THE IMPACT OF TRAINING ON THE HUMAN BODY’S ADAPTATION TO EXTREME CONDITIONS
Freediving is a sport where freedivers try to hold their breath and dive as long or as deep as possible. Anyone can learn how to freedive by engaging in freediving courses and trainings. However, it can be dangerous because divers risk not getting enough oxygen and too much carbon dioxide, which can cause them to lose consciousness, that can be fatal if they can’t get immediate help. The longer and deeper a diver goes, the more dangerous it becomes if the proper safety protocols are not followed. Don’t get me wrong, freediving is a beautiful and safe sports, but only when divers follow the rules of the industry, mostly: always dive with a buddy.
Experienced freedivers have developed special adaptive mechanisms that help them manage their oxygen levels while they’re underwater. But you don’t need to be a pro to be able to develop these adaptations, by engaging in freediving courses, engaging with the local freediving community* to learn freediving skills will exponentially increase your physiological adaptation. These mechanisms slow down their heartbeat, increase their blood pressure, and centralize their blood to important organs like the brain and heart. The spleen and adrenal glands also help out by producing hormones that support these mechanisms. So, while freediving can be dangerous if not done properly, there are ways for experienced divers to manage their oxygen levels and stay safe.
*Reach out to us if you want to connect with sydney freediving courses, central coast freediving courses, and join a freediving community anywhere in Australia.
Freediving competitions have different disciplines, such as:
static apnea (holding your breath while stationary),
descending and ascending with a sled and balloon (No Limits),
distance diving without fins on a single breath (Dynamic Without Fins),
distance diving with fins (Dynamic With Fins),
descending and ascending with a ballast weight and a rope (Variable Weight),
depth diving without propulsion equipment (Free Immersion),
descending and ascending with fins and/or arms without a rope or ballast on a single breath (Constant Weight), and
descending and ascending using only muscle strength with a constant ballast (Constant Weight Without Fins).
Usually, during any freedive courses you would be introduced to most of these disciplines. An experienced diver has probably tried them all and picked a few favourites.
A new study investigated the effects of specialised training on the development of adaptive mechanisms of the cardio-respiratory system during breath-hold diving. The study reviewed the world literature on this topic, and here we will discuss its findings.
During breath-hold diving, oxygen levels decrease and carbon dioxide levels increase. However, well-trained athletes can maintain arterial blood oxygen saturation close to 100% even after a breath-hold for over 3 minutes. The dilation of blood vessels in the brain due to increased CO2 concentration can compensate for the decrease in arterial oxygen saturation and maintain cerebral tissue oxygenation. The Bohr effect allows for more oxygen to be transferred to tissues, particularly the brain, with high CO2 concentrations. The factor enhancing this effect is 2,3-diphosphoglycerate synthesized in red blood cells as one of the glycolysis products.
CARDIOVASCULAR ADAPTATIONS AND RESPONSES TO APNEA IN DIVING
Free diving can cause a decrease in oxygen levels in the brain which can lead to unconsciousness. This unconscious state is a protective mechanism that helps save oxygen for the brain as the most vital organ, but if the lack of oxygen continues for more than 4 minutes, the brain can suffer from irreversible damage.
Safety measures such as attentive diving and quick responses to an unconscious diver can help prevent brain damage. The good news: you can reverse it if you breathe.
Free diving causes changes in the cardio-pulmonary system to conserve oxygen and ensure constant supply to the most vulnerable tissues like the heart and brain. Bradycardia, a reflex that slows down the heartbeat, is a protective mechanism that economizes oxygen usage in breath-hold diving. The reflex is caused by the simultaneous activation of the sympathetic and parasympathetic parts of the nervous system. Bradycardia occurs during submersion of the face in water, especially cold water, and increases activity of the face vagus nerve during diving. Proper breathing and taking necessary precautions can help prevent accidents in breath-hold diving.
When we go deep underwater, our bodies experience a lot of pressure. This can cause our lungs to compress and not be able to take in as much air. To make up for this, our bodies send extra blood to the chest area, including the lungs. This extra blood helps to balance out the pressure and protect our ribs from excessive pressure and injury. The deeper we go, the more blood is sent to our chest and lungs. This can cause the size of our heart to increase and our diaphragm to move up. It also means that blood flows more in the middle and upper parts of the lungs rather than the lower parts. When freedivers hold their breath and dive deep, this effect is even more pronounced. However, once they return to the surface, their body returns to normal.
BLOOD FLOW SHIFT: THE BODY’S RESPONSE TO EXTREME ENVIRONMENTS
When you go breath-hold diving, your body goes through some serious stress. This stress causes your adrenal glands to produce chemicals called catecholamines, which get released into your bloodstream. These chemicals prepare your body for physical effort by increasing your blood pressure, accelerating your heart rate, and raising your blood glucose level.
As a result of decreased blood flow to the kidneys, they don’t get enough oxygen and produce a hormone called EPO. This hormone stimulates the production of red blood cells, which enhances your body’s ability to transport oxygen.
When you dive, your spleen releases more red blood cells into your bloodstream, which helps you hold your breath for longer. Warm-ups involving several breath-holds are a crucial part of free diving training, as they help your body prepare for the increased demands of diving.
Overall, breath-hold diving causes hormonal reactions that prepare your body for the physical effort required, stimulate the production of red blood cells, and increase your oxygen-carrying capacity.
When we hold our breath, our spleen contracts and releases more red blood cells into our bloodstream. This can help increase our oxygen supply and buffer carbon dioxide, which can allow us to hold our breath for longer periods of time. This effect is more pronounced in breath-hold divers and can remain active even during short breaks between dives. Multiple dives can intensify this effect and cause an increase in hematocrit and hemoglobin in the blood. However, this effect only lasts for a short time and can cause blood vessel resistance in already narrowed blood vessels.
Researchers are still not sure why the spleen contracts during breath pause, but there are a couple of possible explanations. One is that adrenaline secretion causes contraction. Another possibility is that a decrease in SaO2 (a measure of how much oxygen is in the blood) during breath-holding may trigger the mechanism that leads to spleen contraction and an increase in Hb and Hct (two components of blood).
INSIDE OUT: EXPLORING THE IMPACT OF HORMONES ON THE BODY’S FUNCTIONS
When free diving, where the diver hold their breath underwater for extended periods, the level of the EPO hormone in the blood may also influence Hb levels. This hormone is secreted during intermittent hypoxia, which happens during breath-holding. One study found that the EPO level in apnea divers was, on average, 24% higher than the initial value. The researchers achieved this by having the subjects perform a series of 15 breath-holds, with hyperventilation prior to each one to increase the duration of the breath-holds and arterial oxygen desaturation.
DETERMINANTS FOR GREAT FREEDIVING ABILITY
Extreme breath-hold diving is a sport that requires many individual factors to be successful. A good foundation is necessary, which includes being healthy with no issues related to the cranial sinuses, cardio-pulmonary system, or respiratory system. Although having a good vital lung capacity is important, it is not necessary for success in freediving. Freedivers with small or large vital lung capacities can still achieve great results in the sport. Age is also a less important factor in freediving compared to other sports. Younger athletes between 20-30 years old are usually the most successful, but older athletes have also beaten world records due to the body’s adaptive abilities and building experience through training and slower metabolic rates. Therefore, even an elderly diver can achieve record results in skin diving due to their improved adaptive mechanisms.
Freediving, which involves diving without equipment, can be done by people of all ages and experience levels. In fact, a young freediver has achieved world records in skin diving, Guillaume Néry who set the world record for deep dives of up to 87 meters when he was only 20 years old. However, most world record holders are in their 30s and 40s. This may be due to advancements in technology and training techniques, as well as the fact that mental toughness is just as important as physical ability in freediving.
Freedivers need to be able to handle extreme conditions and potential dangers, and their mental state can strongly affect how long they can hold their breath. Overcoming fears related to diving and staying calm in stressful situations is crucial for success in freediving. Upgrading freediving skills by joining freediving courses to deepen one’s freediving journey creates an amazing boost in confidence, helping overcome fears and self-doubt.
DIVE DEEPER, TRAIN HARDER: THE SCIENCE OF DEVELOPING DIVING REFLEXES
Training in breath-hold diving enhances the efficiency of the body’s adaptive reactions to low oxygen levels, known as the diving reflex. This reflex is more pronounced in well-trained freedivers, who can hold their breath for several minutes due to intensified chemical reactions caused by a decrease in SaO2. Training causes lower blood acidity, higher tolerance to anoxia, decelerated metabolism, and increases in the Hct value, Hb and EPO concentration, as well as the mass and volume of the lungs.
The diving reflex helps to maintain increased oxygen supply to the most important organs, especially to the brain and heart, which protects the brain from an insufficient O2 concentration in the blood. Intermittent anoxia, which lasts between 20 and 30 minutes, is sufficient enough to intensify sympathetic nervous system activity and increase blood pressure.
Highly trained breath-hold divers are able to survive the so-called breaking point after which the struggle phase follows. The moment at which the reflex to increase the frequency of unintentional diaphragm contractions kicks in is dependent on the level of anoxia and blood CO2 concentration.
TO WRAP IT UP
Breath-hold diving is a sport where people dive under water for as long as they can without breathing. It’s an extreme sport that athletes compete in to see who can stay under water the longest or cover the most distance. A group called AIDA International oversees the competitions. Very experienced deep divers attend and compete in these. The sport can be dangerous because the longer and deeper you dive, the more your body is affected by a lack of oxygen and too much carbon dioxide. However, the body has ways to adapt to this, and a freediver who trains a lot can develop better lung capacity and better ways of coping with the effects of diving. There are different types of diving, and some are more intense than others. People of all ages can be good at skin diving, and it’s unclear what the limits of human capability are. Some people even think that using yoga techniques could help a freediver set world records for how long they can stay under water. The sport of freediving is likely to continue to develop and change over time.
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LUCIANA BLANCO VILLEGAS
Luciana is a yoga and SUP yoga teacher, breathwork instructor, reiki master, freediving instructor and sports and ocean lover. Freediving is her greatest passion and can’t stay a day away from the salty water. Her practice has helped her transcend autoimmune diseases and conquer her fears. She uses the power to breath and movement to help others transcend their own limits, expand their boundaries and heal past and present wounds.
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