The Chemistry of Calm

How should we breathe? This is a simple enough question, but the answer is sometimes complicated – and important to understand.

We need to pay attention to breathing biomechanics and biochemistry. By changing where the breath is being directed and how many breaths you take per minute (respiration rate), you can increase oxygen delivery, feel calmer, enhance lung volume and even increase heart rate variability (HRV). All of this we owe to a hardworking chemical, technically a toxic waste product, that is swimming in your blood right now.

Importance and benefits of CO2 in the body

CO2 is a waste gas produced through metabolic stress. However, it provides the body with several incredible benefits. CO2 helps maintain blood pH and supports the relaxation of smooth muscles surrounding airways and blood vessels.

Most importantly, it acts as a catalyst for the release of oxygen from haemoglobin, the protein molecules in red blood cells. As CO2 levels rise, chemically sensitive cells detect the shift in pH, which in turn increases minute ventilation – the total volume of air moved in and out of the lungs per minute. This is determined by respiration rate (breaths per minute) and tidal volume (the amount of air exchanged per breath).

So, the counterintuitive secret to breathing better? Breathe less.

Let’s try a quick exercise. Take a small breath – through your nose or mouth, your choice. Now hold it. And hold it. And hold it. Before long, you’ll start to feel uncomfortable. You’ll crave air. Soon, your body will scream for it. Your lungs will ache, and a suffocating panic will set in. Soon, the only thought in your mind will be when you can take another breath.

This overwhelming need to breathe is CO2 poisoning in action. If we take in no air while cellular respiration continues, CO2 levels in the blood rise. This increase activates a cluster of neurons in the brainstem called central chemoreceptors, which initiate alarm signals in the brain, urging our lungs to breathe faster and deeper.

Now, contrast this intense discomfort with the extraordinary control of freedivers. For example, the world record for breath-holding is 24 minutes and 37 seconds. This proves that we can train ourselves to endure extreme conditions with the right techniques.

The benefits of carbon dioxide tolerance (CO2T)

Reduces anxiety

Many individuals with anxiety experience shallow breathing as a trigger. CO2 helps regulate breathing patterns, and higher CO2 tolerance can mitigate anxiety. Research shows that increased CO2 levels can induce panic, so by training CO2T we can build resilience and stress tolerance over time.

Enhances athletic endurance

Higher CO2 tolerance lowers heart rate and reduces stress on the body, delaying fatigue. A low CO2 tolerance forces the heart to work harder, increasing physiological stress. Over-breathing also makes it harder for oxygen to reach working muscles.

Reduces inflammation

CO2 has been shown to reduce inflammation in the body. By increasing CO2 retention, we may improve recovery and resilience.

Boosts energy

CO2 retention can increase both mental and physical energy. It helps multiply mitochondria in cells, boosting overall energy levels.

So, now that we understand that having more CO2 in the blood and increasing our tolerance to it is good for our optimisation, how do we actually train ourselves to improve our tolerance? One easy and non-invasive way is with breath-hold training.

Breath-hold techniques – increasing your CO2 tolerance

I will preface this by saying there will always be a certain amount of danger and risk when holding your breath. If you’re pregnant or trying to get pregnant, please don’t use these techniques.

The aim here is to build your tolerance to rising CO2, so that you don’t need to breathe as much. Less is more, remember.

And who better to learn from than the people who do this for a living: freedivers. In the freediving world, they often practise using a thing called apnoea tables, which consist of CO2 and oxygen (O2) tables: two simple but powerful tools for breath training. They’re structured routines of breath holds and recovery periods, designed to help you build tolerance to either high carbon dioxide or low oxygen levels – both of which are key to staying calm and in control during breath holds.

CO2 tables focus on helping your body and mind cope with rising carbon dioxide levels. The breath-hold time stays the same (say, 1 minute), but the rest periods in between get shorter with each round. This gradually increases the CO2 in your system and challenges you to stay relaxed under pressure – it’s great not just for breath control, but also for building resilience and mental toughness.

O2 tables flip the focus. In this version, the rest time stays constant (for example, two minutes), but the breath holds get longer and longer. This helps your body adapt to functioning with lower levels of oxygen, improving your efficiency and endurance.

Apnoea tables

The word apnoea means to ‘suspend respiration’ – essentially, to hold your breath, and that’s what you’re practising here. These structured routines outline both the holds and the rest periods. Choose whether you’re going to work on CO2 or O2, then follow that schedule.

You will get better at staying calm and relaxed as CO2 builds up in the body.

CO2	O2
Breathe 2:30	Breathe 2:00
Hold 1:30	Hold 1:00
Breathe 2:15	Breathe 2:00
Hold 1:30	Hold 1:15
Breathe 2:00	Breathe 2:00
Hold 1:30	Hold 1:30
Breathe 1:45	Breathe 2:00
Hold 1:30	Hold 1:45
Breathe 1:30	Breathe 2:00
Hold 1:30	Hold 2:00
Breathe 1:15	Breathe 2:00
Hold 1:30	Hold 2:15
Breathe 1:00	Breathe 2:00
Hold 1:30	Hold 2:30

By consistently breathing through your nose with light, slow breaths and practising breath-hold techniques, your CO2T will improve. Be patient and consistent. Breathwork, like any other mental or physical discipline, rewards regular practice and dedication.

The benefits from practising breathwork can be felt immediately, but they build over the long term. As our CO2 tolerance increases, so does our capacity to perform.