Ventilatory Threshold Test (VT1/VT2): What They Are, How They're Detected, and What They're For

The ventilatory threshold test is the "respiratory" version of the lactate threshold test: instead of taking blood samples to measure lactate, it analyzes the breathing pattern and gas exchange (O2 and CO2) during an incremental effort to identify the points where the body's energy production shifts.

What Does This Test Measure?

It identifies two inflection points in the ventilatory response to incremental exercise:

• VT1 (first ventilatory threshold): ventilation starts increasing disproportionately relative to VO2, roughly coinciding with the onset of lactate accumulation (aerobic threshold)
• VT2 (second ventilatory threshold or respiratory compensation point): a second sharp shift in ventilation, where the body can no longer compensate for metabolic acidosis through increased breathing alone (roughly equivalent to the anaerobic threshold)

Equipment Needed

• Gas analyzer / metabolic cart (mask or mouthpiece connected to an O2/CO2 analysis system)
• Treadmill or cycle ergometer
• Heart rate monitor
• Cardiopulmonary exercise testing (CPET) analysis software

How to Perform the Test

1. Fit the subject with the gas analysis equipment (mask or mouthpiece with nose clip)
2. Warm up for 5-10 minutes with the equipment already on, so the subject gets used to it
3. Apply an incremental protocol (treadmill or bike, similar to the incremental treadmill test), with increments every 1-3 minutes until voluntary exhaustion
4. The software continuously records VO2, VCO2, ventilation (VE), respiratory exchange ratio (RER), and breathing rate
5. VT1 is typically identified as the point where VE/VO2 starts increasing without a corresponding increase in VE/VCO2 (a disproportionate rise in ventilation relative to oxygen consumption)
6. VT2 is identified where VE/VCO2 also starts increasing disproportionately (the system can no longer compensate for acidosis through hyperventilation alone)

Common Mistakes

• The subject isn't used to breathing with a mask/mouthpiece, which alters their natural breathing pattern
• Load increments that are too fast, leaving no "room" to identify two clear inflection points
• Relying solely on automated software without visual review of the curves by an experienced professional

How to Interpret the Results

Threshold	Reference % of max HR	Approximate equivalent	Training use
VT1	65-75%	Aerobic threshold / LT1	Upper limit of the "easy zone" / aerobic base
VT2	85-92%	Anaerobic threshold / LT2	Reference for threshold intervals; don't spend too much time above this in long sessions
> VT2	> 92%	High-intensity zone	Short intervals, VO2max work

These percentages are reference values and vary by training level: highly trained athletes may have VT2 close to 90-92% of max HR, while less trained individuals may reach it at relatively lower intensities.

Related Tests

The ventilatory threshold test shares its protocol with other incremental tests, but adds the respiratory dimension:

• Incremental treadmill test — same protocol structure, with or without gas analysis
• Lactate threshold test — alternative blood-based method, usually gives results similar to VT1/VT2

Centralize Your Results in Movalytics

A ventilatory threshold test generates very rich data (VO2, HR, speed/power at each threshold), but what coaches need day-to-day are the resulting training zones. With Movalytics you can save the test summary (VT1, VT2, VO2max, and HR at each point) in the athlete's profile and reference it when planning sessions.

Frequently Asked Questions

Are VT1/VT2 the same as LT1/LT2 (lactate thresholds)? They're related concepts that tend to align approximately, but they're obtained through different methods (gases vs. blood) and don't always give exactly the same intensity value. Do you need to reach exhaustion to identify VT2? Yes, VT2 typically appears in the last stages of the test, so the protocol needs to bring the subject close to their maximal effort to identify it clearly. What's the advantage over a lactate test? No needles required, it's continuous (doesn't depend on point-in-time samples), and provides more simultaneous metabolic information (VO2, VCO2, RER), though it requires metabolic cart equipment, which is more expensive than a lactate analyzer.