Polar M400 GPS Sports Watch - Review

Sports Watch Tracks Workouts, Steps, Activity, Sleep


The Polar M400 GPS sports watch has impressive features that start with workout speed and distance (with optional heart rate monitor). It is also an always-on activity monitor that counts all-day steps, gives you inactivity alerts to reduce sedentary time, and tracks your sleep quality. With the M400, you don't need a separate fitness band to track these all-day measures.

Who is the Polar M400 Right For?
The M400 is built for those of us who want to improve our workouts and also want to track our all-day activity.

If you are training for a half marathon or marathon or want to improve your speed, the M400 is a great training tool. Whether you run, walk or bike you can track workout speed, distance, and altitude with the built-in GPS. Using the optional Polar H7 Bluetooth heart rate monitor strap, you can track your intensity zones.

You don't leave the M400 in your gym bag for workouts only. Wear it all day and all night as a watch. It tracks all-day steps as a pedometer watch and tracks your progress towards a daily activity goal, giving more credit for more vigorous activity. To reduce the health risks of sitting too long, the M400 gives you alerts when you haven't gotten up and moved around yet during an hour. It also automatically tracks sleep duration and quality.

Is it Walker-Friendly? Yes, you can choose walking as one of the workout types and set it as a favorite. You get speed, distance, and splits for walking workouts.

It also tracks all of the steps you take each day.

Setting up the Polar M400: Sign up for a free Polar Flow account online or through the Polar Flow App (either iOS or Android). With this account, all of your Polar devices will sync to the account for tracking activity and workouts and for using their Smart Coaching features.Set up a Polar Flow account online to get the full benefit of their fitness tracking and Smart Coaching features.

Sync your Polar M400 via Bluetooth Smart (4.0).

Power: The M400 charges via a standard micro-USB cable (aren't you sick of custom cables?) The M400 has eight hours of battery life if you use the GPS and/or heart rate functions. For only using the 24/7 activity tracking, the battery life is 30 days. The watch gives you both low battery and "charge before training" alerts.

Ease of Use: The M400 is the most-intuitive Polar design I've used. The five buttons make sense and I am able to quickly check my daily activity, start a workout, pause, and resume without having to bring along a cheat sheet. The watch itself gives you lots of data to review during and after your workout without having to open the app or connect to the web service. Workout data views are highly customizable so you can choose what you see on each screen. You can easily lock and unlock the buttons.

Style: The M400 comes in white, black, pink or blue. It is only about a half inch thick, not much different from my usual watch. The pink version has a slightly shorter wristband for smaller wrists. The polymer watchband has a standard watch buckle. The back of the watch case is metal and is in contact with your skin. It has a polymer cover for the USB port on the back of the watch.

It is waterproof for bathing and swimming.

Smart Notifications: This functionality was added in July 2015, first for iOS and coming later for Android. Users can read text messages, see incoming caller ID, get calendar alerts and social media push notifications on the M400.

What the Polar M400 Tracks

Watch Display: The watch display is always on and you can choose between four different watch face displays. I prefer the display that includes an activity bar so I know if I am on target towards my daily activity goal. The Polar M400 has a backlight for night viewing and you can set an alarm and use a  snooze feature.

More: Pedometer Watches

Today's Activity: You can track your total steps per day with the M400, and I found it logged the same number of steps as the Fitbit Charge when I wore them side-by-side. The M400 senses the intensity of your physical activity and sets an activity goal for your age, gender, and physical condition.

The Today's Activity screen shows you:

  • Minutes of Active Time: this includes any physically active minutes for all exercise intensities.
  • Calories: This total starts a midnight as it includes basal metabolic rate calories you burn at rest as well as the extra calories you burn with physical activity. This is a useful number to balance against the number of calories you eat.
  • Steps
  • Active minutes needed to reach your daily activity goal by either jogging (vigorous-intensity activity), walking (moderately-intense activity) or being up (light-intensity activity such as standing or moving slowly). This is a real wake-up call to how much activity you really need to put into your day.
  • Inactivity alerts: The M400 alerts you if you haven't gotten up and moved around for a minute during the past hour. Unless you get up and move for at least a minute, or press a button on the M400, you get an inactivity tag on the online diary for the hour.
  • Diary: See your activity and workout history for past days.

On the Polar Flow app and dashboard, you can get a quick sense of your day as each minute of a clock is color-coded for how active you were. It also lists the total time spent in each activity zone and your time sleeping.

Workout Sessions
Get quick access to your favorite workout activities by setting spot profiles for them. You can track outdoor workouts by GPS for speed and distance. You can track indoor or non-distance activities via a timer. For either, you can add a heart rate strap to measure the intensity and better track calories burned.

You can customize the data views during your workouts.

GPS Workout Features for Walkers and Runners
The M400 had everything I wanted from a GPS sports watch. I was easily able to move between features without accidentally ending my workout. The Quick Menu via the backlight button is awesome.

  • Speed and pace, including current, average, and maximum
  • Distance: training, lap, trip and total.
  • Auto start/stop if you choose.
  • Auto laps and manual laps, with stats for each lap
  • Interval timers
  • Altitude
  • Speed zones: runners can set speed zones and see time in the zone.
  • Finish time estimator
  • "Back to Start" arrow to guide you back if you found yourself a little lost and without a map/map app.
  • After workouts, view map of your workout and all of your lap stats on the app and website.
  • Workout summary on the watch includes duration, distance, calories, fat burn % of calories, average pace, maximum pace, maximum altitude, ascent, descent, lap details, trophies for best achievements. You can view 14 past workouts and 30 hours of data.

Heart Rate Workout Features
If you use the M400 with a Bluetooth heart rate strap, you can also see your automated heart rate zones and you can get in-zone and out-of-zone alerts. I enjoyed setting it to display my heart rate percent of maximum.

Five zones are set and for each 10% between 50 to 100% and at the end of the workout, you can see the time you've logged in each zone. On the Polar Flow app or site, I like viewing the heart rate graph to see where it peaked during my workout. It lists average heart rate plus the minimum, maximum and the time you were in each of the five zones. You can also see your total workout calories and time.

Sleep: The M400 automatically detects sleep, you don't need to remember to start and stop sleep recording. The app and dashboard display total sleep time and duration for restful sleep, restless sleep, and a percentage of restful sleep. You can also spot the times you got up during the night on the activity clock.
More: Sleep-Tracking Activity Monitors

Activity Analysis and Coaching: Beyond numbers, the M400 shows you how each workout session and your daily activity contributed to your fitness level or can reduce health risks. It also suggests fun ways to get in more activity to reach your goal.

More: 10 Ways Your Pedometer Can Motivate You

Portability: You can leave your smartphone at home and record your workouts with the M400, it uses its own GPS receiver for speed and distance and tracking. You can't view a map on it, but you will be able to do so when you sync it with the app. It needs to be synced after 30 hours of activity tracking or it will lose data.

Bottom Line on the Polar M400


  • The app and dashboard don't include a way to track what you eat, you have to use a separate site.
  • Eight hours of GPS/heart rate tracking might not be enough battery life for a long hike.
  • You need to use the heart rate monitor to get meaningful workout stats for indoor workouts and non-GPS workouts.
  • It doesn't do all-day background sync, you have to tell it when to sync.


  • I was very pleased with the accuracy of the GPS speed and distance, it definitely was an improvement on my phone's GPS apps. 
  • As you'd expect with a Polar product, it is well-integrated with using a Polar heart rate monitor strap and tracking your time in training heart rate zones.
  • It coaches and encourages you to reach your activity goal in different ways.
  • Training tools for those who are dedicated to improving their speed, distance and workout intensity.

I recommend the Polar M400 for walkers and runners who want to improve their workouts and reach new goals. The 24/7 activity tracking is excellent and can help you reduce inactivity and get the right mix of activity each day.

Disclosure: Review samples were provided by the manufacturer.