BOLT Score Test
Measure your CO₂ tolerance in under a minute. The Body Oxygen Level Test is the simplest reliable marker of how efficiently you breathe — and the first number to track when you start breathing training.
How the BOLT test works
The Body Oxygen Level Test, developed within the Oxygen Advantage method, is one of the simplest reliable ways to measure breathing efficiency at home. After a normal exhale, you hold your breath and time how long it takes until you feel the first involuntary urge to breathe: a swallow, a contraction of the diaphragm, or the impulse to inhale. That moment reflects how your body responds to rising carbon dioxide.
Athletes with efficient breathing tolerate more CO2 before feeling the urge to breathe, which translates into calmer breathing at high intensity, better oxygen delivery to working muscles, and less gasping when it matters most.
Why your BOLT score matters for performance
A low score usually means you over-breathe at rest and fatigue early under load. Raising your BOLT score through respiratory training improves breathing economy, and pairing breath holds with inspiratory muscle training strengthens the diaphragm itself, the muscle doing most of the work every time you inhale.
Frequently asked questions
What is a BOLT score?
The BOLT score (Body Oxygen Level Test) measures how long you can comfortably hold your breath after a normal exhale, until the first natural urge to breathe. It reflects your body's tolerance to carbon dioxide, a key marker of breathing efficiency.
What is a good BOLT score?
A BOLT score above 30 seconds is considered excellent and typical of well-trained athletes. Scores between 20 and 30 seconds are good, 10 to 20 seconds indicate room for improvement, and below 10 seconds suggests low CO2 tolerance and over-breathing patterns.
How can I improve my BOLT score?
Consistent breathing training raises your BOLT score. Daily nasal breathing, light breath holds, and inspiratory muscle training with a resistance device like the O2Trainer strengthen your diaphragm and improve CO2 tolerance, typically showing measurable gains within 3 to 4 weeks.
Is the BOLT test the same as a maximum breath hold?
No. The BOLT test measures the time until the first urge to breathe after a normal exhale, not your maximum breath hold. Stopping at the first urge is what makes the score a reliable measure of breathing chemistry rather than willpower.
Ready to raise your score?
The O2Trainer strengthens your diaphragm with 16 levels of progressive resistance — the fastest way to move your BOLT score up.
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