top of page
Search

Zone 2: How can you be sure you'll really stay there?

Breathing as the most reliable guide


Why is there so much talk about Zone 2?


Zone 2 has become one of the most popular intensities in endurance training. And for good reason: it's the zone that most develops the capacity to burn fat , improves basic endurance, strengthens mitochondria, stabilizes the nervous system, and prepares you for all other types of exertion.


But there is a major problem:

👉 Many athletes think they are in Zone 2… when they are already too high.


Power and heart rate alone are not enough for measurement. Breathing, on the other hand, reveals exactly if you are in the true Zone 2.



1. What is the “real” Zone 2?


Zone 2 corresponds to a specific physiological state:

  • dominant aerobic lipid pathway

  • slow, stable combustion

  • moderate CO₂ production

  • controlled ventilation

  • mild acidosis

  • ability to last a long time


👉 The true Zone 2 is located just below the ventilatory threshold 1 (VT1) .

Not at a certain percentage of FTP.

Not at a theoretical heart rate.

But to a physiological marker measurable by respiration .


2. Why is heart rate so often misleading?


Many define their Zone 2 as:

  • 65–75% of HRmax

  • or 60–70% of the reserve heart rate


But in reality, heart rate varies enormously depending on:

  • stress,

  • the heat,

  • hydration,

  • fatigue,

  • sleep,

  • caffeine,

  • blood sugar.


➡️ A “Zone 2” session can quickly become a Zone 3 session without the heart rate immediately showing it .


3. Power is also not a good indicator


Zone 2 is sometimes thought to be a stable power.

But power says nothing about your metabolism:

  • whether you burn fat or carbohydrates,

  • if you approach VT1,

  • if you are accumulating acidosis,

  • if the effort can be sustained for several hours.


Two athletes can pedal at 180 W:

  • one in pure Zone 2 (lipids),

  • the other in disguised Zone 3 (carbohydrates).


👉 Power measures the outside .

👉 Breathing measures what's inside .


4. Breathing: the most reliable indicator of your Zone 2


Your breath immediately reveals:

✔ If you are in the lipid pathway

Stable, fluid, regular breathing.


✔ If you start switching to carbohydrates

Deeper breathing, increased respiratory rate.


✔ If you are close to VT1

A slight “plateau” in the ventilation → a sign that you are leaving Zone 2.


✔ If acidosis begins to develop

CO₂ buildup → rapid increase in ventilation.


In short:

👉 if your breathing changes, you are leaving Zone 2.



5. The most frequent errors in Zone 2


❌ 1. Use only heart rate

Very common error → Zone 3 disguised.


❌ 2. Doing Zone 2 too fast uphill

Even 20–30 W too much → ruined output.


❌ 3. Ignoring respiratory signals

Breathing “speaks” before the legs.


❌ 4. Stabilize power as breathing increases

Zone 2 depends on metabolism, not wattage.


❌ 5. Do not adjust according to fatigue

A moving VT1 → a moving Zone 2.


6. How can I be sure I'm staying in a true Zone 2?


Here is a checklist based on breathing:

✔ 1. 100% controlled breathing

No conscious need to amplify respiratory effort.


✔ 2. Ability to speak in complete sentences

If you have difficulty speaking → too loudly.


✔ 3. No marked “breathing pauses”

No break or abrupt change in respiratory rate.


✔ 4. Stable airflow despite slight variations in slope

The breath → not the watts → must remain stable.


✔ 5. Feeling like you can last for hours

If the effort becomes “active”, you are too high.


7. How ZoneX guarantees a perfectly calibrated Zone 2


ZoneX real-time measurement:

  • your ventilation (VE),

  • your CO₂ production,

  • ventilatory transitions (VT1 and VT2),

  • the stability of your breathing.


Next, ZoneX:

🔹 accurately detects your VT1

→ the EXACT point that limits Zone 2.

🔹 Automatically generates your actual Zone 2

→ based on your physiology, not an estimate.

🔹 Analysis to see if you are staying on the right track

→ Instant feedback on effort.


👉 With ZoneX: your Zone 2 is no longer a “guess”.

👉 It becomes measured, objective and reliable.



Conclusion: the true Zone 2 is the one defined by your breathing


Zone 2 is the most valuable zone for developing endurance. But it is also the least mastered.


Through breathing, you can:

  • to know exactly where she is,

  • to stay within it without drifting,

  • optimize your sessions,

  • accelerate your progress.


👉 Breathing is the most reliable guide to your metabolism.

👉 With ZoneX, it becomes accessible, simple and usable data for everyday use.



 
 
 

Comments

bottom of page