BOLT score and control pause: what your number really means

What the control pause is

The control pause comes from the Buteyko method. It’s the time you can comfortably hold your breath after a normal exhale.¹ It’s explicitly not about holding out as long as possible: the test ends at the first clear urge to breathe, which makes it a subjective measure.² One version of it goes by BOLT score.

How to measure it

1. Sit quietly for a few minutes and breathe normally through your nose. Ideally at the same time of day each time, for example in the morning.
2. Breathe out normally and gently, not especially deep.
3. Pinch your nose and start the timer.
4. Stop at the first clear urge to breathe, not when you can’t hold on any longer.
5. Then keep breathing calmly through your nose. If you need to gasp, you waited too long.

–

seconds to first urge to breathe

…

What the number means, and what it doesn’t

It doesn’t measure carbon dioxide in your body. Buteyko assumed that a longer control pause means more carbon dioxide in the lungs. But among 83 adults, the relationship was weak and actually went the other way.³ A second study from the same group found no link with carbon dioxide at all.⁴ A review by breathing and exercise scientists calls Buteyko’s assumption disproven.⁵

It doesn’t show how fit you are. In 28 active college students, the BOLT score wasn’t linked to endurance.⁶ In 49 elite athletes, it wasn’t either, and the researchers note that the test hasn’t been scientifically validated.²

A lot plays into it. Why we can’t hold our breath any longer isn’t easy to explain; blood gases, lungs, muscles, and willpower all interact.⁷ Even an unnoticed deeper breath before the hold can noticeably lower carbon dioxide and change your number.⁸

1. It measures how long you can comfortably hold your breath after a normal exhale, until the first clear urge to breathe.
2. How you measure changes the number a lot, for example whether you took a deeper breath first.
3. Lung volume, muscles, willpower, and discomfort play a part too, as does how strongly your body reacts to carbon dioxide.
4. The number doesn’t predict the carbon dioxide level in your body. It’s only comparable with your own number under the same conditions.

Play again

Are there norms by age?

No. I found no validated norms by age in PubMed or Europe PMC, and the charts online don’t cite a source. For context, not as a norm: in one study, 30 healthy adults had an average control pause of 18 seconds, with a wide spread.¹ What’s meaningful is only your own number over time, measured the same way.

Can you improve your score?

Yes, you get better at holding your breath with practice. In healthy athletes, several studies found that breath-hold training improved hold times, but not performance.² So a higher number mainly shows that you’ve practiced holding your breath, not that you’re healthier or fitter.

What about the “CO2 tolerance test”?

In the Stanford breathing study, participants timed how long they could slowly breathe out after a deep inhale. The result was only used to set the length of the phases for box breathing, and the study doesn’t report any results for the test itself.⁹ I found no study validating it as a measure of “CO2 tolerance.”

Common questions

What’s a good BOLT score?

Studies can’t say. There are no validated norms. In one study, healthy adults averaged 18 seconds, with a wide spread.¹

Does the control pause measure my CO2 tolerance?

Partly at most. It doesn’t predict the carbon dioxide level in your body, and many other things play a part.^{3, 7}

Does my BOLT score say anything about my fitness?

Not in two studies, neither in active college students nor in elite athletes.^{6, 2}

Is a low score a sign of stress or anxiety?

No, the control pause isn’t a test for stress or anxiety. If anxiety weighs on you often, talk to a professional.

How often should I measure?

There’s no study on that. What matters is measuring under the same conditions every time, for example sitting in the morning before your day gets going.