The five-zone intensity scale used by athletes to classify endurance training
| Intensity zone | Typical blood lactate (mmol/L) | Typical heart rate (% max) | Binary model |
|---|---|---|---|
| 5 | >5.8 | >94 | |
| 4 | 3.7–5.7 | 89–93 | HIT |
| 3 | 2.1–3.6 | 84–88 | |
| 2 | 1.3–2.0 | 74–83 | LIT |
| 1 | <1.2 | 54–73 |
Reference values presented are derived from the average self-reported zone cut-offs of 29 elite XC skiers.6