The Body Oxygen Level Test (BOLT)

The Oxygen Advantage® By Patrick McKeown

Measure BOLT Now

As far back as 1975, researchers noted that the length of time of a comfortable breath hold served as a simple test to determine relative breathing volume during rest and breathlessness during physical exercise [1,2]

The Body Oxygen Level Test (BOLT) is a very useful and accurate tool for determining this relative breathing volume.

The ideal BOLT score for a healthy individual is 40 seconds. In the book entitled 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].” 

In short, the lower the BOLT score, the greater the breathing volume, and the greater your breathing volume, the more breathlessness you will experience during exercise.

Measure your BOLT Score now

To obtain an accurate measurement, it’s best to rest for ten minutes before measuring your BOLT score. Read the instructions carefully first and have a timer on hand. You can measure your BOLT now:

  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. Time the number of seconds until you feel the first definite desire to breathe, or the first stresses of your body urging you to breathe. These sensations may include the need to swallow or a constriction of the airways. You may also feel the first involuntary contractions of your breathing muscles in your abdomen or throat as the body gives the message to resume breathing. (Note that 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.)
  4. Release your nose, stop the timer, and breathe in through your nose. Your inhalation at the end of the breath hold should be calm.
  5. Resume normal breathing.

How the Body Oxygen Level Test (BOLT) Works

When you hold your breath, you prevent oxygen from entering your lungs and prevent excess carbon dioxide from being expelled into the atmosphere. As the breath hold continues, carbon dioxide accumulates in the lungs and blood while oxygen levels slightly decrease. Since carbon dioxide is the primary stimulus for breathing, the length of your breath hold time is influenced by how much carbon dioxide you are able to tolerate, or your ventilatory response to carbon dioxide [1]

A strong ventilatory response to carbon dioxide means that your threshold will be reached sooner, resulting in a lower breath hold time. Conversely, a good tolerance and reduced ventilatory response to carbon dioxide results in a higher breath hold time.

When your BOLT score is lower, your breathing receptors are especially sensitive to carbon dioxide and your breathing volume will be greater as the lungs work to remove any carbon dioxide in excess of programmed levels. However, when you have a normal tolerance to carbon dioxide and a higher BOLT score, you will be able to maintain calm breathing during rest and lighter breathing during physical exercise.

You may find that the first time you measure your BOLT, you are surprised that your score is lower than expected, but remember that even elite athletes can have a low BOLT score! The good news is that your BOLT score can easily be increased with a series of simple breathing exercises incorporated into your existing way of life or exercise regime.

A common starting BOLT score for an individual who exercises regularly at a moderate intensity will be approximately 20 seconds. If your BOLT score is below 20 seconds, depending on genetic predisposition, you will probably find you experience a blocked nose, cough, wheeze, disrupted sleep, snoring, fatigue and excessive breathlessness during physical exercise. Each time that your BOLT score increases by five seconds, you will feel better, with more energy and reduced breathlessness during physical exercise.

The aim of the Oxygen Advantage® program is to increase your BOLT score to 40 seconds, and this can be realistically achieved.

Improving your BOLT score is an important key to attaining greater physical endurance. As we have already seen, having an improved tolerance to carbon dioxide means you are able to achieve a higher VO2 max and improved performance. The Oxygen Advantage® program is all about increasing your BOLT score and maximising your potential!

How Your BOLT Score Relates to Breathlessness During Sports

The truth is that the vast majority of individuals, including elite athletes, have a comfortable breath hold time of about 20 seconds, often less. However, to achieve your full potential, a BOLT score of 40 seconds should be the goal.

Breath hold measurements have also been used to study the onset and endurance of breathlessness (dyspnea) 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 both rest and exercise.


  1. Stanley et al. concluded that, ‘the breath hold time/partial pressure of carbon dioxide relationship provides a useful index of respiratory chemosensitivity’.See: Stanley,N.N.,Cunningham,E.L.,Altose,M.D.,Kelsen,S.G.,Levinson,R.S., and Cherniack, N.S.
    Evaluation of breath holding in hypercapnia as a simple clinical test of respiratory chemosensitivity. Thorax.1975;30():337-343
  2. Japanese researcher Nishino acknowledged breath holding as one of the most powerful methods to induce the sensation of breathlessness, and that the breath hold test ‘gives us much information on the onset and endurance of dyspnea (breathlessness)’. The paper noted two different breath hold tests as providing useful feedback on breathlessness. According to Nishino; because holding of the breath until the first definite desire to breathe is not influenced by training effect or behavioural characteristics, it can be deduced to be a more objective measurement of breathlessness.See: Nishino T. Pathophysiology of dyspnea evaluated by breath-holding test: studies of furosemide treatment. Respiratory Physiology Neurobiology.2009 May 30;(167(1)):20-5
  3. McArdle W, Katch F, Katch V. Exercise Physiology: Nutrition, Energy, and Human Performance. 1st ed. North American Edition. Lippincott Williams & Wilkins; Seventh, (p289) (November 13, 2009)
  4. The Department of Physiotherapy at the University of Szeged, Hungary conducted a study that investigated the relationship between breath hold time and physical performance in patients with cystic fibrosis. Eighteen patients with varying stages of cystic fibrosis were studied to determine the value of the breath hold time as an index of exercise tolerance. The breath hold times of all patients were measured. Oxygen uptake (VO2) and carbon dioxide elimination was measured breath by breath as the patients exercised. The researchers found a significant correlation between breath hold time and VO2 (oxygen uptake), concluding ‘that the voluntary breath-hold time might be a useful index for prediction of the exercise tolerance of CF patients’. Taking this one step further, increasing the BOLT of patients with CF corresponds to greater oxygen uptake and reduced breathlessness during physical exercise.See: Barnai M, Laki I, Gyurkovits K, Angyan L, Horvath G. Relationship between breath-hold time and physical performance in patients with cystic fibrosis. European Journal Applied Physiology.2005 Oct;(95(2-3)):172-8
  5. Results from a study of 13 patients with acute asthma concluded that the magnitude of breathlessness, breathing frequency and breath hold time was correlated with severity of airflow obstruction and, secondly, that breath hold time varies inversely with the magnitude of breathlessness when it is present at rest.9 In simple terms, the lower the breath hold time of asthmatics, the greater the breathing volume and breathlessness. See: Pérez-Padilla R, Cervantes D, Chapela R, Selman M. Rating of breathlessness at rest during acute asthma: correlation with spirometry and usefulness of breath-holding time. Rev Invest Clin.1989 Jul-Sep;(41(3)):209-13

© Patrick McKeown 2015