Calories burned during physical activity are measured based on the data received from the accelerometer (your arm movement) and piezo sensor (your heart rate). This means that the accuracy of the device during workouts in which your hands are not active enough (treadmill, cycle, ellipsoid, some weight training workouts) may decrease.
For more details on tracking of burned calories you can check our infographics at https://healbe.com/us/info_calories/
At the moment our team is working to improve the accuracy in measuring your heart rate during different types of physical activity. We plan to add support for different types of workouts and sports modes. The improved algorithm will be implemented in one of the next GoBe releases.