How long to hold your breath underwater

An explanation of the mechanics and physiology of breath-holding.

In this article I'll try to explain the mechanics and physiology of breath-holding and tell you why diving is a very complex and dangerous process. It's very important, especially if you're planning to dive deep, to clearly understand this and to take the right approach to organising your training and your safety measures.

Remember that holding your breath underwater is dangerous. Never train alone; it's better to go to experienced instructors who can teach you and point your thoughts and ambitions in the right direction.

So, apnea is a conscious or involuntary holding of the breath. It's true apnea that is the foundation of all spearfishing. Breathing is an automatic function, but all living creatures are able to hold it consciously. Whales, dolphins, seals, elephants, rats, monkeys and ... humans. An ordinary untrained person can hold their breath for 30 - 40 seconds, while yogis at the peak of their mastery reach astonishingly long apneas - up to 20 minutes and even more. Good divers sit somewhere in the middle of this hierarchy; their records today hold firmly at around 6-7.5 minutes. Air is life, every person has to breathe, and who can hold their breath and for how long depends solely on training. What sets a trained underwater athlete apart from most people is that for them breathing is a conscious and active function.

Anyone can develop the ability to control their breathing and extend their breath-hold time. But to master the basics of apnea, we first of all need to understand how a person breathes.

The human body has an innate adaptation to the aquatic environment - the diving reflex - a phenomenon of our body's readiness for apnea. Immersion in water automatically slows the heart rate, and regardless of whether you're an experienced diver or a beginner, the muscles generally relax and blood pressure drops. The reason lies in the origins of each of us - it's the aquatic nature of a human being showing through, someone who spends nine months of development in the mother's womb. Compression of the chest by water pressure also contributes to the fact that at great depth athletes' pulse sometimes drops to 20 beats per minute. During prolonged diving, the human body reorganises itself. During deep dives the liver contracts under pressure, releasing additional blood cells into the bloodstream. It can shrink in volume by 20 %, raising the concentration of haemoglobin in the blood by 9-10 % and thereby increasing the oxygen supply to the most important parts of the body during a dive. This kind of adaptation is seen in marine animals (whales can increase the concentration of blood cells by 65 %). The contraction of the liver and the rise in haemoglobin concentration in the blood is not an instant reaction; it only shows up after 15-20 minutes of diving. And only after 30-40 minutes of training can you talk about the full effect kicking in. When oxygen levels drop, blood vessels constrict and leave more blood for the more important organs - the heart, the brain, the major muscle groups. These changes allow the oxygen in the blood to be used more efficiently. In this way the diver's body adapts to longer and longer apneas.

For us land dwellers, breathing is fully automated and doesn't depend on consciousness. When we inhale air consisting of 78.08 % nitrogen, 20.93% oxygen, 0.03 % carbon dioxide and a small amount of inert gases (about 1 %), our body consumes the oxygen, using it for its vital functions, and produces carbon dioxide - a product of metabolism. This excess carbon dioxide is removed from the lungs with every exhale. Oxygen drives the oxidative processes in the body, nitrogen isn't absorbed, and carbon dioxide is expelled. So what controls this process? The central nervous system, which, in response to a rise in the CO2 concentration in the blood, "gives the command" to inhale, reacting specifically to the raised CO2 concentration rather than to a lowered oxygen concentration. After all, the air we normally exhale still contains enough oxygen to be safely breathed in another 2-3 times. A diver going underwater artificially holds their breath, suppressing the instinctive urge to inhale through sheer willpower. Meanwhile the CO2 concentration in the blood rises, which stimulates the chemoreceptors, excites the respiratory centre and causes an unbearable urge to take a breath.

Most accidents with a tragic ending that happen to spearfishers, especially experienced ones, follow a standard scenario - the diver is found on the bottom wearing a mask and weight belt, with a discharged speargun. Everything suggests that the misfortune came completely unexpectedly for the diver, and there's no external cause of the tragedy. Why does this happen, why do even experienced and trained divers die? The culprit is "shallow water blackout" (SWB), or in other words latent hypoxia (hypoxia - oxygen starvation). To understand the causes of this phenomenon, you need to get to grips with the processes going on in the diver's body during a dive. When descending to depth, a person, all their organs and the gases inside them are subjected to increased pressure. Dalton's law of partial pressures comes into play.

The pressure of a gas mixture equals the sum of the partial pressures of all the gases that make it up, and the partial pressure of each gas in the mixture is proportional to that gas's percentage share and to the absolute pressure of the whole mixture.

It follows that when diving to a depth of, say, 10 m, where the pressure is roughly 2 times greater than at the surface, the partial pressures of all the components of air also increase 2 times. And the deeper we go, the higher the partial pressures. This is very important to understand, because what plays the decisive role in normal human functioning under increased pressure is not the percentage of a gas in the mixture, but its partial pressure at a given depth. The percentage of oxygen left in an athlete's lungs by the end of a long apnea still gives a perfectly acceptable partial pressure at depth, but on the ascent it may turn out to be insufficient. Henry's law should also be taken into account: the amount of gas dissolved in a liquid (blood) is directly proportional to its pressure on the surface of the liquid. Gas pressures in the body change constantly during a dive. During the descent, lung volume decreases under water pressure, and the partial pressures of the gases rise. The body uses oxygen as needed and produces CO2, whose partial pressure at depth reaches critical values. On the ascent, the partial pressure of oxygen keeps falling and the percentage of carbon dioxide rises. What's more, the expansion of the lungs promotes the reverse process - "sucking" oxygen out of the tissues to stabilize the composition of the alveolar air. As a result, in the last 5-6 m of the ascent, the elevated CO2 concentration and critically low partial pressure of oxygen shut down consciousness, because the brain "forces" the body to do what is harmful to it -produce toxic carbon dioxide.

Loss of consciousness happens suddenly, in the middle of active effort, while striving toward the surface, and there are no warning signs. To avoid accidents, you need to prepare for the dive properly.

There are two main approaches to training for long breath-holds. One approach is hyperventilation of the lungs, and the other is true apnea, based on proper breathing, complete relaxation and self-control. This type of breathing originates from pranayama - the yogic teaching that deals with the dynamics of breathing.

The most popular way to lengthen a breath-hold is hyperventilation, which is intense breathing, faster and deeper than usual. Its goal is to accumulate the maximum amount of oxygen and flush the maximum amount of CO2 out of the body. Hyperventilation leads to certain changes in the central nervous system, a state of mild euphoria, overconfidence. But! It is impossible to store up excess oxygen; only getting rid of excess carbon dioxide allows you, by tricking the body, to extend the breath-hold for a while (a rather short one). And this is exactly what leads to dangerous consequences - loss of consciousness.

Hyperventilation, or rapid forced breathing, leads to a drop in the partial pressure of CO2, This is a dangerous state, and when the body tries to return to normal, fainting is very likely. During apnea after hyperventilation, with low CO2 levels, the first diaphragm contraction is delayed. But the interval between the first and second contractions noticeably shortens, and the intensity of the contractions increases When hyperventilating, heart rate and blood pressure increase, and many muscle groups inevitably contract involuntarily. These three states are completely alien to and unacceptable for normal apnea. Here are the processes that take place in the body during hyperventilation:

- as a result of intense breathing before the dive, the partial pressure of carbon dioxide in the lungs decreases; as depth increases, the partial pressure of all gases rises, including carbon dioxide;

- in response, the blood increases the amount of oxyhemoglobin;

- the pulse slows down;

- hypoxia causes the blood vessels of the brain to dilate, oxygen continues to be consumed, while the amount of CO2 is still insufficient to trigger the "inhale" command;

- active effort leads to slight dizziness, chills, an acute urge to take a breath;

- the rise in carbon dioxide pressure in the arterial blood causes the body's tissues to start accumulating it.

On the ascent:

- the pressure drops, the lungs expand, the partial pressures of the gases, including oxygen, fall sharply, and carbon dioxide starts flowing from the tissues into the lungs; at a critical point, usually at a depth of less than 5 m, the chemoreceptors of the respiratory center give the command to inhale;

- at the same time, the blood vessels dilate, which leads to increased oxygen consumption,

- as a result, the preconditions arise for latent hypoxia and, as a consequence, for loss of consciousness and drowning.

So how do you breathe properly!? Proper breathing right before apnea is crucial. Calm, relaxed breathing before the dive will let you get the most out of your time underwater. Proper breathing technique is impossible without mastering relaxation and concentration techniques, managing your psychological state, and autogenic training. Breathing before a dive is not easy It's important to remember once and for all: Never hyperventilate before apnea!!!

Before a long breath-hold, breathing should be very light, even and long. You lie calmly on the water, your body relaxed. The exhale should last twice as long as the inhale. At the first stage of training you can count in your head, but over time the 1:2 ratio of inhale to exhale duration will become normal and natural. With this approach, we can talk about regular, consecutive apneas, progressing in time and linked together by periods of relaxation and rest. It's impossible to specify exactly how long the rest period before a dive should last; for each person this time is strictly individual and varies over the course of training depending on many factors: fatigue, time of training, type of work done, stress.

If you are not pressed for time, your breathing rhythm stays unchanged; if time is limited, the rhythm and intensity of ventilation can increase, but in any case they must stay controlled. Breathing should be diaphragmatic. The diaphragm is a flat muscle located between the lungs and the abdominal cavity, and it helps ventilate the lungs more fully. It compresses and stretches the lower part of the lungs, which is the largest and the least used. Ordinary people, and most breath-hold divers too, both spearfishers and freedivers, use chest breathing and hardly use the lower, largest parts of the lungs at all. Diaphragmatic breathing lets you ventilate almost the entire volume, moving large volumes of air in and out thanks to the movement of the diaphragm. If you are a fairly experienced diver, changing your breathing technique will take a lot of effort and a mental readjustment. You need to understand this way of breathing, accept it and believe in its effectiveness. Then, after a while, after practice and training, you will be able to say: "Yes, this is exactly what I need!".

Besides changing your breathing technique, psychological preparation remains very important, along with relaxation and concentration techniques and special physiological adaptations that lead to deeper and longer dives.

Relaxation and concentration, and how good they are, depend directly on a person's psychological state. When problems or troubles come up, a situation becomes hard to resolve and demands immediate decisions, and we are put under stress. In itself, stress is not a dangerous state at all: it helps concentration, sharpens attention and mobilises inner reserves. But if the state of stress goes on, it can lead to serious physiological changes: vasoconstriction, arrhythmia, hypoxia, trembling, chills, cramps, shortness of breath. As a result of stress, negative effects such as reduced concentration and attention, loss of strength and loss of mobility can appear. The conclusion: eliminate stress, and any possibility of stress, wherever that is up to us. Preparing for a dive should look roughly like this: you lie on the surface, easy and relaxed, and get ready for a long apnea. Calm, drawn-out breathing leads to deep relaxation. A wetsuit that fits well but is not tight lets you lie calmly on the water. Nothing distracts you. You are focused on yourself, breathing calmly, with relaxed diaphragmatic breathing. Your muscles are relaxed, and you feel as if you are half asleep, watching yourself from the outside. Then comes one last, even and relaxed breath in. You let the snorkel out of your mouth, bend downward and, without hurrying, using only the muscles you need and controlling every movement, you begin the dive.

Every diver has their own descent speed that lets them reach the bottom with minimal loss of air, energy and time. After many dives, having tried many kinds of fins and different techniques of moving through the water, a diver will work out for himself which descent speed suits him. Each of us has individual traits that depend on fitness, how we feel and our concentration at any given moment.

During preparation, you need to concentrate on your breathing and on relaxing your muscles, and on taking the last breath correctly. When you start moving down at the moment of the dive, your attention switches to finning and to equalising pressure during the descent. Then you need to focus on overall relaxation on the bottom and on a strictly vertical position on the ascent. As you ascend, do not change the speed or pace of the ascent; just rise calmly to the surface.

10 rules:

1. Never train alone, only with a partner, and better still, with an experienced coach.

2. Do not dive when you are overtired, let alone drunk.

3. Watch your breathing rhythm.

4. Try not to panic in critical situations. If you lose your orientation, remember that the surface is where the air bubbles are going.

5. Do not train near nets. It is dangerous.

6. Never be afraid or reluctant to drop your weight belt. Your life is worth more!

7. Alcohol and smoking are a diver's worst enemies. The only things that can be worse are haste, unjustified risk, bravado and the urge to prove something at any cost!

8. Avoid hyperventilation, and never keep it up for more than 3-4 breaths in and out.

9. Load your speargun only in the water, with the spear pointing down, toward the depth.

10. Go spearfishing far away from beaches and crowded places.