CO2 Tables for Freediving: How They Work and How to Use Them

A CO2 table is a set of dry breath-holds in which every hold is the same length and the rest between them gets shorter each round. With less time to clear carbon dioxide, it builds up as the table goes on, and you practise staying relaxed through a strong urge to breathe and through contractions. Holds are set well below your maximum, usually around half your personal best, and the whole session is done lying down on land.

Used two or three times a week, CO2 tables are one of the simplest ways to become more comfortable in a static breath-hold. Used badly (too hard, too often, or anywhere near water), they give you headaches and not much else.

What a CO2 table actually trains

The urge to breathe comes mostly from carbon dioxide. For most beginners, a breath-hold ends not because oxygen has run low but because the discomfort of rising CO2 and the first contractions feel unbearable. A CO2 table targets exactly that.

What you are training:

• Tolerance of high CO2. Over weeks, the same level of CO2 starts to feel less urgent.
• Calm through contractions. You meet contractions in every late round, at a point where you are nowhere near your limit, so they stop feeling like an emergency.
• A repeatable breathe-up. Every rest period is a short breathe-up, so you rehearse it eight times a session.

What it does not train is lung size, or your body’s ability to cope with low oxygen. That is the job of an O2 table, which works the other way round and is harder on the body.

How a CO2 table is structured

The classic format has eight rounds. The holds stay fixed and the rests shrink.

• Hold: around 50% of your personal best dry static, the same every round.
• Rest: starts at 2:00 and drops by 15 seconds each round, down to 0:15 before the last hold.
• Position: lying on your back, on a bed or a yoga mat on the floor.

The early rounds feel almost too easy, by design. The work happens in the last three rounds, when you start each hold with CO2 still high from the one before.

Example CO2 table for a two-minute personal best

If your best relaxed dry hold is 2:00, your fixed hold is 1:00.

Round	Rest (breathe-up) before the hold	Hold
1	2:00	1:00
2	1:45	1:00
3	1:30	1:00
4	1:15	1:00
5	1:00	1:00
6	0:45	1:00
7	0:30	1:00
8	0:15	1:00

The whole table takes about 17 minutes. A 15-second rest is short enough to be unpleasant, and for your first few sessions it is fine to stop after round 7, or to keep the final rest at 30 seconds.

Scaling the table to your own personal best

Take half your PB and round down to the nearest five seconds. A PB of 1:30 gives a 45-second hold; a PB of 3:00 gives 1:30. Keep the rest schedule the same.

Use a recent, relaxed best, not the one heroic hold you managed six months ago after a perfect night’s sleep. If you don’t know your PB, test it on a separate day (two warm-up holds, then one calm attempt) and don’t do a table on the same day.

How to run a CO2 table session, step by step

1. Choose a time two to three hours after a meal. Before breakfast or before dinner both work.
2. Lie down on a bed or a mat on the floor, in a cool room. In an Indian summer, that may mean waiting until the AC has done its work.
3. Put your phone on do-not-disturb and enter the table into a timer app, ideally one that speaks the countdown so your eyes can stay closed. Several free breath-hold apps do this; a stopwatch and a printed table also work.
4. Use every rest period as a breathe-up: slow, relaxed, with the exhale longer than the inhale. Do not breathe fast to “catch up” in the short rests. That is hyperventilation, and it defeats the purpose of the table.
5. Take one full, comfortable breath before each hold. No packing.
6. During the hold, scan for tension in your face, jaw, shoulders and hands.
7. When the hold ends, take two or three recovery breaths (exhale a little, inhale firmly, pause briefly at the top) before settling into the next rest.
8. Write down when contractions started in each round and how the last round felt.

How often to do CO2 tables, and when to make them harder

Two or three sessions a week, with a rest day between them, is plenty for beginners. Do one table per session, and don’t put a CO2 table and an O2 table on the same day.

Progress one variable at a time. When the last two rounds feel controlled for two sessions in a row, add five seconds to the hold. Or keep the hold and start the rests a little shorter. Not both at once.

Track the first-contraction time in rounds 6 to 8. It is the most useful number a CO2 table gives you, and over a few weeks it should drift later, or the contractions should feel softer. A simple freediving log makes that trend easy to see.

Signs you should stop the table

End the whole session, rather than skipping a round, if you notice any of these:

• Vision narrowing, greying or sparkling at the edges
• Feeling confused, floaty or oddly euphoric when you start breathing again
• Twitching, shaking or loss of control in your hands or face
• Tingling in your fingers or lips, usually a sign you have been overbreathing in the rests
• A headache that builds through the session
• Chest pain, palpitations or nausea, which also need a doctor

A CO2 table should leave you feeling like you did some work, not wrecked. If several sessions in a row leave you wrecked, your holds are set too long.

Safety: CO2 tables are a dry, land-only exercise. Do them lying down on a bed or the floor, never in a pool, bath or the sea, and never while standing, walking or driving. Even dry, an overambitious table can make you faint, which is harmless on a mattress and deadly in water.

Common mistakes with CO2 tables

• Hyperventilating in the short rests. It feels like recovery. In fact you are lowering CO2 and making the table pointless. Our post on why hyperventilating before a breath-hold is dangerous explains the risk.
• Setting holds from an inflated PB. If round 3 already feels hard, your PB figure is wrong.
• Fighting contractions. Let them happen. Bracing against them uses oxygen and makes the next one worse. Our guide to mental training for freediving has a few ways to sit with them.
• Training after a big meal or a bad night. Neither helps, and both make your notes harder to read.
• Adding time every session. Gains arrive over weeks. A table you cannot finish is a table that is too hard.

Your first two weeks of CO2 tables

Week one: two sessions, with rests starting at 2:00 and stopping at 0:30, so seven rounds. Week two: three sessions, running the full table down to 0:15 if week one felt controlled. Keep notes after every session, and don’t test your PB until the end of week two.

If you want to understand what is happening in your blood during all of this, read CO2 vs O2: what really makes you want to breathe. Stay tuned for the freediving.in community, launching soon.