Freediving and the Science of the Breath Hold

Underwater yoga

Breathing – it is something we do everyday, many of us are not even aware of it. With each inhale, we bring a fresh supply of air into our chests; and with each exhale we release stale air back to where it came from. And in that intimate space in between, an exchange of oxygen and carbon dioxide takes place.

We may not be conscious of our breathing, but we may become aware of it when our breathing pattern changes. In stressful moments, we may find ourselves holding our breaths. In moments of over-exertion, we find ourselves out of breath. We may not know it but breathing is the rhythm of our lives.

It may come as a surprise, then, to know that there is a group of people who specializes in holding their breaths. Apnea is a discipline that involves the suspension of breath. The word “apnea” derives from Greek and means to be without wind. It is this act of apnea that enables a diver to dive into the ocean without any breathing aid and with just one breath of air, in the relatively new sports discipline known as freediving.

Freediving may be new to sports but it is not new to human existence. In many parts of Asia, freediving had been an important cultural activity of people who live by the sea. From ages of old, sea people have dived into the ocean for various resources, such as for fish for food, sponges for cleaning, and oysters for their pearls. These divers can stay under water for up to five minutes and attain depths of up to 30 meters.

Whether it’s the Bajau or sea nomads who ply the waters between Malaysia, Indonesia and the Philippines, the Ama or sea women of Japan, or the Haenyeo or women divers of Korea, many cultures have discovered and honed the curious ability of the human body to hold its breath and to resist the pressure of water to explore and exploit the living oceans. Modern man has much to learn from these traditional people of the sea. They only take what they need, not more, living symbiotically with the ocean.

I first became acquainted with apneists or freedivers at a dive fair in Singapore. Most divers are scuba divers who dive with their Self-Contained Underwater Breathing Apparatus (SCUBA), which is a tank of compressed air connected to a regulator that releases ambient air to the diver’s mouth. Curious about freediving, I approached Suzy, a freediving instructor, and asked her how was it possible for humans to hold their breaths for an extended period of time? Were we not designed to breathe? After giving a short introduction about freediving, she urged me to give it a try, pointing me to the booth of a local freediving school.

Some of us would ask who are the freedivers and why do they do it? For us scientists, the more pressing question is, “How do they do it?” It may come less as a surprise when we remember our origins. The human foetus spends nine months fully submerged in the amniotic fluid in the mother’s womb. The baby only takes its first breath at birth. While in the womb, the baby is technically holding its breath. And at birth, the baby does not lose this ability until it learns how to walk. Babies are known to be natural “swimmers” and will instinctively hold their breaths for up to 45 seconds underwater.

I signed up for my first freediving class and arrived at the swimming complex, uncertain of what to expect. In preparation at home, I tried holding my breath, and like a baby, I found that I gave up after 45 seconds. After an introduction on freediving, our jolly instructor, John, led us to a routine of increasingly longer breath holds. We were asked to stand in the water, let go of the ridge of the pool, and lie in the water, relaxed, like dead bodies, with long fingers and long toes, releasing every tension in our bodies.

Scientists are beginning to understand more and more about what is called the mammalian dive reflex. With other aquatic mammals like the whales, dolphins, seals, dugongs and otters, we humans share the ability to make the necessary bodily adaptations needed for a successful dive. What happens when sensors in our faces touch cold water and we begin to hold our breath and descent is a series of bodily adaptations that happen to enable that dive to take place.

First, our heart rates would fall, in a phenomenon known as bradycardia, helping us to conserve precious energy. The heart rate at 100 meters of depth can fall as low as 15 beats per minute. Second, bloodshift occurs and blood leaves our extremities and enters the chest to protect the lungs from collapsing. Third, peripheral vasoconstriction takes place. This is the narrowing of blood vessels in the limbs to divert blood to oxygen sensitive organs like the brain and the heart. These adaptations allow the freediver to descent into the deep.

Because water is much denser than air, the human body is subjected to increasing pressure and compression the deeper it goes. The tissues of the body are mainly liquid (blood) and solids (bones) and are therefore incompressible. But what is compressible are the air found in our lungs and nasal cavities. For every 10 meters of descent, the lung compresses to half its original volume. By the time world record holders attain a depth of a hundred meters, their lungs would have compressed to the size of two clenched fists.

Back at the swimming pool, I find myself head down in the water, holding my breath. Breath holding is as much a mental exercise as it is physical. It helps to occupy the mind to give the illusion that time is passing faster than it really is. Closing my eyes, I begin to isolate and relax each body part. I imagine heaviness at the tips of my fingers, traveling up to my shoulders, then heaviness at the tips of my toes, traveling up to my thighs. I listen to the sounds around me, all amplified with my concentration. Not knowing how long has passed, I started to feel my chest convulse and then contract rhythmically. I try telling myself to hold on a little more, just a little more.

Any dive has its limits where the freediver has to decide to return. It is usually not too difficult a decision to make, as divers will feel what I felt, signs that the carbon dioxide build up has become uncomfortable for the body, and the diaphragm contracts to induce forced breathing. Divers who misjudge their limits can go into a state called the blackout, a loss of consciousness caused by an inadequate supply of oxygen to the brain. This state of non-breathing will last for about two minutes. It is vital that buddies help their blacked out counterparts immediately out of the water and to blow gently on their cheeks to awaken them from their “slumber”. Should there be a delay and the diver wakes up underwater, drowning will most certainly occur.

This worst-case scenario keeps many people far from this sport. However, with the right training and safety procedures, and awareness of and respect for our bodies and their limits, anyone can experience the miracle of the breath hold. It is vital that divers never dive alone but always buddy up!

More than a physical activity, many have claimed the psychological and spiritual benefits of the sport. Freediving has been described as meditation, looking within oneself, returning to one’s roots, being one with the ocean, and deeply relaxing. In fact, freediving is rising in popularity in Asia. More and more Asians are picking up the sport. And people from all over the world are choosing places in South-East Asia such as Koh Tao, Thailand, the Gili Islands, Indonesia, and Bali, Indonesia to learn freediving.

Coming out of my apnea, I held one hand onto the ridge of the pool, and then the other, and then one foot down onto the floor, and then the other, and I slowly lifted my head out of the water. Three minutes and two seconds. It was a most surreal experience! When I told my friends about this the next day, few could believe me, one of them even exclaimed that it was not possible!

Freediving, in this way, challenges not only the limits of the human body, but also our perceptions of the possible, and surprises us with what our bodies were apparently also made to do – to hold our breaths.

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