The Many Pressures of Freediving

The Many Pressures of Freediving

In competitive freediving, athletes experience psychological pressure as well as physical pressure. Combined these two sources of pressure can easily combine to make for a bad day, and at the extreme, potentially your last.  Finding constructive methods for limiting the risks associated with these pressures can go a long way toward keeping us out of trouble.  I’d like to discuss several potential sources of pressure and methods for dealing with them.

Psychological pressures are probably the most difficult to master.  They can create forces that we cannot measure with a gauge, and yet they move us just the same as any other force.  Sometimes, they move us into dangerous situations.

I train for freediving.  I invest countless hours and dollars.  I build custom equipment to improve my ability to perform.  I stress my body, forcing it to evolve so that I can do things underwater that most others cannot.  I dive deeper, further, longer.  I sometimes travel thousands of miles to compete and prove, to myself and others, what I can do.  When after months of effort, I finally claim a record for myself, the rush of exhilaration takes over.  The feeling of accomplishment is intoxicating, and I think to myself, “This feels really good; even better than I expected”.

Author, Ron Smith as "Captain America" at the head of the pack.  Our buddy, Nick Mevoli at the end of the line.

Author, Ron Smith as “Captain America” at the head of the pack. Our buddy, Nick Mevoli at the end of the line.

Last year at the AIDA World Championships in Nice France, I was fortunate enough to be able to claim a national record in the freediving discipline Dynamic with Fins.  It was the year for team competitions, not for individual glory, and up until a half hour before my performance I didn’t think it was going to be my day.  Too many things didn’t feel right and our training day did not demonstrate I could guarantee a white card for my team while also exceeding the current record.  The responsible thing to do would be to shave a few meters off my swim and have a clean performance.  I was disappointed and felt like I had invested too much not try for the record.  I was so close and I knew that on a good day I could make it.  I just was not sure about that particular day.  A half hour before my dive, fate intervened and my teammate’s decision to push too far left me no reason to be conservative.  With one red card, our team was done, and everyone was in agreement that I should do my best, and do it for myself.  I quickly switched psychological gears, and went into a trance like state as I prepared to attempt a national record swim.  I had an all or nothing attitude, and fortunately for me the swim turned out to be within my capabilities that day.

When we have invested so much effort to deliver a specific level of performance, the psychological dive can take on a significant amount of inertia.  The initial feeling that I was not going to accomplish my personal goal was difficult for my mind to process, but I had all morning to come to grips with it before the situation changed and I allowed myself to go for it.  With proper safeties in place, dynamic swims are low risk compared to depth diving where you can physically damage your body if things don’t go well.  You don’t have all morning to come to grips with the logical conclusion that it is not a good idea to continue, and adopting that “all or nothing attitude” can really get you into trouble.

Can I be trusted to make a split second decision to abort in the middle of a dive, just a few meters from my goal?  After I have invested so much effort, could I make the right decision under the effects of narcosis?  I sometimes think about that day of dynamics and the psychological inertia behind my dive and wonder what it would be like to be so close to a depth record instead.  The psychological inertia of the event keeps pushing us to reach for our goal, and it is much more work to stop short and turn around than it is to let the momentum of our expectations carry us on down deeper and sustain an injury.

…it is much more work to stop short and turn around than it is to let the momentum of our expectations carry us on down deeper and sustain an injury.

I’m no where near a record in constant weight diving, but that does not mean that I don’t have personal goals.  Goals plus the sunk costs of training and getting to the competition carry momentum that we must learn to counter with other forces to create balance in our diving.  One of the things I like about team competitions is that the structure of the “team” has an energy of it’s own that counteracts our personal ambitions.  It forces us to be more conservative and it brings the wisdom and experience of the entire team to bear on many critical decisions regarding our dives.  Competing as part of a team is a really good method for divers to learn restraint.

Without a team backing us up, we need to rely on ourselves to make good judgment calls.  Even if we learn to suppress the psychological pressures, if we do not have a good understanding of the physical pressures of depth diving, we will not be able to make good decisions.  The physics of diving must be ingrained into our thoughts and we must know of all the ways we can get hurt while diving if we are going to avoid injury under the pressures of a competition, our ambitions and goals.

Many divers are not giving the physics of diving injuries the influence over their egos and ambitions that it deserves. If we all were, diving related injuries would be more rare.

Perforated eardrum model.

Perforated eardrum model.

When we first start to dive the first sign of barometric pressure on our bodies is pain in the ear. We learn to equalize the pressure of the inner ear with Valsalva, Frenzel or BTV, which alleviates the stress and the pain and we can dive deeper. Without this equalization, the eardrum would rupture in a painful burst and a flood of water that usually results in instant vertigo and a nasty ear infection. As we advance in our depth diving abilities, at some point, usually in the 30 to 40 meter depth range for most people, we hit our failure depth. This is where the lungs become so compressed that there is not enough air volume left in them to be able to equalize our ears. The rib cage acts as a frame holding our chest structure open, and the water pressure begins to squeeze the diaphragm and soft tissues of the abdomen up into the chest structure. The pressure creates stresses in the soft tissues of the abdomen and strains, or displaces them into the chest cavity which alleviates some, but not all of the pressure differential. The more flexible the diver’s diaphragm and soft tissues, the more it can stretch and displace to relieve tissue stresses, and less residual pressure differential will remain between the external water pressure and the internal air pressure of the lungs.

The same things are happening in the inner ear as a result of the remaining pressure differential in the lungs (the pressure that is not alleviated from soft tissue strain). External pressure acting on the eardrum creates stress that strains the membrane of the eardrum. When the rib cage holding the lungs open creates enough pressure differential between the lungs and the external water, it can create strain exceeding a threshold of elongation for the eardrum material, and it tears. However, the eardrum has nerves that detect the strain of the membrane and these nerves send signals of pain to the brain that strongly encourage us to stop doing whatever we are doing that is causing the pain. In this case, we stop diving deeper, and turn to head back to the surface. Hence the name “Failure Depth”, as we fail to be able to dive any deeper. This is the same physics in action within the ear that happens closer to the surface when we start to dive, except the pressure gradient is now backward of what is required for Valsalva, Frenzel or BTV to work, and without that pressure equalization we can proceed no further. Pain is an effective tool for overriding our psychological pressures and forcing us to stop when we really need to stop.  However, in advanced diving, we learn that there is a way to cheat our failure depth.

It is possible to trap a reservoir of air in our mouth and, with the right techniques, create the proper pressure gradient with it to be able to use this mouthful of air instead of the air in our lungs to equalize our ears. With no more pain, and the risk of a ruptured eardrum gone, we press on to deeper and deeper depths. However, the effects of pressure described above are still acting on the chest cavity, diaphragm and lungs; and their effects are increasing with every meter of depth added to the dive. The basic physics is the same as for the ear, and when soft tissues are strained beyond their limit, the tissue will stretch no further and tear instead*. The difference this time is that the tissue under strain that will tear is lung tissue full of blood vessels instead of an eardrum. This is significant for a couple of reasons.
First: Lung tissue does not contain any nerves that register pain sensations from tissue strain or damage.  This is why people can smoke cigarettes, afflict significant damage to the lung tissue and not “feel” affected by it. Unlike the eardrum under dangerous levels of strain, lung tissue will not send those important messages of pain encouraging you to stop doing what you are doing. Without those pain signals forcing us to pay attention to what is happening to our bodies, we are far more likely to let our higher level ambitions driven by our ego dominate our actions. If that ambition is to reach a depth that is beyond our physical property limits for tissue strain, the result will be a tear of the soft tissue, or what is called a squeeze.

Second: Whereas the eardrum keeps the potentially infectious environment out of the inner ear, the lungs are responsible for exchanging the gases that keep us alive. Although the lungs have far more capacity than is normally required to keep us alive, after a long dive when we are depleted of resources, we need to recharge. If the lungs are too damaged to do this bad things can happen. The important thing I want people to consider when evaluating risk vs reward and filling out their announcement card for the depth they will be diving, is that the eardrum is equipped with nerves to signal of an approaching problem. It protects our hearing and balance. Yet our lungs will offer no such warnings, and they keep us alive. If you have never thought of it this way before and I have gotten you to reconsider the potential seriousness, then I have done some good. The situation is certainly not ideal and it would be nice if we were built with better abilities and warning signals, but this is the way it is and having a good understanding of the situation and a good attitude will go a long way to keeping yourself out of trouble.

So, how do these amazing divers like William, Alexey and Guillaume dive so deep without suffering lung squeezes? From flexibility of their diaphragm muscle and other soft tissues in the abdomen which they developed over years of diving and slowly stretching them out. Unlike the “mouth fill” to cheat the failure depth posed by the eardrum, there is no known technique that can bypass the lung squeeze. We need to learn to be patient and earn the ability to dive deeper by getting there slowly over time.

* Whereas the eardrum is a membrane that tears, lung tissue is like a sponge filled with blood vessels. When we say the lung tissue tears, it is actually the blood vessels that build the pressure differential and burst as opposed to something that looks like a linear tear is a membrane sheet. In this case the membrane is actually the many walls of the blood vessels.

Post by Ron Smith

All commentary and opinions in this post are exclusively of the author, Ron Smith.  They do not reflect the opinions of the USFA or any other associated organizations or people mentioned.

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