previous article which used the BMI as a measure of fitness.

At that time I was reasonably fit, but nothing remotely near what you see in the professional athletes listed above. I had just completed a hydrostatic body fat test, which is the very best way to determine body composition. In that test, your weight is measured both in and out of water to create a comparison. It had me at 16% body fat, which was pretty good for a guy my age. The BMI had me as nearly obese. The analysis I received included a chart that showed what my body fat composition would be if I were to lose different amounts of weight solely through the loss of fat. In order for me to get down to the weight at which the BMI would say I was no longer overweight, I would have had to get down to BELOW 0% body fat. In other words, the only way I could get out of the overweight category on the BMI would have been to stop exercising so that I would lose muscle mass.

Now, I don't know how that pertains to the OP in this thread. I just wanted to point out that you really can't tell ANYTHING by the BMI alone.

I do do believe I am overweight and could lose 10 or so lbs... But who really couldn't? I exercise regularly and do weight train. If I was 185lbs I would lose 20lbs of muscle. I am trying to figure out my breathing techniques and how to improve on them. I do notice when I am underwater and focus on my breathing I burn through it more. I do take long slow deep breaths and slow exhales underwater but that is not how I normally breathe. Short quick breaths is how I breathe followed by a long one.

 

[RJP]

Please don’t comment about buoyancy issues as mine is near perfect.

Congratulations! I know GUE cave instructors that don't believe that THEY have "near perfect" buoyancy control.

I really can only account for it being low is that I constantly breathe.

Air consumption is - for the most part - a DEMAND issue. It's very easy to be an inefficient diver but its very hard to be an inefficient breather. Your body simply cannot USE air (O₂ actually) any faster than it NEEDS it.

Let's assume for a moment that your buoyancy control actually is perfect. What's your trim like? How streamlined is your gear? How about propulsion techniques?

I do notice when I am underwater and focus on my breathing I burn through it more.

Stop paying attention to how you are breathing... and start paying attention to how you are diving.

The best way to reduce air consumption is to reduce your body's demand for O₂.

There are 13 key "Demand Reduction Strategies" that any and every diver can employ to improve their O₂ consumption:

1. Slow down
2. Get more comfortable in the water
3. Slow down
4. Get your weighting fine-tuned
5. Slow down
6. Get horizontal trim dialed-in
7. Slow down some more
8. Stop swimming with your hands and arms
9. Slow down even more
10. Utilize efficient kick styles
11. Just a little bit slower... please?
12. Streamline your gear
13. Slow down - you're still moving too fast!

 

[Imla]

Congratulations! I know GUE cave instructors that don't believe that THEY have "near perfect" buoyancy control.



Air consumption is - for the most part - a DEMAND issue. It's very easy to be an inefficient diver but its very hard to be an inefficient breather. Your body simply cannot USE air (O₂ actually) any faster than it NEEDS it.

Let's assume for a moment that your buoyancy control actually is perfect. What's your trim like? How streamlined is your gear? How about propulsion techniques?

The best way to reduce air consumption is to reduce your body's demand for O₂ 2.

There are 13 key "Demand Reduction Strategies" that any and every diver can employ to improve their O₂ consumption:

This is... all due respect... utter nonsense!

Assuming what you are breathing is 21% or richer and you are deeper than 10m, there is basically fat chance you will spend the amount of oxygen your body can extract from the blood. However... What IS driving your need to ventilate is increased levels of CO2 in the bloodstream. Ie. You need to ventilate CO2 long before you need to get more oxygen. And putting into play the increased PPO2 of inspired gas, your need to "breathe for oxygen" is lowered even further.

My best advice... Stop caring so much. Get a bigger tank. Get better buoyancy. Get correct weighting and breathe what you need!

 

[RJP]

This is... all due respect... utter nonsense!

Assuming what you are breathing is 21% or richer and you are deeper than 10m, there is basically fat chance you will spend the amount of oxygen your body can extract from the blood. However... What IS driving your need to ventilate is increased levels of CO2 in the bloodstream. Ie. You need to ventilate CO2 long before you need to get more oxygen.

The (missed) point is that it is the body's metabolic needs that drive how much O2 is required. Of course cellular metabolism results in CO2 production. Increased metabolic activity will result in increase NEED for O2 and increased PRODUCTION of CO2.

What would be utter nonsense - in all feigned respect - is trying to discuss the body's need to ventilate CO2 separate and apart from its O2 demand/consumption, much less ascribing primacy to to it. Yes, C02 levels cause the autonomic trigger of ventilation. But metabolism of O2 causes CO2 production.

 

[ScubaInChicago]

An unfit person generates up to 50% more Co2 than a fit diver. Our breathing is triggered for Co2 expiration and not for additional o2. It's the reason we can go hypercapnic and feel like we are not getting enough breathable gas. All this basic physiological stuff is covered on the first day of GUE-F.

 

[Imla]

The (missed) point is that it is the body's metabolic needs that drive how much O2 is required. Of course cellular metabolism results in CO2 production. Increased metabolic activity will result in increase NEED for O2 and increased PRODUCTION of CO2.

What would be utter nonsense - in all feigned respect - is trying to discuss the body's need to ventilate CO2 separate and apart from its O2 demand/consumption, much less ascribing primacy to to it. Yes, C02 levels cause the autonomic trigger of ventilation. But metabolism of O2 causes CO2 production.

Yes, but there is a major difference in the supply of O2 and the need to get rid of CO2. There is such a high supply of O2, that the body simply does not "empty" the resourses, and hence, this has absolutely NO effect on regulation of ventilation. The point is, that unless you dive a rebreather, you will never utilize all the oxygen in your breathing gas and effects to lower O2 consumption will not have adequate effect if you don't at the same time consider the real driving force of ventilation, which is the production of CO2. Which again can overpower the "exhaust system". Again, in other words. You could swim as much as you wanted, you will still not exhaust the supply of oxygen that you are offered. What IS the problem, is that PPCO2 can increase quite rapidly. The techniques that should be focused on would be those that aim to increase ventilation of CO2. Of course, lowered activity will cause lowered production of CO2, but the limiting factor will always be CO2, and not access to O2.

(Assuming 21%->) there WILL be enough oxygen!

There can EASILY be to MUCH CO2...

So... don't complicate the matter with "Need" for O2... There IS NO NEED... the body gets all the oxygen it needs. It NEEDS to expel CO2... THis i the difficult part.

 

[Nemrod]

I just looked at the Denver Broncos roster, and here are the first two names:

OFFENSE POS. W H
C.J. Anderson Running Back 224 5-8
Montee Ball Running Back 217 5-10

Those guys are pretty fit, but the BMI says they are obese.

A number of years ago DAN wrote an article about dive fitness and how it can be measured. The conclusion was that the BMI was the worst possible way to measure fitness in an individual. It is only useful in dealing with averages in large populations. I remember the article well because it was written in response to a letter to the editor I had written about a previous article which used the BMI as a measure of fitness.

At that time I was reasonably fit, but nothing remotely near what you see in the professional athletes listed above. I had just completed a hydrostatic body fat test, which is the very best way to determine body composition. In that test, your weight is measured both in and out of water to create a comparison. It had me at 16% body fat, which was pretty good for a guy my age. The BMI had me as nearly obese. The analysis I received included a chart that showed what my body fat composition would be if I were to lose different amounts of weight solely through the loss of fat. In order for me to get down to the weight at which the BMI would say I was no longer overweight, I would have had to get down to BELOW 0% body fat. In other words, the only way I could get out of the overweight category on the BMI would have been to stop exercising so that I would lose muscle mass.

Now, I don't know how that pertains to the OP in this thread. I just wanted to point out that you really can't tell ANYTHING by the BMI alone.

It is a known issue that the BMI alone is not the whole story and that it does not work with certain types of athletes. But the fact also remains that their hearts have to pump through all of that mass. The OP is not a pro ball player who makes his money abusing his body (and probably taking HGH). If you look at a lot of the pro players, they are carrying some jelly around their belly. Check with them again in an another twenty years and see how they are doing.

Do not fool yourself into thinking the BMI is not a useful tool just because pro ball players do not fit into the charts, technically, they are obese and if you did a body fat percentage I bet many of them would show it. I think a healthy number is under 17% for a fit adult male.

N