Heart Rate Reserve: Better Zones with the Karvonen Method
Heart rate reserve (HRR) is the gap between your maximum and resting heart rates. If your max is 190 and you rest at 50, your reserve is 140 beats. The Karvonen method takes a percentage of that reserve and adds your resting heart rate back on top. That one adjustment makes your zones more personal, especially if you are very fit or just starting out.
What is heart rate reserve?
Your heart rate never drops to zero, so not all of your 190 bpm is usable training range. Heart rate reserve is the part that is:
HRR = maximum heart rate − resting heart rate
A fitter heart pumps more blood per beat, so it beats slower at rest. A fitter person therefore has a larger reserve than an unfit person with the same maximum.
The Karvonen formula
The Karvonen method, published by Finnish physiologist Martti Karvonen in 1957, sets each zone boundary like this:
Target HR = resting HR + (intensity % × heart rate reserve)
Say your max is 190, your resting heart rate is 50, and you want the bottom of Zone 2 at 60% intensity:
- Heart rate reserve = 190 − 50 = 140 bpm
- 60% of 140 = 84 bpm
- Add resting back: 84 + 50 = 134 bpm
A plain "60% of max" would give 114 bpm, 20 beats lower.
Heart-rate reserve
135bpm
185 − 50
Max heart rate
185bpm
Resting heart rate
50bpm
| Zone | Range | What it trains |
|---|---|---|
| Z1 | Recovery 118–131 bpm | Active recovery and warm-up; promotes blood flow without adding fatigue. Very easy, RPE 1–2. Full conversation, barely breathing hard. |
| Z2 | Endurance 131–145 bpm | Aerobic base, fat oxidation and capillary density, the bread-and-butter zone. Comfortable, RPE 3–4. Can hold full sentences. |
| Z3 | Tempo 145–158 bpm | Aerobic capacity and muscular endurance; 'moderately hard' steady work. Working, RPE 5–6. Short sentences only. |
| Z4 | Threshold 158–172 bpm | Lactate threshold, your sustainable race-pace ceiling. Hard, RPE 7–8. A few words at a time. |
| Z5 | VO₂max 172–185 bpm | Maximal aerobic power and VO₂max via short, hard intervals. Very hard to maximal, RPE 9–10. No talking. |
Z1 · Recovery. Active recovery and warm-up; promotes blood flow without adding fatigue. Very easy, RPE 1–2. Full conversation, barely breathing hard.
Z2 · Endurance. Aerobic base, fat oxidation and capillary density, the bread-and-butter zone. Comfortable, RPE 3–4. Can hold full sentences.
Z3 · Tempo. Aerobic capacity and muscular endurance; 'moderately hard' steady work. Working, RPE 5–6. Short sentences only.
Z4 · Threshold. Lactate threshold, your sustainable race-pace ceiling. Hard, RPE 7–8. A few words at a time.
Z5 · VO₂max. Maximal aerobic power and VO₂max via short, hard intervals. Very hard to maximal, RPE 9–10. No talking.
- Karvonen anchors zones to your heart-rate reserve (HRmax − resting HR), so it personalizes zones to your fitness better than plain %HRmax, a fit athlete with a low resting HR gets correspondingly lower targets.
- Measure resting heart rate first thing in the morning, lying down, before caffeine. A 5-bpm error in RHR shifts every zone.
A PDF of your personalized results, with a QR code to reopen them anytime.
Why does Karvonen beat plain %HRmax?
Percent-of-maximum zones treat everyone with the same max identically. Karvonen folds in resting heart rate, a rough proxy for fitness:
- It accounts for your conditioning. A trained athlete resting at 45 and a beginner resting at 75 get different zones even with the same max.
- The zones track your fitness. As resting heart rate drops, your reserve grows and the zones update. A fixed %HRmax band never moves.
- It spreads the easy end out. Plain %HRmax puts easy efforts at implausibly low heart rates. Adding resting heart rate back lifts the low zones to numbers you can train at.
For how the different systems carve up the range, compare the heart-rate zone models.
How do I find the two numbers I need?
Resting heart rate (RHR). Measure it first thing in the morning, before you get up, averaged over several days. A chest strap or the overnight reading from a wearable both work. A daytime desk reading runs high.
Maximum heart rate (HRmax). Age formulas (220 − age, or the more accurate Tanaka, 208 − 0.7 × age) can be off by 10+ beats for any individual. A field test gives a far better number. See finding your maximum heart rate for both, or the max heart rate calculator for the estimate.
Karvonen vs. lactate-threshold zones
Karvonen is still anchored to your maximum, which barely responds to training and is hard to measure safely. The most individual anchor is your threshold. Zones set from your lactate-threshold heart rate sit where your physiology changes and rise as you get fitter. Many athletes start with Karvonen and move to LTHR zones after a 30-minute test.
For easy aerobic work, see Zone 2 heart rate, explained.
Sources
- Karvonen, M. J., Kentala, E., & Mustala, O. (1957), the original heart-rate-reserve study
- Tanaka, Monahan & Seals (2001), maximum-heart-rate estimation