Track Your Way to Better Health with Active Zone Minutes

In March we introduced Active Zone Minutes (AZMs), a new, personalized, heart rate-based metric that goes beyond step activity to provide tailored activity targets for improving health and well-being. At the same time, AZMs help show the most effective types of workouts so you can work out more efficiently. Our team recently dug into our data to explore relationships between AZMs and health indicators to see how our users can track their way to better health with AZMs. But first, here’s what you need to know:

AZMs track the amount of time a user spends engaging in a heart-pumping activity. Using our 24/7 continuous PurePulse heart rate tracking, we automatically set personalized “Active Zones” based on your resting heart rate and age. AZM uses your personalized heart rate zones to track your effort for any workout that gets your heart pumping, from spin class to yoga, because moderate and vigorous activity varies depending on your fitness level. Active Zone Minutes goes beyond steps to give you credit for all the activities relevant to you.

Specifically, users earn one AZM for each minute spent in their “fat burn” zone and two AZMs for each minute spent in their cardio or “peak” zone. The goal is to get to 150 minutes of weekly heart-pumping activity, as recommended by the World Health Organization and American Heart Association. 

We looked at anonymized global data from 20,000 Fitbit users over the course of one month and retrospectively computed what AZMs they would have earned. We studied how their weekly AZMs correlate to their health indicators like resting heart rate (RHR) and body mass index (BMI). Here is what we found:

AZMs do a body good. Our data shows that the more AZMs a user earns each week, the more positive health indicators a user sees, as shown through a lower RHR and BMI. 

“Our cross-sectional analysis shows a clear association between the acquisition of AZMs and our users having the tools they need to improve their health. Now that the feature is available for the masses, we are excited to use this physical activity metric further in longitudinal analyses,” said Fitbit data scientist Aubrey Browne. 

On average, this data showed that men and women with 150 AZMs per week had a lower RHR compared to users who did not. The differences in RHR were also statistically significant for both genders when looking at these same cohorts: men’s RHR on average was 2.45 fewer beats per minute and women’s RHR was 2.7 fewer in those with 150 AZMs per week. For BMI, those men who had 150 AZMs had a 0.7 lower BMI, while women who had the same had a 0.9 lower BMI. For context, the BMI for someone within the normal weight range is typically 18.5 to 24.9, so a difference of 0.9 can determine if someone falls into a normal or overweight BMI category. 

No pain, no gain. Intensity matters! We found that when the majority of AZMs come from cardio and peak zone minutes, the users were likely to see even better indicators. More specifically, the more cardio and peak zone minutes a user had compared to moderate minutes, the lower their resting heart rate and body mass index. 

Of the data analyzed, users who had approximately 1 vigorous AZM for every 2 moderate AZMs had lower BMIs and RHRs than users who very rarely had vigorous AZMs. Between these two groups, women show a decrease in their BMI on average and men have about half as much, with a decrease in BMI of 0.651. For RHR, there is also a statistically significant difference between genders. RHR decreased by 1.9 beats per minute for women and RHR decreased by 0.24 beats per minute for men.

Consistency is key. Users who consistently had the recommended amount of AZMs showed better indicators for RHR and BMI. This data showed that meeting weekly and daily goals helps reduce resting heart rate and BMI across most age groups. 

On that note, our team found that Fitbit users tend to have more cardio or peak zone minutes earlier in the week on Mondays and Tuesdays, with intensity declining through the week into the least intense workouts on the weekend.  

But no matter what activity you do, it’s important to meet your daily and weekly goals with consistency to see the most health benefits.

Block, don’t sprinkle. This data showed that users who worked out in blocks (i.e., had at least one period where they get 10 consecutive zone minutes) have lower RHR and BMI than those who sprinkled activity throughout the day in shorter chunks. 

Additionally, “blockers” tended to exercise with more intensity, and as a result see a decrease in their RHRs and BMIs compared to the “sprinklers” who exercise moderately throughout the day. 

With consistency and intensity, people can make progress toward better health and AZMs can help them track their progress along the way. We hope these findings help motivate you to start earning more AZMs, which are available on Charge 4™ and coming soon to the Fitbit Versa and Fitbit Ionic families.

So what are you waiting for? While it’s not always easy, finding time every day to get your heart pumping can help you start burning fat and improve your overall health! 


*Most of the analysis was between d1 (8 AZMs on avg) and d5 (150 AZMs on avg). See below chart for decile specifics:

DecileWeekly AZMs

*Suggested daily goal for Active Zone Minutes is based on American Heart Association, US Health Department, and World Health Organization recommendations to get 150 minutes of moderate or 75 minutes of vigorous activity per week, which has been linked to better overall health and well-being, disease prevention, and improved quality of life.

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