Carbon Dioxide Training & Breathwork
Introduction
Ever notice how the best athletes are the calmest people? The most relaxed, stress-free, in-control athletes are the ones who are usually winning. The ability to be relaxed and stress-free stems partly from how our bodies deal with carbon dioxide. Lucky for us, carbon dioxide tolerance is a trainable quality, so we have the ability to train our nervous systems to be calmer in stressful situations. In the world of breathwork and athletic performance, how you breath and how your body and mind relate to oxygen and carbon dioxide can be the difference between good and great performance.
CO₂ is not just a byproduct we breathe out when we exhale, it’s a critical signaling molecule that governs how oxygen is delivered to tissues, how blood vessels dilate, and how resilient your nervous system becomes under stress. Training your tolerance to carbon dioxide through specific breathwork practices can lead to:
Enhanced oxygen utilization
Improved aerobic capacity
Greater mental calm under pressure
Increased lactic acid buffering
A calmer nervous system
Carbon Dioxide’s Role in the Body
CO₂ is produced in the mitochondria as a byproduct of cellular respiration. CO₂ tells the body when and where to deliver oxygen. Most people associate breath-holding discomfort with a lack of oxygen, but it’s actually the buildup of CO₂ that triggers the anxious feeling you feel when you have the urge to breathe.
Why Train CO₂ Tolerance?
Modern breathing patterns (shallow, rapid, stress-induced) often lead to chronic over-breathing , which reduces CO₂ levels and results in:
Poor oxygen delivery
Higher heart rate
Anxiety
Poor endurance and poor tolerance to lactic acid
Improving CO₂ tolerance helps your body:
Use oxygen more efficiently
Maintain a calm mind under stress
Recover faster between efforts
Perform better with less effort
Benefits of CO₂ Tolerance Training
1. Increased Oxygen Efficiency
By adapting to higher CO₂ levels, your body becomes more tolerant of low oxygen environments — leading to better endurance and mitochondrial function.
2. Enhanced Lactic Acid Buffering
By training your ability to handle CO₂, you're also improving your ability to buffer acidity in muscles which is crucial for maintaining high-intensity performance.
3. Lower Resting Heart Rate and Better HRV
Higher CO₂ sensitivity correlates with:
Enhanced parasympathetic tone (calmer state)
Greater heart rate variability (HRV)
Lower resting heart rate and blood pressure
4. Stress Resilience and Mental Calm
CO₂ activates the chemoreceptors responsible for the panic response. Training with elevated CO₂ increases your stress threshold, making you mentally tougher and better equiped to handle any stress better. People with anxiety disorders have a much lower tolerance to carbon dioxide. People who are generally calmer human beings and tolerate stress better have a higher tolerance for carbon dioxide.
5. Improved Breathing Mechanics
Training CO₂ tolerance requires nasal breathing and diaphragmatic control which improves posture, rib mobility, and oxygen utilization.
CO₂ Tolerance Breathwork: Key Techniques
1. CO₂ Tolerance Table (Breath-Hold Protocol)
Inhale through the nose
Exhale slowly, fully
Hold your breath after exhale
Time it until moderate discomfort
Rest with normal breathing for 1-2 min
Repeat for 5–8 rounds
Over time, your CO₂ tolerance will improve, meaning you can hold your breath longer comfortably, with reduced urge to inhale.
2. Nasal Breathing During Exercise
Perform light cardio (e.g., zone 2 running, biking, rucking) using only nasal breathing
Forces CO₂ buildup and trains tolerance
Enhances diaphragm use and nitric oxide production
Great for aerobic base building
If you feel the urge to mouth-breathe, slow your pace and train up gradually.
Another technique I like to use here is gradually pushing harder on an aerobic machine such as a rower while nasal breathing until there is a strong urge to breath through the mouth then hop off the machine and control the breath back down then hope back on and repeat.
3. Box Breathing
Cadence example:
Inhale 4 seconds
Hold 4 seconds
Exhale 4 seconds
Hold 4 seconds
Repeat for 5-10 rounds or more.
Box breathing balances CO₂/O₂ exchange and improves vagal tone. It’s ideal pre-workout, pre-sleep, or in high-stress situations. I particularly like doing this one in a sauna and gradually increasing the number up to 8 or 9.
4. Breath Holds Post-Exhale During Walks
Walk while holding breath after an exhale
Stop and breathe when uncomfortable
Count steps held — this becomes your "CO₂ score"
Repeat with rest between sets
This is one of the most effective CO₂ buffering techniques. You can track progress week-to-week by the number of steps taken. You should be going on daily walks anyway so this is an easy one to toss into your daily life.
How to Measure CO₂ Tolerance
Try this BOLT (Body Oxygen Level Test):
Sit calmly and breathe normally for a few minutes
Inhale through nose, exhale through nose
After the exhale, pinch your nose and time how long until you feel the urge to breathe
Stop the timer when you let go then resume normal breathing
Time Interpretation:
< 10 seconds: low CO₂ tolerance (poor O₂ usage)
10–20 seconds: moderate
20–40 seconds: excellent
40 seconds: elite
Advanced Techniques
Contrast With Cold Exposure
Cold plunges naturally raise CO₂ through hypoventilation
Combine cold exposure with nasal breathing
Extend exhale to calm nervous system
Cold exposure while nasal breathing enhances mental control under stress
Final Thoughts: Rewire Your Breath, Rewire Your Body
Carbon dioxide training is a foundational upgrade for any athlete, performer, or health enthusiast. It trains the brain, breath, and body to work together building a calm state, mental control, and aerobic capacity. Train your breath, and you train your nervous system.
If you want guidance with implementing carbon dioxide tolerance training or any other fitness guidance set up a consultation with me here.