Breathe Better, Ride Stronger

As an endurance cycling coach my advice for clients usually focuses on intervals, nutrition, pacing, and recovery. But there’s a quieter performance lever hiding in plain sight—your breath.

Breathing is one of those “low-hanging fruit” improvements that most cyclists overlook. It’s automatic, it’s always there, and yet, few of us have been taught how to breathe well. Recent research (see below) sheds light on how breath training can build CO₂ tolerance, improve oxygen uptake, and even support nervous system regulation. Let’s unpack it.

The Hypercapnic Advantage

We’re conditioned to think of CO₂ as a waste gas—something to get rid of. But for endurance athletes, learning to tolerate more CO₂ (a hypercapnic state) is a superpower.

When CO₂ rises in the blood:

• It stimulates the release of oxygen from haemoglobin (thanks to the Bohr effect).
• It encourages better oxygen delivery to working muscles.
• It boosts nitric oxide levels, improving vasodilation and oxygen absorption.

Put simply: better CO₂ tolerance = better oxygen efficiency.

Hypocapnia (low CO₂ from overbreathing or panting) is, by contrast, not helpful for endurance. It limits oxygen availability because haemoglobin holds onto it too tightly.

Biochemical Mechanics: Why You Feel the Urge to Breathe

Here’s a surprising fact: the urge to breathe isn’t driven by low oxygen—it’s triggered by rising CO₂.

When CO₂ levels rise:

• Blood pH drops (becomes more acidic).
• Oxygen binds less tightly to haemoglobin, making it more available to tissues.
• However, the brain is sensitive to pH changes and interprets rising CO₂ as a red alert.

Over time, breath training can raise your brain’s CO₂ alarm threshold. This reduces feelings of breathlessness during efforts and improves your ability to stay calm under duress.

Breath Training for Cyclists

The good news? You can train this.

Breath Light exercises (from the Oxygen Advantage approach, check out their App) involve nasal breathing to “feel air hunger.” Start with 1–2 short sessions per day, just 5–10 minutes. Gradually build up, aiming for 10 sessions a week.

This builds CO₂ tolerance and can shift your perception of breathlessness, improving stamina and VO₂ max without adding a single watt.

Biomechanics: The Gears of Breathing

Your diaphragm is your breathing engine, and it’s meant to do the heavy lifting. Mouth breathing bypasses that system, often triggering shallow, inefficient chest breathing.

Nasal breathing, by contrast:

• Forces engagement of the diaphragm.
• Adds resistance, strengthening respiratory muscles.
• Helps optimise breathing mechanics for endurance.

A typical breath is around 500ml, but due to “dead space” in the airways, about 150ml doesn’t participate in gas exchange. Slow, deep breaths (like 10 per minute) give you far more usable oxygen than rapid, shallow ones (say 23 per minute).

When cycling we should use "a three gear" breathing technique in the same way as we use our conventional gears.  I will cover these three gears in different article, or ping me a request for more information in the comments.. 

Neurological: How Breathing Shapes Recovery

Breathing doesn’t just move air—it modulates your entire nervous system.

By slowing your breathing rate (e.g., inhale for 4 seconds, exhale for 6), you stimulate the parasympathetic nervous system. This is your “rest and digest” mode—essential for recovery, sleep, and emotional regulation.

Over time, you can shift your autonomic balance toward this calmer state, improving Heart Rate Variability (HRV) and reducing chronic stress load.

Your Next Steps

1. Nasal breathe on easy rides – Especially during warm-ups and cooldowns.
2. Try “Breath Light” drills off the bike – 5 minutes, nose-only, until you feel mild air hunger.
3. Breathe slower, not deeper – Focus on extending your exhale.
4. Use breath to regulate effort – Shallow panting? Ease off.

You don’t need fancy equipment or more intervals. Just your breath. Train it like any other system, and your endurance engine will thank you.

If you would like more information on this topic, for example the "three gears of breathing" or other topics, feel free to contact me at grant@cycleforfitness.com

Supporting Research

Bohr Effect & CO₂ Role in Oxygen Delivery

Bohr, C. (1904). Ueber die Lungenatmung. Skandinavisches Archiv für Physiologie. This foundational research explains how increasing CO₂ (and decreasing blood pH) reduces haemoglobin’s affinity for oxygen, facilitating O₂ release to tissues — essential for endurance performance.. This foundational research explains how increasing CO₂ (and decreasing blood pH) reduces haemoglobin’s affinity for oxygen, facilitating O₂ release to tissues — essential for endurance performance.. Additional modern support: Hopkins, S. R. (2007). “Gas exchange and the Bohr effect in exercising humans.” Respiratory Physiology & Neurobiology, 159(2), 221–229..

CO₂ Tolerance and Performance.

McKeown, P., & Campbell, D. (2015).   The Oxygen Advantage. HarperCollins.While not a peer-reviewed paper, this book synthesises the work of researchers and practitioners around the benefits of CO₂ tolerance and reduced breathing volume in athletic performance.Stickland, M. K., et al. (2007). “Does respiratory muscle training improve exercise performance?” Sports Medicine, 37(9), 703–724. Highlights how adaptations in breathing, including resistance and tolerance, can improve endurance capacity. 

Nasal vs. Mouth Breathing.

Dallam, G. M., & Kies, S. M. (2020).  “The effect of nasal-only breathing on physiological and perceptual responses to exercise: A systematic review.” International Journal of Kinesiology and Sports Science, 8(1), 12–19. Demonstrates that nasal breathing improves CO₂ retention and diaphragmatic activation and may support better endurance and recovery.

Heart Rate Variability (HRV) & Breathing

Lehrer, P., & Gevirtz, R. (2014).   “Heart rate variability biofeedback: How and why does it work?” Frontiers in Psychology, 5, 756.Explains how slow breathing (especially at 6 breaths/minute) increases HRV and improves parasympathetic tone.Laborde, S., Mosley, E., & Thayer, J. F. (2017). “Heart rate variability and cardiac vagal tone in psychophysiological research – Recommendations for experiment planning, data analysis, and data reporting.” Frontiers in Psychology, 8, 213.

Respiratory Biomechanics in Endurance Sport.

 Lomax, M. (2010). “Inspiratory muscle training, oxygen cost, and exercise performance.” Sports Medicine, 40(6), 495–510. Reviews how improved respiratory mechanics (like diaphragm use and slowed breathing) can reduce ventilatory fatigue and improve cycling efficiency.