Clubhouse #28 | Breathwork for Performance: Oxygen, CO2, and the Athlete’s Secret Weapon 🌬️🏃‍♂️

Most athletes overlook one of the most powerful tools for improving performance: their breath. While strength, endurance, and mobility get most of the attention, the way you breathe dictates how efficiently your body uses oxygen, how well you manage stress, and how quickly you recover.

In this Clubhouse, we explore the physiology of breathwork, the performance benefits of CO₂ tolerance training, and how to integrate breath control into your workouts and recovery routine.

The Physiology of Breath: More Than Just Oxygen

At first glance, breathing seems simple: inhale oxygen, exhale carbon dioxide. But under the surface, your breath is a powerful regulator of cellular metabolism, neurological state, and athletic output. The way you breathe influences not only how much oxygen you take in, but how effectively that oxygen is delivered to working muscles, how carbon dioxide is tolerated, and how energy is produced at the mitochondrial level.

Oxygen (O₂) is essential for producing ATP (adenosine triphosphate), the energy currency of the body, via aerobic metabolism. But the story doesn’t end at intake. Optimal performance depends on your body’s oxygen utilization—how efficiently cells extract and use oxygen from the bloodstream. This depends on capillary density, mitochondrial health, and hemoglobin function. Increasing mitochondrial biogenesis through Zone 2 training, altitude exposure, or certain breath holds can boost your oxygen economy significantly. A fitter athlete doesn’t just inhale more oxygen—they waste less.

Carbon Dioxide (CO₂) is often wrongly dismissed as a mere waste product. In truth, CO₂ is fundamental to oxygen delivery through the Bohr Effect—a physiological mechanism where higher CO₂ levels signal hemoglobin to release oxygen more readily to tissues. This means that a higher tolerance to CO₂ allows you to perform better under stress by improving oxygen offloading precisely when your body needs it most. Low CO₂ tolerance, on the other hand, prompts excessive ventilation, disrupts CO₂ balance, and paradoxically limits performance.

Moreover, CO₂ plays a crucial role in maintaining acid-base balance (pH) in the blood. Rapid, shallow breathing—especially mouth breathing—lowers CO₂ too much, leading to respiratory alkalosis. This shift in pH reduces calcium availability in muscle fibers, impairing contractility and force production. In high-pressure scenarios, poor CO₂ regulation can affect cognition, coordination, and your ability to stay composed.

Breath training isn’t just about taking in more air. It’s about mastering the balance between oxygen intake and carbon dioxide retention. Proper breath control improves gas exchange efficiency, enhances aerobic metabolism, increases vagal tone (rest-and-digest response), and trains the nervous system to function effectively under physiological stress.

CO₂ Tolerance: The Key to Endurance and Calm Under Pressure

CO₂ tolerance refers to how well your body handles the accumulation of carbon dioxide during breath holds, exertion, or stress. Athletes with high CO₂ tolerance can buffer the physiological urge to breathe longer, maintain mental focus under duress, and sustain more efficient oxygen delivery at higher intensities.

This is especially relevant in endurance sports, combat sports, and high-stakes competitive environments. Low tolerance to CO₂ triggers earlier breathlessness, limits VO₂ max potential, and accelerates fatigue. Conversely, improving CO₂ tolerance increases ventilatory efficiency and unlocks greater work capacity.

One simple diagnostic tool is the Control Pause or BOLT score (Body Oxygen Level Test). After a normal exhale, time how long you can hold your breath comfortably without straining:

• <20 seconds: Indicates low CO₂ tolerance. Suggests a reliance on over-breathing and reduced aerobic efficiency.

• 20–40 seconds: Moderate tolerance. Sufficient for most moderate intensity efforts.

• 40+ seconds: High tolerance. Reflects strong respiratory economy and superior buffering capacity.

How to Train CO₂ Tolerance:

• Box Breathing (4–4–4–4): A square rhythm of inhale-hold-exhale-hold. This technique boosts parasympathetic tone, reduces anxiety, and recalibrates your breath control.

• Walking Apnea Drills: After a gentle exhale, walk while holding your breath. Track how many steps you can complete without air. Repeat for 5–10 rounds. Improves functional breath control under locomotion.

• CO₂ Ladder Drills: Gradually reduce the duration of your inhale-exhale cycle across repetitions (e.g., 4–4, then 3–3, 2–2, etc.). This increases CO₂ concentration in a controlled environment and helps your nervous system adapt.

CO₂ tolerance drills stimulate chemoreceptors that govern your breathing reflex. Over time, your body learns to withstand greater internal CO₂ buildup without panicking. This not only delays the onset of fatigue but also enhances your ability to stay calm, collected, and efficient under race-day pressure.

Training your breath is training your brain, blood vessels, and mitochondria—foundational systems for elite performance.

The Role of Nasal Breathing in Performance

Nasal breathing has emerged as a cornerstone of breath training due to its unique ability to regulate respiratory mechanics and enhance physiological efficiency. Unlike mouth breathing, which tends to be shallow and rapid, nasal breathing encourages a slower, deeper, and more controlled breathing pattern that optimizes the body's use of oxygen and carbon dioxide.

One of the key physiological advantages of nasal breathing lies in its ability to generate resistance to airflow. This resistance increases negative pressure in the lungs, drawing air deeper into the lower lobes where gas exchange is most efficient due to higher capillary density. As a result, more oxygen is absorbed per breath and carbon dioxide is retained longer, which supports better oxygen delivery to working muscles via the Bohr effect.

Additionally, nasal breathing helps stimulate the parasympathetic nervous system—enhancing vagal tone and reducing stress reactivity. This autonomic benefit is particularly important for athletes, as a balanced nervous system promotes faster recovery, improved heart rate variability (HRV), and more stable energy regulation.

From a biochemical standpoint, nasal breathing supports nitric oxide (NO) production in the paranasal sinuses. Nitric oxide is a potent vasodilator that increases blood flow, improves oxygen uptake, and has antimicrobial effects—further supporting both performance and immune defense during training.

Athletes who incorporate nasal breathing into their aerobic sessions, especially during submaximal efforts such as Zone 2 training, develop greater CO₂ tolerance and improved aerobic economy. While nasal breathing becomes more difficult at maximal intensities, its use in lower-intensity training and recovery periods builds a strong foundation for respiratory control and endurance.

In summary, nasal breathing is not just a technique—it is a training tool that enhances oxygen utilization, nervous system regulation, and recovery. By embedding it into regular practice, athletes can elevate both performance and resilience across the board.

Breathwork Protocols for Athletes

There’s no one-size-fits-all, but breathwork protocols can be tailored to meet specific training goals:

• For Pre-Performance Focus: Try box breathing or tactical breathing (4–2–6) for 3–5 minutes before competition. This calms the nervous system and sharpens mental clarity.

• For Recovery: Use extended exhales (e.g., 4s inhale, 6–8s exhale) to activate parasympathetic dominance post-exercise. This reduces cortisol and improves HRV.

• For VO₂ Max: Incorporate breath-hold intervals post-warmup or mid-run, especially after an exhale. Repeat 4–6 times. Builds tolerance to breathlessness.

• For Sleep Optimization: Try a 4–7–8 breathing pattern (inhale 4, hold 7, exhale 8) for 2–3 minutes in bed. Promotes vagal tone and transitions the brain into recovery mode.

Over weeks and months, consistent breath training can lead to lower resting respiratory rate, improved HRV, enhanced aerobic economy, and greater mental resilience under load.Enhance sleep quality

Integrating Breath Training into Your Program

You don’t need to overhaul your training plan to benefit from breathwork. Start with small, structured insertions:

• Warm-up: 3 minutes of nasal-only breathing + mobility

• Main set: Add 1–2 breath-hold intervals (e.g., during walks or cooldowns)

• Cool-down: 5 minutes of cadence breathing to restore balance

Track metrics like CO₂ tolerance time, HRV, and perceived exertion. Over weeks, improvements in these markers often correlate with better aerobic endurance and resilience to fatigue.

Conclusion: Breathe Better, Perform Better

Breath is the link between the nervous system, cardiovascular efficiency, and muscular endurance. By training your breath, you train your brain and body to handle stress, recover faster, and push harder. Breathwork isn’t a fringe protocol—it’s a foundational performance tool that every athlete should master.