How to Measure Your BOLT Score

The Body Oxygen Level Test (BOLT) is a simple breath-hold test from the Oxygen Advantage Method that gives you direct feedback on your breathing volume, CO2 tolerance, and breathlessness during exercise. 

As far back as 1975, researchers noted that comfortable breath-hold time can be used to determine relative breathing volume during rest and breathlessness during physical exercise [1,2].

The ideal BOLT score for a healthy adult is 40 seconds. In the book Exercise Physiology: Nutrition, Energy, and Human Performance by William McArdle and colleagues, the authors observe: "If a person breath holds after a normal exhalation, it takes approximately 40 seconds before the urge to breathe increases enough to initiate inspiration" [3].

The lower your BOLT score, the greater your breathing volume is likely to be. The greater your breathing volume, the more breathlessness you will experience during exercise.

In this article you will learn how to measure your BOLT score, what your result means, and how to improve it for better health and exercise performance.

How to Measure Your BOLT Score

For an accurate measurement, rest for ten minutes before testing. Have a timer to hand. On a day-to-day basis, we recommend taking the test first thing in the morning.

1. Take a normal breath in through your nose and allow a normal breath out through your nose.
2. Hold your nose with your fingers to prevent air from entering your lungs.
3. Start your timer.
4. Time the number of seconds until you feel the first definite desire to breathe, or the first signs of your body urging you to breathe. These may include the need to swallow, a constriction of the airways, or the first involuntary contractions of your breathing muscles in your abdomen or throat. The BOLT is not a measurement of how long you can hold your breath, but simply the time it takes for your body to react to a lack of air.
5. Release your nose, stop the timer, and breathe in through your nose. Your inhalation at the end of the breath hold should be calm.
6. Resume normal breathing.

Important note: BOLT measures how quickly you experience the first clear urge to breathe during a comfortable breath hold. This threshold is influenced by multiple factors: your chemoreceptor sensitivity to CO₂, your starting blood gases, your breathing mechanics, your psychological state, even your lung volume. BOLT is most useful when tracked over time as your personal baseline—watching your score improve as you practice—rather than as a comparison to others or as a diagnostic measurement.

Why the BOLT Is a Breath Hold After Exhalation

When someone tells you to hold your breath, the normal instinct is to first take a big breath in. But breath holding after inhalation is an unreliable way to test breathing.

Lung capacity differs from person to person, and some people are more competitive than others. Holding after a normal exhalation removes these variables and gives a consistent, objective measurement.

How Does the BOLT Score Work?

When you hold your breath, several things happen simultaneously:

• Oxygen entering your lungs stops, and oxygen reserves gradually decrease
• Carbon dioxide accumulates in your lungs and blood
• Your respiratory muscles begin to sense increasing demand
• Your brain receives multiple signals: rising CO₂, declining O₂, increasing respiratory drive
• Air hunger emerges—the sensation that you need to breathe

How BOLT Relates to CO₂: CO₂ is a powerful stimulus to breathing. As CO₂ accumulates during a breath hold, your chemoreceptors detect this change, and your brain signals an urge to breathe. However, CO₂ is not the only influence. Your starting blood gases (which depend on your resting breathing pattern), your psychological state (anxiety about the sensation), your breathing mechanics, and even your lung volume all influence when you feel that first urge.

What BOLT Actually Measures: Your BOLT score reflects your threshold for air hunger—the point at which the sensation becomes noticeable. This threshold is influenced by your chemoreceptor sensitivity to CO₂, but also by your perception of that sensation, your familiarity with air hunger, and your psychological response to respiratory stress.

When BOLT is Lower: A lower BOLT often correlates with faster, higher-volume breathing at rest. Why? Multiple possibilities: your nervous system may be more reactive to respiratory sensations; you may be more anxious about breathing; your breathing mechanics may be less efficient; or your chemoreceptors may be more sensitive. Breathing training can shift this through multiple routes—not just by changing your chemoreceptor sensitivity, but by changing how you breathe mechanically, how calm your nervous system is, and how you interpret respiratory sensations.

What Will My BOLT Score Be?

Your BOLT score is a personal baseline. It's influenced by many factors:

• Chemoreceptor sensitivity: How responsive your breathing system is to rising CO₂
• Breathing mechanics: Your resting breathing pattern (diaphragmatic vs. chest-based), airway size, breathing muscle strength
• Psychological state: Your anxiety about respiratory sensation, past experiences with breathlessness
• Nervous system state: Whether your nervous system is in a calm or activated state
• Starting blood gases: Determined by your resting breathing pattern

Many people with asthma, anxiety, or dysfunctional breathing patterns start with a BOLT score of 10-20 seconds. This is not permanent. With consistent practice, BOLT typically improves within weeks.

Important: Your BOLT score is most useful when you track YOUR improvement over time. Comparing your score to someone else's is less meaningful, because individual variation is large.

Your BOLT Score in Seconds: What to Expect

Below 10 seconds: Your everyday breathing is often noisy, irregular, and effortful. You may sigh or yawn frequently, and sleep is typically disrupted. Breathing training can help significantly.

10 to 20 seconds: Your breathing may be compromised by nasal obstruction, wheezing, or coughing. Sleep quality and daytime energy are often affected. This is a common starting point for breathing training, and improvement usually happens relatively quickly with consistent practice.

20 to 30 seconds: Your resting breathing is relatively quiet and calm. If you exercise regularly, a BOLT in this range is typical. As your BOLT improves, most people notice they feel calmer, have more energy, and experience less breathlessness during exercise.

40 seconds: This is our advanced training target in Oxygen Advantage. At this level, breathing is typically light and economical during rest and moderate-intensity exercise. Your nervous system is usually well-regulated. However, this is a training goal, not a threshold that separates "healthy" from "unhealthy" breathing.

Note: The relationship between BOLT score increases and feeling better varies from person to person. Some people notice significant improvement with each 5-second increase; others notice gradual changes over time.

How Your BOLT Score Relates to Breathlessness During Sport

BOLT provides useful information about how your body responds to respiratory stress. A lower BOLT score is often associated with faster, less efficient breathing and greater perceived breathlessness during exercise.

The first time you measure your BOLT, you may be surprised to find your score is lower than expected. Even elite athletes can have a low BOLT score.

Breath-hold measurements have been used extensively to study the onset and endurance of breathlessness (dyspnoea) and asthma symptoms [4,5].

The result that comes up again and again is that the lower the breath-hold time, the greater the likelihood of breathlessness, coughing, and wheezing during rest and exercise.

For athletes, a BOLT score below 20 seconds typically corresponds to disproportionate breathlessness during moderate-intensity exercise. A score above 30 seconds generally reflects efficient breathing patterns, good CO2 tolerance, and better endurance.

Improving your BOLT can enhance breathing confidence and breathing economy (doing the same work with less effort). Whether this translates to faster times or higher power depends on other elements of your training.

How to Increase Your BOLT Score

Your BOLT score can be improved with consistent practice of several simple breathing exercises:

• Nasal breathing during rest, sleep and low-intensity exercise: The nose adds natural resistance to airflow and trains your breathing system to work more efficiently. At moderate intensities, this can help you reduce your breathing frequency while maintaining your required ventilation.
• Slow, rhythmic breathing: This activates your parasympathetic nervous system (rest-and-digest state), naturally slows your breathing rate, and helps your brain interpret respiratory sensations with less alarm.
• Breathing light exercises: Breathing slightly less than your normal volume creates a mild training stimulus. Your body adapts by improving breathing efficiency and your perception of air hunger becomes less threatening.
• Breath hold exercises: Short, comfortable breath holds during walking provide a training stimulus similar to altitude exposure. Your respiratory system adapts by improving how it tolerates temporary increases in CO₂.
• Nasal breathing during sleep (using MtoTape): Maintaining nasal breathing while sleeping improves sleep quality and prevents the nocturnal over-breathing that interrupts deep sleep.

Mechanism: These practices work through multiple routes. Nasal breathing improves your breathing mechanics. Slow breathing calms your nervous system. Familiar exposure to air hunger makes the sensation less threatening. Improved sleep quality reduces overall nervous system activation. The result: your BOLT improves, and you feel calmer and less breathless.

With consistent daily practice, most people see meaningful improvement within 2-4 weeks.

The Link Between Your BOLT Score and Asthma

Research on breath-holding and asthma shows a relationship between shorter breath-hold time and greater breathing volume during exercise. For people with exercise-induced asthma, nasal breathing and breathing training can help. As your BOLT improves, many people notice reduced exercise-induced asthma symptoms, though the extent of improvement varies from person to person.

Start Improving Your Breathing with Oxygen Advantage

The BOLT score is the foundation of the Oxygen Advantage method. It is the starting point for understanding your breathing, tracking your progress, and connecting your breathing patterns to your health, sleep, and athletic performance.

To learn the OA method for yourself, please see our online breathing course, become a certified breathwork instructor, or find an Oxygen Advantage instructor near you.

References and Notes

1. Stanley et al. concluded that "the breath hold time/partial pressure of carbon dioxide relationship provides a useful index of respiratory chemosensitivity." Stanley NN et al. Evaluation of breath holding in hypercapnia as a simple clinical test of respiratory chemosensitivity. Thorax. 1975;30:337-343.
2. Nishino acknowledged breath holding as one of the most powerful methods to induce breathlessness, and noted that holding the breath until the first definite desire to breathe is not influenced by training effect or behavioural characteristics, making it a more objective measurement of breathlessness. Nishino T. Pathophysiology of dyspnea evaluated by breath-holding test. Respir Physiol Neurobiol. 2009;167(1):20-5.
3. McArdle W, Katch F, Katch V. Exercise Physiology: Nutrition, Energy, and Human Performance. 7th ed. Lippincott Williams and Wilkins. 2009. p289.
4. Researchers at the University of Szeged, Hungary, studied 18 patients with varying stages of cystic fibrosis and found a significant correlation between breath-hold time and VO2 (oxygen uptake), concluding that voluntary breath-hold time is a useful index for predicting exercise tolerance. Barnai M et al. Relationship between breath-hold time and physical performance in patients with cystic fibrosis. Eur J Appl Physiol. 2005;95(2-3):172-8.
5. A study of 13 patients with acute asthma found that breath-hold time varies inversely with the magnitude of breathlessness, confirming that the lower the breath-hold time, the greater the breathing volume and breathlessness. Pérez-Padilla R et al. Rating of breathlessness at rest during acute asthma: correlation with spirometry and usefulness of breath-holding time. Rev Invest Clin. 1989;41(3):209-13.