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Breathing & triathlon: how to adapt VT1 and VT2 in swimming, cycling and running

Triathlon is one of the sports where intensity management is the most complex. Three disciplines, three body positions, three different respiratory constraints… and yet a single respiratory system to manage everything.


Understanding your ventilatory thresholds (VT1 & VT2) is the most reliable way to control effort from start to finish, avoid burning out during running, and optimize your race management.


1. Why breathing is essential in triathlon


Unlike heart rate (which reacts slowly and varies according to heat or stress), breathing:

  • reacts instantly

  • reflects the balance between lipids and carbohydrates in real time.

  • signals metabolic transitions (VT1/VT2),

  • allows the intensity to be adapted to each discipline,

  • helps stabilize pacing before and after each transition.


👉 Breathing is the most reliable internal indicator for structuring effort in triathlon.


2. VT1 & VT2: what they mean for a triathlete


🔹 VT1 = the savings threshold

Below VT1:

✔ sustainable effort

✔ Fat burning

✔ stable breathing

✔ Minimal fatigue


This is the key area:

  • in long-distance swimming

  • on a half or full bike,

  • at the start of the running race.


🔹 VT2 = the sustained intensity threshold

About VT2:

✔ Running effort (10 km / half marathon),

✔ Managing bumps while cycling,

✔ Transition intensity (T2 → start of race).


Above VT2:

🔥 lactate

🔥 acidosis

🔥 very short holding time

🔥 long recovery



3. Using breathing techniques in swimming


Why swimming is unique:

  • Breathing controlled by the technique

  • water pressure on the chest,

  • Hypercapnia (CO₂ accumulation) is very common,

  • disrupted respiratory transitions.


Swimming objectives:

✔ Stay below VT1 to avoid CO₂ accumulation

✔ Limit hyperventilation when exiting the water

✔ Stabilize ventilation in preparation for cycling


Useful respiratory signs:

  • Breathlessness = intensity too high

  • Strong urge to breathe = CO₂ too high

  • Explosive ventilation at the water outlet = poor management


👉 In triathlon, tiring yourself out respiratoryly during the swim is a common mistake .


4. Use VT1/VT2 on the bike


Cycling is the part of the race where it's easiest to:

  • skidding above VT1 in the bumps,

  • to rise too high due to drafting,

  • exceeding VT2 without realizing it during restarts.


How to use your thresholds:

  • half / full: 90% of the time under VT1

  • Olympic: between VT1 and VT2, without exceeding VT2 continuously

  • Sprint: around VT2, with very short overtakes


Common mistake:

Starting too fast on the bike → VT2 reached too early →👉 impossibility of running properly afterwards.



5. Using breathing while running (the critical moment)


The ability to run hard after cycling depends primarily on accumulated ventilation :

  • If you have exceeded VT2 too often ➝ chaotic breathing ➝ unsustainable pace

  • If you remained in control ➝ stable breathing ➝ effective pacing


Respiratory strategy:

  • 0–2 km: aim precisely below VT1 , stabilize breathing

  • Mid-race: Gradually ascend towards VT2

  • End of race: controlled overtaking above VT2


👉 In triathlon, breathing is the final arbiter of your pacing.


6. T1 & T2 Transitions: A Key Moment for Ventilation


Transitions are genuine physiological shocks.

Transition T1 (water → bike):

  • The CO₂ accumulated during swimming disrupts breathing

  • Hyperventilation is common

  • The triathlete starts breathing too fast = overconsumption of energy


Transition T2 (bike → run):

  • posture that changes

  • Breathing is often too shallow

  • need to restore a stable respiratory cycle


👉 Good management of VT1/VT2 allows these transitions to be approached without ventilatory panic .


7. How ZoneX optimizes breathing for triathletes


ZoneX allows you to:

  • Measure your VT1/VT2 precisely in each discipline

  • monitor ventilation in real time

  • detecting ventilatory drift on the bike

  • assess the respiratory impact of swimming

  • adjust pacing while running

  • stabilize ventilation during transition

  • avoid metabolic overload too early in the race


This is a huge advantage for triathletes who want to structure their effort intelligently.


Conclusion


In triathlon, understanding and controlling your breathing is a strategic advantage.


With VT1 and VT2, you can:

  • manage swimming without exhausting yourself,

  • to properly calibrate the intensity while cycling,

  • running with steady breathing

  • negotiating transitions without explosion

  • Optimize your pacing from start to finish.


👉 Triathletes who control their breathing control their race.

👉 ZoneX makes this management accessible, precise and actionable.



 
 
 

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