The Mammalian Diving Reflex

How can people possibly hold their breath for so long or dive that deep?

The human body has a set of physiological reactions that helps it deal with breath hold diving. These adaptations where inherited through evolution and can be found shared by all mammals. Of course this includes dolphins, whales, seals… The same mechanism we see in marine mammals can be observed in humans. This is truly the magic behind free diving. All those changes combine to optimize your O2 consumption and can extend your breath hold abilities. With relaxation and training we can take advantage of these changes making free diving easier and more enjoyable.

Bradycardia and freediving

The first thing we can notice is bradycardia, the slowing down of the heart rate. It can be drastic, down to 30bpm in trained free divers. This will help conserving O2. As the heart pumps less blood the arterial pressure drops as well. To counteract this effect vasoconstriction of the blood vessels in the arms and legs takes place. Squeezing the blood out of the extremities and channelize it in the core where it is the most needed. In the heart, the vital organs and the brain of course. Any time you are holding your breath, your body will take the steps needed to protect you and these changes can start to be seen. Just having the face immersed in cold water will trigger the mammalian diving reflex.

Dealing with the pressure at depth

As pressure increases the next phase of the mammalian diving reflex comes into play. In the past physicians had predicted that people would get crushed by the surrounding pressure if they were to dive deeper than 50m. Freedivers proved them wrong and it is now understood that thanks to the blood shift. This newly available volume of blood is going to be concentrated in the lung area. Blood fills in the void left by the reduced air volume effectively protecting the lungs from collapsing as blood is not compressible. The spleen effect will also assist the free diver. This organ will be squeezed and release it’s stores of blood and red blood cells in to the circulation. This phenomenon occurs on deeper dives, further enhancing the availability of oxygen and it’s delivery to the body tissues.

Everyone is a natural born freediver

It’s only up to you to tap in this potential and experience one of the best feeling of relaxation as you make one with the environment. Just let go of your apprehensions and trust your body, it knows what to do. Learning the proper freediving techniques you too can dive deeper, longer and enjoy the rewards of being able to become a dolphin even if it’s just for a few minutes. We make it happen here in El Nido, Philippines most amazing freediving destination.



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