What’s Your Carbon Dioxide Tolerance?
For freedivers, breath-hold performance is not just about lung capacity—it’s about your body’s ability to tolerate carbon dioxide (CO2). Testing and improving your CO2 tolerance can enhance your breath control, reduce stress, and elevate your freediving capabilities. Here’s how to test your CO2 tolerance and actionable steps to improve it over time.
Why Test Your CO2 Tolerance?
CO2 tolerance determines how your body and mind handle rising CO2 levels during a breath hold. A high tolerance means you stay calm and efficient as CO2 builds up, while a low tolerance can trigger early breathing urges, stress, or even anxiety. Testing gives you a baseline to track progress and focus your training.
The CO2 Tolerance Test
Step-by-Step Instructions:
1. Prepare with Coherence Breathing:
Spend 2 minutes breathing in for a count of 5 and out for a count of 5. This helps regulate your system and sets the stage for the test.
2. Take Four Full Breaths:
After coherence breathing, take 4 controlled breaths:
• Inhale for 3-5 seconds.
• Exhale for 5-10 seconds.
• Pause for 1 second before starting the next inhale.
3. Perform the Test:
On the fourth inhale (completely full), start a timer. Exhale as slowly as possible, aiming to stretch out the exhale for as long as you can.
• Close your eyes to stay relaxed.
• Stop the timer when you run out of air or need to inhale.
Interpreting Your Results
Use the chart below to evaluate your score:
| Time in Seconds | Skill Level | Description |
| >80 | Elite | Excellent pulmonary adaptation, breathing control, and stress management. |
| 60-80 | Advanced | Healthy pulmonary system and good stress control. |
| 40-60 | Intermediate | Improves quickly with dedicated CO2 training. |
| 20-40 | Average | Indicates moderate stress and room for improvement. |
| <20 | Poor | High stress sensitivity, possible mechanical restrictions, or low pulmonary capacity. |
How to Improve Your CO2 Tolerance
Whether your score is elite or needs work, CO2 tolerance training is key to advancing your breath control. Here are three effective ways to improve:
1. Nasal Breathing During Training
Close your mouth while exercising to slow down CO2 offloading. It’s tougher than it sounds, but it trains your pulmonary system for greater efficiency and strengthens your CO2 tolerance over time.
2. Counted Breathing Exercises
• Beginner: Inhale for 8 seconds, exhale for 10.
• Intermediate: Inhale for 8 seconds, hold for 4 seconds, exhale for 10.
• Advanced: Inhale for 8 seconds, exhale for 10, and hold for 4 seconds at the end of the exhale.
Repeat these patterns for 10 minutes in a quiet, focused setting.
3. Incorporate CO2 Tolerance Techniques into Freediving Practice
Use CO2 training tables and targeted breath-hold exercises to replicate conditions you’ll face underwater.
Dive into the Anatomy of Freediving to understand how your body adapts to pressure and breath-holding demands.
Factors That Can Impact CO2 Tolerance
Your CO2 tolerance isn’t fixed—it’s influenced by lifestyle and habits, including:
• Smoking: Reduces lung efficiency and tolerance.
• Exercise: Regular training improves pulmonary health and CO2 capacity.
• Mental Grit: Staying calm under stress plays a big role in high CO2 tolerance.
• Medical Conditions: Asthma or other lung issues may affect results.
By identifying and addressing these factors, you can tailor your CO2 tolerance training to meet your needs.
Why It Matters
Improving CO2 tolerance is a game-changer for freedivers. It helps you stay calm, hold your breath longer, and perform better underwater. Even outside freediving, building CO2 tolerance benefits stress management, focus, and respiratory health.
Explore Freediving Techniques for Better Sleep for more ways to use breathwork to calm your body and mind.