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CO2 Tables and O2 Tables for Freediving – All You Need to Know

Freediving, often referred to as apnea diving, is a discipline that has enthralled enthusiasts for decades. It’s a pure and minimalist form of diving, devoid of cumbersome equipment, allowing the diver to connect deeply with the underwater world.

As its popularity grows, so does the interest in mastering the art of holding one’s breath. Central to this is understanding the human body’s responses to breath-holding and how to safely train to extend one’s time beneath the waves.

Breath-hold training is not just about willpower; it’s rooted in physiology and science. By improving our physiological responses and understanding the interplay between oxygen and carbon dioxide in our bodies, we can enhance our performance and safety in freediving.

Understanding the Science

Every breath we take serves a crucial purpose – to oxygenate our blood and remove waste carbon dioxide produced by our cells. This delicate balance becomes pronounced when we decide to hold our breath, especially during freediving.

Carbon Dioxide (CO2)

When we hold our breath, we aren’t introducing fresh oxygen into our lungs, but our body continues to metabolize oxygen and produce carbon dioxide. Over time, the levels of CO2 in our bloodstream rise. It’s this rising CO2 level that triggers our brain’s urge to breathe, often experienced as a sharp, uncomfortable feeling in the diaphragm or a contraction.

This is the body’s way of saying, “I need to exhale this CO2 and get fresh oxygen!” So, when training for freediving, a significant part of the challenge is increasing the body’s tolerance to higher levels of CO2.

Oxygen (O2)

As one might expect, as CO2 levels rise in the bloodstream, O2 levels fall. Our body consumes the stored oxygen in our lungs, bloodstream, and muscles. When O2 levels drop to a critical point, it can lead to hypoxia, a condition where the body doesn’t receive enough oxygen to function correctly.

In the worst-case scenario, this can lead to blackouts underwater. Thus, understanding and monitoring O2 consumption is essential not just for improving performance but also for ensuring safety during freediving.

CO2 Tables: Purpose and Benefits

CO2 Tables and Their Mechanism: CO2 tables primarily focus on increasing an individual’s tolerance to higher levels of carbon dioxide in the bloodstream. As we’ve established earlier, rising CO2 levels are the primary trigger for the body’s urge to breathe.

By regularly practicing CO2 tables, a freediver can train their body and mind to remain calm and delay the onset of this urge, even as CO2 levels rise.

Here’s how CO2 tables generally work: They manipulate the recovery (or rest) intervals between breath-holds while keeping the breath-hold duration constant. As the diver progresses through the table, the rest periods get shorter, not allowing CO2 to be fully expelled, thereby increasing its accumulation over the course of the exercise.


  1. Delayed Urge to Breathe: By increasing CO2 tolerance, a freediver can comfortably extend their breath-hold durations because they can better manage and delay the initial urge to breathe.
  2. Mental Fortitude: Constantly challenging one’s limits with increasing CO2 helps in strengthening mental resilience, an essential trait in freediving.
  3. Safety: Understanding and being comfortable with the feeling of elevated CO2 can prevent panic in unexpected situations underwater.

Sample CO2 Table

Note: Before attempting any breath-hold exercise, always ensure you’re in a safe environment, preferably under the supervision of a trained buddy or instructor. Never practice in water alone.

Beginner CO2 Table:

SetBreath-hold DurationRest Period
11 minute2 minutes
21 minute1 minute 50 seconds
31 minute1 minute 40 seconds
41 minute1 minute 30 seconds
51 minute1 minute 20 seconds
61 minute1 minute 10 seconds
71 minute1 minute
81 minute50 seconds

Guidance and Tips:

  • Start Slow: If you’re new to CO2 tables, begin with longer rest intervals, even more than mentioned above, and gradually reduce as you feel comfortable.
  • Listen to Your Body: It’s essential to remain attentive to how you feel. If any set feels too challenging, it’s okay to increase the rest period or stop the exercise altogether.
  • Consistency is Key: Like any training regimen, consistency is vital. Regular practice, even if in shorter durations, can lead to steady improvements.
  • Progress Gradually: As you progress and feel more comfortable, you can modify the table by further reducing rest intervals or increasing the breath-hold durations. But always prioritize safety and comfort over pushing limits.

O2 Tables: Purpose and Benefits

O2 Tables and Their Mechanism: O2 tables, in contrast to CO2 tables, focus on improving the body’s efficiency in utilizing and conserving oxygen. Whereas CO2 tables challenge your CO2 tolerance by reducing recovery times, O2 tables challenge the actual breath-hold durations, allowing the body to adapt to lower levels of oxygen over time.

Here’s the essence of O2 tables: They incrementally increase the breath-hold durations while keeping the recovery periods long and relatively constant. This approach helps the body to slowly adapt to functioning efficiently with decreasing levels of oxygen.


  1. Enhanced Oxygen Efficiency: Over time, the body becomes more adept at conserving oxygen during longer breath-holds, helping divers remain underwater for extended periods.
  2. Delayed Onset of Hypoxia: By familiarizing the body with low oxygen levels, O2 tables can help delay the onset of hypoxia, a state where the body is deprived of adequate oxygen supply at the tissue level.
  3. Mental Composure: By practicing longer breath-holds, divers can train their minds to stay calm and focused even as the body signals oxygen deprivation, essential for those challenging moments during deep dives.

Sample O2 Table

Safety Reminder: Always practice breath-hold exercises in a safe environment. If practicing in water, always have a trained buddy or instructor nearby. The risk of shallow water blackout is real; always prioritize safety.

Beginner O2 Table:

SetBreath-hold DurationRest Period
11 minute2 minutes
21 minute 15 seconds2 minutes
31 minute 30 seconds2 minutes
41 minute 45 seconds2 minutes
52 minutes2 minutes
62 minutes 15 seconds2 minutes
72 minutes 30 seconds2 minutes
82 minutes 45 seconds2 minutes

Guidance and Tips:

  • Start Comfortably: Begin with breath-hold durations that you find comfortable and then slowly push your limits as you progress through the table.
  • Quality Over Quantity: It’s more beneficial to have quality holds where you feel calm and relaxed rather than pushing too hard and feeling uncomfortable.
  • Progressive Increase: Once you feel comfortable with a particular table, consider increasing the breath-hold durations. Alternatively, if a certain duration feels too challenging, you can either repeat a previous duration or extend the rest period.
  • Listen and Adapt: Always be in tune with your body’s responses and adjust your training accordingly. Remember, the goal is steady and safe progress, not setting records each session.

Creating a Personalized Table

Why Personalize? Everyone’s breath-hold capability, physical conditioning, and experience vary. A table that works perfectly for one person might be either too easy or too challenging for another. Customizing a table ensures that it aligns with an individual’s specific needs and aspirations, enabling them to progress at their own pace.

Factors to Consider

  • Current Breath-Hold Capability: Before designing a table, measure your comfortable breath-hold duration. This serves as a benchmark, ensuring the table starts at an appropriate level.
  • Training Frequency: How often you train will influence how quickly you progress. Those training more frequently might progress faster, but it’s also essential to consider adequate rest to prevent overtraining.
  • Training Goals: Are you training for recreational freediving, spearfishing, or competitive freediving? Your goals will help define how aggressive or relaxed your table should be.

Steps to Construct Your Table

  1. Determine Starting Point: Based on your current comfortable breath-hold duration, set this as your starting point.
  2. Define Incremental Increases: Decide on the incremental time increase for each subsequent breath-hold. For beginners, increases of 5-15 seconds might be appropriate. For advanced divers, longer increments might be suitable.
  3. Set Rest Periods: Decide on a consistent rest period, usually double the breath-hold time for O2 tables and decreasing for CO2 tables. Adjust based on how challenging you find the exercise.
  4. Regularly Review and Adjust: As you progress, regularly review your table. If it becomes too easy or too challenging, adjust the durations accordingly.

The Adaptive Approach: Remember that your body’s response can vary from one day to another based on various factors like sleep, diet, and stress. On some days, you might find it harder to hold your breath. Listen to your body, and don’t be afraid to adapt your table on such days.

Woman holding breath

A Word About Safety

Freediving and breath-hold training, while incredibly rewarding, come with inherent risks. Being aware of these risks and practicing safe training protocols are vital to ensure you enjoy the sport while minimizing potential dangers.

Golden Rule: Never Alone: I will sound like a broken record, but never mind. Whether you’re practicing in a pool, open water, or even dry training on land, always have someone nearby. This person should be aware of what you’re doing and be ready to assist if things don’t go as planned.

Recognize the Signs: Pushing your limits is part of training, but it’s crucial to distinguish between a challenging hold and a dangerous one. If you experience strong contractions, dizziness, or tingling in your extremities, it’s time to stop. Always err on the side of caution.

Gradual Progression: It’s tempting to chase rapid progress, especially when you’re starting. However, the body needs time to adapt to the demands of breath-holding. Focus on consistent, gradual progression rather than making significant leaps in hold durations.

Stay Educated: Continuously educate yourself about the physiological aspects of freediving. Understanding what happens in your body can guide your training and keep you safe.

In Conclusion: Embrace the journey of freediving with respect and mindfulness. It’s a sport of patience, and the rewards are profound. Always prioritize safety, stay informed, and enjoy the serene world of breath-hold diving.

Final Thoughts

Breath-hold training, especially through structured methods like CO2 and O2 tables, holds the promise of significant advancements for freedivers, spearfishers, and underwater enthusiasts. These tables, carefully constructed, offer a systematic way to push our limits, better understand our physiological responses, and help adapt our bodies to the unique demands of prolonged breath-holding.

However, as with any training, it’s imperative to approach it with mindfulness. While the desire to achieve longer breath-holds can be exhilarating, the journey there should be marked with patience, consistent practice, and above all, safety.

Frequently Asked Questions

How often should I practice with CO2 and O2 tables?

It varies depending on the individual and their goals, but a common recommendation is 2-3 times a week. Ensure you have rest days in between sessions to allow your body to recover.

Can I practice CO2 and O2 tables on the same day?

It’s possible, but for beginners, it’s advisable to focus on one type of table per day. This allows you to give your full attention and energy to that specific training.

I’m finding my custom table too easy/hard. What should I do?

Listen to your body. If it’s too easy, slightly increase the breath-hold durations or adjust the rest intervals. If it’s too challenging, reduce the durations or extend the rest periods. Remember, the goal is gradual progression.

Can I practice these tables outside the water, like at home?

Yes, CO2 and O2 tables can be practiced dry (outside water). In fact, many divers practice them dry before moving to a pool or open water setting.

I often feel dizzy or lightheaded after a session. Is this normal?

Feeling mild discomfort or the urge to breathe is expected during training, but dizziness or lightheadedness can be a sign you’re pushing too hard. Always prioritize safety and consider reducing your breath-hold durations or increasing rest times.

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