The Benefits of CO₂ Tolerance Training for Freedivers
CO₂ tolerance training helps you manage the urge to breathe during breath-holds by increasing your body's ability to handle elevated carbon dioxide levels. Contrary to popular belief, it's the rise in CO₂, not the lack of oxygen, that triggers the brain's reflex to breathe.
For freedivers, training to tolerate higher CO₂ levels is a game-changer. Improving CO₂ tolerance allows you to extend your breath-holds, stay more relaxed during dives, and enhance overall efficiency underwater. In this guide, we’ll break down what CO₂ tolerance is, why it’s crucial for freedivers, and how to train it effectively.
What Is CO₂ Tolerance?
CO₂ tolerance refers to your body's ability to withstand higher levels of carbon dioxide without feeling the urgent need to breathe. When you hold your breath, oxygen levels gradually decrease, but it's the rise in CO₂ that triggers discomfort and diaphragm contractions.
Freedivers who train their CO₂ tolerance can delay these signals, allowing them to stay calm and comfortable longer before surfacing.
Why Is CO₂ Tolerance Important for Freedivers?
1. Longer and More Comfortable Breath-Holds
Since the urge to breathe is triggered by CO₂ rather than low oxygen, improving your tolerance allows you to move past that early mental barrier and extend your dives safely.
2. Better Relaxation and Mental Control
A buildup of CO₂ can create a sense of urgency or mild panic. With consistent training, you learn to stay calm and in control, making dives feel more meditative and enjoyable.
3. Improved Oxygen Efficiency
CO₂ tolerance training teaches your body to function with higher CO₂ levels while conserving oxygen. This results in more efficient gas exchange, allowing you to delay hypoxia and perform better at depth.
4. Increased Composure in Challenging Situations
Whether you're diving in strong currents, dealing with longer descents, or taking extra time to equalize, a higher CO₂ tolerance helps you stay composed and make better decisions underwater. Freedivers with poor CO₂ tolerance often surface quickly due to discomfort, while trained divers can remain relaxed and efficient.
The Physiological Impacts of Increased CO₂
Training your body to tolerate elevated CO₂ levels triggers powerful physiological adaptations that enhance freediving performance:
✅ Increased Blood Flow to the Brain: Higher CO₂ levels cause vasodilation, improving oxygen delivery to the brain and helping maintain mental clarity.
✅ Bohr Effect and Oxygen Utilization: Increased CO₂ lowers blood pH, which enhances oxygen release from hemoglobin, making more oxygen available to muscles and organs when needed.
✅ Enhanced Respiratory Efficiency: Training with higher CO₂ conditions the body to tolerate hypercapnia (excess CO₂), reducing the urge to breathe and improving overall oxygen efficiency.
✅ Improved Relaxation Response: Some research suggests controlled exposure to elevated CO₂ can stimulate the parasympathetic nervous system, promoting relaxation and reducing stress—both crucial for freediving.
How to Train CO₂ Tolerance for Freediving
1. CO₂ Tables (Classic and Effective)
CO₂ tables are structured breath-hold exercises that gradually increase your exposure to higher CO₂ levels while keeping oxygen levels stable.
How CO₂ Tables Work:
Each round, you hold your breath for the same amount of time. This time should be set at approximately 60%-75% of your maximum.
The rest period between each hold gradually decreases, meaning CO₂ accumulates over time.
Example CO₂ Table (for a 1:30 breath-hold):
🔹 Pro Tip: Stay relaxed during contractions. The discomfort is exacerbated by resisting!
2. Exhale Breath-Holds (Simulating Higher CO₂ Conditions)
This technique involves performing static breath-holds after a partial or full exhale, which leads to a faster buildup of CO₂.
How Exhale Breath-Holds Work:
Take a full inhale, then exhale about 50% of your breath.
Hold your breath for as long as comfortable.
Repeat for 3-5 rounds.
✅ Why It Works: Since you start with less oxygen, your CO₂ levels rise quicker, helping your body adapt to high CO₂ sensations in a controlled way.
3. Apnea Walks (Building CO₂ Tolerance and Oxygen Efficiency at the Same Time)
Apnea walks are an excellent way to simulate CO₂ buildup while in motion.
How to do Apnea Walks:
Take a full inhale and walk as far as possible while holding your breath.
Exhale and recover with controlled breathing.
Repeat 4-6 times, gradually increasing your steps.
✅ Why It Works: This method trains your body to handle breath-holding in an active state, improving both CO₂ tolerance and oxygen efficiency—perfect for freediving!
Common Mistakes in CO₂ Training
🚫 Pushing Too Hard Too Soon – CO₂ training should be gradual. Overexertion can lead to stress or loss of motivation.
🚫 Not Staying Relaxed – CO₂ training is as much about mental control as physical adaptation. If you panic during contractions, focus on relaxing and embracing the discomfort.
🚫 Holding Your Breath with Tension – Always aim for a relaxed breath-hold, whether static or dynamic. Tension burns oxygen faster and decreases comfort.
🚫 Skipping Recovery Breathing – After each breath-hold, use proper recovery breathing (quick inhales with passive exhales) to recover oxygen levels.
How Long Does It Take to See Results?
Most freedivers notice substantial improvements within 1-2 weeks of consistent CO₂ tolerance training. If practiced 3-5 times per week, expect to:
✔ Feel more comfortable during longer breath-holds
✔ Experience fewer diaphragm contractions early on
✔ Stay more relaxed underwater
✔ Increase your ability to handle high CO₂ levels with ease
Like any training, progress takes patience and consistency—but the results are worth it!
Key Takeaways
✅ CO₂ tolerance is essential for longer, more comfortable dives.
✅ Higher CO₂ tolerance improves relaxation, oxygen efficiency, and mental control.
✅ Training methods include CO₂ tables, exhale breath-holds, and apnea walks.
✅ Avoid pushing too hard—progress should be gradual and relaxed.
✅ Regular practice leads to noticeable improvements in just a couple weeks!
By training your CO₂ tolerance, you’re not just increasing your breath-hold time—you’re building the foundation for deeper, safer, and more enjoyable freediving.