How this instrument works
The Karvonen method targets a percentage of heart rate reserve — the gap between resting and maximum pulse — rather than a flat share of maximum alone. Two joggers with the same top-end pulse can have very different rest-day numbers depending on fitness, so pinning the zone to maximum alone ignores real ground each of them has already covered. Subtract resting from maximum to get the reserve, take the desired fraction of that reserve, then add resting back on: the result sits above resting and below maximum, scaled by effort.
This instrument asks for maximum pulse as a direct entry — a number from a supervised max-effort test, a sports-watch reading, or your own honest estimate — rather than baking in any one age formula to guess it for you. That's deliberate. The '220 minus age' shortcut that shows up on gym walls and older cardio machines is not from Karvonen's own paper at all; it traces to a 1971 review (Fox, Naughton, Haskell) that was never formally validated as a predictive rule, just eyeballed off a scatter of data. Real individuals routinely sit 10 to 15 beats or more away from what that line predicts, in either direction.
If you don't know your measured maximum and need a starting guess, a better-supported alternative comes from Tanaka, Monahan, and Seals, who derived 208 minus 0.7 times age from a meta-analysis spanning thousands of subjects and cross-validated it in a controlled lab study. It still carries real spread person to person — it is a population average, not a fingerprint — so treat either formula as a rough starting line to refine with field testing, never as a substitute for a number you've actually recorded.
- Enter Maximum heart rate in bpm — from a max-effort test, a wearable's recorded peak, or an age-based estimate used only as a placeholder.
- Enter Resting heart rate in bpm, ideally measured first thing in the morning before you've sat up.
- Set Target intensity as a fraction of reserve — 0.5 for an easy recovery day, 0.7-0.85 for a solid aerobic session, higher for interval work.
- Read Target heart rate in bpm — the pulse to aim for once warmed up.
Worked example — max 190, resting 60, 70% effort
A runner with a measured maximum of 190 bpm and a resting pulse of 60 bpm wants a solid, sustainable aerobic effort — 70% of reserve. Reserve first: 190 minus 60 leaves 130 beats of headroom between fully rested and fully spent. Take 70% of that: 130 times 0.7 equals 91. Add the resting pulse back on: 91 plus 60 lands the target at 151 bpm.
Drop the same runner to a light recovery jog at 50% effort instead, with a slightly higher resting pulse of 70 and a lower measured maximum of 180: reserve is 180 minus 70, or 110; half of 110 is 55; plus the resting 70 gives a target of 125 bpm — a full 26 beats gentler, entirely from lowering the intensity fraction and starting from a different rest-and-max pair.
Questions
Why use heart rate reserve instead of just a percentage of maximum?
Because maximum alone ignores fitness. Two people can share an identical top-end pulse yet sit worlds apart in conditioning, and a flat percentage of maximum would hand them the same target regardless. Reserve folds resting pulse — a decent proxy for cardiovascular fitness — into the math, so the same effort fraction lands at a different, more personally accurate bpm for each of them.
Where do I get my maximum heart rate?
The most reliable route is a supervised graded exercise test pushed to true exhaustion, which isn't practical for everyone. A recorded peak from a hard race or interval session on a chest-strap monitor is a reasonable stand-in. Failing both, an age-based estimate works only as a rough placeholder — expect it to be off by a meaningful margin.
Is 220 minus age accurate?
Not particularly, and it isn't even from Karvonen's research — it comes from a 1971 trend line that was never rigorously validated as a prediction equation. Actual measured maximums commonly deviate from it by 10 to 15 beats or more in either direction. A newer, better-derived option is 208 minus 0.7 times age, from Tanaka, Monahan, and Seals' large meta-analysis, though it too is a population average rather than a personal guarantee.
What intensity fraction should I pick?
Roughly 0.5-0.6 for easy recovery days, 0.6-0.7 for comfortable aerobic base building, 0.7-0.85 for tempo or threshold work, and above 0.85 for short, hard intervals. These bands are common coaching convention rather than a fixed law, so treat them as a starting point and adjust by how sessions actually feel and recover.
Does resting heart rate change over time?
Yes — it typically drops as cardiovascular fitness improves, sometimes by ten beats or more over months of consistent training, and it can also rise with poor sleep, illness, dehydration, or stress. Because the target depends directly on the resting figure, re-measure it periodically rather than reusing one number indefinitely.
Can this replace medical clearance for exercise?
No. It is an arithmetic aid for pacing training sessions, not a substitute for a clinician's judgment. Anyone with a heart condition, chest pain history, or other cardiovascular risk factors should get individualized medical guidance before starting an intense exercise program, since a formula cannot account for arrhythmias, medications, or other conditions that shift what's safe.
References
- Karvonen MJ, Kentala E, Mustala O. 'The effects of training on heart rate; a longitudinal study.' Ann Med Exp Biol Fenn. 1957 (PubMed)
- Tanaka H, Monahan KD, Seals DR. 'Age-predicted maximal heart rate revisited.' J Am Coll Cardiol. 2001 (PubMed)
Read this first: This instrument computes a screening figure from population formulas — it is not a diagnosis, and it cannot see the whole picture a clinician can. Use it to inform a conversation, not to replace one.