How Freedivers Hack Their Own Bodies to Go Without Air
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How Freedivers Hack Their Own Bodies to Go Without Air

What happens when you hold your breath underwater—and how to delay that process.
August 11, 2015, 5:34pm

With the disappearance and presumed death of champion freediver Natalia Molchanova last week, it seems freediving has taken another life. Molchanova disappeared while on a recreational dive, descending only 30 or 40 meters—relatively shallow for someone who has been 91 meters below the surface. She never surfaced.

Freediving is the sport of taking deep dives with no oxygen, and one of the most crucial disciplines in freediving is static apnea (breath-holding). The current world record is 11 minutes and 54 seconds on one gulp of air.

Molchanova's death is likely attributed to an underwater current and not to the side effects of holding her breath. However, the sport is inherently dangerous. While it seems completely unbelievable that one could survive for so long without breathing, there are ways to override your body's most powerful instinct.

The human ability to voluntarily hold our breath is not unique among land-dwelling mammals. All air-breathing mammals possess the "mammalian diving reflex," a physiological response triggered specifically by cold water hitting the face. The reflex is designed to optimize what oxygen is still in our system at the moment of impact, by slowing the heart rate and constricting blood vessels in the extremities. It is the reason behind the odd fact that we can survive without oxygen for longer when we're underwater than we can on dry land.

But we can still only last for so long. When we don't exhale, the carbon dioxide that is a byproduct of respiration recirculates through our veins and begins to acidify our blood. More oxygen is converted to keep our hearts pumping, and more CO2 circulates. Our diaphragm spasms, our lungs burn, and we involuntarily gulp for air—and if we're still underwater, we take in a chestful of water instead, and begin to drown.

But the blood of an experienced freediver acidifies much more slowly, enabling them to last longer before their diaphragm starts to seize with desperation. In order to achieve this ability, they have to be able to dramatically slow their body's metabolic rate, and thus slow oxygen's conversion to CO2. Freedivers practice meditation as one of several ways to literally calm the heart and slow its beating. It's a straightforward process, but it's not easy.

Freedivers also have to suppress the natural instinct to panic. In an interview with Der Spiegel, Guillaume Nery reveals how he mentally prepares for a dive. "I put myself into a relaxed state. It should be roughly like the feeling you have after getting up in the morning, when you are still a bit tired, not entirely awake." Freediver Tanya Streeter says, "the reality of it is our physiological blueprint absolutely allows for us to do it. But our mind, you know, is there as a protection device. And you either make your mind a weapon or your weakness."

Once a diver has learned to conquer their fear, they learn to manipulate their body. Hyperventilation is perhaps the most direct way to cheat the oxygen to CO2 conversion process. By breathing pure oxygen for up to 30 minutes before a free dive, competitors have cracked 22 minutes without a breath (though of course, these oxygen-assisted performances are judged separately).

Another trick is called "buccal pumping," and has been practiced by spear fishermen for much longer than recreational divers have known about it. In buccal pumping, you control internal muscles to hold your throat shut while dumping gulps of air into your lungs, increasing lung capacity by up to three liters. (Buccal pumping could also theoretically cause your lungs to rupture, so please don't try it at home.)

While it may be possible to hold off our body's natural response to a lack of oxygen, it's not recommended, and Molchanova is not the first freediver to perish. Nicholas Mevoli died in 2013 from a pulmonary edema caused by an especially deep dive. There are a few practical applications to longer-term breath-holding—notably, halting one's breath would enable cancer patients to receive large doses of radiation in one shot, instead of just getting smaller pulses between breaths. (Radiation cannot be safely administered to the thoracic region if the patient's chest is moving.) But this would only be a few minutes of hyperventilation with an oxygen tank, supervised by medical staff.

Freediving is a relatively small athletic community, and it inevitably gets the most attention when it takes a life, which is perhaps unfair. But there is little reason to push your body so far beyond its limits outside of sheer thrill-seeking. Our physiological instincts have been honed throughout millennia, and they exist for a reason.

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