Breathing & CO2 Tolerance
Measure and train how well you handle carbon dioxide. Andy Galpin's CO2 tolerance test doubles as a free recovery gauge, and nasal plus box breathing builds the control that steadies performance and stress.
Measure your controlled exhale Take 4 easy breaths, then a full inhale, then exhale as slowly as possible through pursed lips; time the exhale. Same time of day, ideally morning
It is a fast, free gauge of recovery and nervous-system readiness.
Read the number as a trend, not a verdict ~30 to 60s controlled exhale suggests well-recovered; a short, strained exhale suggests stress or fatigue. Compare only to your own baseline
Like HRV, it is most useful tracked against yourself over time.
Breathe through your nose by default Nasal breathing at rest and in easy training; Galpin calls it a 'cheat code' for better mechanics
Nasal breathing is more efficient and supports better posture and breathing mechanics.
Practise box breathing to lower resting rate Equal counts in, hold, out, hold (e.g. 4-4-4-4), a few minutes daily; lengthen as control improves
Builds mechanical control over breathing and reduces resting respiratory rate.
Manage breathing in hard efforts Avoid over-breathing early; return to nasal-only breathing between intervals before starting the next round
Composed breathing prevents the early over-breathing that wrecks later efforts.
Track the test alongside training Check periodically (especially after hard blocks); a sustained drop is a cue to back off
It flags under-recovery before it becomes injury or burnout.
Carbon dioxide tolerance reflects how well you can mechanically control the diaphragm and stay calm as CO2 builds, which is what actually drives the urge to breathe.
View sources
How to Breathe Correctly for Optimal Health, Mood, Learning & Performance
How to Breathe Correctly for Optimal Health, Mood, Learning & Performance
How to Breathe Correctly for Optimal Health, Mood, Learning & Performance (Huberman Lab episode)
Not medical advice. This page is for education only and is not a substitute for professional medical care. Consult a qualified clinician before changing your health routine.
Independent curation. YourProtocol is an independent platform. This protocol is based on the publicly available work of Andy Galpin and is not created, reviewed, endorsed by, or affiliated with Andy Galpin or Parker University / Performance.
Is this for you
- Endurance athletes and lifters
- Anyone wanting a free recovery gauge
- People who default to mouth breathing
- Those who panic-breathe under exertion or stress
Cautions
- The CO2 tolerance test is a useful trend tool, not a validated clinical measure; treat it as directional and compare only to your own baseline
- Breath-holds and intense breathwork are not for everyone: avoid them in pregnancy, with cardiovascular or seizure conditions, and never do breath-holds in or near water
- Build gradually; if controlled breathing makes you lightheaded, stop and breathe normally
- Educational only, not medical advice
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