Heart-Rate Reserve (Karvonen Method)
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A target-heart-rate method that scales intensity to the span between resting and maximal heart rate, individualizing the zone to each person's resting HR.
Detail
Heart-rate reserve (HRR) is the difference between maximal heart rate and resting heart rate:
HRR = HRmax − HRrest
The Karvonen formula computes a target heart rate for a chosen intensity percentage:
Target HR = (HRR × %intensity) + HRrest = [(HRmax − HRrest) × %intensity] + HRrest
HRmax is commonly estimated as 220 − age (see Maximum Heart Rate (220 − Age)), and HRrest is measured (ideally on waking; see Resting Heart Rate (RHR)).
The advantage over a plain percentage of HRmax (see Percent of Maximal Heart Rate (%HRmax)) is individualization: by anchoring to the person's own resting heart rate, the Karvonen method gives a higher, fitter-adjusted target for someone with a low resting HR. The %HRR scale also lines up closely with %VO2 reserve (see %VO2max and VO2 Reserve (VO2R)), which is why ACSM expresses intensity in both. For reference, ACSM classifies 40–59% HRR as moderate intensity and ≥60% HRR as vigorous (see Aerobic Intensity Classification (Light / Moderate / Vigorous)).
Worked example: a 40-year-old with HRrest 60 bpm. HRmax ≈ 220 − 40 = 180; HRR = 180 − 60 = 120. A 60% target = (120 × 0.60) + 60 = 132 bpm.
Key facts
- HRR = HRmax − HRrest.
- Karvonen target HR = (HRR × %intensity) + HRrest.
- HRmax often estimated as 220 − age; HRrest measured at rest.
- More individualized than %HRmax because it accounts for resting HR.
- %HRR ≈ %VO2 reserve; ACSM moderate = 40–59% HRR, vigorous = ≥60% HRR.
Connections
- Percent of Maximal Heart Rate (%HRmax) — the simpler alternative this improves on.
- %VO2max and VO2 Reserve (VO2R) — the metric %HRR closely matches.
- Heart-Rate Zones (5-Zone Model) — zones can be built on %HRR.
- Aerobic Intensity Classification (Light / Moderate / Vigorous) — the %HRR moderate/vigorous cutoffs.
- Maximum Heart Rate (220 − Age) — supplies HRmax for the formula.
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Educational content only — not medical advice. Always consult a qualified professional for individualized guidance, especially around injury, pregnancy, or medical conditions.