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One of my pet worries as a freediver is that someone will call me out, and say “I heard you can hold your breath for eight minutes. Go on then, show us!” In fact, if you take any of the top athletes in the sport and without warning chuck them in the deep end in a lead straightjacket then most will be lucky to last two or three minutes. Without the freediver’s indispensable routine of preparation, neither their mind or body is in any condition to be able to spend much time in apnea (breath holding).

Preparation varies greatly between athletes: some will spend 15 minutes stretching the body, 20 minutes doing breathing exercises, 30 minutes of meditation and then 40 minutes of warm-up breath holds. Others cut straight to the chase, and go for their longest hold or deepest dive on the first attempt, with minimal physical preparation. The one thing that everyone has in common is some kind of a breathe-up. Even if their breathe-up is just to continue breathing normally, and shallowly, in as relaxed a fashion as possible for ten minutes, this is still a breathe-up strategy.

The aim of breathing is to ventilate the lungs, so that oxygen can be absorbed into the blood and carbon dioxide can be removed from the system. However the ideal concentrations of these gases isn’t ‘as much oxygen and as little carbon dioxide as possible.’ We actually need a degree of carbon dioxide to be present in our blood for our body to realise it is holding its breath! Without it, the body would continue with its regular rate of wolfish oxygen consumption, and you would run dry much sooner. It’s the CO2 that stimulates the body to conserve oxygen (via shutting down blood flow to your extremities and other physiological responses) and gives you signals that you are running out of breath, such as hunger for air or involuntary breathing contractions. Also the haemoglobin in blood will only release the oxygen it’s carrying in the acidic presence of CO2, and if you rid the body of all CO2 in the breathe-up then it’s even possible to black out with a high amount of inaccessible oxygen still in your blood!

Think of CO2 as the fuel gauge in your boat, where oxygen is the fuel. When the needle gets into the red you start heading back to shore, and driving more conservatively. In the same way, when CO2 levels rise (triggering an urge to breathe) your body becomes more oxygen-efficient and you start thinking about heading for the surface.

So the goal of the breathe-up has to be to retain enough CO2 so that your body doesn’t get blasé and burn off all its oxygen, and so that you will have a kind of bodily alarm clock (in the form of extreme discomfort!) to tell you when to stop holding your breath. This is why extreme hyperventilation – fast and furious breathing that purges all CO2 from the system – is all but suicidal in freediving. But hyperventilation doesn’t just mean breathing like a maniac, in fact it is defined as any kind of breathing that ‘increases the rate of loss of carbon dioxide.’ Even long, deep breaths can have this effect, and what is too much for one person might be too little for someone else. The easiest way to maintain constant CO2 levels is to try and mimic the kind of shallow, relaxed breathing that you perform instinctively when you are relaxing in front of the TV or reading boring physiology articles in a spearfishing magazine.

There is of course another goal in the breathe-up: to store oxygen. In hospital emergency rooms we have a pulse-oximeter clipped to a finger: this device measures the saturation of oxygen in your arteries (vessels carrying blood away from the heart and lungs). Unless you’ve smoked a packet a day since high school then the oximeter reading will always be between 98-99% – for all intensive purposes the blood is 100% fully saturated, meaning the oxygen-carrying red blood cells simply cannot take on board any more oxygen. Whether you’re asleep in bed or trying to blow out trick birthday candles, you can’t get more saturated than 100%, so that’s even more reason not to hyperventilate.

However there is one way we can store more oxygen in the body. The blood that is returning to the heart, via the veins, has had its oxygen expended in the muscles, organs and tissues it has passed through. How much oxygen has been used depends on the workload of those muscles, organs and tissues. If you are asleep in bed, with minimal energy expenditure and a slow metabolism, then your venous blood will be well-oxygenated. If you’re huffing and puffing, tense, stressed out, digesting food, or doing anything else that requires energy, and hence oxygen, then your venous blood will be more oxygen-depleted. The more oxygen you have in your veins at the start of a breath hold, the less oxygen will be taken from lung air during the breath hold in order to re-saturate the blood before it goes back into the arteries – the net result is that the oxygen in your lungs will last you longer.

So the two keys are to breathe in a way that doesn’t change CO2 levels, and to stay relaxed in order to ensure venous oxygen saturation. That way you know you will have the most oxygen possible at your disposal, as well as the most economic and safest physiology to use it.

For what we call a ‘max attempt’ in freediving – a once-off dive to near your limits – the standard preparation is a long period of complete relaxation with great care to breathe ‘passively’ so that CO2 levels are maintained. Personally I like to lie on my back in the water with my feet resting on a float, letting my head loll in the water as I breath slowly and shallowly using the diaphragm. With eyes closed, I can relax into a kind of pre-sleep meditative state, building high venous oxygen saturation while maintaining CO2 levels.

Diaphragmatic breathing or ‘belly breathing’ is a technique that is taught in all yoga classes, and is indispensable not just for freediving, but for all sports and life in general. The diaphragm is a plate of muscle separating the ‘royal’ organs (heart and lungs) from the digestive organs underneath. It works like a piston: when it is pulled down by contraction it draws air into the lung’s chambers; when it recoils back the air is expelled. There are several advantages to this kind of breathing over thoracic breathing, where the ribcage is expanded by means of the intercostal muscles.

  1. there is less resistance to movement of the diaphragm than there is to expansion of the not-so-flexible ribcage
  2. the diaphragm is a more oxygen-efficient muscle
  3. the lungs are shaped like pyramids, so breathing into the diaphragm inflates the more voluminous lower region of the lungs.

Okay, so far we have: passive breathing – check; relaxation – check; use your diaphragm – check.

But how does this apply in spearfishing?

When we exert ourselves, whether with repetitive dives, fighting current on the surface, loading a gun, or disciplining greedy reef sharks, we burn oxygen, creating an oxygen debt in the muscles and venous blood, and we produce ample carbon dioxide. Clearly we need to address this imbalance before starting the next dive. In some cases time might be a factor, such as when a speared grouper is working its way deeper into a cave, or a blitzkrieg of tuna has materialised to attack the burly and you need to dive before your buddies see them.

There are so many variables, and no single breathe-up protocol will satisfy more than a handful of them. The important approach is to be aware of the underlying physiology, and to be conservative in your breathing. If you know that you need the CO2 in your system then you will steer towards less aggressive breathing, and stay safer during the dive. If you know that relaxation actually causes oxygen to be stored in your body (by venous saturation) then you will find yourself doing a mental check for unnecessary tension or fidgeting on the surface. And if you know that the diaphragm is the Toyota Prius of breathing muscles then you will use it more during the breathe-up.

There is no substitute for learning to read your body’s signals, not just during the dive but also during the breathe-up. For example, any pins-and-needles, or even mild tingling in the fingers is a sign that you have over-breathed, and CO2 stores are dangerously low: if you dive like this then you will feel marvelous underwater but your body will be guzzling oxygen and won’t give you motivation (contractions / urge to breathe) to head back up.

If there is any kind of a rule then it is that we should err on the side of less breathing. Since breathing replenishes oxygen stores quicker than it disposes of CO2 then if you under-breathe (e.g. come to the surface, take five quick breaths and pop back under) then it will be almost impossible to resist the contractions given by the still-high CO2 levels for long enough such that the newly-replenished oxygen stores in the lungs become dangerously depleted. When I do training tables in the pool in order to develop tolerance to hypercapnia (high CO2) I have such short recoveries that I am hammered by contractions right from the start of each successive lap, but never is my oxygen lower than that of a middle-length static apnea.

Remember however that no method is foolproof: since our body chemistry changes day by day, our interpretation of its vital signs can easily become flawed. Also, the longer we are in the water the more the body’s signals will become delayed (via changes to blood pressure and pH), making dives feel easier, when actually our true potential is fading. So buddy-diving will always be indispensable, but we can go a long way to improving our safety by an awareness of our breathing and how it influences the body’s stores of critical gases.

A freediving course, or yoga class that includes pranayama (breathing techniques) will show you more ways to enhance your air supply. Freediving pool training with your buddy or a local club will enable you to experiment combining breathing techniques with breath holds in a controlled environment.

A lifetime can be lived in the space between one breath and the next - control the breath and you will live many lifetimes.