Activity Trackers: Polar M400 running watch review

The wallet-friendly younger sibling to the Polar V800, the M400 is one of the first fitness devices to bridge the gap between the fitness band and the GPS sports watch. For £169/$179, it offers full activity tracking from your wrist, whether you’re walking up the office stairs or speeding through your local park on a 5km training run.


Polar M400: Design and build

While it does have some multisport credentials (it will track the GPS related stats for cycling and even horse riding) the M400 is built to be a running watch with added intelligence.

Let’s face it, being the younger relation to a multi-talented piece of tech like the V800 was always going to be difficult but the M400 stands up remarkably well.

Unlike the V800 it won’t pair up with quite as many accessories and cycling cadence sensors are not an option, but on the plus side, the design is actually better than its rather pricier stablemate.

For starters the strap is more comfortable on the wrist. Added to that the watch face is a little smaller and more ergonomic.

Then there’s the simple USB charging that does away with the need for a unique charging cable or dock; a bone of contention with many other GPS watches, including the V800. Despite this, it still manages to be fully water-resistant in water up to 30m, taking the activity tracking element off of dry land.

There’s also a high-contrast display that makes it easier to see your stats even in direct sunlight.

It’s a real shame that it doesn’t have the built-in heart rate monitoring that some running watches like the Adidas miCoach Smart Run or the TomTom Cardio Runner now offer, but it can be paired with a chest strap for added accuracy andthe Polar staple heart rate zone training.

Weighing in at 56.6g and measuring 11.5mm thick, it’s also not the bulkiest of the running watches, which adds to the overall comfort.

Polar M400 GPS Sports Watch & Activity Tracker


The PolarM400 GPS Watch with HRM combines popular fitness band features with advanced GPS and training plans to create a sporty and functional training partner. Helping you make adjustments to both ...

Made by: Polar, Available: In stock

Polar M400: Features

Let’s start with what the M400 tracks. There is, of course, the basics including distance, pacing, altitude and calorie burn. But where the M400 cuts a new path is in its ability to deliver data for the times when you’re not running.

The internal accelerometer of the unit will track steps, activity and sleep. It’ll also give you a nudge if you’ve been stationery for a long period just like you’d get from a Jawbone UP24 or a Fitbit Flex.

The Activity Guide feature is basically like having a Polar Loop built into your running watch.

While the activity and sleep tracking don’t offer the depth of some of these devices, having all your data pushed to a single platform is extremely appealing to the point that you’re happy to forgo some of the deeper data.

In terms of running, one of the features we found most useful was the Back to the Start feature that guides you home via the most direct route using a GPS marker stored at the start of each run. It’s brilliant for running in a foreign city, or for people who just tend to get lost easily.

There are also a range of smart coaching features just like those we’ve seen on the V800 and competitors like the Garmin Forerunner 220 or 620.

Running Estimator calculates how long it’ll take you to cover a distance at the pace you’re currently clocking, while PB support gives you feedback on any records you’ve broken during a run.

There’s also handy post-run feedback on the overall training benefit from the work you’ve just done. This helps you determine whether you’ve been burning fat, improving cardio and what effect this has had on your body. Running Index gives you a window into how your running is improving based on heart rate and speed. This is great if you’re training towards a specific goal.

The Polar smart calorie counter is far more accurate than you would get with a regular fitness band as it takes into account your height, weight, age, gender and activity levels to form a much more accurate estimate off the calories you are using during exercise.

The Polar fitness test has been developed from years of trial and error, and is now so accurate it rivals any lab-based sub-maximal VO2 test. Using heart rate data and fluctuations at rest it will provide you with a VO2 max figure, that you can use to track your performance in just 5 minutes of testing.

If you’re not entirely sure what this means, check out our GPS running watch jargon buster.


Polar M400: Syncing, apps and web tools

Thanks to Bluetooth Smart technology, all the data from your M400 can be easily, and instantly, synced to a connected smartphone. Your vitals end up in the Polar Flow app and web tool, which both offer a competitive range of options to enhance your training. From customisable training plans to elite athlete level data, Polar Flow is one of the best tracking tools we’ve come across.

Running guide: How to stay injury free with wearables

It might not have the gloss and social features that Nike+ Running has, or the range of off-the-shelf training plans you get with Adidas miCoach, but it’s a great tool for runners.

Polar M400: Battery life


A full charge of the M400 will get you around eight hours of GPS tracking. On that front it’s competitive with most of the other running watches in this category.

When it comes to the day-to-day tracking or general watch mode you’re looking at closer to 21 days. That’s a lot more than most fitness bands.


Bang for your buck, the Polar M400 is a fantastic option for anyone looking for a wearable that offers a complete picture of everyday activity and training. If you’re a serious cyclist there are better products out there and some runners might like to see more running form data but for anyone who’s about to take on their first marathon or just embarking on the couch-to-5km, then this is as good as any device you’ll find right now.


  • Full 360 tracking
  • USB charging
  • Decent battery life


  • No built in HR monitor
  • Activity tracking is basic
  • Lack of accessory support

Polar M400 GPS Sports Watch & Activity Tracker


The PolarM400 GPS Watch with HRM combines popular fitness band features with advanced GPS and training plans to create a sporty and functional training partner. Helping you make adjustments to both ...

Available: In stock
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a little expensive but SOOO worth it. this device is a great upgrade to my last polar that lasted 10 years.things you should know, this does not have a battery in the watch device itself, but rather usb charger. if you do it at your computer, you will download the sync application and be directed to the polar flow website where you will have profiles to choose from from yoga to multi and triathletic to trotting for all of those pony people out there.the ability to do this helps keep track of your training, it also enables upgrades to software as polar releases them. like your computer. there are two prices you will see out there, a 229-249 and a cheaper model. the cheaper model is such because you need the heart rate monitor strap(the one that goes around your torso) the f7 bluetooth.yes the gps can be turned off to save your battery. the display is very easy to use not like my old rs200. its also EASY to see especially when your moving alot or have to squint to keiser, spinners and lemond all hook up and sync with the bluetooth on their equipment. so i dont foresee any problems there.I have not used the i phone app yet but will keep you posted how it works its too new, but i am so excited about this device. and im persnickety tooi had tried another model of polar and it felt bad on my wrist. this m400 is super velvety on the skin. i have the white, and it too new to tell but i assume it wont look entirely trashy.I am active alot! i teach fitness classes from boot camp to yoga to spin, and heart rate monitoring since i started it 9 years ago changed my habits!i would give this a try, its new and great web tutorials over at polar website view those. i doubt you'll be disappointed in this.Read more ›
November 12, 2014
Overall, I like the watch. It seems to offer a ton of features not typically found in a $180 watch (fully customizable data fields with up to 4 items per screen, a pretty useful "Back to Start" feature, elevation gain/loss, and the ability to count down the time until your activity is finished, sort of like a GPS unit you'd use in your car.What I like:-The watch looks very attractive and has a very low profile-The watch uses a normal USB cable to charge, not an awkward looking device-specific charger like the other companies utilize-The route tracked on the map appears to be very accurate. So far, it looks identical to the actual running route, right down to the particular side of the street I ran on. Better than my previous Garmin watch-Tons of items can be added to the training screens (1-4 data items per screen, up to 8 total screens), and these screens are easily accessible by pushing the down/up buttons while running. This is all customizable through Polar Flow, which I actually prefer compared to setting this up on the watch itself-There are tons of different sports profiles that you can set up, and with each profile (cycling, treadmill, running, even badminton... yes, badminton), you can completely customize the information you see on your training screens. This is useful for seeing metrics in MPH when cycling versus min/mile when running, and seeing exactly the items you want for specific activities.What I don't like:-There is no alert vibration and the alert beep is barely audible. You have the option of increasing the volume, and even at "very loud" I can still barely hear it when I have headphones in.-I'm not a fan of Polar's lap feature.Read more ›
November 7, 2014
I've had my M400 for about a week and have had a chance to put it through a few paces - it is an incredibly powerful device and I'm still learning some of the tricks, but here's my take:Out of the box initial impression: Very attractive watch and very comfortable to wear. Even though it is large, it doesn't seem that big on my wrist.First takes: I have now taken it on two outdoor bike rides, a few indoor stationary bike rides, and some treadmill walks, and it works flawlessly. The GPS is fantastic - it took less than a minute to lock on and stayed on. The HRM also quickly picks up and reads out very accurately. The Polar Flow software is easy to set up and provides a wealth of information, including good sleep data (it knows when you're sleeping so you don't have to turn it on and off to register sleep). I used to have a Garmin Vivofit which fell off my wrist while on a business trip - this watch will not fall off. The watch also has excellent battery life when you aren't using the GPS.Cons-My only very modest complaint is with the information that displays on the watch while you are wearing it, but this is by no means a deal breaker. Maybe I'm missing something (I'm still learning the watch's capabilities), but so far while I have been exercising, I have not been able to display the regular watch face and have the activity record in the background (or be able to switch back and forth). However, I do not that one of the view displays the time as well as information relating to the workout.This is a very high quality product and an excellent value when you weigh it against the competition.(I wrote this review a few days ago and updated it on 12/9/14 to add another star and modify some of what I write earlier based on additional usage)
December 7, 2014
Activity Trackers: Polar M400 running watch review
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