By Anders Olsson · Updated November 2026
The control pause, also known as the BOLT score, measures how long you can comfortably hold your breath after a normal exhale. It's the same measurement behind Conscious Breathing's CO2 Tolerance Test (CTT). It takes one minute to do. A longer pause generally points to better CO2 tolerance; a shorter one suggests your breathing may be faster or heavier than your body needs. Developed by Konstantin Buteyko, the Russian physician who spent fifty years studying breathing patterns, it's a simple self-check, not a medical diagnostic test.
Exercise 1: hold your breath while sitting
Note: keep your mouth closed throughout.
- Sit upright, back straight, and relax for a couple of minutes. Take a small breath in and a small breath out, calmly through your nose (about 2–3 seconds each way).
- After the exhale, pinch your nose and start the timer.
- At the first urge to breathe, let go of your nose, stop the timer, and breathe calmly through your nose again as in step 1.
If you're inhaling forcefully in step 3, you've held too long, which is common when there's pressure to perform well. The first urge to breathe, not the limit of what you can bear, is the number to record.
Exercise 2: hold your breath while walking
Note: keep your mouth closed throughout.
- Sit and relax for a few minutes first.
- Stand, then take a small breath in and out calmly through your nose.
- After the exhale, pinch your nose and start walking, counting your steps.
- When you can't hold any longer, let go of your nose, breathe calmly through your nose, and note the step count.
What your score means
The table below is a CO2 tolerance guide based on the Buteyko framework. It's a pattern to track over time, not a medical diagnosis — if you have a health concern, see a doctor rather than relying on this test.
| Control pause | Steps while walking | What it suggests |
|---|---|---|
| 60+ seconds | 120+ steps | Strong CO2 tolerance |
| 40 seconds | 80–100 steps | Good CO2 tolerance |
| 30 seconds | 60–80 steps | Moderate CO2 tolerance |
| 20 seconds | 40–60 steps | Lower CO2 tolerance |
| 10 seconds | 20–40 steps | Breathing likely faster/heavier than needed |
| Under 5 seconds | Under 10 steps | Worth a closer look at breathing habits; consider talking to a doctor if you have symptoms |
If you're a free diver or have sleep apnea, this test won't give an accurate read — both change breath-hold time for reasons unrelated to everyday CO2 tolerance.
Track your score
Test once a week, same time of day, and log the two numbers (seconds, steps). A rising trend over 4–6 weeks is the more useful signal than any single test.
Raise your score
The Relaxator is built for this: breathing out against its adjustable resistance slows and extends your exhale, which is the same pattern this test measures. Used regularly, it supports the slower, calmer breathing that tends to go with a longer control pause. For the full Relaxator-based CO2 Tolerance Test (CTT) protocol and score, see the CO2 Tolerance Test page.
Two other habits that support the same goal:
- Nasal breathing at night. Mouth breathing during sleep works against CO2 tolerance. Sleep Tape is a simple way to keep your mouth closed overnight so breathing stays nasal.
- Nasal breathing during activity. Keeping your mouth closed during light exercise builds the same tolerance. See how to unblock a stuffy nose if that's what's stopping you.
For the physiology behind why CO2 tolerance matters, see What Carbon Dioxide Does in the Body.
A test to track, not to chase
This test is simple on purpose. It's also not the whole story: your score can creep up just from practicing the test itself, and breathing researchers don't all agree on how much one number like this really tells you. That's exactly why we suggest tracking the trend over several weeks rather than chasing a single good result — and why steady Relaxator practice, not repeating the test, is what actually builds CO2 tolerance over time.
Want the deeper science, including where the research gets more contested? It's in the references below [1][2].
References
- Kowalski T, Rebis K, Wilk A, Klusiewicz A, Wiecha S, Paleczny B. Body Oxygen Level Test (BOLT) is not associated with exercise performance in highly-trained individuals. Frontiers in Physiology. 2024;15:1430837. https://doi.org/10.3389/fphys.2024.1430837
- McPhilimey M. The Truth About CO2 Tolerance. School of Breath Science, 7 Sept 2026. https://www.schoolofbreathscience.com/the-truth-about-co2-tolerance/
FAQ
What's a good BOLT score? Around 40 seconds is a commonly cited marker of good CO2 tolerance in the Buteyko framework. Most people who breathe fast or through the mouth habitually score well under 20.
How often should I test? Weekly, same conditions each time, is enough to see a trend without obsessing over day-to-day noise.
Does a low score mean I have a disease? No. It's a self-check for CO2 tolerance, not a diagnostic test. If you have symptoms you're worried about, see a doctor.
Can I improve my score quickly? Most people see gradual change over weeks of consistent practice (nasal breathing, slower exhales, tools like the Relaxator), not overnight.
Does practicing the test itself make my score go up, even without real change? Somewhat, yes — that's a known limitation, not a reason to ignore the test. Breath-hold time can improve a little just from familiarity with the sensation. That's why we suggest watching the trend over weeks rather than any single best attempt, and building CO2 tolerance through Relaxator practice rather than by drilling the test itself.
