How to Make a CO2 Table for Static Apnea

If you've been freediving for a while, you've likely hit a plateau where your breath-hold time just won't budge. Most of the time, the limiting factor isn't oxygen — it's carbon dioxide. The urge to breathe, that burning sensation in your chest and the involuntary diaphragm contractions, is triggered by rising CO2 levels long before your oxygen runs out. This is where the CO2 table becomes the single most powerful tool in your static apnea training arsenal.

A well-designed CO2 table systematically teaches your body to tolerate higher levels of carbon dioxide, pushing back the moment those uncomfortable contractions begin. Freedivers who train consistently with CO2 tables often see their static apnea times increase by 30–60 seconds within just a few weeks — without any increase in their oxygen capacity.

What Is a CO2 Table?

A CO2 table is a structured breath-hold training protocol designed to elevate carbon dioxide levels in your bloodstream and train your body's tolerance to that discomfort. Unlike oxygen (O2) tables, which focus on extending the breath-hold duration, CO2 tables keep the hold time constant while progressively shortening the recovery periods between repetitions.

Here's the physiology behind it: when you hold your breath, your body continues to metabolize oxygen and produce CO2. As CO2 accumulates, it dissolves in your blood as carbonic acid, dropping blood pH. Your brainstem detects this drop and sends signals that you experience as the urge to breathe — a tightening of the throat, rising anxiety, and eventually involuntary diaphragmatic contractions (often called "contractions" or "diaphragm spasms").

By repeatedly exposing your chemoreceptors — the sensors in your brainstem and carotid arteries that detect CO2 — to elevated CO2 levels, you desensitize them over time. Your body learns that CO2 is manageable, that contractions don't mean you're about to black out, and that you can stay calm and extend your hold through the discomfort. This is the core adaptation that CO2 tables train.

CO2 Table vs O2 Table — Quick Difference

It's easy to confuse the two table types, so here's the essential distinction:

• CO2 Table: Fixed breath-hold duration, decreasing rest periods. The challenge is surviving shorter and shorter recovery windows with the same hold time. This trains CO2 tolerance.
• O2 Table: Fixed rest periods, increasing breath-hold duration. The challenge is pushing your hold time further each round with a consistent recovery. This trains hypoxic tolerance and extends maximum apnea time.

Both are essential for a complete freediving training program, but most coaches recommend beginning with CO2 tables. CO2 training is generally considered safer and more approachable for beginners because the hold times stay manageable. For a deeper breakdown, see the full comparison here.

How to Build a CO2 Table

The Basic Formula

Building a CO2 table is straightforward once you know your personal static apnea maximum. Here are the key rules:

• Hold time: Set it at approximately 50% of your personal maximum. If your max is 2:00, your training hold is 1:00. This ensures you can complete all rounds without becoming dangerously hypoxic.
• Starting rest: Begin with a rest period equal to roughly 2× your hold time. For a 1:00 hold, start with 2:00 of rest.
• Rest reduction: Decrease the rest by 15–30 seconds each round. A 15-second reduction makes for a longer, more gradual session; 30 seconds creates a more aggressive stimulus.
• Number of rounds: 6 to 8 rounds is the standard. Eight rounds with 15-second reductions gives a total session of about 20–25 minutes including holds.

The goal is to arrive at the final rounds with minimal rest — 30 seconds or less — while maintaining the same hold time. This is where the real CO2 adaptation happens.

Example — Beginner CO2 Table (2-minute max)

If your best static apnea is around 2:00, this table is designed for you. Hold time is fixed at 1:00 throughout all 8 rounds.

Total session time: approximately 17 minutes. The final two rounds at 30 seconds rest will feel genuinely challenging — that discomfort is the signal that the training is working.

Example — Intermediate CO2 Table (3-minute max)

For freedivers with a 3:00 static apnea personal record. Hold time is fixed at 1:30.

Total session time: approximately 27 minutes. At the intermediate level, contractions will typically start during rounds 6–8. Learning to stay calm and relaxed through them is the primary skill being developed.

How Often Should You Train CO2 Tables?

CO2 table training is effective, but more is not better. The adaptation happens during recovery, not during the session itself. Here are the guidelines that most elite coaches recommend:

• Frequency: 2–3 sessions per week. This provides enough stimulus without overloading your nervous system.
• Minimum rest: At least 48 hours between CO2 table sessions. Training daily will accumulate fatigue without additional adaptation benefits.
• Progression: After 2–3 weeks, if the final rounds feel manageable, increase the hold time by 10–15 seconds or reduce the starting rest by 15 seconds.
• Deload weeks: Every 4–6 weeks, take a lighter week with fewer rounds and more rest to allow deeper physiological adaptation.

Many beginners make the mistake of training every day thinking more practice equals faster progress. In breath-hold training, this approach leads to diminishing returns and increases the risk of hypoxic blackout during sessions.

Safety Rules You Must Follow

Static apnea training carries real risks, and CO2 tables must always be practiced with strict safety protocols:

• Never train alone. Even in a pool with lifeguards, have a dedicated, trained buddy watching you at all times. Shallow-water blackout can occur without warning.
• Never hyperventilate before a hold. Rapid deep breathing before a breath-hold artificially lowers CO2 without raising oxygen meaningfully, removing your body's primary warning signal and dramatically increasing blackout risk.
• Stop if you feel dizzy, lightheaded, or experience tingling in your extremities. These are warning signs of excessive hypoxia. End the session immediately.
• Do not push through failure. If you cannot complete a hold, end it early and rest. Finishing a round at 0:50 instead of 1:00 is not failure — it's smart training.
• Always train in a safe environment. Dry static training (on a couch or bed, not in water) is the safest option for solo practice. Water-based CO2 tables must always involve supervision.

Track Your Progress With Anima Apnea

One of the biggest challenges with table training is building and timing sessions consistently. Mental math while oxygen-deprived is not ideal — and neither is watching a clock during your rest periods, which adds psychological stress that shortens your holds.

Anima Apnea automatically generates personalized CO2 tables based on your current personal record. Enter your max hold time, and the app calculates the optimal hold duration, starting rest, and reduction pattern for your level. During sessions, it guides you through each round with clear audio cues so you can focus entirely on relaxation and technique.

Beyond session guidance, the app tracks every hold, every contraction onset, and every rest period. Over weeks and months, you can see exactly how your CO2 tolerance is improving — when contractions start later, when your recovery heart rate drops faster, when that last round stops feeling impossible. This kind of objective data turns subjective improvement into something you can actually see and celebrate.

Whether you're chasing your first 3-minute static or training for competitive freediving, CO2 tables are the most direct path to measurable improvement. Build the habit, train smart, and stay safe.