What is my zone 2 heart rate?

Three separate choices sit between your age and that band, and each one moves it. The first is the equation that produced your maximum: at 50, Tanaka gives 173 bpm, Fox gives 170 and Gulati - derived in 5,437 asymptomatic women - gives 162. Zone 2 becomes 104 to 121, 102 to 119 or 97 to 113 accordingly.

The second is the method. Scaling a percentage of maximum and scaling heart-rate reserve through Karvonen are different operations: at a maximum of 190 with a resting rate of 60, 70 percent by Karvonen is 151 bpm while 70 percent of maximum is 133. Karvonen bands always sit higher at the same nominal percentage.

The third is the chart itself. The ten-point bands running 50, 60, 70, 80, 90, 100 percent are a training-industry convention with no paper deriving those edges. ACSM does publish an intensity classification, and its boundaries are different: light 57 to 63 percent, moderate 64 to 76, vigorous 77 to 95. Zone 2 straddles the first two of those.

Sitting under all of it is a prediction error of 7 to 11 beats per minute on the maximum itself, which is wider than zone 2 is in some age rows. Read the band as a broad region of conversational effort rather than a boundary to defend to the beat. Zone 2 explained has the table by age, both ways.