Heart rate zones
Training zones from maximum or resting heart rate (Karvonen method).
Educational only — talk to a clinician before starting hard training.
Measured first thing in the morning
From a lab or field test
Tanaka: 208 − 0.7 × 35
Max − resting
The older formula, kept for comparison
Your zones
Warm-up, cool-down, easy movement · 50–60% of reserve
Fat oxidation, endurance foundation · 60–70% of reserve
Aerobic capacity, sustained effort · 70–80% of reserve
Lactate threshold, race pace · 80–90% of reserve
Maximum aerobic power, short intervals · 90–100% of reserve
How it works
Heart rate zones translate “how hard should this feel” into a number you can watch. Zone boundaries are conventions, not physiology — the underlying thresholds are real, but the 5-zone split is a coaching convenience.
Karvonen: target = resting + (max − resting) × intensity
Simple: target = max × intensity
Tanaka: max ≈ 208 − 0.7 × age Karvonen versus percentage of max
The simple method ignores your resting heart rate, so it gives the same zones to a sedentary person and a trained athlete of the same age. Karvonen works from heart rate reserve, which accounts for fitness — a low resting rate shifts the zones up. Karvonen is the better default for anyone who has been training for a while.
220 − age is worse than its fame suggests
That formula came from a 1970s review and was never validated properly; its standard deviation is around 10–12 bpm, so it can be badly wrong for an individual. Tanaka's 208 − 0.7 × age fits the data better, especially for older adults. Neither replaces an actual measured maximum.
Zone 2 gets the attention for a reason
Sustained easy aerobic work builds mitochondrial density and capillarisation without much recovery cost, which is why endurance athletes spend most of their volume there. The common mistake is running zone 2 sessions at zone 3 — hard enough to accumulate fatigue, easy enough to miss the high-intensity adaptations.
Sources
Tanaka H, Monahan KD, Seals DR, “Age-predicted maximal heart rate revisited”, Journal of the American College of Cardiology, 2001. Karvonen MJ et al., 1957.