Revision as of 13:41, 28 September 2015

The Polar M400.

The Polar M400 is a disappointing watch, with poor GPS accuracy and limited support for Cadence. Even at its low price point it I don't think it offers good value for money. If you're after a midrange GPS watch, I'd suggest looking at the Garmin 610. While it's an older watch, it offers far more features than the M400. The Garmin 220 is more expensive, but offers better functionality. For a simple evaluation of a GPS watch, I look at how well it can answer some basic questions:

• How far did I run? This is the most basic question, and the M400 has stunningly bad GPS accuracy. I've had the M400 be out by a mile on an 18 mile run, which could really screw up your marathon training.
• How fast am I running? Knowing how fast you're running can be a 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 signal alone tend to have serious problems with current pace. Without the ability to display current Pace from a Footpod while getting all other data from GPS, combined with such poor GPS accuracy, the M400 can't answer this question.
• Where am I? The M400 has no navigation features.
• What's my cadence? Cadence 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. The M400 has limited support for a Footpod, no support for Cadence from the internal accelerometer, and no Cadence alerts. It's better than nothing, but it's not great.

The M400 is not a good choice for ultrarunners, as its battery life is too short. See Watches for Ultrarunning for more details.

1 Polar M400 Pros

• The user interface is nicely designed and intuitive; the buttons, display, and the menu system combine aesthetics with usability. The M400 has five hard buttons, which I much prefer over a touchscreen interface, especially when wearing gloves or in the rain.
• Like the Suunto Ambit2 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 provides more information when you press the lap button than most other watches.
• 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.
• The cable to charge and sync the M400 is a standard micro-USB that's waterproof. Most watches use a specialist cable that's expensive to replace if lost.

2 Polar M400 Cons

• Unlike the Polar V800, the M400 has poor GPS Accuracy; see below for a detailed discussion.
• Polar has added support for a Footpod with version 1.4 of firmware, but this is problematic.
  • 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. Error: Could not parse data from Amazon!
  • Some third party Bluetooth Footpods, like the "i-gotU" will pair with the M400, but then won't display cadence and prevent the M400 from recording any distance travelled.
  • 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). Error: Could not parse data from Amazon!.
  • Even though the M400 has an internal accelerometer, this is not used to display cadence.
• The M400 claims to have more rapid initial satellite acquisition than earlier watches, but I have not found this to be the case.
  • In my testing, I found "Time To First Fix" (TTFF) on the M400 is comparable or slightly slower than the older Garmin 610. (I tested after a 4+ hour gap since the last fix as most devices will reacquire rapidly if the gap is shorter.)
  • Polar states they use 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 Bipolar and M400_downloader, but this is a far cry from the open approach that Garmin has taken.
• Like the Polar V800, the M400 uses visual tricks to appear smaller than it is. The watch is curved, so the first part of the watch strap is really part of the watch body. This can cause problems for runners with smaller or larger wrists. I have to wear the V800 and M400 over a wrist sweat band as my writs are quite small. (I have no problem with watches that appear to be bigger, like the Garmin 310XT.)
• There is no vibration alert, something I miss.
• I've found the battery on the M400 seems to run low far earlier than the claimed 8 hours. I've had the low battery alert after only 4 hours, though I was using the backlight. I've also found that leaving the M400 in the state where it is ready to start, with the GPS signal acquired, the battery will run down quite quickly. Slower marathon runners could have problems with the battery life of the M400, and it could not be used for most ultramarathons.
• The polar website has some basic functionality, but it has the feel of an unfinished beta release rather than a complete solution. This feeling of being unfinished extends to the watch itself, but at least Polar are giving a timeline for new functionality.
• The M400 will give an estimate of V̇O₂max if you're wearing a Heart Rate Monitor, but I didn't find its estimate as accurate as the Firstbeat software used by Garmin and Suunto.
• It's a minor problem, but if you have a Heart Rate Monitor strap paired with the M400 but don't have it on you, the M400 will wildly overestimate your calories and effort.

3 What's Missing

While I don't consider these missing features as 'cons', it's worth understanding the features that are missing compared with other watches.

• Altimeter. GPS is far less accurate vertically than horizontally, so a barometric altimeter can provide a much better idea of your ascent and descent. It can also be useful for navigation if you're ascending or descending a mountain. In some races I've been far more interested in how much ascent is left rather than the distance to the top.
• Navigation. The navigation capabilities are useful if there is a risk of getting lost. I've made good use of this feature when running in an unfamiliar city, or when running remote trails. There is a rudimentary "back to start" functionality that gives you an arrow pointing back, but that's a poor substitute.
• Downloadable Apps. Smart watches have got is used to the idea of a device that can be extended with new functionality, and this concept is being introduced to running watches.
• Extended battery life. Some porches can extend the battery life by turning the GPS reception off for short periods. This can dramatically reduce GPS accuracy, but it's a useful trade-off for some ultramarathons.
• Training Effect. The Firstbeat Training Effect gives you a sense of how hard each workout is, and this sometimes includes the time for recovery.
• Graphs. Instead of simply displaying a numeric value for things like heart rate, some watches will display a graph of the value over time, giving you a sense of how things are progressing.
• Running Dynamics. Some of the newer Garmin watches can show and record Vertical Oscillation (VO) and Ground Contact Time (GCT).
• Alerts. Some watches will alert you when a metric is out of range. The alert for Cadence is really useful and one of my favorite features. (Of course the M400 doesn't even support Cadence.)
• WiFi/Bluetooth Uploads. While the automatic upload of workouts via WiFi or Bluetooth to a Smartphone is nice, the upload will typically only go to the manufacturer's web site.

Please support this site This review was made possible by readers like you buying products via my links. I buy all the products I review through normal retail channels, which allows me to create unbiased reviews free from the influence of reciprocity, or the need to keep vendors happy. It also ensures I don't get "reviewer specials" that are better than the retail versions.

4 GPS Accuracy

The M400 has the worst GPS accuracy of any device I've tested, worse even than the Garmin 620 was before the firmware fixes improved things.

• Both Trueness and Precision are remarkably poor. The M400 is nearly always giving a shorter distance than I actually ran, over 250 feet/mile short on average.
• The M400 does a better on repeatability, which is a measure of how likely it is to give the same indicated distance on a particular part of the course. This tends to give an illusion of being correct, as it is easy to mistake consistency for accuracy.
• An out-and-back turnaround is challenging for any GPS watch, and this often shows up the difference between a good and bad a device. A really good GPS watch will typically be out by 2 to 3%, but the M400 does particularly badly with an error of over 13%.
• Running in a straight line on the other hand, is a fairly easy task for most GPS watches, and hear the M400 does vastly better than in other conditions. However, when it's compared to other devices, it's still one of the worst.
• Rather strangely, the M400 does remarkably well going under the bridge. It's almost like it does better without the GPS signal than with it. If you look at the image below and compare it with the V800, you can see the M400 does much better when emerging from under the bridge.
• 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 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.

This image shows the tracks from the M400 color coded for accuracy. 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.	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.
This is a detailed image of a small zigzag in my course, that shows up how well a device is tracking. You can see a mixture of colors from green indicating good accuracy through to read indicating poor accuracy. Notice that the M400 is typically tracking the shape of the six ag but is often out by a fair distance. If you were to shift the tracks so the blue lap marker was positioned over the red spot that indicates the true map position you'd probably find things lined up much better.	The Polar V800 follows this small zigzag quite well. The overwhelming majority of the lines are green indicating a good accuracy, even though the lap markers are quite spread out.
Here is the zigzag with the M400 tracks color-coded for direction, with green coming from the right, blue from the left. Typically GPS watches record tracks that have the green lines shifted slightly down and to the left, blue up and to the right. However the M400 appears to be a little more random than that.	As you would expect from a device as accurate as the V 800, the tracks are close together and follow the line of the zigzag nicely.

5 Visual Comparison

Polar M400 top	Polar M400 side
Polar V800 top	Polar V800 side
Suunto Ambit3 top	Suunto Ambit3 side
Suunto Ambit2 top	Suunto Ambit2 side
TomTom Cardio Runner top	TomTom Cardio Runner side
Garmin Epix top	Garmin Epix side
Garmin 920XT top	Garmin 920XT side
Garmin 620 top	Garmin 620 side
Leikr 1 top	Leikr 1 side

6 Comparison Table

I evaluate running watches in three distinct ways. Firstly, you can use a watch on its own, without any kind of Footpod. This is probably the most common way runners use their watch, but you miss out on a lot. The second rating is with a standard Footpod that is available quite cheaply. These Footpod's can be reasonably accurate once the calibrated, but calibration is a little tedious. The final evaluation is with the Stryd Footpod, which is vastly more accurate than any other type of Footpod, or and more accurate than GPS. The table below looks at the score, and the value for money of each watch for each of the three conditions. (I’ve also tested the Apple Watch 3, but I’ve not included it in these tables as it’s not really a running watch.)

The score is the sum of how well each watch can answer the four basic questions (how far, how fast, where are you, what's your cadence), plus some bonus points.

1. The "How far you've run" will be based on GPS only for "without Footpod" and "with Standard Footpod", but based on Stryd if supported in the "with Stryd Footpod" table..
2. How fast you're running assumes you're using a Footpod if it's supported, otherwise the rating is 0-2 based on GPS accuracy.
3. The "Where are you?" is based on various navigation features such as back to start, breadcrumbs, and preloaded maps. For some watches, you have to turn GPS off to get the benefit of Stryd, so those watches have worse "where are you scores" with Stryd than without.
4. The cadence score uses 1 point for an internal cadence sensor, 2 points for footpod support, 1 point for support from chest strap cadence, and 1 point for cadence alerts.
5. I give 1-2 bonus points for application support, 1-2 bonus points for data upload, 1-2 bonus points for Optical Heart Rate Monitoring, and 0-1 bonus points for battery life.
6. Value for money is the score divided by the price (at the time I last updated the table.) Your needs may be different, so you might weight the different aspects of the watches differently, or be basing your decision on different criteria totally. Hopefully this table will give you a good starting point for your decision.

6.1 Score Breakdown without a Footpod

6.2 Score Breakdown with a Standard Footpod

6.3 Score Breakdown with a Stryd Footpod

6.4 Basic Features

7 Navigation Features

For "navigation":

• Color Maps gives you full color maps, rather like a smart phone, with roads and paths marked out.
• Track Outline is a display of where you've run, rather like a breadcrumb trail. If there are maps, the outline is superimposed otherwise this is just the outline on its own without any context.
• Course Outline is an outline of a route that can be downloaded. I've found this useful during ultras or in unfamiliar cities where I've needed to know where to go.
• Back To Start is a simple arrow point to your starting point, so it won't help you backtrack.
• Back To Waypoint returns you to a previously marked location using a simple arrow to point.
• Compass. A magnetic compass can help you orient yourself or the map. Without a magnetic compass you have to be moving for the GPS to give you a sense of direction.

(Older Reviews: Polar RC3 GPS, Soleus 1.0, Motorola Motoactv.)