Mouthfill : Make peace with your glottis

glottis peace

This exercise aims at improving the comfort and efficiency of the mouthfill equalization. It is an exercise to be done during a neutral/empty lung session and preferably with a nose clip.

It is based on the idea that the glottis remains closed by itself past a certain pressure difference level, and we do not need to generate any kind of tension to “hold” the mouthfill.

For those who wish to know more about the logic and theory behind the exercise, I recommend this article :
Mouthfill : Open / Closed ? What is the natural position of the glottis?

General principle :

The exercise aims to minimize the tensions in the glottis, the oral cavity, and the face while holding a mouthfill at depth. The principle here is not to perform but to OBSERVE. Observe what? To observe the minimal amount of energy needed to hold your mouthfill. You will therefore perform several dives with neutral lungs (possibly empty for the more advanced), during which you will observe and test your glottis. To do this, try to take into account the following principles:

  1. Keep the line at a “very-easy” depth: The goal is to have 100% of your attention to observe what is happening in your mouth/glottis without worrying about performance. If you are used to diving at 30m in FRC, I recommend setting the line at 20/22m maximum.
  1. “Let it leak”: “Let it leak”: as it is not a question of performance but observation, do not hesitate to release the whole of your oral cavity. You will see what happens; worst-case scenario, it will leak. So what? The exercise aims to redefine the level of tension that you feel necessary to keep the mouthfill, and only an exploration attitude can help you.
  2. The most important is the time “between” equalizations. The deeper you go, the less frequently you will need to equalize, and the longer the time between equalizations will be. Subsequently, do not hesitate to make a slow dive that will allow you to artificially increase this “non-equalizing” time and focus your attention on this part. Concentrate on relaxing your tongue, jaw, cheeks, and face… It is normal to generate a little bit of tension during an equalization to compress the air; you must make all forms of action disappear between two equalizations.
  3. Forget about “constant pressure.” If you are normally using this strategy, put aside your habits and adopt (at least for this exercise) a sequential pressure to minimize tensions (see point 3).
  4. Take a comfortable mouthfill of about ⅔ of your maximum capacity. By maximizing comfort, you will increase your attention level where it matters and be better able to extract the benefits of this exercise.


You have now redefined the level of passivity, of relaxation that your mouthfill requires. You still need tYou have now redefined the level of passivity, of relaxation that your mouthfill requires. You most likely still need training and repetition at easy depth to make it “auto-pilot.” but I hope it will improve the quality of your diving experience and, subsequently, your results.