Analyze Your Heart Rate
The Fitbit Charge 2 and Fitbit Surge both can track your heart rate, but it's important to know what that data means if you're resting, working out, or sleeping.
If your goal is to burn fat, you'll probably want to focus on low-intensity exercise. If your tracker has a heart rate monitor, you can make sure your workout stays within a "fat burn" zone. If you have a Charge 2, for instance, press the button on the side of your tracker to navigate to heart rate, and if you're in your fat-burning zone, that will be indicated on your screen, and the same goes for your cardio workout zone.
Generally, your maximum heart rate is 220 minus your age, according to Live Science. Your target heart rate should be somewhere between 50 percent and 85 percent of that number.
If you know that your resting heart rate is lower or higher than normal, the default heart-rate-zone calculations may not be accurate for you. In that case, you can adjust them in your account settings, by tapping on Heart Rate Zones and entering beats per minute manually.