Zone 2

[Huntingnorseman]

There isn't substitute for doing a VO2 Max test to find your zones if you are serious about training. Most people I test have a Max HR within 5 BPM of their calculated Max HR and their zone 2 is lower than the Max HR based formulas show. With a VO2 max test done a machine with a CO2 sensor the maximum aerobic HR is very clear. In most people you will also see clear metabolic changes at the zone 3, zone 4, and zone 5 transitions.
The most accurate formula based calculation I have found is MAF (Maximum Aerobic Function) if you are honest with yourself and use adjustments. https://philmaffetone.com/method/process/