Generic charts are built for an average person who is not you. Enter your age and resting heart rate to get zones that are actually calibrated to your physiology.
Resting HR: measure first thing in the morning before getting up. If you skip it, zones are estimated from age alone.
Leave blank and we use 220 minus your age. If you have a real number from a VO2 max test or a hard race effort, use that instead.