How do you perform CO2 tolerance testing?

To perform a CO2 tolerance test effectively, follow these steps as outlined by Andrew Huberman:

1. Preparation: Begin in the morning right after waking up. If necessary, use the restroom but avoid distractions like your phone. Use a timer, either on your phone (in airplane mode) or a stopwatch 1.

2. Initial Breathing: Sit or lie down comfortably. Inhale deeply through your nose and exhale through your mouth. Repeat this process four times. This helps bring awareness to your diaphragmatic breathing 1.

3. Main Test - Fifth Breath: After the initial breaths, take a deep fifth inhale through your nose, filling your lungs completely. Ensure your diaphragm is fully engaged by making your belly expand during the inhale.

4. Exhalation: Begin timing as you exhale slowly through your mouth, as if there is a tiny straw, to control the release of air. The goal is to prolong the exhalation as long as possible.

5. Ending the Test: Stop the timer as soon as you can no longer exhale any more air. This duration is known as your CO2 discard time 2.

6. Interpret Results:

   • 20 seconds or less indicates incomplete recovery.
   • 30 to 60 seconds suggests readiness for more work.
   • 65 to 120 seconds signals that your nervous system is well-recovered 2.

This process helps assess how well your body manages CO2 levels, which is a reflection of your nervous system's recovery state and your ability to engage the parasympathetic nervous system effectively. Regularly tracking this can provide valuable insights into your overall recovery from exercise or stress.