by David Deppeler, PT, DSc
There is a rapidly growing recognition of the value of improving CO2 tolerance for health, physical wellbeing, and athletic performance [1-9]. The CO2TT has been used by Free divers to help determine daily training tables. The CO2TT can be used as a test and an activity. The benefits of the activity are derived from first engaging (stimulating) the nervous and biochemical systems, then allowing them to quiet to a blissful place.
The science on this test is scarce. A recent study, yet to be published by researchers at USC and California State University – Fullerton, showed an inverse relationship between the CO2TT score and anxiety levels. The authors of this study caution against this measure being used for anything more than an “in-this-moment” assessment.
The Procedure – 4 Breaths
- Take three easy, calm breaths in and out through the nose
- Take one full nasal inhale, filling the abdomen, upper chest, and lungs
- Start a timer as you exhale through the nose, as slow as possible
- Stop the timer when you run out of air, swallow, or feel that you must take a breath in
How we use the CO2TT
As a test, it can be used to help determine the appropriate BYT phase in which to play.
- < 30 seconds = BYT Phase 1 activities
- 30-45 seconds = BYT Phase 2 activities
- 45 seconds = BYT Phase 3 activities
Note: Your gut wisdom will also be a valuable guide and may override the results of this test. If a repeated test yields improved scores, this is a valuable activity for you, in this moment. Keep playing.
As an activity, the CO2TT can be done as either a stealth version of Over breathing and Recovery or the BYT Deep Meditation practice. If you feel better after doing this activity once, we recommend a few rounds. Follow up the activity with meditation, quiet reading, light yoga, or QI Gong. This will allow your nervous and biochemical system to realize the greatest rewards.
SH//FT, an athlete training system report:
>80 seconds –> Elite. Reflects an advanced pulmonary adaptation, excellent motor control, and low arousal. You get to play big.
60-80 seconds –> Advanced. Reflects a healthy pulmonary system, good motor control, and relatively low arousal.
40-60 seconds –> Intermediate. This range generally improves quickly with a focus on CO2 tolerance training.
20-40 seconds –> Average. Moderate to high arousal state. Breathing mechanics may need improvement.
<20 seconds –> Awesome candidate for breathwork. Very high arousal and stress sensitivity.
Option: See the SH//FT calculator or recommended apnea and cadence breathing schedules
- McKeown, P., The oxygen advantage : the simple, scientifically proven breathing techniques for a healthier, slimmer, faster, and fitter you. First edition. ed. 2015, New York, NY: William Morrow, an imprint of HarperCollinsPublishers. xiv, 352 pages.
- Camacho-Cardenosa, A., et al., Repeated sprint in hypoxia as a time-metabolic efficient strategy to improve physical fitness of obese women. Eur J Appl Physiol, 2020. 120(5): p. 1051-1061.
- Galvin, H.M., et al., Repeated sprint training in normobaric hypoxia. Br J Sports Med, 2013. 47 Suppl 1: p. i74-9.
- Haider, T., et al., Interval hypoxic training improves autonomic cardiovascular and respiratory control in patients with mild chronic obstructive pulmonary disease. J Hypertens, 2009. 27(8): p. 1648-54.
- Hamlin, M.J., et al., Hypoxic Repeat Sprint Training Improves Rugby Player’s Repeated Sprint but Not Endurance Performance. Front Physiol, 2017. 8: p. 24.
- Hinghofer, H., Intermittent hypoxic training: Risks versus benefits. European journal of applied physiology, 2009. 108: p. 417.
- Serebrovska, T.V., Z.O. Serebrovska, and E. Egorov, Fitness and therapeutic potential of intermittent hypoxia training: a matter of dose. Fiziol Zh, 2016. 62(3): p. 78-91.
- Nestor, J., Breath : the new science of a lost art. 2020, New York: Riverhead Books. pages cm.
- Nestor, J., Deep : freediving, renegade science, and what the ocean tells us about ourselves. 2014, Boston: Houghton Mifflin Harcourt. 266 pages, 8 unnumbered pages of plates.
- Bentley, T. and B. Mackenzie CO2 Tolerance and Anxiety Study. 2020.