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If you practice a cardio-intensive sport, like running or cycling, you may have run across something called zone training. Here, the word zone refers to your heart rate. When you keep your heart rate in an easy zone—at, say, 50 percent of your HR maximum—different metabolic processes take place than when you push yourself and your heart to work harder.

The idea is that to improve your performance, you need to spend more time in your lower HR zones. This builds in recovery time and greater tolerance for cardiac stress. In the month that I wore Polar’s new running watch, the Polar Pacer Pro, I practiced zone training involuntarily. Despite keeping my runs at a grimly slow and unsatisfying pace and keeping my heart rate under 140, the Polar Pacer Pro simply found my workouts unacceptable.

Every day, I logged into the Polar Flow app and Polar’s software sternly informed me that not only was I overreaching, injury was likely on the way. There did not seem to be a way to tell the app that I have a resting HR of about 60 (this is good) and I’ve been running this way for over 20 years. Polar's software is probably its standout feature, but as with the last Polar watch I reviewed, it might be trying to do a little too much. 

The Pacer Pro is just one of the latest of a crop of sports watches determined to horn in on the success of the Garmin Forerunner series. What features attract both new and experienced runners? Well, like the Coros Pace 2 (8/10, WIRED Recommends), they generally hover around the $200 price point, have satellite capabilities, are lightweight, and offer data that is both easy to understand and actionable.

Polar's $200 Pacer is probably the most comparable to its competitors, the Pace 2 and the Garmin Forerunner 55 ($200). The version I tried is the Pacer Pro, which unlike the Pacer, has a barometer to measure altitude changes and little upgrades like an aluminum bezel. To be honest, it looks a ton like both the Pace 2 and Polar's previous watch, the Vantage M ($399). It weighs 41 grams, which is about 11 grams more than the Pace 2, and it has a bright, crisp memory-in-pixel (MIP) display.

To establish your baseline, Polar offers a series of fitness tests. The first test measures your VO2 max, which is how much oxygen your body uses while working as hard as you can. I lay down on the floor and started breathing. Nailed it, I thought. The Polar Flow gave me a VO2 max score of 40, about the same as an average fit man. (It's worth nothing here that absolute VO2 max may be a less useful metric than relative VO2 max, which takes into account your body weight.) Polar's results tally with my Garmin results.

I then tried to take the cycling test. Because I am a gear editor, I have an exercise bike in my basement. However, I could not use it to take the cycling fitness test because I didn’t have a third-party power meter. That's OK, I thought. I can't leave the house because I'm home with the kids, but I will simply move to the treadmill to take the walking fitness test, since—again—I am a gear editor and also have a treadmill. 

That also didn’t work, because the walking test needs to be mapped outside. Fine, I thought. I waited until my spouse got home, changed again, and went outside to start the running test. I ran three blocks down the street, keeping my heart rate within the Polar Pro’s carefully prescribed warm-up parameters, until I got to a stop light. The watch informed me that I'd failed the running test because I had to stop. 

I started to ask myself: Who is this for, again? What kind of watch makes you travel, not just outside, but to an enclosed outdoor track, and have a somewhat obscure third-party sensor just to take the baseline tests? I did finally take the test, which took about 40 minutes and gave me a VO2 max score of 30. Of these, the only test whose operation and results made sense to me was the one where I lay down on the floor.

None of the features that Polar offers on this watch are particularly new. We've seen software like FitSpark, which recommends different workouts, FuelWise, to tell you when to eat and drink, and Training Load Pro, which acts like Garmin Coach to tell you if your workouts are productive or overreaching, on previous Polar watches. 

For me, the newest aspect of the Pacer Pro was how puzzling its recommendations were, even compared to previous Polar watches that I've tried. For weeks, the watch told me every day that I was risking mortal injury by continuing to exercise. Every single other fitness tracker, even Whoop, rates me as being a pretty fit person. Polar explained that Training Load Pro only takes into account the past 28 days of training sessions, so discrepancies can throw it off; but I work out pretty consistently. Those baseline tests were just for funsies, I guess.

It was doubly puzzling because the metrics were comparable to my Apple Watch and Garmin measurements. The Pacer Pro uses three separate satellite positioning systems, and I did not notice any discrepancies on my previously mapped out routes. With two tracked activities per day for a month, I still got under the full 7 days of advertised battery life. 

Like all of Polar’s watches, the Polar Pro collects an unusual amount of data, like your ANS charge. While sleep charging looks merely at your sleep cycles and the length of time that you’ve spent asleep, Polar also checks your heart rate, heart rate variability, and breathing rate to make sure you’re actually calming down and relaxing during the first four hours you’re in bed.

After about a month of testing, the only way I would know this is meant to be a new, running-specific watch is from Polar's own marketing materials. The baseline tests incorporate both walking and cycling, so it seems pretty clear that this is a multisport watch. It also lacks many of the features that I, a runner, find handy in even a basic running watch, like Garmin’s fall detection or Coros’ super-long battery life and light weight. 

Every wearable manufacturer is trying to create software that makes it easier to accomplish your fitness goals without getting a degree in exercise science or hiring your own coach. Polar's experiments are more ambitious than most, but that generally means that I find them … not that helpful. If you already like Polar and your old M2 is dying, then this watch offers a lot of value for your money. But if I, a person who tests dozens of these things a year, have no idea how to apply the concept of running power, it's hard for me to imagine even a more experienced runner finding many of their metrics useful. 

Who knows—you could very well be smarter than I am, Polar, but I haven't injured myself yet.