Lactate Threshold Formula
Understand lactate threshold — how it is measured, estimated, and used to set training zones for endurance athletes.
Lactate Accumulation Concept
Below LT1 (about 2 mmol/L), the body clears lactate easily. Between LT1 and LT2 is the moderate training zone. Above LT2, accumulation outpaces clearance and fatigue sets in quickly.
FTP as LT2 Estimate (Cycling)
Functional Threshold Power is the cyclist equivalent of LT2 — it represents the highest power sustainable for approximately one hour.
LT2 Heart Rate Estimate
For trained athletes, lactate threshold heart rate typically falls in this range. Less trained individuals may find their LT2 at a lower percentage.
Variables
| Term | Meaning | Typical Value |
|---|---|---|
| LT1 | First lactate threshold (aerobic threshold) | ~2 mmol/L |
| LT2 | Second lactate threshold (anaerobic threshold) | ~4 mmol/L |
| OBLA | Onset of blood lactate accumulation | 4 mmol/L |
| FTP | Functional Threshold Power (cycling) | 95% of 20-min power |
Example 1 — Cycling FTP Test
A cyclist averages 310 W over a 20-minute all-out effort.
FTP ≈ 0.95 × 310
FTP ≈ 294 W — this is their estimated LT2 power
Example 2 — LT2 Heart Rate
A trained runner has a max HR of 190 bpm.
LT2 HR ≈ 0.85 × 190 to 0.92 × 190
LT2 HR ≈ 162–175 bpm — the threshold training zone
When to Use It
- Setting tempo and threshold workout paces
- Planning race pacing strategies for distances of 5K to marathon
- Measuring training adaptations over a season
- Identifying when to push harder versus stay easy