McKeown, Patrick. The Oxygen Advantage

First of all, we can start with a self-diagnose. You can determine your sensitivity to carbon dioxide using the Body Oxygen Level Test (BOLT), which measures the length of a comfortable breath hold. This gives an idea of our vital capacity (the sum of tidal capacity, inspiratory reserve and expiratory reserve volume).

When there is an increase of carbon dioxide and a decrease of oxygen, breathing is stimulated.   The sensitivity of your receptors to carbon dioxide and oxygen will have implications for the way your body copes with physical exercise.

When your breathing receptors have a strong response to carbon dioxide and reduced pressure of oxygen in the blood, your breathing will be intense and heavy. When breathing receptors are less sensitive to carbon dioxide levels, your body is able to work harder with far less effort; one method of boosting performance during a sport activity is to practice breath-hold techniques, which have been proven to improve respiratory muscle strength and endurance.

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.

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. Hold your nose with your fingers to prevent air from entering your lungs.
4. 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 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.)
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.

Considerations when taking the BOLT:

1. The breath is taken after a gentle exhalation.
2. The breath is held until the breathing muscles first begin to move. You are not measuring the maximum time that you can hold your breath.
3. If you do not feel the first involuntary movements of your breathing muscles, then release your nose when you feel the first definite urge or first distinct stress to resume breathing.
4. The BOLT is not an exercise to correct your breathing.
5. Remember that measuring your BOLT involves holding your breath only until you feel the first involuntary movements of your breathing muscles. If you need to take a big breath at the end of the breath hold, then you have held your breath for too long.

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, coughing, wheezing, disrupted sleep, snoring, fatigue, and excessive breathlessness during physical exercise. Each time that your BOLT score increases by 5 seconds, you will feel better, with more energy and reduced breathlessness during physical exercise. The idea 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.

If you breathe through the nose, day and night and practice consistently different type of breathing exercises (like the ones described below) your BOLT score will increase and subsequently, you will experience a lighter breathing and be able to train at a higher pace, for longer distances, your body will be prepared to do more with less!