Breathe less, gain more! The Surprising Power of CO₂

Why is Carbon Dioxide Important for the Body?

Carbon dioxide (CO2) is important for the body because it regulates blood acidity, determines how efficiently cells absorb oxygen, and dictates your tolerance to stress.

Most people assume we breathe because our bodies are running low on oxygen, but the urge to inhale is actually triggered by rising CO2 levels. Carbon dioxide is not simply a waste product to get rid of; it is the quiet conductor of the entire respiratory orchestra. When CO2 levels are balanced, it naturally dilates blood vessels, improving circulation and lowering the heart rate [1]. Learning to work with carbon dioxide, rather than trying to aggressively exhale it, is one of the most profound shifts you can make in your relationship to breath.

What is the Bohr Effect?

The Bohr Effect is the physiological principle stating that hemoglobin releases oxygen to the tissues more effectively in the presence of higher carbon dioxide levels.

If your CO2 tolerance is low due to chronic overbreathing, you blow off too much carbon dioxide. Without enough CO2 in the blood, hemoglobin holds onto oxygen tightly instead of releasing it to your muscles and brain [2]. This means you can experience poor oxygen delivery and fatigue even if you are breathing heavily. By slowing your breath and gently raising your CO2 tolerance, you activate the Bohr Effect, allowing oxygen to detach from the blood and properly fuel your cells [3].

How Does Overbreathing Affect the Nervous System?

Overbreathing affects the nervous system by blowing off too much CO2, which constricts blood vessels and signals the brain to trigger a fight-or-flight stress response.

Fast-paced living, stimulants, and high-intensity fitness culture push many people into chronic mouth breathing and overbreathing. This habit lowers CO2 levels in the blood, which restricts cerebral blood flow and heightens anxiety sensitivity through CO2-sensitive chemoreceptors in the brainstem [4]. This physiological cascade leaves the nervous system on high alert, creating a cycle of tension and fatigue. Reversing this requires building CO2 tolerance, which trains the nervous system to remain calm under pressure and stabilizes the respiratory rhythm [5].

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Is CO2 Important? with Travis Steffens

A foundational introduction to why CO2 is essential for health and why breathing less may be exactly what your body needs.

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What Do Breath Masters Say About CO2 Tolerance?

Breath Masters teach that building CO2 tolerance through slow, intentional breathing is the key to athletic endurance, mental clarity, and emotional resilience.

Travis Steffens, CEO of The Breath Source, notes that "CO2 is the most important molecule to both the planet and to your body," and that we breathe not because we need oxygen, but because CO2 rises. This foundational insight reframes the entire practice of breathwork: the goal is not to take in more air, but to develop a healthier relationship with the CO2 your body naturally produces.

Breath Master Jesse Coomer explains that improved CO2 tolerance leads to better oxygen delivery, lower heart rates during exercise, and faster recovery, noting that you must train your body to handle rising CO2 levels to stay calm under stress [6]. Breath Master Mike Maher teaches that practicing extended exhales safely raises CO2 tolerance, which acts as a quick vagus nerve reset to instantly lower anxiety [7]. Breath Master Ed Harrold emphasizes that nasal breathing is the most effective way to build this tolerance, as it naturally slows the breath rate and improves oxygen uptake, acting as a built-in altitude training tool for peak performance [8].

4-6 Breath Bubble with Mike Maher

A soothing guided practice with extended exhales, designed to help you safely raise CO2 tolerance and feel the benefits immediately.

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How Do You Train CO2 Tolerance?

You train CO2 tolerance by practicing slow nasal breathing and introducing controlled breath holds after a normal exhalation.

The goal is to gradually expose your body to slightly elevated levels of carbon dioxide and train your nervous system to remain calm. Start by breathing exclusively through your nose during daily activities, which naturally slows your respiratory rate. Practice a 4-8 breathing ratio (inhaling for 4 seconds, exhaling for 8 seconds) to retain more CO2 safely. Over time, your breath will become quieter, slower, and more stable, allowing your physiology to reorganize itself around oxygen efficiency and resilience.

The Expanding Box Breath with Ryan Bean

A progressive box-breathing journey into extended holds and controlled hypoxia to deepen CO2 adaptation.

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Hypoxic Hypercapnic with AJ Fisher

A powerful, athletic-style session using controlled low-oxygen breathing to train efficiency, CO2 resilience, and calm under intensity.

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Frequently Asked Questions

What are the signs of low CO2 tolerance?
Signs of low CO2 tolerance include getting winded easily during light exertion, feeling lightheaded after holding your breath, chronic mouth breathing, and experiencing anxiety during moments of stillness.

How does CO2 affect athletic performance?
Higher CO2 tolerance improves athletic performance by allowing the body to use oxygen more efficiently via the Bohr Effect, stabilizing the breathing rhythm, and reducing the onset of fatigue during high-intensity exercise [3].

Is it safe to hold my breath to build CO2 tolerance?
Yes, gentle breath holds after a normal exhalation are a safe and effective way to condition your body to tolerate higher CO2 levels, provided you do not push to the point of severe stress or dizziness.