Measuring breathing efficiency over time help to establish a performance and health baseline. Most people assume they breathe well. Regular rhythm, no obvious problems. But the relevant question isn’t whether breathing feels comfortable, it’s how much CO₂ your body can tolerate before it demands another breath.
That number tells you more about your breathing efficiency than any other single metric. The BOLT test gives it to you in under two minutes.
What Is the BOLT Test?
BOLT stands for Body Oxygen Level Test. It was developed by Patrick McKeown, one of the leading figures in functional breathing research and founder of the Oxygen Advantage method. The test does not measure how long you can hold your breath at maximum effort. It measures your CO₂ sensitivity: the threshold at which your body triggers the urge to inhale.
That distinction matters. CO₂ is not simply a waste product, it’s the primary signal that drives breathing. When CO₂ rises past a certain point, the brain sends the inhale signal, not because oxygen is depleted, but because CO₂ has crossed a threshold. People with a low threshold breathe frequently, shallowly, and inefficiently. People with a higher threshold breathe calmly, economically, and with greater oxygen delivery to tissues via the Bohr effect.
How to Do the BOLT Test
No equipment required. The test takes two minutes.
- Sit upright and breathe normally for 2-3 minutes. Don’t breath differently.
- Take a quiet, normal inhale through the nose.
- Exhale fully and calmly through the nose.
- Pinch the nose closed with your fingers, no deep breath beforehand.
- Time how long until you feel the first definite urge to breathe, not the point of maximum discomfort, but the first involuntary impulse to inhale.
- Release and breathe in through the nose. The first breath should be controlled, not a gasp.
Important: If you need to gasp or take a deep breath immediately after releasing, you held too long. Rest and repeat the test.
What Your Score Means
| BOLT Score | What It Indicates |
|---|---|
| Under 10 seconds | Very low CO₂ tolerance. Commonly associated with stress, sleep problems, and impaired performance. |
| 10-20 seconds | Low. Mouth breathing and over-breathing likely. Immediate room for improvement. |
| 20-30 seconds | OK – good. Nasal breathing possible but efficiency under load still limited. |
| 30-40 seconds | Very good. Solid foundation for functional breathing and athletic performance. |
| Over 40 seconds | Excellent. Corresponds to the level of well-trained endurance athletes. |
A BOLT score under 20 is the norm for many people, including those who exercise regularly and consider themselves healthy. This isn’t about willpower. It’s about a respiratory system that has never been systematically trained.
Want to use your BOLT score as a starting point for structured training?
At Atemstark, every Personal Programme engagement begins with a breathing assessment, including the BOLT test as a key baseline. We build the training protocol from there, specific to where your breathing currently stands.
→ Learn more about the Personal Programme
How to Improve Your BOLT Score
Consistent nasal breathing, including under load
This is the single most important factor. Breathing through the mouth during exercise processes more air volume, but less efficiently. Try sustaining nasal breathing even if it means slowing your pace. The restriction is feedback, not a ceiling. As CO₂ tolerance builds, the pace at which nasal breathing remains comfortable rises with it.
Related: Nasal Breathing for Better Performance
Reduced-breathing exercises
Practice breathing less than your body demands, controlled, not aggressive. The goal is to build and hold a mild air hunger sensation without panic. This directly increases CO₂ tolerance. Guided exercises are available on the Exercises page.
Test consistently
The BOLT test functions both as a diagnostic and a progress marker. Test once per week under identical conditions, e.g. morning, pre-breakfast. The trajectory will become visible within weeks. The first impact to breathe is not the same for everybody, it is diffuicult to compare between individuals and to apply the score rigidly and exclusively; however, it does provide you with a baseline against which you can compare yourself over a period of time. Having a professional guide you also helps interpreting the number and your performance/development.
Reduce habitual over-breathing
Deep sighs, frequent yawning, speaking without pauses, all of these lower CO₂ and keep the BOLT score down. Calm, nasal breathing throughout the day is itself a training stimulus, not just a practice to do during dedicated sessions.
Also relevant: What Is CO₂ Tolerance?
What Trainees Report After 6-8 Weeks
People starting with a BOLT score under 15 and training consistently typically reach 25-30 seconds within six to eight weeks. That progression translates into tangible outcomes: calmer breathing under load, deeper sleep, lower baseline stress reactivity, increased ability to hold attention and focus.
A BOLT score of 40+ is the target for advanced trainees, achievable without elite athletic conditioning, but requiring consistent daily practice.
Ready to train systematically?
The BOLT test tells you where you are. The Personal Programme maps the path to where you want to be.