We’ve all been taught that Carbon Dioxide (CO2) is a useless waste product of the breathing process, and oxygen is King. But what if I told you that CO2 is actually the key to more stamina on the bike, faster recovery and less stress?

Yep, you heard that right. Cycling isn’t just about the strength in your legs or the aerodynamics of your gear, the efficiency of your built-in respiratory system is also key. Incorporating breathwork techniques into your training routine can increase your CO2 tolerance, which is the body’s ability to handle an imbalance of O2 and CO2, leading to improved athletic performance on the saddle.

Let’s walk you through:

• The role of CO2

• Benefits of CO2 tolerance

• A simple CO2 tolerance test

• Breathwork exercises to increase tolerance

 

What is the role of Carbon Dioxide in athletic performance?

 

The science of the breathing process

You breathe Oxygen into your lungs, it’s absorbed by your blood and attaches to haemoglobin to be transported to the cells that need it. Then, your muscles absorb the oxygen, and it combines with glucose to create energy (ATP), releasing H20 and CO2 as by-products. The CO2 swaps seats with O2, attaching onto the haemoglobin, to be transported back to the lungs via the blood for you to breathe it out.

 

The role of CO2 in breathing

Your CO2 levels are constantly monitored by chemo-receptors that sense changes in the chemical composition of your blood. These chemoreceptors signal us to take our next breath when our CO2 levels pass a certain critical threshold. That means it’s not your oxygen levels that inform your urge to breathe, but actually your CO2 levels. Your oxygen saturation generally remain between 95-98% at all times. So how can you harness this knowledge for your athletic performance?

 

How to use CO2 tolerance for athletic performance

When you’re pacing up a mighty mountain on your ride, increasing the concentration of CO2 in your blood will urge you to breathe more effectively in order to keep up with your muscles demands. This is all thanks to the Bohr Effect: Higher CO2 levels make the blood acidic, allowing haemoglobin to release oxygen much more easily into the tissue cells. If CO2 is too low due to a faster breathing rate, and huffing and puffing up that mountain, not enough oxygen will be released into the cells. Being able to withstand a slightly higher level of CO2 in the blood allows for oxygen to flood the cells, delaying breathlessness.

 

Benefits of CO2 Tolerance

 

Better Performance

Balancing your CO2 levels and tolerance maximises oxygen utilisation. More O2 is offloaded into the muscle tissues, translating into an accelerated creation of energy (ATP) that is available for your muscles, outpacing your competition.

 

Improved Endurance and Recovery

Tolerating higher CO2 results in a slower breathing rate and therefore a lower heart rate, a key measure of fitness that aids a faster return to your baseline after exertion. This enhanced endurance will allow you to keep pace for longer, fatigue later and be first up that mountain. By prioritising breathwork and an efficient gas exchange, your muscles will recover much faster, meaning you’ll be back in the saddle ready for more, sooner.

 

Decreased Stress

Stress and anxiety come hand in hand with shallow, fast breathing which can lead to CO2 build up due to hyperventilation. CO2 tolerance facilitates a slower, deliberate breathing pattern, which stimulates your parasympathetic nervous system, dissipating any stress, so you can tackle the challenges on the road in a state of calm.

 

Reduced Inflammation  

Elevated blood CO2 has been scientifically proven to suppress inflammatory pathways and cytokines, meaning CO2 tolerance protects you against muscle soreness and injury. Your rides will be much more enjoyable without the post-ride discomfort.

 

How to test your CO2 tolerance

 

Measure your tolerance using the BOLT score.

It’s important to be at rest when you take the test, so try doing this soon after waking up.

1. Relax your breathing for a few breaths

2. Take a normal breath in and out through the nose, at the end of the exhale pinch your nose to prevent air entering

3. Time how long you can hold your breath out at the end of the exhale. As soon as your body recognises the first desire to breathe again, stop the clock. (Note: A BOLT score is not how long you can hold your breath for, but how long your body take to react to the lack of air, so try not to forcefully extend the breath hold)

4. Relax the nose, take a breath in through your nose and resume normal breathing.

 

Interpreting your BOLT test results

Don’t worry if it’s low, even athletes start with a low BOLT score before training with breathwork! The average tends to be around the 20 second mark, whilst increasing up to 25- 40 seconds is ideal. Lower scores indicate poor CO2 tolerance and higher stress and anxiety.

> 10 seconds: Poor - Your breathing may be irregular, shallow or laboured on a daily basis. You may have trouble sleeping, feel fatigued and struggle with anxiety. Breathwork training would greatly enhance your health.

10–20 seconds: Average - Breathing may be compromised, causing poor sleep, low energy and trouble focusing. Breathwork will reduce breathlessness and enhance overall health.

20–30 seconds: Intermediate - Your breathing is usually quiet, calm and effortless. Breathwork will quickly enhance fitness levels.

40 seconds: Advanced - Great breathing control and stress control. You are essentially a pro athlete, congratulations!

 

3 Breathwork practices to enhance CO2 tolerance

 

So, you took the test and decided you’d like to improve your CO2 tolerance with some training – you’re in the right place.

The basics rely on techniques that allow you to regulate your breath and hold your breath for longer periods of time.

 

Nasal Breathing

Practise nasal breathing during exercise, resting and sleeping. This can improve breathing mechanics, increase aerobic output, reduce anxiety and lower overall fatigue. Investing in mouth tape during sleep is a great way to train nasal breathing and improve sleep quality. Breathing through the nose regulates CO2 levels and can prolong exhales.

Benefits of Nasal Breathing

• Increased CO2 tolerance

• Reduced breathing rate

• Regulates breathing pattern

How to practise nasal breathing

Gently close your mouth, and keep reminding yourself throughout the day to breathe in and out of your nose.

Check out this study done on cyclists on why nasal breathing lowers fatigue in long races, here.

 

Box Breathing

This exercise helps to regulate your nervous system, bringing it into parasympathetic (rest-and-digest) mode, creating balance and releasing stress. It includes breath holds which trains your body to withstand CO2. As your CO2 tolerance improves, you will be able to extend the breaths and holds for longer.

 

Benefits of Box Breathing

• Trains longer holds and CO2 tolerance

• Reduces stress, anxiety and improves sleep

• Reduces heart rate and blood pressure

 

How to practise box breathing

1. Sit or lie down comfortably.

2. Inhale through your nose for 4 seconds

3. Hold your breath for 4 seconds

4. Exhale through your nose for 4 seconds

5. Hold your breath for 4 seconds

6. Repeat for 2–4 minutes

This technique is called “box breathing” as you can visualise your inhale as drawing an upward line, your first hold as a horizontal line, your exhale as a downward line, and the forth hold as a horizontal line along the bottom, closing the “box”.

Feel free to extend the inhales, exhales and holds for longer. Increasing the exhales is especially effective for increasing CO2 tolerance.

 

Recovery Interval Breath Holds

After physical exercise – or whenever you notice laboured breathing or high stress – doing breath holds can regulate your breathing pattern and increase CO2 tolerance. Breath holding can stimulate training at high altitudes.

 

Benefits of breath holds

• During the breath hold your body diffuses more oxygen and increases tolerance for CO2

• Improves lung function

• Replicates high altitude training, making haemoglobin more efficient

 

How to do recovery interval breath holds

1. During your recovery, whilst breathing is still laboured, exhale normally through your nose

2. Pinch your nose and hold the breath for 5 seconds

3. Let go and breath normally for 10–15 seconds

4. Repeat 3 to 4 times

 

Warm-up light nasal breaths

Used by free divers to enhance CO2 tolerance, this technique requires light aerobic activity such as walking, a light jog or your warm up before a long cycle. During the activity, focus on light, slow and deep nasal breaths. You can practise this one daily as you walk to work.

 

Benefits of light nasal breaths

• Gentle CO2 build-up acts as a vasodilator and will flood the tissues with oxygen

• Trains a delayed onset of breathlessness

• Activates the diaphragm and improves lung function

 

How to practise light nasal breaths

1. Whilst walking, jogging or warming up, close the mouth and breath only through the nose, very light, slow and deep

2. As you breathe in, focus on the lower belly expanding first, followed by the ribs and chest expanding. Try to breathe in for 4 counts.

3. Exhale for 4 counts, allowing the chest and then the belly to drop

4. Place your hands on your lower ribs or belly to feel this movement

5. Continue the movement only at a gentle enough pace to maintain nasal breathing. Do this for as long as you can maintain.

 

Try to implement these exercises into your training routine and check back a week later to see if your BOLT score has increased or if that long ride with the steep climb feels any easier! Unlocking the potential of breathwork techniques to improve carbon dioxide tolerance will elevate your cycling game to new heights.

If you have any medical issues or are pregnant, please consult a doctor before trying these breathwork techniques.