Big lung capacity - a hinderance?

[TooTall]

I have big lungs.

Stop it - stop it now - this is serious.

When I initially did my dive medical, the doc swore and made me repeat some breath tests - it seems I have a lung capacity almost double normal adult males. I'm 6'7" tall with a 48" chest and fairly fit, so given that males, tall people and fitter people all have larger lung capacities, it was going to happen.

Will this be a big hinderance for diving? I'm only really just getting into proper calculations of my consumption, but I accept that a 15l tank will be my destiny. Any issues with buoyancy (other than a larger tidal volume for me) or anything else? I guess I'll always be known as the heavy breather :(

[Tony Dwyer]

I have big lungs.

Stop it - stop it now - this is serious.

When I initially did my dive medical, the doc swore and made me repeat some breath tests - it seems I have a lung capacity almost double normal adult males. I'm 6'7" tall with a 48" chest and fairly fit, so given that males, tall people and fitter people all have larger lung capacities, it was going to happen.

Will this be a big hinderance for diving? I'm only really just getting into proper calculations of my consumption, but I accept that a 15l tank will be my destiny. Any issues with buoyancy (other than a larger tidal volume for me) or anything else? I guess I'll always be known as the heavy breather :(

Don't worry, it's not really a problem.

I have a 47" chest and large bellows to match. It's true that with a full inhale / exhale I shift a lot of gas.
However, while relaxed and taking it easy, I only burn enough O2 to support my body's needs and don't breathe heavily. My usual equvalent surface air consumption is about 9 ltrs per minute. When I work hard though, I can shift a good deal of air very quickly.
The solution is obvious and icludes all the following;

Get trained and practice a lot!
Be relaxed
Be confident (anxiety increases breathing rate)
Avoid conditions which will make you work too hard
Achieve first class buoyancy control
Stay fit

There will always be someone who uses much less gas than you (for me it's SWMBO). Don't get in a fuss about it, you will breathe what you need.

Having large lungs enables VERY precise buoancy adjustment when taking piccies. At depth, I can rise and fall appreciably just using breath control. I achieve this by increasing / decreasing the the volume in my lungs beyond my normal low level.

[John Bantin]

I once asked the little Japanese girl I was diving with why her tank was twice as big as mine. She was confused by the question because we both had 12 litre tanks. However hers reached down almost to the back of her knees whist mine reached only my buttocks. That's because I was 6'4" and she was 4'4". Just take enough gas for the dive. You are big and strong enough to carry two 12 litre cylinders if you need to. I am.

[kath2407]

I agree with the bouyancy comment. I am able to tune my bouyancy by taking bigger breaths. Can be very useful, means less faffing with other bouyancy devises but a great inderence if I get a fit of the giggles on my 6m stop!!!

Its just about being aware of yourself, and your bouyancy. It does mean I can clear my large volume mask in one breath!

K XX

[ChristianG]

I have big lungs.

Stop it - stop it now - this is serious.
Unless you're working underwater (currents etc) you should only be taking quite shallow and short breaths just like the ones you are unconsciously using as you sit comfortably at your desk reading this.

At your desk you're working at keeping yourself upright whereas u/w you're working by paddling along - the two largely cancel themselves out. Extra lung capacity is useful, as someone else pointed out, for minor corrections in the water column and I, completely unconsciously nowadays, do it all the time. Mind, I will have balanced myself out at the optimal depth at half my standard breath - which allows me to descend a few metres by exhaling and breathing at the bottom of my lungs and, conversely, breathing at the top of my lungs to go up a few metres.

Mind, I'm a photographer and you haven't learnt proper buoyancy control until you really and truly nail it as a photographer.

[ozone1]

I have big lungs.

Stop it - stop it now - this is serious.

When I initially did my dive medical, the doc swore and made me repeat some breath tests - it seems I have a lung capacity almost double normal adult males. I'm 6'7" tall with a 48" chest and fairly fit, so given that males, tall people and fitter people all have larger lung capacities, it was going to happen.

Will this be a big hinderance for diving? I'm only really just getting into proper calculations of my consumption, but I accept that a 15l tank will be my destiny. Any issues with buoyancy (other than a larger tidal volume for me) or anything else? I guess I'll always be known as the heavy breather :(

Big lungs does not = high air consumption.
Once you have dived half a dozen times and start to get experienced
you will find that you can reduce you weights and gas usage.

Cheers ozone

.

[MartinJ]

Big lungs does not = high air consumption.
Once you have dived half a dozen times and start to get experienced
you will find that you can reduce you weights and gas usage.

Cheers ozone

.

I would have to agree. Have just seen my doctor and been told I have very large lungs. My air consumption was absolute ****e when I started diving (I could get through it quicker than beer) even though I didnt feel stressed and was told I had very good buoyancy control. Having done plenty of diving now my air consumption is now up there with the guys I used to think "how they hell do they do that!" The more you dive, the more you relax, the more your buoyancy improves etc etc and the less gas you use. And then the less you worry about high air consumption so you relax even more not worrying about shortening someone elses dive.

We have all been there......

[TooTall]

OK - but what about the rest of the physiology? I'm not concerned - just aware of my overall size (99th percentile for height etc) so trying to understand better.

I'm trying to get some sort of understanding of the overall physiology - big lungs alone does not mean higher consumption - but won't a fit-ish 250lb 6'7" tall bloke use more air than someone 5'6"? I'm trying to look at me as a whole - and the lungs are a part of that.

[tony J]

I'm trying to get some sort of understanding of the overall physiology - big lungs alone does not mean higher consumption - but won't a fit-ish 250lb 6'7" tall bloke use more air than someone 5'6"? I'm trying to look at me as a whole - and the lungs are a part of that.
Most of air consumption is abut buoyancy

my note here : http://www.twiki.co.uk/diving/air_usage.html.htm

The fitness is not relevant to most of underwater as we are not raising our heart rate (what does fitness mean anyway ? - for me its the ability to recover from exercise. So being fit helps in diving as it means you can do a surface swim before going under and be back to normal breathing more quickly)

What matters if you are trying to reduce air consumption is to only use your muscles for propulsion and not other ancillary options (stabilization / buoyancy etc). Get too good at it and you can get cold !

And as far as using lungs as buoyancy control - I think its in one of the ocean diver pool lessons - so it shows how important we think the skill is (unless you are on a rebreather...)

Tony (6ft4)

[TooTall]

I understand the difference between noob diver and ninja diver - that is crystal clear. What I want to understand are the anthropomorphical differences. Every ninja diver doesn't use exactly the same air on a dive - they use slightly different volumes as they are all different. It is that difference that interests me - not the n00b / ninja one.

[tony J]

I understand the difference between noob diver and ninja diver - that is crystal clear. What I want to understand are the anthropomorphical differences. Every ninja diver doesn't use exactly the same air on a dive - they use slightly different volumes as they are all different. It is that difference that interests me - not the n00b / ninja one.
I've found the difference between peoples sizes to be the noise rather than the signal so have no worried (the big people have less heat loss problems as well)

You original question was what was the effect of having larger lungs, I would say nil as you are using a small fraction of the max tidal volume capacity.

So replying to the title of the post. "big lung capacity - a hindrance?" no !

tony

[deveugle]

Hi Tootall,

I am 6'4" and have a lung capacity of about 10 liters and am reasonably fit: I won't run a marathon but wouldn't shy away from 5 or 10 miles. So, although my case is probably not quite as extreme as yours (even so I firmly believe airplane seats are designed by dwarfs with a vengeance), I have gone through a similar thought process as you when I started diving. I thought I would need tanks twice as big (at the very least ! :rolleyes: ) as all the - experienced - people I was diving with. On one "memorable" occasion I even breathed a 12l empty under Swanage pier in just under twenty minutes (no I have no idea how that is even possible). Over time, using the techniques described above by other people I became more and more relaxed and my breathing rate has plummeted significantly - even to the point that I can now make an Alu80 last almost 2 hours at 10m in the Bahamas. Mind you, such a reduction tends to happen in jerky steps and gets temporarily worse from time to time (usually when adding a new stress factor in to the mix such as when first diving a twinset or breathing pure oxygen for instance) but that is probably the subject of a different thread.

At the end of the day, people with a similar comfort level in the water will have a very similar gas consumption rate, independent of their physical size. If you would be reassured by a more scientific explanation, you would probably have to look up size related factors for gas consumption such as tidal lung volume, perfusion rates and oxygen uptake per pound of lean body mass and see how small the differences are between differently sized people relative to stress related factors such as breathing rate, unnecessary adjusting of buoyancy or overly energetic movement in the water. So theoretically there would be a disadvantage for "bigger" people but in reality what has been said by other people holds firmly true: lung capacity, general fitness or size have an almost negligible effect on gas consumption rates and experience and comfort in the water are far more important. So big lungs are not a hinderance to diving ! Woohoo !

However, there will always be people with a similar experience level who have a better gas consumption than you (although this in itself might vary from day to day or from dive to dive) and these tend to be the ones with a smaller physique.

So yes, your consumption rate will always look bigger than the rate of that tiny Asian woman on the boat who seemingly metabolises oxygen straight out of water and carries a tank purely for show. Then again, so will the consumption rate of 99% of divers. You can get quite long and/or deep dives out of standard size cylinders and there is no need to carry significantly bigger sizes (which in itself might actually increase gas consumption - ie: I breathe a lot, so I take a bigger tank, now I have to exert more effort carrying everything around, hence I have a higher breathing rate, hence I need a bigger tank ,....).

Peter