Breath analysis: the next revolution in sports wearables?

Connected devices have transformed training: heart rate, power, cadence, speed, oxygen saturation… but one essential parameter is still largely absent from current wearables: breathing .

However, breathing is the most direct, sensitive and reliable physiological signal for understanding what is happening in an athlete's body.

After years of innovations focused on cardio and power, a new generation of sensors is emerging: respiratory wearables .

And this revolution begins now.

1. Why is respiration the forgotten biomarker of sport?

While heart rate fluctuates with:

• the heat,

• stress,

• dehydration,

• sleep,

• caffeine…

… respiration , on the other hand, reacts directly to metabolism .

It immediately reflects:

• the increase in CO₂,

• lactate production,

• energy transitions,

• muscle fatigue,

• ventilatory drift on ascent.

In other words:

👉 Breathing is the body's internal language.

If we want to understand the actual load, we need to listen to what the ventilation system is saying.

2. The limitations of current wearables (heart rate, power, SpO₂)

❌ Heart rate drift

Heart rate increases even if the intensity does not change.

❌ Power does not reflect internal load

On trails, uphill or on unstable terrain: it becomes unreliable.

❌ SpO₂ is informative… but slow and imprecise in motion

Useful when at rest, but very limited in dynamic situations.

These metrics are useful, but none of them really tell you what the body is experiencing .

The only signal capable of showing the transition from aerobic to anaerobic, live, is: 👉 ventilation .

3. Why respiratory analysis is the next technological breakthrough

The only reason why respiratory sensors are not yet ubiquitous in sports is due to one simple point:

👉 Reliably measuring respiration is extremely difficult.

Major problems:

• condensation and humidity in the sensors,

• accelerations of respiratory flow,

• CO₂ in very low concentration (~4%),

• complex miniaturization,

• signal noise.

For a long time, only a CPET machine costing €35,000 could correctly measure gas, CO₂, ventilated volume… But all this is changing.

4. ZoneX: the first generation of wearables focused on breathing

ZoneX is part of this revolution.

PAIRFS has developed a patented technology, in partnership with CEA LETI, enabling:

• a stable measurement despite the humidity ,

• precise detection of exhaled CO₂,

• real-time identification of ventilatory transitions,

• a reliable analysis in real-world conditions (climbing, trail running, cycling).

Instead of trying to measure everything (like a mini-CPET), ZoneX makes a radical but fair choice:

👉 Measure only one thing perfectly: the ventilatory thresholds VT1 and VT2.

These thresholds are the most reliable physiological markers for defining:

• the training areas,

• the uphill pace,

• the actual Zone 2,

• the ability to sustain effort.

With ZoneX, respiration finally becomes an accessible, reproducible and useful piece of data.

5. What respiratory wearables will change for athletes

✔ Training zones that are finally fair

No more need for estimates based on heart rate or power.

✔ Optimal pacing on climbs

Breathing reacts immediately → never in the red without knowing it.

✔ Accurate monitoring of fatigue

Ventilatory drift → excessive internal load.

✔ Truly personalized training

The thresholds are changing → the zones are adapting.

✔ Towards a future where portable CPET becomes possible

ZoneX is the first step towards a reliable and simple embedded CPET.

6. Why breathing will become as standard as heart rate

Because breathing:

• is measured in real time

• reflects physiology,

• captures metabolic transitions,

• guide the pacing,

• identifies overtraining,

• adapts naturally to the terrain.

It is the central biomarker… and yet still absent from mainstream wearables. But this era is coming to an end.

The next generation of connected devices will be respiratory. ZoneX is the first concrete example.

Go further

1. Nicolò A. et al. (2020). Respiratory frequency as a marker of metabolic transitions. https://pubmed.ncbi.nlm.nih.gov/32281527/

2. Anselmi F. et al. (2021). Ventilatory thresholds define aerobic domains. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8456830/

3. Meyer T. et al. (2005). Criteria for intensity prescription in endurance training. https://pubmed.ncbi.nlm.nih.gov/15907278/

4. Pallarés JG et al. (2016). Validity of ventilatory thresholds. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0163389

5. Poole DC, Jones AM (2021). Oxygen uptake kinetics and ventilation. https://doi.org/10.1002/cphy.c200006