AZM was first introduced on the non-smartwatch activity tracker Charge 4: read our Fitbit Charge 4 review, Fitbit Versa 2 review.
Active Zone Minutes replace the less sophisticated Active Minutes. The measurement uses your resting heart rate as a baseline to target motivational heart-rate zones during exercise.
They are earned for time spent into the different Heart Rate Zones: Fat Burn, Cardio, or Peak. These are personalized based on your fitness level and age.
You earn two Active Zone Minutes for each minute you’re into the Cardio or Peak zones.
The default goal is the to earn 150 Active Zone Minutes each week, which is the based on recommendations from the American Heart Association and World Health Organization, which both recommend at least 150 minutes of moderate-intensity activity or 75 minutes of vigorous activity each week.
Users can change that goal into the Fitbit app.
More intense workouts – such as spinning, interval training, or running – increase your opportunities to earn Active Zone Minutes. If you run for 20 minutes and spend 10 minutes into the Fat Burn zone and 10 minutes into the Cardio or Peak zones, you earn 30 Active Zone Minutes.