Breathwork for Athletes: CO₂ Tolerance, Recovery, and Performance

Breathwork for athletes can sound like one practice. In reality, it solves four different problems.

It helps an athlete stay composed when pressure spikes. It makes breathing less costly when effort gets high. It accelerates the shift into recovery after the work is done. And in specific moments — before a fight, a hard interval, or a dangerous wave — it can deliberately raise arousal instead of lowering it.

Eliud Kipchoge made the efficiency side visible in October 2019, when he ran 26.2 miles in 1 hour, 59 minutes, and 40 seconds — the first human to break the two-hour marathon barrier. Video of the attempt captured something most viewers missed at first: while his pacers were visibly mouth-breathing within minutes of the start, Kipchoge, moving faster than all of them, was breathing through his nose. ^[1]

At sub-four-minute-mile pace.

That image raises the useful question: what exactly is being trained? Not just lungs. Not just fitness. The best athletes are training the breath as a control surface for the nervous system, the mechanics of effort, and the transition between performance states. The same skill looks different depending on the moment.

The Pressure Question

Start with pressure, because it is where the value of breath control is easiest to misunderstand. The goal is not to become relaxed in the middle of competition. The goal is to interrupt the stress response quickly enough that skill can still express itself.

Novak Djokovic is one of the most accomplished tennis players in history, and one of the most open athletes in professional sport about the role breathwork plays in his game. Not general fitness. Not conditioning load. The specific, deliberate act of controlling his breath between points, in tiebreaks, and mid-match.

The No. 1 thing is to learn how to consciously breathe. [...] Conscious breathing, really learning how to master that skill, [...] helps with better sleep, better recovery, more presence in the moment.

What Djokovic is describing is a skill most athletes leave undeveloped: the ability to modulate the nervous system in real time. He has spoken extensively about using deliberate breathing to reset his emotional state and return to focus. ^[2] He has also collaborated with Wim Hof — the Dutch extreme athlete who systematized what is now widely known as power breathing: repeated rounds of forceful, rhythmic breathing followed by a breath retention. ^[3] But Djokovic's day-to-day application is simpler than the full method. In a pressure moment, conscious breathing gives him a reset switch.

LeBron James uses a related lever before games, meditating for 20 to 25 minutes as part of his pre-game routine. ^[4] Tom Brady's mental fitness coach Greg Harden described the breathing mechanism directly: slow the breathing, train the inhale and release, and teach the body to let go on command. ^[5]

Different sports, different rituals, same underlying job: create enough physiological space for decision-making to come back online.

The research explains why this works. When you slow your breathing to approximately five to six breath cycles per minute, your heart rate begins to oscillate in synchrony with your respiratory rhythm, producing a state called baroreflex resonance. ^[6] Heart rate variability — the variation between heartbeats, and one of the most reliable markers of nervous system health and athletic readiness — reaches its peak amplitude. In plain terms: the body shifts from reactive stress-readiness toward composed alertness. Not sedated. Clear.

That is the first takeaway: composure is not just a mindset. It is a state, and breath is one of the fastest ways to train access to it.

Coherence breathing is where that training begins: five to six breath cycles per minute, equal inhale and exhale. It feels almost too simple, which is why many athletes skip it. Practiced consistently, the same pattern becomes a reliable way to shift from reactive to composed.

The Efficiency Question

Pressure control is about what happens between efforts. Efficiency is about what happens inside the effort itself.

Every breath taken during intense exercise has a cost: energy, rhythm, posture, drag, or momentum. Elite athletes do not treat that cost casually. They find a breathing pattern that gives them enough air without stealing from the movement they are trying to perform.

In swimming, the tradeoff is visible. Michael Phelps — the most decorated Olympian in history, with 23 gold medals across four Games — built a breathing pattern that many coaches would call unconventional: in butterfly, he breathed every stroke rather than every other stroke because, as his coach Bob Bowman explained, "he just has a better rhythm when he breathes every stroke." ^[10] The pattern was calibrated to him specifically, but the principle is universal: the right breathing pattern is the one that costs the least and delivers the most. In sprint freestyle events, Phelps would hold his breath for the final 25 meters, prioritizing position and stroke mechanics over another inhale when fractions of seconds decided everything.

Katie Ledecky applies a different kind of precision. She breathes every two strokes and positions her head so that often only one goggle clears the surface. She breathes inside her own bow wave — the pocket of lower-pressure water that forms ahead of her as she moves — which means her head barely moves, her hips stay level, and almost no energy is lost to rotation. ^[11] This is not abstract wellness. It is movement economy.

Caeleb Dressel carries the same idea to its limit. In the 50m and 100m sprints, he does not breathe in the final 25 yards at all. ^[12] A controlled breath hold, in competition, at peak exertion. The technique is legal, intentional, and only useful because he knows exactly how his body responds to oxygen debt.

That brings the article back to Kipchoge's nose.

Nasal breathing at marathon pace is possible because the nose is not a liability. It is an underused training constraint. The nasal passages produce nitric oxide, which dilates the airways and improves how efficiently oxygen transfers into the bloodstream. ^[13] Nasal breathing also demands higher CO₂ tolerance: because airflow is more restricted than through the mouth, CO₂ builds slightly faster, and the body must learn to stay calm under that pressure instead of triggering panic breathing. ^[14] Over time, that adaptation changes how efficiently you breathe at any intensity.

This is the second takeaway: breathing efficiency is trainable, but it is not a hack. It is a long adaptation measured in weeks and months, not single sessions. What Kipchoge breathes on race day is the output of years of altitude training at 2,400 meters in Iten, Kenya, combined with deliberate respiratory practice. The system responds, but slowly.

Before training that system, it is worth knowing where you stand. CO₂ tolerance varies significantly between individuals, and most people have no idea how reactive their breathing is under rising CO₂. Auralize uses a guided slow-exhale assessment: several preparatory breaths, one gentle final inhale, then the slowest soft exhale you can maintain without forcing. The result gives you a baseline for respiratory control and CO₂ sensitivity. From that baseline, Auralize prescribes a daily CO2 tolerance training methods block — score-matched box breathing inside short coherence frames — so the work is calibrated, not guessed. Athletes with stronger CO₂ control tend to breathe less frequently, recover faster, and stay calmer under load. It is the metric that connects this entire section.

Recovery as a Skill

The next performance problem starts after the effort ends. A complexShift, point, possession, heat, or race may be over externally, but the nervous system can stay switched on. If an athlete cannot downshift, the body keeps acting as if the demand is still happening.

Stephen Curry is the cleanest example because basketball turns recovery into tiny windows. His advantage is not just that he can run for four quarters. It is that he can come down quickly enough during short breaks to do it again. An ESPN profile described Curry training this directly: after exhausting complexShifts, his trainer Brandon Payne places sandbag weight below his rib cage to overload the diaphragm, and through conditioning and breathing work Curry can bring his heart rate down during a 90-second timeout. ^[17]

That is recovery as a skill. Not the spa version of recovery. Not even sleep, nutrition, or tissue repair, although all of those matter. This is the immediate ability to lower arousal after a hard burst so the next effort starts from a cleaner state. The same mechanism that supports between-rep recovery also underwrites longer-term cardiovascular regulation — see breathing exercises for blood pressure for the slow-paced practice that anchors that baseline outside of training.

Lorenzo Sonego shows the slower version of the same idea. The ATP player described working with breathing coaches and doing breathing exercises every day, not only for calm on court but also for recovery, mental state, and focus through long matches. ^[18] The practice is not dramatic. That is why it fits the recovery section: repeated, low-intensity downshifting that teaches the nervous system how to return.

This is a different job from the CO₂ tolerance work in the efficiency section. Breath holds, nasal restriction, and air hunger train the body to tolerate rising CO₂ under load. Recovery breathing does almost the opposite. It removes the threat signal: slow rhythm, relaxed diaphragm, longer exhale, no forcing. The goal is not to tolerate stress. The goal is to tell the body the stress is over.

This is the third takeaway: recovery is not only passive. Athletes cannot force adaptation, but they can train the transition into the state where adaptation becomes more likely. Curry's timeout reset, Sonego's daily practice, and the post-exercise breathing research all point at the same skill: get out of effort-mode on command.

Slow, diaphragmatic breathing after intense effort is where to start: four to six breath cycles per minute, with the exhale slightly longer than the inhale, for five to ten minutes. No breath holds. No air hunger. No attempt to win the cooldown. The cleaner the signal, the better the downshift.

The Activation Question

So far, breathwork has been framed as a way to downshift: reduce pressure, reduce respiratory cost, reduce stress chemistry after effort. But not every athletic moment calls for lower arousal. Some moments demand a controlled upshift.

Alistair Overeem has held world titles in both MMA and kickboxing — a rare combination that required him to compete, across two decades of professional fighting, at the highest level in the most demanding combat sports on earth. In an interview on the official Wim Hof channel, he described incorporating power breathing into fight preparation: rounds of rhythmic, forceful breathing followed by a breath hold, repeated before training and before competition. ^[22] His explanation was direct: it gets him into a state he cannot reach any other way. Not calmer. Sharper.

Georges St-Pierre — two-time UFC welterweight champion and widely considered the greatest mixed martial artist of his generation — took a more systematic approach. His published training program, The Path, treats respiratory training as a structured pillar of conditioning, not an add-on. St-Pierre has spoken about the mental dimension explicitly: what separates fighters at the elite level is not always physical. It is who can maintain composure and aggression simultaneously, and who arrives in the cage already inhabiting the right state. Breath training, for St-Pierre, is part of how that state gets built.

Djokovic appears here again because he uses both sides of the system. The slow, deliberate breath control he uses mid-match is a downshift. His power breathing work with Wim Hof is a separate practice. ^[3] That is not contradictory. It is the core point of the article: different breathing tools serve different performance moments.

What these athletes are accessing is voluntary activation of the sympathetic nervous system, triggered entirely by breath. The physiology was documented in a landmark 2014 study at Radboud University, in which trained practitioners were injected with bacterial endotoxin — a substance that normally triggers a strong, automatic inflammatory immune response. The power breathing group showed dramatically reduced symptoms and measurably suppressed immune activation compared to controls. ^[23] They had used breath to influence a system that science had, until that point, considered entirely outside conscious control.

This is the fourth takeaway: activation can be trained too. Fighters and extreme athletes cluster around power breathing because their sports place them repeatedly at the edge of what the nervous system can tolerate. They do not need relaxation before the moment of demand. They need a controllable on-ramp into readiness.

Power breathing is built into Auralize as a guided session: metered rounds, cued holds, and structured progression. It is the same category of practice Overeem, St-Pierre, and Djokovic have built into preparation, guided so you can find your footing without guesswork.

Start With the Baseline

The through-line across every athlete in this article is not that they all use the same technique. They do not. Kipchoge's nasal efficiency at marathon pace, Djokovic's mid-tiebreak reset, Overeem's pre-fight activation, and Sonego's daily breathing practice solve different problems.

The shared principle is simpler: breath is trainable. The raw material is automatic. The performance value comes from building enough control to use the right pattern at the right time.

That is exactly what Auralize is built around. You begin with the CO2 tolerance test online, then use that baseline to choose the right kind of breath training: composure work before pressure, efficiency work under load, recovery work after effort, or activation work when you need to arrive switched on. Progress becomes visible because the starting point was measured. If you prefer to run the protocol with a stopwatch first to understand what it feels like, the step-by-step at-home protocol walks through the same five-breath warm-up and timed exhale.