Best Running Watch for a Marathon: Why the Polar M430 is my new go-to tracking tool for 26.2

Best Marathon Running Watch

As a running-obsessed tech writer who mainly tests fitness wearables, new toys come along pretty frequently. I get to play with artificially intelligent running coaches, heart-rate-tracking headphones and lots and lots of running watches. I’ll be honest, most devices end up back in their boxes pretty soon after I’ve written about them but every so often one product comes along and earns itself a place in my running kit bag for good. The Polar M430 is one of those. Here’s why the Polar M430 might be the best marathon running watch you can buy and is my new go-to training and tracking tool.

It’s got all the good bits of the M400 and more

I was a huge fan of the simplicity of the Polar M430’s predecessor, the M400 and it’s really pleasing to see with this latest incarnation, that Polar hasn’t messed too much with a winning formula. The the overall design is largely unchanged, in fact side by side they’re quite hard to tell apart, and that means the M430 still isn’t really going to win any style awards. But personally I don’t care, I don’t buy a running watch based on how pretty it looks on my hairy arm. Polar has also stuck with the super-simple interface and five-button controls that made this one of the easiest running watches to use on the move. When your brain’s in meltdown at mile 24, you need a watch that’s stupidly easy to navigate and the M430 ticks this box.

The M400 familiarity doesn’t mean there aren’t changes though, things have moved on. For a start there’s the addition of a built-in 6-LED optical heart rate sensor putting heart rate training skills into this M400 lookalike. While many wrist heart rate devices only have four sensors, Polar believes these extra trackers make this their most accurate yet.

There’s more good news too, while the M430 is slightly bigger, Polar has somehow made it 5g lighter than the M400 at 51g. There’s also new softer, silicone strap to improve comfort, particularly important with wrist-based HR devices where you tend to wear the strap a little tighter than a regular running watch. 

As there was with the M400, there’s a really pleasing no-frills feel to the Polar M430. There’s no touchscreen, whizzbang colour LCD gimmickry here. The retro-looking stats display is controlled by good solid buttons that respond well on the run and menus that you don’t need a manual to decipher. It’s intuitive, fuss-free and most importantly of all it’s very competitively accurate.

Polar M430

It’s reliable and accurate

From the comparison runs I’ve done, the M430’s GPS accuracy fares well while the optical heart rate is about as reliable as you can get on the wrist. Battery life is also solid, with up to 8 hours in normal training mode. Just as important, based on a fairly common training schedule of  3-4 runs a week (where one is a long run of more than 10 miles and the others are up to an hour long),you’re probably looking at having to charge this a couple of times a week. In between runs you’ll still get the all-day activity tracking, a nudge when it’s time to move and smartphone notifications.  

It’s a solid training tool

If you’re looking for a good training companion to get you to that marathon start line in good shape, the Polar M430 is a trusty servant here too. The hardware on the wrist is backed up by the increasingly capable web service and app, Polar Flow, a training partner which  allows you to use off-the-shelf training plans or build your own.  I wrote a guide to Polar Flow for here that goes into more detail about what this tool offers.

You can also sync your run data straight into Strava to keep that competitive, sorry we mean, community, edge. Plus you can pair the M430 and use the heart rate monitor to provide BPM stats to your other apps.

It does have some frills

Other nice touches include the ability to pair your smartphone via Bluetooth and have notifications pop-up on your watch, though I’ve never been a big fan of interruptions while I’m running, particularly on race day when it can be annoying getting a text message notification while you’re trying to see how fast you’re running.

There are also four different watch faces to choose from, though these aren’t going to trouble the Apple Watch any time soon. My personal favourite is the one with the little avatar that stands up and sits down when you do. Most of the time anyway. Presumably this is in case you’re somehow incapable of knowing your own position at any point during the day.

It can it go beyond 26.2

With an 8-hour battery life in standard training mode, the M430 isn’t really built for ultra running, but you can tweak the GPS settings to make less frequent readings and extend the battery life further still. Polar claimed you could get up to 30 hours but when I tested this at The North Face Lavaredo Ultra Trail, not only did the GPS lose any useful accuracy from the get-go but the battery still died after 12 hours. There is a medium setting that I’ve not yet tried which may be enough for some faster runners or shorter ultras. 

Things I’d improve on the Polar M430

Polar M430

Option to switch off heart rate tracking: Watches like the Suunto Spartan Sport Wrist HR give you the option of turning off the heart rate tracking to extend the battery life and this feels like a missed opportunity for the Polar M430. While heart rate monitoring is a really useful tool for training, many people prefer to race without it and would happily trade longer, more accurate GPS tracking for knowing your real-time HR.

Change the charging cable: One frustration is Polar’s decision to ditch micro-USB charging for a new unique dock that means you now only own one cable that you can use to charge the watch. As a travelling runner this is a bugbear of mine. Most brands seem to like reinventing the charging cable with every new watch and it was a big plus in the Polar M400 column that you could use any old Android phone cable to power up. It’s annoying having to remember to carry the M430’s own unique charging cable with you, not to mention that the new connector doesn’t stay put very well. You have to place the watch very carefully once you connected the cable to avoid it falling out.

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