Sprints and accelerations: why VT2 is the key threshold for explosive efforts
- PAIRFS
- 3 days ago
- 3 min read
In endurance sports, we often talk about basic endurance, Zone 2 or threshold training. But when it comes to accelerations, restarts, short sprints or decisive passages , a threshold becomes central: VT2 .
Whether you are a cyclist, runner, trail runner or triathlete, your ability to produce intense effort without "exploding" depends directly on how your ventilation reacts around VT2.
1. Why explosive efforts depend on your ventilation
A sprint or acceleration isn't just about muscular power. Your breathing plays a crucial role:
It eliminates the CO₂ produced by intense exertion
it limits acidosis
it stabilizes the nervous system
it conditions the ability to repeat efforts
During a sprint, CO₂ production skyrockets. If your ventilation system isn't ready to handle it, acidity increases sharply → loss of power → inability to accelerate again.
👉 This is exactly what VT2 indicates: the point where your body starts to lose control of acidosis.
2. VT2: the boundary between “strong” and “too strong”
🔹 What is VT2?
VT2 is the point at which:
Ventilation increases disproportionately.
CO₂ rises very quickly
acidosis sets in
speaking becomes impossible
the duration of fall
In other words: 👉 This is the last sustainable level before violent lactic acid buildup.
For explosive efforts, this is the zone where everything is decided .
3. Why improving VT2 makes your sprints more efficient
✔ You delay acidosis
A higher VT2 = you can withstand the intensity for longer before saturating.
✔ You recover faster between sprints
Effective ventilation removes CO₂ more effectively → faster return to equilibrium.
✔ You maintain more power on restarts
Less acidosis = less loss of strength.
✔ You can repeat the accelerations
This is essential in cycling, trail running or triathlon.
4. VT2 in cycling: the key to accelerations and attacks
In a peloton:
An attack requires a brief pass over VT2
A restart after a turn requires stable ventilation
Holding the wheel requires precise breathing control
Cyclists with a low VT2: → explode on accelerations → accumulate too much acidity → react to the race rather than control it
Cyclists with a high VT2: → can repeat efforts → attack harder → remain efficient on short climbs
5. VT2 in running: maintaining pace and sprinting efficiently
In running:
a final sprint relies on the ability to push back acidosis
a long acceleration takes place around VT2
Technical trails require frequent restarts.
If you cross VT2 too early:
🔥 Breathing becomes disorganized
🔥 The stride loses its economy
🔥 The quadriceps quickly become fatigued
6. How to improve VT2 with intelligent breathing training
🔹 1. Work at the ventilatory threshold (around VT2)
2 × 12 min
3 × 8 min
4 × 6 min
Objective: to delay the onset of acidosis.
🔹 2. High-intensity intervals (above VT2)
30"/30"
45"/45"
1'/1'
Objective: to improve the ability to repeat lactic acid efforts.
🔹 3. Breathing technique work
long exhalations to expel CO₂
abdominal breathing under stress
stabilization of respiratory rate
7. How ZoneX helps master VT2
With ZoneX you can:
Identify your VT2 precisely in less than 10 minutes
monitor the stability of your ventilation in real time
detecting respiratory drift before it escalates
calibrate your threshold sessions without errors
monitor respiratory fatigue
analyze your ability to repeat intense efforts
👉 Without an understanding of VT2, explosive efforts are random.
👉 With ZoneX, they become a controlled strategy .
Conclusion
VT2 is not just an endurance threshold: it is the strategic threshold for all athletes who need to accelerate, sprint or restart.
A well-developed VT2 allows you to:
sprint faster
restart more often
recover faster
to withstand higher intensity
improve performance in competition
👉 To gain explosiveness, you must first understand your breathing.
👉 To understand your breathing, you need to measure your thresholds.
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