Polar Grit X review & 99 kilometers of running

Polar Grit X Review

The Polar Grit X sportswatch first piqued my interest back when I saw that Yuri Klim, the winner of Chornohora 2020, had one.

I got to use it for a couple of weeks while training for Wet Hills and I am ready to share my impression thus far.

As the name implies, the selling point of Grit X is its… grit. Not only is Grit X a multi-sportswatch comparable to Vantage V (Polar’s flagship model), it is also supposed to be extra durable. Let’s find out what makes Grit X different from Vantage V and compare it to products from Polar’s competitors similar in class and price range.

Design and UX

Polar Grit X
Polar Grit X

Just like Polar Vantage M, this model’s design doesn’t seem to fit well into a formal style. Its “sportiness” is quite noticeable even in black, which makes it more suitable for a casual outfit. On the other hand, a leather wristband is also available for this model which likely makes it look more serious.

Though I’d say that it looks a bit too boring in black and with a black wristband, at least for my tastes.

It looks pretty bulky, but I wouldn’t consider that a flaw. It’s not exactly a plastic kid’s watch, but it’s not a humongous beast like the Suunto Spartan Sport Wrist HR (although I like that particular quality of Suunto models). The buttons are bigger than on Vantage M, which is much more convenient. All in all, Grit X’s design leaves a good impression in terms of quality.

It should also be said that this watch adheres to the US MIL STD 810 military standard, which means that it can handle mechanical damage (up to a certain point, of course), dust, moisture, water, sun rays, shaking and many other types of damage, which you can look up on the MIL STD 810 wiki page. Among other Polar models, this one can handle the most abuse.

The first pleasant difference from Vantage M I noticed is that Grit X has a touch screen. Despite it having 5 buttons, I haven’t encountered any problems while navigating it. They are rather intuitive, though I do mix them up sometimes.

Oddly enough, Polar Grit X’s special anti-fingerprint screen coating did not seem to work at all, forcing me to compulsively wipe my fingerprints off the watch face. It also has an Always-On display, which you can see well enough (or really well if you’re using the backlight).

Polar Grit X Menu
Polar Grit X Menu

Another thing that makes Grit X different is that you swipe the menu horizontally, not vertically (unlike Vantage M). It doesn’t really affect anything, but it is still noticeable. There are also two additional menus which you can open by swiping up or down: the quick-access alarm clock menu, “do not disturb” mode and “plane” mode.

Unlike the flagship models, including Vantage V, Grit X’s wristbands are detachable.

It is pretty cool that there are multiple versions of straps for Grit X:

  • Silicone
  • Leather
  • Cloth
Цвет и материал ремешков Polar Grit X
Color and material options for Polar Grit X. I would have bought the leather wristband if the watch were mine, it looks pretty cool. It is a bit expensive, though – 50€ ($60).

There are also multiple case options:

  • Metallic with metallic buttons
  • Black with black buttons
  • Metallic with white buttons
Цвета корпуса Polar Grit X
Color options for the Polar Grit X case: metallic with metallic buttons,
black with black buttons, metallic with white buttons

You can block the watch by holding down the upper left (Light) button

Technical features

  • Screen: Gorilla glass with anti-fingerprint coating;
  • Display: Always On / Color / Touchscreen / Watch face diameter: 47 mm / Resolution: 240 x 240 px;
  • Weight: 64 g / Dimensions: 47 x 47 x 13 mm;
  • Wristband material: silicone, leather or cloth / Case material: extreme high strength stainless steel;
  • Battery life: 7 days with 24/7 heart rate monitoring and notifications, 40 hours in training mode, depending on the GPS precision options and heart rate tracking. More on my personal experience below;
  • Waterproofing: for up to 100 meters. Can track swimming in open water and in pools;
  • Operating temperature: from -20° up to 50°C;
  • Sensors: Navigation – GPS, GLONASS, Galileo, QZSS; Heart rate monitor / Barometer / Accelerometer;
  • Connectivity: Bluetooth® heart rate monitors or power trackers;
  • iPhone® & Android™ compatible. Uses Bluetooth®;
  • “Smart” features: Notifications / Accepting and declining calls / Alarm clock, timer;
  • Activity tracking: step tracker / Manually designated and automatic sleep/sports/walking goals, / Sleep monitoring / Burnt calories;
  • Training: Interval training / Customized lap, autolap / Displayed information settings / Autopause / Multisports mode / Navigation / Training Load Pro™ / FitSpark™ / ZoneLock / Running index / VO2Max / Running programs / Back to Start (more on that later).

Smart features

Credit where credit’s due, the UX designers at Polar made a lot of steps forward in terms of “smart” features since Vantage M.

For example, whenever you get a notification (which tend to arrive with a delay), you can see a red circle at the bottom of the screen, and, unlike in Vantage M where you have to scroll all the way to a separate menu, you can just swipe up and see who sent what right away.

Прогноз погоды в Polar Grit X

There is also an additional weather menu, which has a decent hourly forecast for two days ahead.

I go into more detail on the sleep tracking features below.


Earlier, I mentioned that autonomy in training mode is an extremely important factor in my choice of sportswatches.

Polar Grit X’s battery allows for 40 hours of usage while using GPS and constant heart rate tracking.

Otherwise, the battery life is about 5-6 days, one or two days short of what Polar declared.


Приложение Polar Flow
Polar Flow app

You can use the Polar Flow app and web-interface to work with your watch and the data you get from it. I’ve been using Polar Flow for about two months now and I can confidently say that this is one of the best running apps I’ve used so far.

Polar Flow App

It’s a pretty simple app which aggregates various data on your activity, training, running programs and sleep.

There are four intuitively-named tabs:

  • Activity
  • Training
  • Nightly Recharge
  • Sleep

The “Activity” tab allows you to view data on your sleep, pulse, steps, kilometers, active time and calories. The app sums up your day based on hours of sleep and training, maximal and minimal pulse. You can also view that data in the scope of a week or a month.

Приложение Polar Flow: вкладка Activity
Polar Flow app: Activity tab

The “Training” tab contains more detailed information on your previous training sessions or the ones that you have yet to do if you’re using a training program (more on that later).

Приложение Polar Flow: вкладка Training
Polar Flow app: Training tab

Nightly Recharge” is one of Polar’s unique features, the point of which is to measure the quality of your sleep based on heart rate variability and hours of sleep. The tab also tells you what kind of training you can handle that given day based on this data. This metric was very unstable for the first couple of days when I was using it, but after a while it did begin to coincide with how I felt. More on this technology later.

Приложение Polar Flow: вкладка Nightly Recharge
Polar Flow app: Nightly Recharge tab

For some reason, Polar Flow has a separate tab named “Sleep“. It tracks the stages of your sleep and whether it was interrupted. It evaluates the quality of your rest based on that information. I have no idea why “Nightly Recharge” and “Sleep” are separate tabs and what the point of that separation is.

Приложение Polar Flow: вкладка Sleep
Polar Flow app: Sleep tab

You can’t start a training session in the Polar Flow app, it’s only used for data analysis. Polar Beat is a separate app used specifically for training.

You can, of course, analyze a specific training in the Polar Flow app:

Тренировка в Polar Flow с Polar Grit X
A training in Polar Flow using Polar Grit X

If you synchronize Polar Grit X with the app, the data gets sent to a web-interface with even more features than Polar Flow App.

You can also export the data into your Strava account, which I did right away.

Polar Flow Web

The Polar Flow web-interface is a bit of a rabbit hole. There is a lot of data here and the visualization is great.

Polar Flow web
Polar Flow web
Polar Flow web
Polar Flow web

Here, you can choose a running program for 5K, 10K, a half-marathon and a marathon. More on running programs later.

You can also track your sleep, fitness, activity and trainings here.

Here’s what a report on your cardio load looks like:

Cardio load report it Polar Flow Web
Cardio load report it Polar Flow Web

And this is what your Running Index dynamics look like (more on that below), as well as an estimation of how long it would take you to run certain distances:

Running Index report in Polar Flow Web
Running Index report in Polar Flow Web

Here are your VO2Max dynamics according to the results of a fitness test (I’ll go into more detail on it in the “Sports features” section):

VO2Max report in Polar Flow Web
VO2Max report in Polar Flow Web

There really is a lot of data and I can’t say that I know how to use it all effectively just yet.

Sports features

Running trainings

Беговая тренировка на Polar Grit X

You can start a running training from the menu (bottom left button) or you can just hold the “OK” button (the one on the middle right).

The watch will display the estimated battery life time, heart rate monitor and GPS signals, the pictogram of your pre-installed training or map navigation (if you are using it) and your training settings.

That same menu contains an adjustable list of available sports profiles (not all of them, though). For example, trail running wasn’t in there by default, so I had to manually add it in the Polar Flow app. You can have up to 20 different sports profiles at the same time and I can’t begin to imagine who would want more than that. The amount of profiles in Polar Flow is pretty insane and it includes swimming, dancing, rugby, sailing and surfing.

Things you can do in the training settings:

  • Regulate battery usage: adjust the frequency of the GPS signal, turn off heart rate tracking, install a screensaver instead of sports data
  • Turn the backlight on/off
  • Choose a training according to FitSpark’s™ recommendations (more on that later)
  • Choose a training out of your favorites (I set up my interval trainings first and then choose them from this menu)
  • Designate your desired race pace
  • Set up your interval timer (not that convenient, more on that below)
  • Set up a countdown timer;
  • Set up a navigation route;
  • Use navigation back to your starting point.
Trainig settings in Polar Grit X
Trainig settings in Polar Grit X

You can find more detailed sports profile settings (like training autopause) in the Polar Flow app/web-interface.

Here’s what a report on your pulse / pace / power / cadence and elevation changes looks like in Polar Flow Web:

Polar Grit X review & 99 kilometers of running 1

Heart rate monitor

Precision Prime heart rate monitor in Polar Grit X
Precision Prime heart rate monitor in Polar Grit X

Polar is famous for the precision of their heart rate monitors, since they invented the first wireless one.

Polar Grit X has its own photoplethysmographic heart rate tracking technology called Precision Prime™. Here are its advantages:

  1. The pulse sensor is synchronized with a 3D accelerometer, which excludes “noisy” signals that are made when you’re simply moving your wrist;
  2. There are a lot of small synchronized LED-lights, which allows the algorithm to pick the value received by the majority of the lights in case the data is incosistent;
  3. There is also a contact sensor on the back of the watch, which can determine how tightly the watch fits on your wrist and if it’s sliding back and forth. Any such movements negatively impact the reliability of the received data.

To be honest, there’s nothing here that you wouldn’t expect from a high-class sportswatch. Polar Grit X is absolutely precise when you’re resting or if the conditions are perfect. If it gets cold, however, or if you wear it closer to your hand than is suggested, the data goes haywire.

Here are a couple of examples:

  1. This is the interval training that got me the “elite” 68 Running Index, with 4 minute/km intervals and an average pulse of 150-160. My real Running Index, however, is about 54 and my pulse was in the 170’s/180’s. The tracker simply lost a few dozen beats somewhere along the way.
  2. And this is the recovery training, which I ran with a pace of about 5:30. For the first kilometer or so, the watch thought my pulse was 170+. After that, it finally came to its senses and lowered the value down to 140.
Интервальная тренировка
Интервальная тренировка
Recovery training
Recovery training

During the course of 3 weeks, the heart rate monitor data was more or less precise, but there’s no getting around the fact that wrist-based heart rate monitors are far from perfect as of now.

To sum up, if you can make your peace with the inevitability of occasional errors and if you don’t like carrying too many gadgets while running, Polar Grit X will suit you just fine.

But, as is often the case, those who are looking for precision only will have to buy a chest HRM. Thankfully, you can connect it using Bluetooth, but I’d recommend googling whether it’s compatible or not before buying a chest HRM. For example, Polar doesn’t even mention anything about Wahoo HRMs, which are quite popular.

Running programs

If you want to set up a program, you’ll have to do it on the Polar Flow web-interface. Click on “Programs” and you’ll see the option to start your own running program, which you’ll have to synchronize with your watch after you create it.

Running program in the Polar Flow web-interface
Running program in the Polar Flow web-interface

The minimal and maximal durations of programs are from 14 weeks up to 20 months. In case your base trainings take up more than 4 weeks, the program will update every 4 weeks in the base period (source).

As you can see, the plan considers the amount of trainings you can do, their duration and your subjective evaluation of the load.

After you start the program, the individual trainings are formed. I really like the variety their programs have to offer. There, you have: recovery, intervals, long rungs, power runs, running trainings with varying intensity, core exercise, stretching. It’s a bit of a shame that there’s no separate category for uphill running, but hey, that’s just me 🙂

Here’s how Polar describe their program (right now, I’m using their half-marathon program): “This training program prepares you for the 21k event. It is intended for experienced runners who want to improve their time in the 21k event. It can also help you prepare for the 42k training program. Your estimated final time for the event will be evaluated based on data received during the course of the program. Recent experience with long distance events, like 10k or 21k, is recommended.”.

If the race isn’t anywhere in the nearest future, the program includes a base period, which will slowly, but surely improve your fitness.

You can take a day off or postpone a training within the week. Polar says that the program adapts to the trainings you assign yourself, but I haven’t seen that yet.

Interval trainings

Interval trainings with Polar Grit X

There are multiple ways of setting up interval trainings in Grit X:

  • Set up a timer in training settings. Upper left button when selecting training type;
  • Create a training in the Polar Flow web-interface;
  • Create a training in the Polar Flow app.

There is, however, one significant “but” here (which is also the case for all Polar sportswatches).

When setting up an interval run directly on your watch, you can only set up two timers in a row. For example, you can set up a timer for your warm-up and your first interval, but you’d have to set up another “interval/recovery” timer during your first recovery. This isn’t all that comfortable and it is pretty distracting, which is why I think Garmin does this better (just take Forerunner 645, for example).

However, if you set up that training through Polar Flow (the app or the web-interface), that won’t be an issue: the watch will notify you when it’s time for the next interval and Polar Flow will analyze them in detail.

Here’s my example of an interval training report

By default, an interval run consists of a warm-up, the actual intervals and a warm-down. Even then, you can adjust that as well. You can set up your own time, distance and heart rate zone for each of those phases.

Example: 10 min warm-up in 2nd zone, (3 min interval in 4th-5th zones, 2 min rest)x8, warm-down in 1st-2nd zones. You can also run intervals by distance instead of by time.


Polar Grit X is a multisportswatch. This is a good thing for triathlon athletes since you can track each of the sports in order and track your time in the transit zone. You can, of course, track swimming, both in pools and in open water.

I use the “Multisports” feature to track my running, stop at the nearest jungle gym, do a couple of strength exercises there while using the corresponding mode and carry on running afterwards.


Navigation in Polar Grit X
Navigation in Polar Grit X

Navigation is a useful feature for anyone who likes trail running or getting into the backwoods just to see if they can find their way out.

I decided to test this feature on a 26-kilometer run in the Kyiv oblast.

I drew myself a route in Strava, exported it to GPX and imported it through Polar Flow. After you synchronize the watch, choose navigation in the training settings and it will be displayed on the screen. By the way, you have a couple of options when it comes to navigation: start to finish, finish to start and midpoint to either start or finish.

The routes in Strava are really cool: I found myself in the forest, 10 km away from the nearest town. I thought I’d check Google Maps to see where exactly I was, but it didn’t seem to know that the trail Strava told me to run along even existed.

The reason for that is that Strava uses Mapbox instead of Google Maps and the former appears to be much more detailed.

The watch shows you how many kilometers you have left to run and it will vibrate if you go off the trail. The nice thing is that it only vibrates once, thus prolonging the battery life, and immediately shows you how to get back to your route.

Back to Start

This allows you to get back to your starting point if you’re tracking your GPS in training mode.


Polar ZoneLock

This feature is quite an interesting one.

During your training, switch to the pulse screen and designate the zone you want to run in.

For example, if you want to run in the 4th zone, hold the OK button once you’re in it.

Now the watch will notify you if your pulse goes above or below the designated zone.

You can do the same thing for pace and power. I’m still not entirely sure what “running power” actually means or what it does, but if you’re doing a tempo run, ZoneLock will help you keep the pace.

Polar Fitness test (VO2Max)

This feature evaluates your aerobic fitness using the VO2Max metric. I was under the impression that you can only evaluate VO2Max while your body is under strain, the higher the better, since it’s basically testing your body’s limits.

I’m not sure how it works, but Polar says they can get your VO2Max using your biometric data (height, weight, sex, age), pulse and heart rate variability.

The Polar Fitness Test entails laying down, relaxing as much as possible and not moving for some time (5 minutes by my estimation).

Running index

According to Polar, your Running Index correlates to your VO2Max, which allows you to track your training progress with time.

Polar warns that the Running Index is evaluated on different kinds of runs lasting longer than 12 minutes and with speeds above 6 km/h.

Your Running Index value depends on your fitness and your age. Here is a table of values for men:

Running index for men
Running index for men

And one for women:

Running index for women
Running index for women

Bear in mind, the tables only concern short-term Running Index values, you can find more on the long-term in the manual.

Training Load Pro™

This is a pretty useful feature which measures your strain and your tolerance of said strain by comparing it to the previous period (a week, as far as I understand). It tells you whether you should be running more or less, whether you’re in shape or not.

Training Load Pro™ consists of Cardio Load and Perceived Load. Cardio Load is based on training impulse measurements, which depend on your heart rate while training and throughout the day as well as training time (source). Perceived Load is your subjective evaluation of how difficult the training was for you, which you have to input manually after each training.

Hill Splitter™

Polar Hill Splitter

This feature is pretty interesting as a concept: the watch recognizes whenever you’re going uphill or downhill and shows you relevant data: your distance and your pace. This is possible due to the fact that Polar Grit X has a built-in barometer. At the end of your run, you will get a report containing information on the amount of climbs/descents and your performance on them.

Alas, this feature seems to be pretty imprecise. The stairs you see on the picture above were completely ignored by the watch, even though I went up and down twice. But, for some unknown reason, it detected three climbs and five descents… during an interval training on a perfectly flat stadium.

This is what a Hill Splitter™ report looks like in Polar Flow Web:

Hill Splitter™ report in Polar Flow Web
Hill Splitter™ report in Polar Flow Web

Running Power

Running Power in Polar Grit X
Running Power in Polar Grit X

This is a very interesting measurement, well-known to bike riders: they’ve been using FTP to evaluate fitness for ages. FTP (Functional Threshold Power) is the value of a runner’s power output in one hour.

Let’s figure out what sort of problem this feature solves and take me as an example. When I was training for a marathon, I ran about 200 km a month (can’t remember how many hours it was). I ran exclusively on asphalt roads with little to no climbs or descents.

Right now, I’m training for Wet Hills, where the distance will be slightly longer than a marathon. I choose routes with climbs and descents of about 400-800 meters (the more, the better) to get my muscles acquainted with that kind of strain. This also means that I run significantly less in terms of pure kilometers, since the strain of running on a flat surface for three hours and the strain of running on hills with climbs of up to 800 meters are hardly the same. In other words, they require different outputs of power. This is why you shouldn’t rely on distance alone, especially when it comes to trail running.

Running Power considers your biometric data, the distance you’re running, your pace and whether there are any climbs. Alas, Polar are silent on what goes into the final formula for power. In the end, you get a value corresponding to your power output in one training. Combined with data on your heart rate, this can be used to plan further runs or to evaluate your shape.

I’ll be honest, I don’t know how to apply this information in any practical sense, but I definitely see the potential.

Strava Live Segments

Strava Segments

A feature for maniacs whose lives are dedicated to becoming Segment Kings in Strava. Shows the nearest segment (if you added it through Polar Flow) and your results on that segment.



As of now, this feature is only available in Polar Grit X and the new Polar V2. It consists of:

  • Smart Carbs Reminder
  • Manual Carbs Reminder
  • Drink Reminder

As the name suggests, this is essentially a reminder for you to eat or drink while running. The last two features are basically just notifications that you get every X minutes while the Smart Carbs Reminders tells you how many carbs you need based on your biometric data. More on FuelWise here

I’m not sure how useful (or not) this feature actually is, since my body tells me what I need and when I need it reliably enough. If you know someone who could use a feature like this, tell me down in the comments!

As the name suggests, this is essentially a reminder for you to eat or drink while running. The last two features are basically just notifications that you get every X minutes while the Smart Carbs Reminders tells you how many carbs you need based on your biometric data. More on FuelWise here

I’m not sure how useful (or not) this feature actually is, since my body tells me what I need and when I need it reliably enough. If you know someone who could use a feature like this, tell me down in the comments!



FitSpark™ suggests various types of training based on your Nightly Recharge™ data and physical activity.

I really like this feature because it instills some sort of discipline and reminds me that I have to do strength training, stretching and warm-ups, not just running.

You have a couple of options and you can choose any one of them depending on what you feel like doing, which is pretty cool.

You can also see what the exercises look like in the app while the watch will remind you of them with a fun animation.

Nightly Recharge™

Nightly Recharge™

Nightly Recharge™ is another one of Polar’s unique features, the point of which is to evaluate the quality of your sleep. It becomes available after three days of constant (or nightly) heart rate tracking and, of course, after you sleep while wearing the watch.

When you wake up, you’ll receive a rating that goes from “very poor” to “very good”, “very poor” being when you have a drink of rum to relieve all the stress you’ve been getting and then wake up in the middle of the night because your kid is growing her first tooth (true story) and “very good” being nothing more than a sober and healthy full night’s sleep.

I’ve noticed that my ANS status goes down after a difficult training (as well as after drinking). Am I the only one?

Nightly Recharge™ is based on the duration of certain sleep phases and heart rate variability. Since everyone’s “normal” is different here, the watch needs to figure out what’s normal for you first. This is really great because it follows the golden rule which states: “everyone has a unique body”.

It was pretty unstable for the first couple of days, but at this point the ratings Nightly Recharge™ gives me correspond to how I feel.


Polar Grit X feels more at home on rough terrain than on a stadium, given how sturdy and autonomous it is. This model will suit ultra-marathon runners just fine, since the battery life with GPS tracking and heart rate monitoring is up to 40 hours.

Polar Grit X’s heart rate monitor is quite precise, although not without the faults that plague every photoplethysmographic HRM.

The Polar Flow app is easily one of the best running apps I’ve ever used. Polar Grit X makes tracking your runs and viewing reports on them really convenient. The Power Running, Hill Splitter™ and FuelWise™ features, however, are not convincing enough to be the selling point of this model. The watch does a good job of tracking your sleep and fitness, but it lack the Recovery Pro feature present in Vantage V, the flagship model.

Grit X’s price is pretty steep, and if your intention is to use it as a device for running (especially in harsh conditions), it will definitely be of use to you. However, its “smart” functions are rather weak.

If you own Polar Grit X, I’d be glad to hear your impressions in the comments!

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