Karvonen heart rate zones: Zone 2 (HRR) explained + tables
Karvonen heart rate zones use Heart Rate Reserve (HRR) to personalize training intensity. This is especially useful for Zone 2 training, where a few beats per minute can change how the workout feels.
Karvonen formula (HRR) — the core equation
Practical note: Resting HR can change as fitness improves (or with stress/illness). Re-check zones periodically.
| Term | Meaning |
|---|---|
| HRR | Heart Rate Reserve = Max HR − Resting HR |
| Target HR | (HRR × intensity) + Resting HR |
| Intensity | A fraction like 0.60, 0.70, 0.80 (depending on zone) |
Example zones (HRR model) — quick table
| Zone (common model) | Intensity (HRR) | Typical use |
|---|---|---|
| Zone 1 (easy) | 50–60% | Warm-ups, recovery, very easy days |
| Zone 2 (aerobic base) | 60–70% | Base building, long steady sessions |
| Zone 3 (tempo) | 70–80% | Sustained “comfortably hard” efforts |
| Zone 4 (threshold) | 80–90% | Intervals near threshold |
| Zone 5 (VO₂ max) | 90–100% | Short intense intervals |
Zone 2 training: how to make it actually work
Zone 2 should feel controlled: you can hold a conversation in short sentences and sustain the pace for a long time. If you’re constantly drifting upward in HR, slow down.
- Start conservative if you’re new to Zone 2—err on the lower end of the range.
- Heat & dehydration can raise HR for the same pace; adjust.
- Sleep and stress can push HR up; don’t force the same pace every day.
Hydration matters for HR drift — see the water intake calculator.
Interesting heart rate facts (quick wins)
- Resting HR is a training signal: it often trends down with aerobic fitness.
- Two people, same max HR can have different zones if resting HR differs a lot.
- Wrist sensors can lag during intervals; chest straps are often more responsive.
Related calculators
Karvonen / Zone 2 FAQ
Q:What is the Karvonen formula?
Karvonen uses Heart Rate Reserve (HRR): Target HR = (Max HR − Resting HR) × intensity + Resting HR. It personalizes zones by accounting for resting heart rate, which often improves accuracy compared to % of max HR alone.
Q:What is Zone 2 training?
Zone 2 is an aerobic intensity that is sustainable for long durations and is often used to build an endurance base. Depending on the zone model, it’s commonly around ~60–70% of max HR or a similar HRR range.
Q:How do I measure resting heart rate (RHR)?
Measure in the morning after waking up (before getting out of bed). Take several days and use the average for a better baseline.
Q:Is “220 − age” accurate for max heart rate?
It’s a rough estimate and can be off by a lot for individuals. If you want more precision, use field testing under guidance or clinician-supervised testing, or use alternative formulas as estimates.