Heart rate reserveHRR · Karvonen method
The gap between your resting and maximum heart rate, used to set training zones.
Heart rate reserve is simply maximum heart rate minus resting heart rate. Training zones built on it — the Karvonen method — express intensity as a percentage of that reserve added back onto resting, rather than as a raw percentage of maximum.
It matters because it personalises zones to your fitness. Someone with a resting heart rate of 45 and someone at 75 are doing very different work at the same raw percentage of maximum; using the reserve corrects for that and lines up better with percentage of VO2 max.
In practice you need a reasonably honest resting heart rate — taken on waking, lying still, over several days — and a maximum that is measured or at least estimated sensibly, since age formulas carry a wide margin of error for any individual.
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Written and reviewed by Mathew Beale, MSc Biotechnology, University of Reading.
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