How do I improve my air consumption?

[paulwlee]

Scuba_Vixen once bubbled...
You've compressed the air a bit into the chest area and lowered your total displacement...you still have the same amout of air you started with....

No, if you put a hand on your chest while you suck in your abdomen, you will notice that the chest rises, maintaining the overall volume of your body cavity. Similarly, if you are sucking in your abdomen as you inhale, you are just reducing the amount you are inhaling, not 'compressing' the air you inhaled. If you want definite proof, then try this next time you are diving. Once you reach a hover, hold your breath, (only for divers with perfect bouyancy control) make sure you maintain depth, and then try sucking in your abdomen. If you are right, you should sink. I'll tell you now that you won't.

 

[Scuba_Vixen]

when you pull in your abs..your chest stays the same..the air is just compressed slightly into less space above the diaphram..

An instructor friend showed me that several years ago..can't imagine it only works for females, lol

 

[paulwlee]

People inhale using two mechanisms, both of which increase the volume of the chest cavity. One is to increase the cross section of the chest cavity (rising chest) and the other is to push out the diaphragm that seperates the chest and abdominal cavities towards the abdominal cavity. Both mechanisms are used, although there are differences between sexes and from individual to individual.

Now if one is sucking in the abdomen while inhaling, then that person is just using chest expansion, and hindering that with what would normally be an exhale motion on the abdomen. What doesn't change, is that while you are inhaling air, the pressure inside your lungs is lower than the ambient pressure, (otherwise you can't inhale) which means that your lung volume is expanding as it is taking in air. It's just that you are inhaling less than normal, or said another way breathing shallower.

I hope this will convince you enough.

 

[knobber]

Ok, I'm beyond pi$$ed now. I work out cardio weekly like a freak--45 minutes of stairclimbing, usually burning around 1000-1100 calories. Two weeks before my trip, I started swimming in the pool with just my fins, back and forth along the bottom, holding my breath.
During the trip, I was averaging 80 feet, starting with 3000 lbs or 3100 in my tank. However, although I "appeared" to be the most fit in my group, I was only getting 24-27 minutes of total dive time out of my tank, surfacing with 500 lbs of air.
Everyone else, guys included, was getting 35-40 minutes of dive time. I wasn't even near the yellow of nitrogen saturation on my computer, while everyone else was at or near yellow.
What the hell? I'm 6'1", 205 lbs in great shape. I was not nervous, felt great, and tried as much as I can to breath slower and deeper. hell, I even tried different breathing methods all to no avail. What's going on?

 

[FreeFloat]

I would guess your air consumption to be very basically a result of the fact that proportionately, you just have "big lungs".

Like I said, I'm no expert, but I'm the tiniest person in my OW class. It's not uncommon for me to turn in a tank with 1-1/2 to 2 times the amount of air left in it, than a majority of the other students. Even if I wasn't trying to watch my consumption! My instructor seems to think it absolutely normal that this is the case.

All I can say is, it's going to take some time and quite a few dives for that consumption to come down. I expect it will for me as well.

 

[scubasean]

There are several different reasons a person's air consumption might be greater than they desire.

How much diving have you done?
What exposure suit were you wearing as compared to others?

One of my friends is a larger guy, and he is much more fit than I....Yet, he uses air at a 50% greater rate than I do.

Go figure.

Sean

 

[DiverBuoy]

Assuming you are 1. properly weighted (most divers are not), 2. and your equipment is time tested and well-fitting. The TWO KEY things to remember that have the most significant impact on reducing gas consumption are:

• Establish a breathing pattern such as 4 seconds in 2 seconds out.
• Pay attention to your breathing during your descent.

It's essential that you focus on your breathing at the beginning of your dive ON THE DESCENT. It is during this crucial time-frame that you are setting the pace for the rest of the dive. The vast majority of divers don't realize how much of their gas they burn just getting to the bottom - so worried about all the little things - equalizing, adjusting equipment, mask leak, hair caught, fin strap hurts, cramp, exposure suit leaking, arresting the descent with too much gas ... thus over compensating, dumping, refilling ... blah blah.

 

[BradB]

You sound like you are in great shape, wish I was. Here is a simple solution. If your buddies are diving 80's, go get some LP100's and pump them up. Even if you SAC is not great you still have the bottom time. I am a big guy who primarily spears and I dive LP 120's with cave fills. It still amazes me just how fast I can burn them when things get busy in 100'.

 

[Karl_in_Calif]

Remember Pepin the freediver? He has abnormally big lungs.

That might be your situation as well ... simple physiology.

You may try conserving air by the following methods:

1) Use your B/C as efficiently as possible.

This is accomplished by using deep exhalations on the surface at the beginning of your dive to begin your descent. Deflate only as much air from your B/C as needed, and only in little bits, to minimize the amount of air you might have to subsequently put back into it.

At the beginning of a dive, due to the weight of the compressed air in your tank(s), you will be about 5 lbs negatively buoyant. You need some air (about 1/10th cu ft) to neutralize this negative buoyancy. As you descent to 100 ft, you need to increase this amount four-fold. Doing this efficiently makes a big difference compared with overfilling then bleeding etc.

Diving a zig zag pattern to various depths will also waste air from bleeding and refilling your B/C. Try to stay at a constant depth, the ascend gradually and extend your dive time on your ascent.

2) Keep your diving depth shallower

You will use more compressed air the deeper you dive. By keeping your depth shallower, you can extend your air time. At a 0.75 surface RMV, an 80 cu ft tank should last about 50 mins at 33 fsw, 35 mins at 65 fsw, or 25 mins at 100 fsw. Keeping your depth shallower on the reef allows you to stay longer. You might be plunging down below your friends now and not noticing it much.

3) Breathe in, breathe out, relax, breathe again.

Breathing "properly" will enhance your dive time. Everyone has a different definition of what is proper. Slightly slower than on the surface, and slightly deeper than on the surface, works for most divers.

4) Slow down dont kick

Floating and gliding rather than kicking will require less metabolic energy and consume less oxygen. Some divers think they are in a swimming meet underwater. The ideal is never to kick with your fins, and instead just glide or float around the reef.

 

[BIGSAGE136]

I too am a huffer. I am a large guy and I do have a great set of lungs. Bike commuting puts a plus on that. Any and all pointers will be extremely helpful. It really sucks to be the 1st guy up on a boat dive. Especially when you go out solo.

I went diving with board members a week or too ago. They both outlasted my hp100 with al80's. Jenny, give up the secret b4 the beach party!: