Fitbit Zip Charge HR - Measuring your heart rate; Default heart rate zones; Custom heart rate zones

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Measuring your heart rate
When your heart beats, your capillaries expand and contract based on blood volume
changes. PurePulse™ LED lights on your Fitbit Charge HR reflect onto the skin to
detect blood volume changes, and finely-tuned algorithms are applied to measure
heart rate automatically and continuously.
Default heart rate zones
Heart rate zones can help you optimize your workout by targeting different training
intensities. Your zones are calculated based on a percentage of your estimated
maximum heart rate. Fitbit calculates your maximum heart rate with the common
formula of 220 minus your age.
To quickly determine what zone you’re in, take a look at the heart icon:
Out of zone Fat burn Cardio Peak
• When you’re out of zone, which means you’re below 50% of your maximum
heart rate, your heart rate may be elevated but not enough to be considered
exercise.
• Fat Burn zone, which means your heart rate is between 50% and 69% of your
maximum, is the low-to-medium intensity exercise zone and may be a good
place to start for those new to exercise. It’s called the Fat Burn zone because a
higher percentage of calories are burned from fat, but the total calorie burn
rate is lower.
• Cardio zone, which means your heart rate is between 70% and 84% of your
maximum, is the medium-to-high intensity exercise zone. In this zone you’re
pushing yourself but not straining. For most people this is the exercise zone to
target.
• Peak zone, which means your heart rate is 85% of your maximum or higher, is
the high-intensity exercise zone. Peak zone is for short intense sessions that
improve performance and speed.
At any time you can check your dashboard to see the amount of time you’ve spent in
each zone.
Custom heart rate zones
Instead of using the default heart rate zones you can configure a custom zone.
When your heart rate is above or below your custom zone you’ll see an outline of a
heart, and when your heart rate is in your custom zone you’ll see a solid heart.
To set a custom heart rate zone using the fitbit.com dashboard:
1. Log in to fitbit.com.
2. Click the gear icon in the top-right corner of the dashboard and select
Settings.