Estimate lactate threshold heart rate from your age or max heart rate, or calculate LTHR and FTP from a field test, with matching training zones.
Lactate Threshold and Anaerobic Threshold
Lactate threshold and anaerobic threshold are often used as overlapping training terms, although laboratories and coaching systems may define them differently. This calculator estimates a threshold from a typical percentage of maximum heart rate or from a protocol-specific heart-rate or cycling-power input, then applies the selected zone convention.
Formula and Method
For the heart-rate field-test mode, the final 20-minute average of a hard 30-minute effort is treated as LTHR. For cycling power, functional threshold power is estimated as 95% of a 20-minute average. Known-threshold mode applies the legacy TrainingPeaks/Friel running or cycling heart-rate bands, or Friel’s Ride Inside power bands. Published bands and calculated endpoints are approximate; the 151%+ power zone belongs to this Friel variant, not Coggan’s system.
Threshold inputs and interpretations
| Reference | Range or value | Use or interpretation |
|---|---|---|
| Heart-rate estimate | Final 20-minute average HR | Field estimate of LTHR |
| Power estimate | 20-minute average power x 0.95 | Field estimate of FTP |
| Known threshold | Previously tested LTHR or FTP | Zone construction only |
| Anaerobic-threshold wording | Handled on this canonical page | Not a separate duplicate calculator |
How to Use the Result
Choose the metric and sport convention that match your test and training plan. Heart-rate and power thresholds are not interchangeable. Repeat the same protocol when tracking changes.
Assumptions and Limitations
A field threshold is not a blood-lactate measurement or ventilatory laboratory threshold. Pacing, fatigue, heat, hydration, equipment calibration, and test duration affect the estimate. Zone systems use different breakpoints, so results should be compared within the same system.
Sources
- Allen H, Coggan A. Training and Racing with a Power Meter, protocol guidance; TrainingPeaks, Joe Friel’s Quick Guide to Setting Zones; Joe Friel, Ride Inside Workouts.
