Comprehensive MTB Training with The Polar Grit X Multi-Sport Watch [Review]

“Are we almost to the top yet? We’ve been climbing for three hours now.” The Grit X multisport watch from Polar can answer this and many other riding and training questions, and the battery runs up to an impressive 40hrs in training mode. That’s more twice as long as some other ride tracking watches we have tested. Weighing in at 64g, Polar says that it’s one of the lightest outdoor multisport watches on the market and at a retail price of $429.95 (available at REI, Amazon, and Moosejaw) it includes a long list of useful features.

While the Grit X will do all of the things that any other multisport watch can do and more, the clear intention of this powerful little computer is training — for any of its 130 supported sports.

Fit and function

When I first received this watch I was a little worried by the size. The bezel and face are 47mm in diameter and 13mm thick. The last multisport watch I tested that was this large had to be overtightened to keep it from bruising my wrist, and in the end, It never felt genuinely comfortable. The rounded back of the Grit X, paired with its low weight, gives it a far more cozy feel. Bands come in silicone, textile, or leather, and the silicone strap that I tested feels great in a setting that’s just tight enough to keep the watch body in place without feeling too tight when my forearm flexes on descents.

If the watch does manage to slide down to the slimmer part of my wrist it can definitely bounce around a lot, often enough to press the “lap” button a few times. Fortunately, this only happens on extra rough descents, where any watch would eventually rattle loose, and I have ben able to remedy the issue by sliding it a little further up my arm before descending those trails the second time.

The bezel and face of the Grit X are tough, and though it sits a little higher off the skin I don’t have any issues with the watch getting caught on things or showing wear from the countless time I’ve banged it against something. Regarding overall durability, Polar says that the Grit X is “Tested against military standards (MIL-STD-810G). [With an] operating temperature: from -20° to 50°C. Temperatures below -10°C may affect battery life and performance.” Those standards are at least as rigorous as mountain biking.

General use

For folks who simply want to track their rides, and who may look at heart rate and speed on certain segments of the trail, the Grit X has you covered. Riders can pair it with all of their favorite route-saving and sharing applications, and it’s super easy to load route files for clear realtime turn-by-turn directions while on the trail. This may quickly become a favorite feature if you often ride in areas that are new to you. I have used it to load popular rides in unknown forests, making for an enjoyable day without all of the usual wrong turns.

If you need to use paper maps, or generally like to know what direction you’re headed in, the watch’s magnetometer-based compass will help you find the way even without a GPS signal. The GPS and barometric altitude sensor in this watch are second to none of the others I have tried. It picks up a signal immediately, and I haven’t yet been able to lose the GPS signal while riding high alpine trails in Italy, Switzerland, or France.

Are we still going the same direction? Wasn’t the sun over there an hour ago?

The watch also displays what’s called the Hill Splitter while climbing to show you how much further the top or bottom of a slope is, and you can compare your performance on ascents and descents between different rides. If you’re looking for a simple fitness metric, or want to chip seconds off your descending times, this feature is worth checking out.

For riders and racers who prefer longer adventures, the Grit X has a set of reminders to help you fuel and hydrate properly. Once you have logged some data the software can estimate how much fuel you need to bring for a given ride, hopefully preventing the dreaded bonkfest. You can program drink reminders at any interval you choose, which might be a lifesaver in the hot summer months.

Currently on flat ground, stationary.

If you can’t disconnect from the phone during a ride the Grit X makes checking emails, calendars, and texts easy, with all of the usual updates that we have come to expect from a “smartwatch.” For folks who prefer an offline lunch spin, these features are equally easy to turn off in the main menu or in the Polar Flow app.

Training

One comfortable heart rate monitor.

While wrist-based heart rate monitors (HRMs) are not as accurate as an obnoxious chest strap, the Polar Precision Prime wrist HRM will cover most riders’ beat needs. When tested against a chest strap its accuracy is on par with similarly priced multisport watches I have tested. The watch will set training zones for you based on your typical training loads and sleep regimen, or you can enter them manually. It monitors your heart rate continuously, whether in training mode or not, to more accurately determine your body’s daily calorie expenditure.

As with most fitness devices, you can use Strava Realtime Segments on the Grit X to push yourself. “Get alerts about nearby segments, see real-time performance data during a segment and check your results right after you finish.” While this feature isn’t my jam I can definitely see the benefit for athletes who want to compete with other people, particularly during the pandemic.

The Grit X also lets you know if you are keeping up with your riding or other fitness goals.

The Grit X has a Nightly Recharge function that records how well you sleep, and for how long, to help you rest better between training sessions. I have slept with the watch on enough to appreciate the data it collects, but I would have to be more dedicated to a training goal to sleep with it every night. While its rounded back is more comfortable than some other watch bodies, it’s not exactly a soft pillow to lay on.

Once you dig into the strength, cardio, or core menu options there are examples of each exercise or stretch to follow.

The Fitspark Daily Training Guide is another helpful addition to the watch’s training features. It looks at your sport training data and sleep log and suggests workouts and stretching sessions to help create a more well-rounded fitness program. The software includes loads of realtime workout guidance for aerobic fitness, strength, mobility, and a separate block for core work. All of the workout algorithms are based on the World Health Organization’s recommendations for adult weekly physical activity. Initially, I thought the Fitspark Daily Training Guide was too easy, but the fact that it reminds me to do the work every day means my fitness improves drastically compared to the forgetting that I was doing before.

Additional features

Swimming and running metrics can all be analyzed and evaluated with the Polar Flow app, and there is even a training program for running that’s tailored to your schedule and fitness level. The watch body is waterproof up to 100 meters, so swimmers and divers alike can track their strokes. I have jumped in the Mediterranean sea with this watch on multiple times and it was convenient to be able to check the time while cooling off after a long ride.

Weather in the mountains can flip without notice, and the two-day forecast report on the watch is certainly helpful. While you can typically gaze upon the great sky prediction on a phone, it’s nice to be able to check it when the pocket computer is packed away.

Finally, the watch has one other self-care component called Serene breathing exercises. With the expressed aim of helping relax the mind and manage stress, Serene uses visuals and vibrations to guide you through deep breathing exercises in a series of stages. This is one of the elements I appreciate most about this multisport watch, as mindfulness and the benefits of being present and turning off the brain for a moment are easy for me to forget about.

Polar Flow software

Th is screenshot shows one of my typical lunch laps. You can slide the green “rider” icon around to look at specific segments of the ride.

All of that great data can be analyzed and aggregated in the Polar Flow app. The Grit X is “Compatible with all standard BLE heart rate sensors and running cadence and power sensors as well as cycling speed, cadence, and power sensors.” You can really pack this thing full of info.

The easiest way to set up the watch or change functions and features is through the web or phone app. You can enter all of your data and functionality preferences, as well as any fitness goals or restrictions you may have. You can change things around at any time by clicking a few buttons, so if you want phone alerts on one ride and not the other you won’t need to call the IT department to make it happen.

A little further down the page on Polar Flow you can look at heart rate and speed at any given point, and there are other variables to swap in depending on what you want to analyze.

For cycling, without cadence and power sensors hooked up, the Flow app allows you to look at how much of your ride was uphill verses downhill, average and max speed, average climbing grade, average heart rate, calories burned, ambient temperature, and loads more. You can set laps with the watch to look at specific segments of a workout or descent and go back and analyze that particular segment at home over a cup of tea. You can also share all of the data with coaches or friends who are helping you push toward specific goals.

There is space to enter notes and how the workout felt that can then be sent to a coach. For this particular lunch lap I was feeling hungry as I forgot to eat before climbing.

If you simply want to look at your ride routes and share them with friends, all of that data is there as well. Riders can connect Polar Flow with Strava, Komoot, and other popular apps to share ride files in just a few clicks. If your Strava account is linked to the Singletracks trail database, your ride will be automatically loaded so you can share trail info with our community.

Conclusion

The Grit X uses a proprietary charging chord that you’ll want to keep in a safe place.

This watch is tough. It’s the first multisport piece I’ve tested where I didn’t put a protective cover over the face because Polar said it was tested and tough. They didn’t lie. I have crashed with this watch a few times, scraped it across rocks during hike-a-bike sessions, and banged it against my frame on multiple occasions. It still looks good enough to wear with a suit. It’s not the least expensive timepiece, but if you dig the training and tracking features it is one that will last a while. The massive battery life and broad functionality make it a great companion for training and adventures alike.

⭐️ Find the Polar Grit X online at REI, Amazon, and Moosejaw.

We would like to thank Polar for sending the Grit X for testing and review.

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