Progression over time: how VT1 & VT2 evolve with training — and when to recalibrate your zones

When discussing training zones, many refer to fixed percentages of VO₂ max, heart rate, or power.

However, ventilatory thresholds — VT1 & VT2 — are not immutable . They evolve with training, fitness level, physiological adaptations, and… inter-individual differences.

Understanding their variability is essential to remaining effective, relevant, and accurate in programming.

Why do VT1/VT2 change with training?

• Improved aerobic endurance : As the body adapts to training—particularly hardened, repetitive, and progressive training—oxygen consumption at threshold times (VO₂ at VT1/VT2) increases. This means that higher intensities can be sustained before reaching ventilatory limits. [ reference ]

• Relative shift in thresholds vs. VO₂ max / HR max / maximum speed : just because your VO₂ max increases doesn't mean a fixed percentage (e.g., VT2 = 85% of VO₂ max) remains valid for you. In reality, in well-trained athletes, VT1 and VT2 can be at much higher percentages of VO₂ max than in beginners or sedentary individuals.

• Specificity of training : depending on the dominant type of effort (endurance, interval, strength, volume, etc.), adaptations may favor the aerobic system or tolerance to more intense effort. This influences ventilation, metabolism, buffer capacity — and therefore the position of thresholds [ reference ].

In short: the “stable zone” of one day is not necessarily stable six months later.

Why it's important to recalibrate your zones regularly

Avoid underdosing or overdosing the sessions

If you continue to use your old training zones (for example, those calibrated to your beginner level), your endurance or threshold sessions are likely to be too easy—hindering progress. Conversely, threshold sessions calibrated to old values could be too intense, generating unnecessary fatigue or overexertion.

Follow the actual (not theoretical) adaptations

VO₂max or maximum heart rate are not enough to track adaptive specificity. What matters are the “effective thresholds” — where your ventilation, metabolism, and tolerance actually change.

Optimizing planning — periodization, recovery, workloads

A recalibrated zone allows for more precise training block planning, adjustment of intensity, volume, recovery — and therefore increased efficiency while reducing the risk of overtraining.

When and how to recalibrate your respiratory thresholds (VT1 & VT2)

Here are some practical guidelines to help you know when to repeat a test or recalibrate your zones:

Time / Context	Why recalibrate?
With each significant change in training cycle (volume, intensity, specialization)	Metabolic and ventilatory adaptations may have shifted the thresholds.
As soon as you notice significant improvements in fitness (VO₂max, sensations, endurance, recovery)	The "old" thresholds no longer reflect your current state.
After a long period of inactivity / return from injury	Restarting activity alters respiratory physiology and tolerance.
Every 6 to 12 months — even without noticeable change	To capture slow adaptations, and guarantee the accuracy of the zones.
If you change disciplines (cycling ↔ running ↔ triathlon, etc.)	Each sport has its own specific respiratory and metabolic requirements.

How to recalibrate?

• Ideally, this can be done via a laboratory test with gas exchange analysis (the standard method for detecting VTs). MDPI+1

• If that's not possible, a progressive protocol (incremental testing) can be used, observing ventilation, respiration, sensations, and possibly respiratory rate—as suggested by recently validated wearable methods.Nature+1

• Finally, integrate the new values into your training plans: adjust the zones, reassess the paces, volumes and intensities, and document the adaptations.

The key takeaway: ease of use, but constant vigilance.

• Ventilatory thresholds remain individual and dynamic indicators — avoid fixed “standardized” values (e.g., “VT2 = 85% VO₂max”). Inter-individual heterogeneity is significant.

• Recalibration does not mean “correcting” a test, but adjusting your “training map” to your current physiology.

• In practice, this requires rigor, regularity — and ideally monitoring (test + training logs) to observe progress.

Go further

• Benítez-Muñoz JA et al. (2025) — “Differences in the ventilatory thresholds in treadmill according to training status”. SpringerLink+1

• Capellá IL et al. (2018) — “Determining the ventilatory inter-threshold area in a large sample of athletes”: ScienceDirect+1

• Serna-Martínez M. et al. (2024) — “Oxygen Consumption, Ventilatory Thresholds and Work in Endurance Sports”. MDPI