Lung Volume, Part 2

In Part I we described methods for measuring lung capacities.  But why would we ever do such a thing?  For one thing, it's just interesting to know.  As a freediver, I see it is a measurement as integral as my height or weight.  But more importantly, I want to see how my training affects my lung capacity and better understand what volumes of air I'm using during the various types of dives I intend to do.
A quick look at an online forum will let you know divers are always looking for ways to increase their lung volumes.  Frequently they ask about gadgets like the Expand-A-Lung.  These are unlikely to work, but the good news is you can probably increase your lung capacity without buying anything at all.  It is generally accepted that aerobic exercise will give you small gains in lung volume.  Stretching your upper body has also been reported to result in an increase in volume.  Lung tissue is somewhat elastic, so volume can be limited by an inflexible chest.  Packing relates directly to chest flexibility, but is a subject beyond the scope of this blog.  I intend to use it during my training, but packing-related injuries are numerous and well documented, so take that for what it's worth.  It is also highly advisable to learn proper breathing technique in order to maximize the volume you have.  I personally hope that through cardiovascular exercise, stretching, and breathing exercises to increase flexibility and perhaps lung capacity.
Although you don't need large lungs to dive deep, knowing the volume of your lungs will help you better understand your training.  Many freedivers hit a barrier at around 130 feet where they can no longer equalize.  The reason for this is lung volume, specifically residual volume.  Water pressure at this depth has reduced your lungs to 20% of their volume on the surface (roughly residual volume).  Remember, residual volume cannot normally be exhaled, and so advanced equalization techniques must be learned to go much beyond that depth.  If gains can be made to vital capacity without increasing residual volume (such as by packing or perhaps through cardiovascular exercise) you could push this depth deeper.  FRC dives will also be an integral part of my training, and it will be valuable to understand exactly how much air I'm retaining on a dive of this method (perhaps the subject of a future article).  Lastly, I don't currently pack on my dives.  However, I was surprised to find I add 50% to my vital capacity through packing.  Of course, the last few packs I do make me want to pass out, so through experimentation I hope to find an optimal compromise between added volume and comfort.
So measuring your lung volume can be a fun and informative training tool.  That said, it is far from crucial.  Whether you find out you have small lungs, or you never test your lung volume at all, you can still reach abyssal depths.

Don't forget to check out Deeper Perspectives- Episode 5