Which formula uses resting and maximum heart rate to calculate training zones?

Which formula uses resting and maximum heart rate to calculate training zones? The Karvonen formula does.

The formula first calculates heart-rate reserve by subtracting resting heart rate from maximum heart rate. It then applies the desired intensity percentage to that reserve and adds resting heart rate back: target heart rate = ((maximum heart rate − resting heart rate) × intensity) + resting heart rate. This produces a target that reflects both an athlete’s baseline and upper limit.

The method is named for Finnish physiologist Martti J. Karvonen and is associated with a 1957 study. It is often preferred to simply taking a percentage of maximum heart rate because two people with the same estimated maximum can have very different resting rates and therefore different training targets.

For example, with a maximum heart rate of 180 beats per minute and a resting rate of 70, the reserve is 110. A 50% target is 125 bpm, while an 85% target is 163 bpm. Maximum-heart-rate estimates such as 220 minus age are only approximations, so the resulting zones are not laboratory measurements.