There is an increase in the number of people engaging in Freediving breath-hold for recreational purposes. While it can be risky, with training and practice, many people can hold their breath for a deep dive. The longest deep dive was by an Australian, Herbert Nitsch. He was underwater for close to twenty-five minutes and went 253m deep.
The freediving breath-hold is also known as Mammalian Diving Reflex (MDR). The MDR is an evolutionary adaptation that enables sea animals to dive without succumbing to pressure. It triggers the human body to conserve oxygen and protect organs at deeper sea levels. Physiological responses of the body under water include:
Cardiac Arrhythmia
Cardiac Arrhythmia or bradycardia refers to a slow heart rate. It is a sign of an illness except for freedivers. A fast heartbeat indicates more oxygen consumption; when the heart rate is slow, the body uses less oxygen, which allows freedivers to stay underwater longer. Slower heart rates are more effective in colder waters, and people trained in Freediving reduce their heart rate by up to 50%.
Peripheral Vasospasm
Vasospasm is the narrowing of blood vessels to lower the blood flow rate through the body and heart. Peripheral vasoconstriction occurs during MDR to reserve the blood for only high-priority parts. That means less blood flow to the arms and legs and more to the lungs and heart. The selective blood flow also slows down heart rate, enabling bradycardia.
Blood Shift
Blood shift occurs when the diver is in the depths of the water, and the blood flows towards vital organs, occupying the space left by the compression of the lungs. Failure of blood shift causes the diver’s lungs to crash due to the water pressure. The blood maintains its volume and does not compress despite the freediver’s depth.
Spleen Effect
Spleen, an otherwise vestigial organ, is actually helpful to freedivers. It acts as a reservoir for blood during the blood shift in MDR. It releases the blood into the circulatory system, increasing the red blood cell supply with the increasing depth of the diving.
These harmonized physiological changes are the body’s ways of adapting to the new environment.
What to Expect During Freediving
Freediving breath-hold subjects the body to unnatural extremes on an ordinary day. Thus, the body tries to adjust to the pressure by reacting in certain ways. The most common things that happen include:
Immersion Diuresis
Blood shift causes the body’s midsection to hold more blood than normal. The kidneys try to repair this effect by expelling water from the blood, which leads to the need to pee. All divers pee underwater due to this effect. This can also lead to serious dehydration.
The build-up of Lactic Acid
Reduced blood flow and vasoconstriction lead to lactic acid build and muscle pull which can be detrimental if it occurs underwater. Divers need thorough training to successfully prepare the body to go through strenuous activity.
How to Build Endurance for MDR
Some divers go into months of practicing Vinyasa Yoga. Yoga training employs flexibility and stretching. Meditative yoga also helps stabilize the core by focusing on movements. Yoga is built on the control of the mind, which is helpful when controlling breathing in freediving.
Any exercise that builds your core is important in preparing for freediving. Squats work the core, calves, hamstrings, and lower back, preventing a potential muscle pull in any of these parts during the dive. Pilates improves posture and prevents injuries, as well as increases flexibility.
Most importantly, take actual freediving to practice to put all the exercises to use. Increase the depth of the water slowly and allow the body to adjust to new depths, a meter at a time.
In some situations, divers have either lost their lives or encountered brain damage due to carbon dioxide poisoning. It is vital to practice and train consistently before taking the plunge.
