Equalizing your ears in freediving: Frenzel, Valsalva and mouthfill

Almost every freediver remembers the first time their ears hurt at the bottom of a pool. You were only two or three metres down, your breath-hold was fine, and yet a sharp pressure in the ears made you turn back. That is normal. For most beginners, the real limit on depth is not oxygen but equalization.

Equalizing is a learnable motor skill, like a swimming stroke. Once you understand what is happening inside the ear and why the classic technique fails head-down, the path to a more comfortable descent becomes much clearer. This guide covers the physics, the anatomy, the two main techniques, the idea behind mouthfill, dry drills, and the safety rules.

Why your ears hurt at two metres

At the surface you are under about 1 bar of atmospheric pressure. Every 10 metres of seawater adds roughly another bar. At 10 m the total, or absolute, pressure is about 2 bar; at 20 m, 3 bar; at 40 m, 5 bar.

Boyle's law says that, at constant temperature, the volume of a gas is inversely proportional to its pressure. Double the pressure and the volume halves. Every air space in your body follows this rule: lungs, sinuses, mask, and the middle ear. The rigid air spaces, like the middle ear, cannot shrink, so instead the surrounding tissues are pulled into them, and the eardrum bulges inwards.

The practical consequence is counter-intuitive: the hardest part for your ears is not the bottom of the dive but the beginning. Between the surface and 10 m, the air volume halves. Between 30 and 40 m, it shrinks by only a twentieth of the original. Beginners often feel pain at two or three metres precisely because the relative change is so steep there.

Inside the ear: eardrum, middle ear, Eustachian tube

The outer ear canal is open to the water, so it is always at ambient pressure. Behind the eardrum sits the middle ear, a small air-filled cavity in the bone that contains the three tiny ossicles which transmit sound. Further in lies the inner ear, filled with fluid, which handles hearing and balance.

The middle ear's only connection to the outside air is the Eustachian tube, a narrow channel that runs down and forward to the back of the nose and throat, the nasopharynx. It is normally closed. When you swallow or yawn it opens briefly, which is how your ears adjust on a plane.

Equalizing simply means pushing a little air from the nasopharynx up through the Eustachian tubes before the pressure difference becomes large. If you wait too long, the difference can squeeze the tube shut, and no amount of effort will open it without risk². The same logic applies to your mask: exhale a little air into it through the nose as you descend so it does not press on your face.

Valsalva: the technique everyone starts with

The Valsalva manoeuvre is what most people do instinctively: pinch the nose, close the mouth and blow gently, as if you were trying to exhale through a blocked nose. The pressure comes from the chest and abdominal muscles, which squeeze the lungs and push air towards the throat and up the tubes.

In the first metres, especially head-up, it often works. In freediving it has three limits:

• Head-down, the air is in the wrong place. When you descend head first, the air in your lungs sits towards your feet, away from the head. Your chest has to push it all the way up, which becomes difficult and inefficient.
• It needs air in the lungs. As depth compresses the lungs, there is less and less air available to push, and Valsalva gradually stops working.
• It is easy to push too hard. A strong Valsalva raises pressure in the chest and can transmit a pressure surge to the inner ear. Forceful Valsalva attempts are associated with inner ear barotrauma, which can damage hearing or balance². It also costs muscular effort, and therefore oxygen.

Frenzel: the freediver's technique

The Frenzel manoeuvre uses a much smaller engine: the tongue. With the nose pinched, you close the glottis (the valve at the top of the windpipe, the one that closes when you hold your breath or lift something heavy). This isolates the lungs. You then push the back of the tongue up and back, like a piston, compressing the small volume of air trapped in the mouth and nasopharynx and sending it up the Eustachian tubes.

Because it uses only the air already in the head, Frenzel works head-down, needs very little effort and keeps your chest relaxed. It also gives finer control over the pressure: a series of small, soft pushes rather than one big blow. That is why it is the standard technique taught on freediving courses³.

Valsalva pushes with the whole chest. Frenzel pushes with the tongue. In freediving, the smaller engine wins.

Going deeper: the idea of mouthfill

Even Frenzel needs some air in the mouth. As you go deeper and the lungs shrink, it becomes harder to bring air up from the lungs into the mouth for each new equalization. Mouthfill is the solution used by deep divers: at some point during the descent, they draw a large reserve of air into the mouth, puffing the cheeks, lock the glottis, and then use that reserve with the tongue for the rest of the descent.

The depth at which a mouthfill is taken, and how it is managed, varies with lung volume, flexibility and experience. It is an advanced technique that should be learned progressively in the water, at depth, with an instructor. For now, it is enough to know it exists: if Frenzel works for you down to a certain depth and then stops, that is often where mouthfill begins.

Dry drills to learn Frenzel

The basic Frenzel movement can be learned on land, sitting at a desk. Do these drills gently, in short sessions, and stop if anything hurts.

1. Find your glottisTake a small breath and hold it with your mouth open. You should feel a valve close in your throat: that is the glottis. Try saying a short, sharp "k" and notice the back of the tongue touching the soft palate.
2. Isolate the lungsWith your glottis closed, try to breathe out. Nothing should move. Now pinch your nose, close your lips, and keep the glottis closed.
3. Use the tongue as a pistonKeeping everything closed, push the back of your tongue up and back, as if saying "k" or "t" silently. The air in your mouth is compressed. If your cheeks puff out, the air is going the wrong way; keep them firm.
4. Feel the clickWhen the push reaches the Eustachian tubes you may feel a gentle click or fullness in both ears. Soft, short pushes are enough. If nothing happens, do not push harder; relax and try again later.
5. Practise the rhythmOnce it works, repeat a few soft pushes in a row, then practise with your chin slightly tucked, the head position used during a descent.

How often to equalize

The answer follows directly from Boyle's law. Because the volume changes fastest near the surface, equalize early and often at the start of the dive, then less frequently as you go deeper.

• Before you leave the surface, a gentle pre-equalization can help, as long as it is soft.
• In the first metres, equalize very frequently. Many instructors suggest roughly every metre, or as soon as you feel the slightest pressure.
• Deeper, the intervals naturally lengthen, because each metre changes the volume less.
• Before discomfort, not after. If you feel pain, you are already late, and the tube may be harder to open.

Going slowly at the beginning of the descent makes all of this easier. Relaxation helps too: tension in the neck, jaw and throat makes the Eustachian tubes harder to open. The calm you build in breathing practice and dry tables is directly useful here. For depth, the dive reflex is the other piece of physiology worth understanding.

Never force: barotrauma and congestion

Middle ear barotrauma, the most common injury in diving, happens when the pressure difference across the eardrum becomes too large¹. It can range from bruising of the eardrum to a perforation. If water enters the middle ear through a perforated eardrum, it can cause sudden vertigo, which is dangerous in the water. Inner ear barotrauma is rarer but more serious.

• See a doctor if you have pain that persists, blood from the ear or nose, reduced hearing, ringing in the ears or vertigo after a dive.
• Do not dive with a cold, a sinus infection or an allergy flare-up. Congestion narrows the Eustachian tubes and makes barotrauma far more likely. Decongestants can wear off during a session; ask a doctor rather than relying on them.
• Medical advice first if you have a history of ear surgery, perforated eardrums, heart or lung conditions, epilepsy, or if you are pregnant.
• Learn in water with a certified instructor (AIDA, Molchanovs, SSI, PADI Freediver or equivalent). An instructor can watch your technique, spot tension and guide your first descents on a line safely.

Frequently asked questions