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Focus and calm while your heart rate slows down to 10 beats per minute and the pressure squeezes the lungs to the size of the human fist as you get closer and closer to those dark depths of the ocean. Just thinking about it puts an extra little knot in my stomach and evokes in me a irresistible urge to gasp for the air. For many of us free diving might not be the flashiest feat of athleticism, but going to depths exceeding 100 meters and coming back to surface on a single breath is indeed extreme and extraordinary. Unlike most extreme sports increasing your adrenaline and heart rate, free-diving is all about relaxation and mind-body control techniques which will change your body’s physiological functions to new, opposite extremes.

What Makes You A Free Diver

According to scientists, we all poses this mammalian diving reflex, biologically and physiologically natural abilities for free-diving. It is linked to our origins, when life was thriving in the unique oxygenated ocean existing on our planet. We can all see it in little babies which after 9 months spent in a liquid environment, have that natural swim reflex that lets them swim and hold their breath, making them feel as comfortable in the water as fish.

But these days record dives exceeding depth of 200 meters mean that those who wish to risk their lives in hopes of rewriting the record books, will need to exhibit these natural abilities even more than an average human-being. Increased tolerance for carbon dioxide levels, increased lung capacity, appropriate physical attributes and being able to integrate the body-mind connection, seem to play a big role in addition to regular training regime.

What Happens To Your Body

Photo: Courtesy of Apneista Freediving & Yoga School in Bali


Once your face comes in contact with cold water, your brain will pick up signals from the receptors telling it that your airways are submerged…it is a signal to slow things down. Human heart rate will go down ten to twenty-five percent lessening the need for bloodstream oxygen, at the same time leaving more to be used by other organs.


A few meters down from the surface, the diver might start feeling pressure or pain from middle ear and/or sinus cavities. Air spaces in the middle ear and the sinuses must be equalized to the surrounding water pressure which will increase with depth. There are a few clearing or equalizing techniques that can be used to get rid of discomfort. In some cases sinus or middle ear injury may occur leading to inner ear damage.


The deeper we go, muscular contraction in the blood vessel walls reduces blood flow to organs, which don’t need a high level of oxygen to function. Fingers and Toes close off first, then feet and hands, and lastly legs and arms stop, allowing more blood to be used by the brain and heart. Our muscles account for only 12% of the body’s total oxygen storage, that’s why many people will tend to suffer cramping during this phase. Aquatic mammals musculature can store as much as 25 to 30% of oxygen, thus they can swim long after blood supply to their muscles is stopped.

Spleen contractions

For many years spleen was thought to be defunct, a bit like the appendix. We now know that its ability to store oxygenated blood can be life saving component of our dive response. When our brain detects the oxygen levels start dropping, it sends messages to the spleen to squirt nice fresh oxygen-rich blood into our circulatory system and boost the levels of O2 in all our vital organs.

More Pressure

Unlike in scuba diving where lungs are not crushed because the breathed air is equalizing pressures from the outside and the inside of our lungs, in free diving the deeper you go the smaller your lungs will become. For years doctors used to believe that if you go deep enough your lungs would eventually “crush into themselves”, and dead you are. But the Free-diving champions proved them wrong. After further observations it was found that there is limit to how small can our lungs get before the tissues become damaged. With an increasing depth, at some point blood will start to “shift” from other parts of our bodies to begin to flood our lungs in order to equalize the outside water pressure. This will further drop the heart rate and increase the blood pressure making even more efficient gaseous exchange.

Going Back

As free-divers return to the surface, everything happens in reverse with most dangerous part being the final 10 meters or so, which might result in black -out. While divers oxygen reserves are nearly depleted, the lungs expand while being filled with gases. Some of the gases sucked out of the blood into the lungs, are the last remaining bits of oxygen that keep free-divers awake, and even though it does not seem like, black-out is our body’s final survival response. If brain detects too low levels of oxygen, it will make a decision to protect itself by stoping any further use of oxygen in the system, it simply sends us to sleep to stop our body to work. After safety diver will assist a free-diver back to surface, the body usually starts breathing automatically – the receptors in our cheeks will register air on its surface and give the brain the ‘green light’ to switch bodily functions back on. Amazing, isn’t it!


free diving fitness training - yoga
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Having 15-litre lung capacity might help, but same as in any other sport even the biggest phenomenon won’t get too far without dedication to hard training. Improving your lung capacity can be very beneficial in free diving, but it’s an ability to withstand CO2 levels that matters the most. Many people think that it is a lack of oxygen that urges us to breath, but actually that feeling comes from constantly increasing levels of CO2, while your body still has plenty of oxygen.

As unpleasant as it sounds, to see how low your oxygen can drop, first you need to practice your way to surrender to the discomfort associated with raising levels of CO2, which is a long process taking months or even years of training. Being a free-diver also means that you will need to keep your body flexible and in great shape to enable your body to move with greater ease underwater.

Swimming, running, yoga and other surface fitness activities will help one to develop an anaerobic and aerobic capacity and also appropriate relaxation of the muscles to increase breath holding skills more efficiently. For more tips on training you can check this website.


FREE DIVING BLACK OUT Photo: Sebastian Rich/Hungry Eye Images

Falling unconscious on the surface is not inherently as dangerous as a  life-threatening underwater black out which I mentioned before. Pulmonary oedema, Free diver bends, Barotrauma, Immersion HypothermiaPneumothorax and a few other conditions might also occur during free-dive.

Can Anyone Do It ?

Although diving on a professional level might be beyond the reach of most of us, given the right training structure, instruction and assuming that the one is in a good health condition, the depths of 20 to 30 meters might be achievable by many of ordinary people.

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