Anaerobic Threshold (AnT): Training Intensity Line
Anaerobic threshold is the intensity where steady work turns into fast fatigue. See how AnT relates to FTP, LTHR, threshold pace, and lactate threshold.
Anaerobic threshold (AnT) is the intensity line where a pace or power you can hold steadily starts producing fatigue much faster. Coaches use it to set threshold sessions. It often sits near FTP, LTHR, and threshold pace, but those are field proxies—not the same lab definition.
Key characteristics
- Limited duration: for many athletes it sits near the best steady effort you can sustain for tens of minutes up to ~1 hour (varies by sport and athlete).
- High cost above the line: above AnT, holding the same intensity gets harder quickly.
- Lab definitions vary: some use gas exchange breakpoints; others use blood lactate. Different definitions can yield different numbers—this is normal.
Practical estimation
If you don’t have lab testing, use repeatable field tests to approximate it:
- 20-minute steady test (common approach):
- Do a maximal, as-steady-as-possible 20-minute effort.
- Use the 20-minute average power/pace (or HR) as a reference, and apply a practical adjustment factor.
- This aligns with common FTP estimation practice.
Training relevance
Raising AnT often means you can sustain a higher steady pace or power before fatigue rises sharply. But it is not the only driver of performance: economy, durability, fueling, and pacing matter too.
How Trainingload.ai uses anaerobic threshold
- Threshold context: AnT helps explain why FTP, LTHR, and threshold pace all point toward a similar training intensity range.
- Workout classification: threshold sessions can be reviewed against pace/power, heart rate, RPE, and recent fatigue.
- Zone calibration: when a reliable threshold estimate exists, it can improve pace, power, and heart-rate zone boundaries.
FAQ
What is anaerobic threshold?
Anaerobic threshold is the highest intensity you can hold in a near-steady state before fatigue accumulates much faster. Above that line, the same pace or power becomes hard to sustain.
Is anaerobic threshold the same as lactate threshold?
They often point at a similar training range, but the tests differ. Lactate threshold uses blood lactate; AnT may use gas exchange or a lactate breakpoint. Do not treat the two numbers as interchangeable. See Lactate Threshold.
How do I estimate anaerobic threshold without a lab?
Use a repeatable field test, commonly a maximal steady 20-minute effort. Take average power, pace, or heart rate and apply a practical adjustment—the same idea used in many FTP estimates.
How does AnT relate to FTP and LTHR?
FTP, LTHR, and threshold pace are practical stand-ins for the same intensity band. Trainingload.ai uses a reliable threshold estimate to classify threshold sessions and to tighten pace, power, and heart-rate zones.
Related tools and docs
- Estimate lactate threshold for training load decisions
- Lactate Threshold
- Functional Threshold Power
- Calculate heart-rate training load zones
- Calculate power training load zones
References
Lactate Threshold (LT)
Lactate threshold is the intensity range where lactate begins to accumulate more steadily, used to anchor threshold training, heart-rate zones, pace zones, and power zones.
Anaerobic Capacity
Anaerobic capacity describes short-duration high-power work above sustainable intensity, relevant to sprints, surges, attacks, W′, and FRC.