The Mammalian Diving Reflex

Did you ever wonder why you instinctively hold your breath when you dive?

It's because of the mammalian diving reflex where your body performs an elaborate response to ensure the survival of your vital organs. The diving reflex is a natural response that every person possess. It is also known as the Diving Response or the Bradycardic Response.

The diving reflex mechanism is a response to immersion of all known air-breathing vertebraes. As vertebraes, mammals have this reflex too, which means, you the reader, have it.

Discovery of the diving reflex

kids diving reflex Ever since the scientific world accepted Boyle's law, scientist calculated that diving thirty meters (100ft) were impossible. Under Boyle's Law, the deeper we dive underwater, the higher the pressure. For decades, scientists thought that this high pressure would compress the air in our body and crush our lungs.

But in 1949, two Italian divers proved this theory wrong. Ennio Falco dared Raimondo Bucher (who was also a spearfisher) to dive the limit for 50,000 Lira ($800). Lt. Bucher plunged the thirty meters (100 ft) and won the bet. This feat brought awareness among the scientific community and led them to study more about human physiology.

In 1962, the Swedish physiologist, Scholander discovered the secret of this mechanism. By strapping heart rate monitors to volunteer divers, he found out that these divers had their heart slowed down when they dive.

How does the diving reflex happen?

The human body will conserve the air supply it has when immersed in water. When your body senses that the face is getting wet, it will automatically keep the oxygen inside, and your blood will be moved to your heart and brain.

We have this response even at an early stage of our lives. When you dip a baby in water, it will close its throat to prevent the air from escaping the body and keeping water or anything else out.

Aquatic mammals like the dolphins and whales, even the hippopotamus, are more adept in using their diving reflex. Evolution made their physiology more suited to such conditions.

What triggers the diving reflex?

mammalian diving reflex The diving reflex occurs because of the immersion of the body in water. The need for air made our body more conscious of oxygen consumption. It results in a decrease in heart rate to lessen the oxygen consumption.

Studies found that the diving reflex only works if your face is wet or immersed in water. Scientists have tried simulating different situations with different stimuli but to no avail. Only immersion trigger the mammalian diving response.

Our body responds that way without knowing why it should. It means that the diving reflex is instinctive. But the reflex can become voluntary if you practice on controlling it.

In 1976, the French diver, Jacques Mayol left the world in awe when he dove down to 100 meters underwater (330ft) for the first time. His introduction of yoga to the new sport of freediving gave freedivers the possibility to go deeper.

The changes in the body due to the Reflex

freediving and diving response When the diving response kicks in, the body adapts temporarily to being immersed in water. It means that our body will not function the way it usually does.

It starts with a Bradycardia which involves the slowing of the pace of the heart — followed by the Peripheral Vasoconstriction. The second change constricts blood flow and oxygen consumption. Finally, there will be a blood shift. The shift causes blood plasma from different parts of the body to move to the chest cavity. It is to protect the organs in the chest.

These changes allow the human body to stay longer underwater. It also makes sure that no damage is done even with the deprivation of air.

The benefits of enhancing the diving reflex

mammal diving reflex Practicing to control your diving response can contribute to your health. The diving response makes our body adaptive to conditions where air becomes limited. Your body will function normally even under a similar situation.

Scholander's experiment on divers showed that we could dive deep without the help of any gears. As the divers controlled their breathing, the researchers figured the possibility of treating anxiety.

By practicing apnea, our breathing becomes more controlled, even when our body is lacking in air, we can remain calm.

The Diving Reflex Researches and References

All pictures used for this article are courtesy of Wikimedia Commons and our freediving staff.

If you want to know more about sirens and mermaids, take a look at some of our references below.

Speaking about Mammalian Diving Reflex, do you how deep can a mammal go on a single breath?

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