Breathing is probably the most underrated performance lever for amateur runners. People talk about VO₂max, threshold, cadence, carbon shoes. Nobody talks about respiratory mechanics — even though they directly condition oxygenation, CO₂ management and perceived effort.
In the SAFE PACE episode with Guillaume Néry and Alice Modolo, two world freediving legends, I heard something precious: endurance performance and apnea performance share the same root — CO₂ tolerance and diaphragm mastery.
The "big lung" myth
Néry is unambiguous: performance doesn't come from absolute lung volume, but from O₂ extraction efficiency and CO₂ clearance. Two runners with the same VO₂max can feel the same effort radically differently depending on their breathing pattern.
A mid-level runner ventilates around 90 L/min at half-marathon pace. A runner trained specifically on breathing can drop to 70 L/min at the same intensity. That's 20% energy saved — over a three-hour marathon, it's massive.
The hidden cost of breathing
Diaphragm: your second heart
Modolo calls it that, and physiologically it's accurate. The diaphragm is a muscle. Like all muscles, it strengthens, learns, optimizes. In 90% of amateurs I assess, breathing is upper-chest — shoulders rising, belly locked. Inefficient and costly.
When you learn to breathe through your belly while moving, you unlock 30% of ventilatory capacity without gaining a single mL of VO₂max. It's free.
— Alice Modolo, SAFE PACE episode
The breathing protocol for runners
4-week protocol — Breathing & endurance
- Week 1 — Awareness. 5 min/day of diaphragmatic breathing lying down. Hand on belly, feel the expansion on inhale. No performance goal.
- Week 2 — Breath cadence on easy runs. Aerobic jog with 3:2 ratio (inhale 3 steps, exhale 2 steps). Forces a nasal rhythm.
- Week 3 — CO₂ tolerance. Post-session box breathing: 4 sec inhale / 4 sec hold / 4 sec exhale / 4 sec hold, 5 cycles. Improves resistance to "air hunger".
- Week 4 — Application. One interval session per week in pure nasal breathing up to threshold (impossible above — that's the point).
Nasal breathing: why it's a game-changer
Néry insists on nasal breathing in low-intensity endurance. Three major physiological benefits:
- NO (nitric oxide) production in the sinuses, a natural vasodilator improving tissue oxygenation by 10–18%.
- Filtration and humidification of incoming air, reducing bronchial irritation in winter or polluted environments.
- Intensity self-regulation: impossible to run above threshold in pure nasal. It's a physiological guardrail.
In my plans, I impose nasal breathing on 80% of endurance volume. The feedback is consistent: less fatigue, better recovery, a sensation of "running light".