Heart rate reserve (HR reserve) is the difference between the maximum heart rate and the resting heart rate. It shows how much the heart can speed up from a resting state to peak exertion.
The lower the resting pulse (the better the fitness), the greater the reserve.
How it is calculated
The formula is simple: reserve = max HR − resting HR. For example, with a maximum of 180 and a resting pulse of 60, the reserve equals 120 beats per minute. The reserve is a more individual measure than just a percentage of the maximum, because it accounts for your resting pulse.
The Karvonen method
To set a target training pulse, the Karvonen formula is used: target pulse = reserve × intensity + resting HR. For a person with a reserve of 120 and a resting pulse of 60, a load of 70% gives a target pulse of 144 bpm. This method is more accurate than calculating zones from the maximum alone, and it underlies heart rate zones based on reserve.
What the reserve shows
A large reserve is a sign of good aerobic fitness and, as a rule, a low resting pulse. As fitness improves, the resting pulse falls and the reserve grows. This is indirectly linked to a higher VO₂max and a better health prognosis.
Calculate using this marker
Calculators where Heart rate reserve is used directly:
Frequently asked questions
Why is the Karvonen method better than calculating from the maximum?
It accounts for your resting pulse, so the target zones come out more individualized. For a trained person with a low resting pulse, the zones shift more precisely to their physiology.
How do you increase heart rate reserve?
Regular aerobic exercise lowers the resting pulse and thereby increases the reserve. The maximum heart rate barely changes — it depends mainly on age.