MODIFIED CO2 TOLERANCE TEST

The Modified CO2 Tolerance Test (also known as the Exhale Control & Hold Capacity Test) is a respiratory test developed by Dr. Justin Ternes based on the well-known CO2 Tolerance Test created by Brian Mackenzie. It is a tool aimed at improving the reliability and validity of the popular CO2 Tolerance Test.

This measurement tool is a great way to record your current mental, emotional, physical, and nervous system state + you can develop breath control & capacity.

Continue to see step-by-step instructions, a results chart, and a video tutorial.

STEP-BY-STEP INSTRUCTIONS

1. TAKE 3 FULL BREATHS

This is the preparation to begin the exhale and hold.

In through the nose, out through the mouth.

Deep and effortful — all the way in, all the way out.

2. TAKE A FOURTH BREATH IN, START THE TIMER, AND BEGIN YOUR CONTROLLED EXHALE (AS LONG & SLOW AS POSSIBLE)

This is the most important component - the control of your exhale.

Watch the video below to get more familiar with the technique.

THE EXHALE CONTROL TECHNIQUE

  • Exhale for as long and slow as possible.

  • Hold your palm approx. 6 inches from your mouth and blow just barely enough to feel the stream of air on the palm of your hand.

  • Visualize blowing a candle just enough to make it flicker but not blow out.

3. AT THE END OF YOUR EXHALE, PUSH “LAP” AND HOLD YOUR BREATH FOR AS LONG AS POSSIBLE

As soon as you are unable to continue the constant flow of air, HOLD your breath as long as you can.  

4. STOP THE TIMER AS SOON AS YOU NEED TO BREATHE

When you absolutely need to breathe, push “Stop” on the timer and BREATHE!!

Good job!

5. RECOVER & RECORD YOUR TIME

RECOVER your breath back to normal.

RECORD your time.

You will have 3 times:  
(Exhale Time) + (Hold Time) = Total Time

Note any additional variables that may have contributed to the results:

Quality of sleep, fatigue, full or empty stomach, distracted, time of day, location, etc.

6) REPEAT

REPEAT the test 2 or 3 more times.

Try to get a slightly better score each time!

VIDEO INSTRUCTIONS FOR THE MODIFIED CO2 TOLERANCE TEST

1. Take 3 Full Breaths

2. Take a 4th Inhale

3. Start Timer & Begin Exhale

4. At End of Exhale, Hold

5. Press "Lap" to Record How Long You Can Hold

6. Stop Timer as Soon as You Need to Breathe

7. Recover and Record Your Time

8. Repeat

HOW TO INTERPRET YOUR RESULTS

Total Time // Ranking
Under 0:30 // Below Average
0:30 to 0:45 // Average
0:45 to 1:00 // Intermediate
1:00 to 1:15 // Advanced
1:15 to 1:30 // Very Advanced
Over 1:30 // Elite

Note: If you get below 30 seconds total, there may be an error in how the test is being conducted, or you may be exhaling too hard and too quickly.

Remember to do multiple tests (ideally in various conditions) to get your average. 

What are we testing:

  • Lung capacity

  • Breath control

  • Nervous system stat

  • Stress levels

  • Skill & familiarity with the test

Complete the form below to get more in-depth interpretations of your results!

SHARE YOUR RESULTS!

Remember, your results will have three times:
(Exhale Time) + (Hold Time) = Total Time