One Breath Hold. One Number. Know What It Really Tells You.
The BOLT score is the simplest breathing test in sport. One normal exhale, one comfortable breath hold, one stopwatch.
It is a core tool in the Oxygen Advantage method, and we use it at Vincere Protocol every week. But a sceptical sports scientist will ask the right question: what does the number actually predict?
This article covers how to test it properly, what it measures, how it is trained and, just as importantly, what it does not tell you.
How to Test Your BOLT Properly
BOLT stands for Body Oxygen Level Test. It times a comfortable breath hold taken after a normal exhale, at low lung volume, not after a big gulp of air.
The most rigorous published protocol comes from Kowalski and colleagues (2024). Athletes sat for 15 minutes, took a few normal breaths through the nose, exhaled normally, closed the nose with a clip and held.
The clock stopped at the first definite urge to breathe or the first involuntary contractions of the breathing muscles. It is not a maximal hold. You are timing the first signal, not how long you can fight it.
To use it in a team setting:
Same conditions every time. Test seated, rested and at the same time of day, ideally first thing in the morning before training or caffeine.
Normal breath out, not a forced one. Exhale as you would at rest, pinch the nose and start the clock.
Stop at the first clear urge. Your next breath in should be calm and controlled through the nose. If you need to gasp, you held too long and the score is inflated.
Track the trend. One reading means little. A weekly average over a training block tells you far more.
Safety: never practise breath holds in or near water, never while driving, stop if you feel dizzy, never train holds alone, and get medical clearance first if you are pregnant or have a heart, lung or blood pressure condition.
What the Score Actually Measures
A breath hold ends when the urge to breathe wins. The physiology behind that moment is more complex than most coaches realise.
In his review of breath holding, Parkes (2006) showed that no single factor explains the breakpoint. Lung volume, blood gases and the carotid chemoreceptors do not account for it on their own, and the brain's breathing rhythm keeps running during a hold. The urge is suppressed, not switched off.
Bain and colleagues (2018) reviewed elite breath hold divers and found they can suppress the urge to breathe so effectively that loss of consciousness, not the urge, can end the hold. Near the end of very long holds, the extreme build up of CO2 appears to matter more than low oxygen for changes in brain metabolism.
Two lessons follow. The urge to breathe is not a simple fuel gauge for oxygen. It is a signal the brain generates, and elite divers show it can be trained to arrive later and be tolerated longer. That is exactly why BOLT is useful as a self check of breathlessness and CO2 tolerance.
The Honest Part: BOLT Is Not a Performance Predictor
Kowalski and colleagues (2024) tested 49 well trained speed skaters from elite and development national teams. They compared BOLT with a 30 second Wingate test (peak power, total work and power drop) and a cardiopulmonary test for VO2max.
BOLT showed no significant correlation with any of those measures. The correlations were all close to zero, and a regression model including BOLT explained only about 8% of the variance.
The authors concluded that BOLT should be interpreted with great caution as a marker of exercise performance in highly trained athletes.
We agree. A higher BOLT does not mean a bigger engine, a faster sprint or a higher VO2max. Anyone selling it as a performance predictor in elite athletes is ahead of the evidence.
What it does give you is a fast, free daily read on how calm or reactive your breathing is. Used that way, it is valuable.
How BOLT Is Trained
BOLT improves when the urge to breathe arrives later. In the Oxygen Advantage method that is trained with three pillars.
Nasal breathing, day and night. Dallam and colleagues (2018) followed recreational runners who trained with nasal only breathing for six months. During maximal testing, nasal breathing produced lower breathing frequency, a lower respiratory exchange ratio and a lower ventilatory equivalent for oxygen than mouth breathing. VO2max was about 7% lower with nasal breathing, a difference that was not significant. The study did not measure BOLT, but it shows breathing patterns adapt with sustained nasal training.
Light, slow breathing. Short daily sessions of breathing a little less than you want to, through the nose, so you get used to a mild air hunger without tension.
Breath holds after a normal exhale. Gentle holds at low lung volume while walking or during easy work, recovering through the nose each time. This is the same low lung volume hold used in breath hold sprint training.
Be clear on the evidence. We are not aware of a peer reviewed trial in trained athletes showing which method raises BOLT fastest, or by how much. The program is built on the physiology of breath holding, and the score is your feedback that it is working.
How to Use It With Your Squad
Use BOLT as a monitoring tool, not a selection tool. Track each athlete against their own baseline.
We treat a sudden drop across a week as a prompt to ask about sleep, illness, stress and training load. It starts a conversation. It is not a diagnosis.
Pair it with the measures that actually predict performance in your sport: repeated sprint tests, Yo Yo results, power data and GPS load.
FOR ELITE ATHLETES, THIS CAN HELP YOU
✔ Get a fast, free daily check of how reactive your breathing is to CO2
✔ Track your own trend across a training block and spot unusual drops early
✔ Build CO2 tolerance with nasal breathing, light slow breathing and low lung volume holds
✔ Make better decisions by keeping BOLT in its lane, a self check and not a performance predictor
Performance takeawayBOLT tells you how your breathing responds to CO2. It does not tell you who will win the sprint.
Use it honestly and it becomes one of the most useful numbers in your week.
Want this in your program? Enquire about Vincere Protocol for your team.
