Why Your Resting Heart Rate Changes Your Training Zones
Published 2026-10-04
The simple method ignores fitness entirely
The classic "220 minus age" approach only estimates maximum heart rate, and training zones built purely as a percentage of that number treat every person the same age as identical — which isn't true, since fitness level has a real, measurable effect on how the heart behaves during exercise.
Heart rate reserve is the missing piece
The Karvonen method starts from a different number: heart rate reserve, the gap between your estimated max heart rate and your resting heart rate. A fitter heart is more efficient and beats fewer times per minute at rest, which means a fitter person often has a larger heart rate reserve than a less fit person of the same age and same estimated max.
Why a bigger reserve shifts zones upward
Since each zone is calculated as a percentage of that reserve (added back to resting heart rate), a larger reserve pushes every zone's actual beats-per-minute target higher. Two 40-year-olds with the same estimated max heart rate but different resting heart rates end up with genuinely different, personalized training zones — not just the same numbers copy-pasted from an age chart.
The formula
Max HR ≈ 220 − age. Target HR for a zone = ((Max HR − Resting HR) × zone%) + Resting HR.
Find your real zones
Our Heart Rate Zone Calculator uses the Karvonen method with your own resting heart rate, rather than a generic age-only lookup table.