There are, in my experience, three major factors--make that four--that come into play with people we quite unkindly call 'hoovers' (because of their ability to suck their tanks down quickly).

1) As ikan noted, buoyancy and trim.
• If you are overweighted you will waste a lot of air pumping and dumping gas into and from your BCD in an effort to stay neutral.
• If you are underweighted you will have to breathe in fast and constantly exhale in order to stay down.
• If you have poor trim (you are not horizontal in the water) you expend a lot of energy pushing water ahead of you instead of slicing through it (think about how you spash somebody with your flat hand on the surface of the water), which means you are working harder and getting nowhere fast while you deplete your supply of air in the process.

2) Breathing technique. Shallow breathing leaves a lot of 'dead air' in your airways that is saturated with CO2. Excess CO2 in the respiratory system is what triggers the breathing impulse by the brain. Breathe all the air out of your lungs on every breath to get rid of all that excess CO2 and you will find that you can breathe more slowly and evenly, and therefore improve your air consumption.

3) Large lungs. Big men have big lungs, big muscles, etc. They simply consume more air! I had a dive instructor as a customer last week. This guy dives six days a week in Hawaii and has 7000 dives to his credit. He just couldn't stay down for a full one hour dive at our dive depths with a 12 l tank, and it was obvious this wasn't a newbie problem! Once I convinced him to dive with a 15 l tank, everybody was happy!

4) Fitness and health. Unfit people just breathe more heavily. Fitness is not a question of physical size--that is, slender people with lovely bodies can be horribly unfit, while people with a little lard on their frames can be very fit! If you get out of breath climbing stairs or walking up a slight hill, you should take measures to improve your cardiovascular fitness. Hand in hand with this is the temporary state of your health. When you're ill, or recovering from an illness, you will breathe down your tank faster. It's just a fact!

Despite the jokey replies you have received, I assume your concern is serious. My suggestion:

Take a Peak Performance Buoyancy class. When I teach this course I focus on several coaching points to help my divers cut down on their air consumption:

1) swimming technique--I train my divers to stop waving their hands and arms around. This just uses up air (you need oxygen to fuel the muscle movement) without providing significant propulsion. For fine tuning (steering), your hands may help, but you can also use your feet, and much more effectively. Fold your arms away and leave them there throughout the dive.

2) finning--I see a lot of divers doing what is called a "bicycle kick" (this is the same movement you use to climb stairs). This is inefficient and you have to work very, very hard to go a very, very short distance. If you are kicking inefficiently, you will be exerting your muscles a great deal, and all that movement means you need oxygen to fuel them. Again, your air consumption will be compromised. Make sure you are kicking from your hips (not by bending your knees) with fully extended legs and pointed feet.

3) trim--I make sure my divers are perfectly horizontal in the water. If you swim with your legs dangling down, your finning will push you upward rather than forward. You will be working twice as hard to get half as far; plus you will usually think you need more weight to keep you down since you seem to be "floating" up all the time (when actually you may be kicking yourself towards the surface). Use visualization to help you get yourself into proper trim (horizontal position).

4) weighting--if you are carrying too much weight to counteract a tendency to swim yourself to the surface (due to poor trim), your unhappy muscles have to push all that weight through the water. Imagine your heart and breathing rates when climbing a set of stairs, and then imagine climbing the same stairs with 20 kg of groceries; which scenario makes your heart beat harder and makes you breathe faster? Why work any harder than you have to? Carry only as much weight as you need to maintain a safety stop at the end of the dive with a nearly empty tank and no air in your BCD.

5) breath control--I teach my divers to breathe in and out fully. Shallow, rapid breathing does not provide a good air exchange as it leaves old, dead, carbon dioxide-laden air in the lungs, and since the breathing response is triggered precisely by CO2 levels, you will breathe more by taking shallow breaths than you will by taking deep breaths. By breathing deeply in and out, you expel all the excess CO2 and can achieve better breath control. I recommend a target breathing rate of six breaths per minute on a leisurely dive where you don't have to work hard (e.g., against a current). It will take some practice to reach this goal, but it is perfectly manageable. I am a very experienced diver so have had a lot of practice, but as a benchmark, you might like to know that I breathe in for a count of 4 or 5 and out for a count of 8 to 10, which makes a breath cycle of 12 to 15 seconds. I take just 4 or 5 breaths a minute. Breathe slowly and fully in and out.

Hope this helps.

Q.

bro, you'll get the hang of it. 45mins is respectable. Overtime it will improve.

What are your plans for May? We are going Redang 6-9, then TARP 17-19 and probably celebrating anniversary at Perhentian end of the month.

Didn't get to dive last month.... this month still dry.... hopefully some compressed air end of the month. 

does reducing the flow regulator at the second stage help me?

Quote from: decimal86 on April 14, 2010, 09:47:12 AM

does reducing the flow regulator at the second stage help me?

No, that won't help. That thing is there to prevent free-flows on the surface, where you can put it on the MIN setting. Turn it all the way to the MAX setting for diving.