Running & breathing: how to use VT1 and VT2 to better manage your pace and improve your endurance
In running, many runners rely primarily on heart rate, pace, or perceived exertion to manage their training intensity. However, these indicators are often inaccurate: heat, fatigue, stress, or cardiac drift can completely distort training.
Breathing, on the other hand, reflects in real time how your body produces energy. This is why ventilatory thresholds (VT1 & VT2) are extremely reliable benchmarks for structuring a runner's training.
1. Why breathing is a powerful tool for runners
Unlike pace or heart rate:
Respiration reveals the balance between lipids and carbohydrates .
It precisely detects the transition to sustained effort.
It shows when metabolic fatigue sets in.
It provides instant feedback, regardless of the environment.
👉 In running, where pace varies according to terrain (uphill, downhill, wind), breathing is the best internal indicator .
2. VT1 & VT2: Key benchmarks in running
🔹 VT1: the aerobic endurance threshold
VT1 corresponds to the moment when:
Breathing accelerates slightly,
the body begins to use more carbohydrates,
The conversation becomes a little more difficult.
This is the upper limit of the basic endurance zone.
Below VT1:
✔ Maximum fat burning
✔ economic effort
✔ Low metabolic fatigue
✔ ability to maintain hours
🔹 VT2: the sustained effort threshold / anaerobic threshold
VT2 is the point at which:
The ventilation increases suddenly,
The CO₂ produced rises sharply.
Speaking becomes almost impossible.
Acidosis is starting to set in.
This is the physiological equivalent of a runner's "threshold".
Above VT2:
🔥 costly effort
🔥 very short maintenance time
🔥 shift into lactic acid
3. How to use VT1 to improve your endurance
To progress in running, 80% of training should be in aerobic endurance — therefore below VT1 .
In practical terms, running under VT1 allows you to:
strengthen your aerobic base,
improve respiratory efficiency,
conserve glycogen
reduce fatigue,
increase the ability to sustain a faster pace later.
How to recognize VT1 in a race
light, regular breathing
conversation possible without effort
feeling of “easy, I could last a long time”
With a sensor like ZoneX, VT1 is measured precisely, which avoids approximations.
4. How to use VT2 to become faster
Running around or slightly below VT2 develops:
lactate tolerance,
the ability to run fast for a long time
maintaining pace during competition,
mental resistance to effort.
Use of VT2 during the session:
2 × 15 min at 95–100% VT2
4 × 6 min at 98–102% VT2
progressive threshold blocks
This is the key look for:
➡️ 10 km
➡️ half-marathon
➡️ short trail
5. How to adapt your race pacing using breathing
Over 10 km
Start just below VT2 , stabilize breathing, then push slightly above in the last few kilometers.
On a half-marathon
Stay between VT1 and VT2 , stabilizing ventilation at a comfortable but sustained pace.
On the marathon
Always on VT1 , otherwise glycogen melts too quickly → guaranteed crash.
Trail running
Breathing is ideal because pace is not a reliable indicator:
👉 maintain a steady breathing rate while going uphill,
👉 Breathe calmly on the flat surface,
👉 release on the descent.
6. Why heart rate is less reliable during running
FC depends on:
the heat
stress
cardiac drift
dehydration
muscle fatigue
the heart's reaction time (slow)
Consequently:
➡️ It does not reflect the energy sectors
➡️ It doesn't say whether you are below or above VT1
➡️ It can mislead you about pacing
Breathing, on the other hand:
✔ reacts immediately
✔ directly reflects metabolism
✔ precisely identifies the thresholds (VT1/VT2)
7. The role of ZoneX for runners
ZoneX allows you to:
to accurately measure VT1 and VT2 during the race,
monitor the live ventilation,
detect ventilatory drift,
adjust the pacing according to the terrain.
optimize pace during key sessions,
avoid poorly calibrated areas.
It is the most reliable tool for individualizing running training , whether you are a beginner, experienced or competitive runner.
Conclusion
In running, managing your breathing well means managing your effort well.
With VT1 and VT2, you can:
to structure an intelligent training program,
avoid unnecessary fatigue,
better manage your pacing,
improve endurance,
to become faster in competition.
👉 Breathing is the only indicator that reflects your actual physiology in real time.
👉 It is also the easiest to feel and the most accurate to measure.
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