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[[File:Polar M400.jpg|right|thumb|200px|The {{Polar M400}} .]] I was initially very disappointed with the {{Polar M400}}, but over time I've come to appreciate the M400 more and more. There are a number of factors, not least of which is that it now sells for far less than its release price, making it a disappointing watchlot more competitive. Its [[GPS Accuracy]] has also improved, with poor GPS though it still mediocre. This accuracy and limited problem is offset by its reasonable support for the [[Stryd]] Footpod that is extremely accurate. The main competition the M400 faces is the [[CadenceGarmin Vivoactive]]. Even at The Vivoactive is a better watch in virtually every respect, except for its low price point it Stryd support. In order to get the Vivoactive to get pace and distance information from Stryd you have to turn off GPS, while the M400 can use Stryd for pace and distance whilst still recording a GPS track.* '''How far did I run?''' This is the most basic question, and the M400 has poor GPS accuracy, but this can be offset by using the Stryd Footpod. It may seem odd to spend more on a Footpod than the watch, but I don't think it offers good value for moneyd argue this is actually a reasonable compromise. If * '''How fast am I running?''' Knowing how fast you're after running can be a midrange nice to know, or it can be vital for your training or race performance. Because of the nature of GPS, watches that rely on GPS watchsignal alone tend to have serious problems with current pace. With the Stryd Footpod, you can get extremely accurate pace information, but without it, the M400 is pretty hopeless. * '''Where am I? '''d suggest looking at The M400 has only a simple "back to start" arrow, which is better than nothing, but remember this is an "as the crow flies" direct path, not a backtrack. * '''What's my cadence? '''[[Garmin 610Cadence]]''' '''is one of the most critical and often overlooked aspects of running. If you get your Cadence right, many other things naturally fall into place. While it'The M400 has support for other [[Footpod]]s an older watchbesides Stryd, plus it offers has support for Cadence from the internal accelerometer. There are no Cadence alerts which is a shame, but typically this feature is only available on more expensive devices.The M400 is not a good choice for ultrarunners, as its battery life is too short. See [[Best Running Watch#Watches for Ultrarunning| Watches for Ultrarunning]] for more details.{{BuyAmazon|AZID=B00NPZ7WNU|AZN=Polar M400}}=Should You Buy The M400?=I think that in most cases, at this price point you should buy the [[Garmin Vivoactive]] over the M400. The Vivoactive has far more features functionality than the M400, including Connect IQ that allows for expanded functionality through downloaded apps. The Garmin 220 Vivoactive is more expensivea vastly better activity tracker, but offers especially when combined with a good Connect IQ watch face that gives you better functionalityfeedback on how you're doing. You can even use the Vivoactive on an ultramarathon by [[Charge On The Run]], something that much harder with the M400. Both watches will support the [[File:Polar Stryd]] Footpod for extremely accurate distance and pace information, but they have different trade-offs. The M400can still record a GPS track whilst getting distance and pace from the Stryd, where the Vivoactive has to have GPS disabled.jpgOn the other hand, the Vivoactive can display the Stryd estimate of [[Running Power Meters|none|thumb|200px|The {{Polar Running Power]] far better than the M400}}, and it can record this power estimate along with other metrics such as Ground Contact Time.Therefore, I'd only recommend someone buys the M 400 if they really want to record the GPS track whilst getting pace and distance from a Stryd Footpod, otherwise by the [[Garmin Vivoactive]] .

* The support for [[Stryd]] is pretty good. As noted above, you can get pace and distance information from the Stryd whilst still recording a GPS track. The Limited navigation features mean that the GPS data is of limited use while you're running, but it does allow you to see where you went afterwards. You can only get the Stryd estimate of power through the cadence field, and that feature might disappear in the future.* Like the [[Suunto Ambit2 R]] and [[Polar V800]], the M400 can be configured via the website, which is easier than fiddling with the watch itself. Most of the options can be also set on the watch, which means you're not stuck if you're away from the Internet.

* The M400 can act as a simple activity monitor, but it only has only an internal accelerometer which provides poor accuracy. If you need an activity monitor, I'd recommend the [[Basis Activity Tracker]] which has sensors for heart rate, skin temperature and perspiration.

* Unlike the [[Polar V800]], the M400 has poor [[GPS Accuracy]]. While I rely on detailed measurements and statistical analysis to evaluate GPS accuracy, it's worth mentioning that on one 18 mile run the M400 has lost over a mile. This is the worst a level of error I've seen, even worse than the [[Garmin 620]] before Garmin fixed their problems with a Firmware upgrade. (I tested the M400 with version 1.4 of the firmware and the GPS accuracy is unchanged.)** It looks like Polar are using a different GPS chipset in the M400. The V800 uses the SiRF chipset, where the M400 uses [http://www.u-blox.com/en u-blox].** I have seen the Polar M400 losing satellite signal with the message "There's no GPS signal". This occurred under conditions where another device is doing fine and there are not circumstances that would cause a problem.** The accuracy you might see with the M400 on your runs may vary from my testing. If you look at the [[Detailed Statistics for GPS Running Watches| detailed statistics]] you'll see that the M400 does quite well in straight lines. This is true of nearly all GPS watches, as running in a straight line is not difficult, and even here the M400 does worse than most devices.

** The Polar Stride Sensor is fully supported by the M400, with automatic calibration and it will display stride length as well as cadence. However, the Stride Sensor is huge and heavy when compared with modern Footpods, weighing over three times as much as a Garmin Footpod. Because of its size and weight, it requires lacing into the shoelaces, making it a real pain to move between shoes. <jfs id="B00CCASIMS" noreferb="true" n="Polar Stride Sensor"/>** The [[Stryd]] Footpod and the [[MilestonePod]] work well with the M400.

** The Adidas miCoach Speed Cell will work with the M400, but it's not easy. By default it will pair with the M400, but you can't set the calibration factor nor can you set the M400 to use GPS for pace/distance. You have to pair the M400 with the Polar Speed Sensor to activate the menu items you need to configure the Adidas Footpod, which is far from ideal. However, the Adidas Footpod is then a reasonable size and provides cadence (though not stride length). <jfs id="B00FEJ7FBO" noreferb="true" n="adidas miCoach Speed Cell "/>.** Even though the M400 has an internal accelerometer, this is not used to display cadence.

** Polar states they use [http://www.u-blox.com/en/assisted-gps.html AssistNow], a technology from u-blox] which does satellite prediction. AssistNow can use a downloaded prediction file or simply calculate the positions offline. With version 1.4 of the firmware, the synchronization software was updated to indicate that the offline file had been downloaded, and the watch will now indicate how long the file is valid for. However, even with version 1.4, the TTFF is still slow compared with competing devices. * The M400 uses Bluetooth sensors rather than the more common Ant+, limiting the choice and quality of sensors. This is likely to change over time as more devices are produced and compatibility issues are resolved. * The M400 will only upload the data to the Polar website. Polar has introduced to the export of TCX format data, but this export is incomplete (no laps). You can work around this by using the open source projects [https://github.com/pcolby/bipolar Bipolar] and [https://github.com/profanum429/v800_downloader M400_downloader], but this is a far cry from the open approach that Garmin has taken.

=GPS Accuracy=For quite some time, the M400 had the worst GPS accuracy of any device I've tested, but recent firmware upgrades have improved matters somewhat. The GPS accuracy is still rather mediocre at best, but at least it's not as appalling as it once was. It looks like Polar are using an unusual GPS chipset in the M400. I've not seen any other device using the u-blox chipset, and the replacement for the M400 (M430) returns to using the same chipset manufacturer as the [[Polar V800]] which has outstanding GPS accuracy. The firmware upgrade is also fixed the problem where the M400 would report losing satellite signal with the message "There's no GPS signal". This was occurring under conditions where another device is doing fine and there are not circumstances that should cause a problem{| class="wikitable" |- valign="top"[[File:BridgePolar M400 v1.9.600.jpg|none|thumb|x300px|Here's the tracks from the M400 with the 1.9 firmware. This diagram has tracks color coded with green indicating good accuracy through to red indicating poor accuracy, and the lap markers as blue dots.]]|[[File:BridgePolar M400.jpg|none|thumb|x300px|For comparison, this is the M400 with the earlier 1.4 firmware. You can see a few tracks where the M400 has shifted out of position even though the shape of the course is maintained. The blue lap markers are quite spread out, suggesting some positional accuracy problems. You can see from the green lines going under the bridge that the M400 does quite well in that situation, and there are no sudden changes in position on emerging. I suspect this is because the M400 is doing a lot of smoothing, which works well in that situation. The middle segment that is quite curved is nearly all red, and this is one of the areas where the M400 is a smoothing too much and cutting the corners. You can see the M400 does worse here than in the sharp turn to the right of the image. ]]|- valign="top"|[[File:BridgePolar V800.jpg|none|thumb|x300px|The Polar V800 is one of the most accurate devices I've tested, and you can see that the majority of the tracks are green indicating good accuracy. Notice the problems the V800 is having at the bridge. Rather strangely the lap markers are far more spread out than I would have expected on a device this accurate. ]]|}=Visual Comparison={BuyAmazon|AZIDclass=B00NPZ7WNU"wikitable"|AZN- valign="top"|[[File:Polar M400-top.JPG|none|thumb|150px|Polar M400 top]]|[[File:Polar M400-side.JPG|none|thumb|150px|Polar M400}side]]|[[File:Polar V800-top.JPG|none|thumb|150px|Polar V800 top]]|[[File:Polar V800-side.JPG|none|thumb|150px|Polar V800 side]]|- valign="top"|[[File:Suunto Ambit3-top.JPG|none|thumb|150px|Suunto Ambit3 top]]|[[File:Suunto Ambit3-side.JPG|none|thumb|150px|Suunto Ambit3 side]]|[[File:Suunto Ambit2-top.JPG|none|thumb|150px|Suunto Ambit2 top]]|[[File:Suunto Ambit2-side.JPG|none|thumb|150px|Suunto Ambit2 side]]|- valign="top"|[[File:TomTom Cardio Runner-top.JPG|none|thumb|150px|TomTom Cardio Runner top]]|[[File:TomTom Cardio Runner-side.JPG|none|thumb|150px|TomTom Cardio Runner side]]|[[File:Garmin Epix-top.JPG|none|thumb|150px|Garmin Epix top]]|[[File:Garmin Epix-side.JPG|none|thumb|150px|Garmin Epix side]]|- valign="top"|[[File:Garmin 920XT-top.JPG|none|thumb|150px|Garmin 920XT top]]|[[File:Garmin 920XT-side.JPG|none|thumb|150px|Garmin 920XT side]]|[[File:Garmin 620-top.JPG|none|thumb|150px|Garmin 620 top]]|[[File:Garmin 620-side.JPG|none|thumb|150px|Garmin 620 side]]|- valign="top"|[[File:Leikr 1-top.JPG|none|thumb|150px|Leikr 1 top]]|[[File:Leikr 1-side.JPG|none|thumb|150px|Leikr 1 side]]|}