The Polar M400 is a sports watch and activity tracker that has built-in GPS and will pair with an external heart rate monitor.
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Pro Gives you a lot of options for customizing different types of workouts
The "Sport Profile" feature allows you to customize what stats you want to see for each type of exercise. For example, you may want the GPS on for running but not for a circuit workout. These preset profiles save you from having to set up the device each time you exercise.
Pro Gives you custom activity goals suitable for your level
The daily activity goal is a good way to find out how active you really are in your everyday life. Here you can choose your typical activity level from three options and see how active you need to be to reach your daily activity goal.
The time you need to complete your daily activity goal depends on the level you have chosen and the intensity of your activities. Age and gender also affect the intensity you need to reach your daily activity goal.
Pro Detailed reports
The fitness tracker offers excellent reporting including distance, speed, cadence, heart rate (if paired with monitor), ascent, decent, calories, recovery status, and more.
Pro Ability to add training notes
The app allows you to add additional notes to your workouts for better tracking.
Con Sleep tracking lacks detail and accuracy
If you are awake for an extended period of time in the middle of the night and then fall back asleep, the fitness tracker may not see the additional hours as part of your sleep.
Con Unattractive and bulky design
The tracker is quite wide and hard to miss, it's not something that can blend in with what you're wearing outside of sport/exercise type settings.
Con Short battery life when using the GPS
With the GPS turned on, battery life goes from around 24 days to 9 hours.
This is likely fine for people who will always have opportunities to charge it after their run. However for anyone hoping to use the GPS for longer activities, such as hiking, that may not be long enough to be useful.