With the Loop, Polar is clearly coming for Whoop. Like its inspiration, the Polar Loop is a screenless fitness tracker that measures your activity, heart rate, and sleep with a design that combines a simple black wrist strap and a stainless steel case. At $199.99 for a one-time purchase and with no additional fee for most features, the Polar Loop significantly undercuts the Whoop 5.0, which starts at $239 per year. The Loop is more limited than the Whoop 5.0, as it lacks sensors for skin temperature and blood oxygen levels, and doesn’t offer as much holistic advice or long-term health tracking, but it's certainly a compelling alternative when it comes to cost. That said, if you don’t mind a screen, the Fitbit Charge 6 ($159.95) is a better value than both, so it remains our Editors' Choice winner.

Design and Sensors: A Whoop-Like Look With Fewer Health Features

At a glance, the Polar Loop looks just like a Whoop tracker, which isn’t exactly a compliment. In my review, I noted that the Whoop 5.0 has a functional aesthetic that vaguely resembles an ankle monitor worn by those on house arrest. Similarly, the Polar Loop blends right in at the gym but sticks out like a sore thumb when paired with a fancy outfit for a night on the town.

Like the Whoop, it circles your wrist with a thick, black, woven fabric band that holds a metallic sensor on top. It’s slightly bigger than the Whoop 5.0, measuring 1.7 by 1.1 by 0.4 inches (LWH) compared with the Whoop's 1.37 by 0.94 by 0.42 inches. It's lightweight at just an ounce, and it never irritated my skin like the older Whoop 4.0. It has a somewhat durable WR30 water-resistance rating, meaning it can withstand immersion down to 30 meters (98 feet). It's rated to withstand temperatures ranging from -4 to 122 degrees Fahrenheit.

(Credit: Andrew Gebhart)

The band feels comfortable to wear, and it dried off quickly when I rinsed it after a workout. Polar includes both small/medium and medium/large bands in the box to ensure you can find the right fit. I tested mine with the larger of the two.

Looking closely, the Polar Loop distinguishes itself from Whoop with subtle details. The fabric has a different pattern and closes with Velcro after looping through a separate metal buckle, which is not part of the stainless steel sensor. Whoop’s band attaches to both ends of a clasp that closes around the sensor and swings open so you can remove it. I found Whoop more prone to pinching my skin when finding the right fit initially, but easier to put on and take off after that. I often had to thread the Polar Loop’s band back through the buckle each time I put it on or took it off, but this is a minor gripe, as it only took moments.

(Credit: Andrew Gebhart)

Under the surface, the Loop features an Optical Gen 3.5 sensor that measures heart rate and heart rate variability, and an accelerometer to detect movement. It uses Polar's Precision Prime technology to rule out motion artifacts, or data distorted by movement.

The Polar Loop lacks several sensors commonly found in other wrist-based wearables, such as a barometer, gyroscope, or magnetometer. It also omits sensors for electrocardiography (ECG) and blood oxygen saturation (SpO2). It has a skin-temperature sensor, but it's inactive and intended only for developers. The Whoop 5.0 has skin temperature and SpO2 sensing, while the Fitbit Charge 6 offers all the health-tracking capabilities of the other two, plus ECG readings.

Setup and App: Easy Pairing and a Flexible Activity Diary

The Loop sensor comes packaged with two bands, a metal buckle, and a charging cable (no brick). To get started with the setup process, download the Polar app (for Android and iOS) and create an account if you don’t already have one. Plug the sensor in to wake it up, then sync the device with your phone via the app.

(Credit: Andrew Gebhart)

The Polar app will show you a video about finding the right fit, with important information that I didn’t find elsewhere. It suggests using the tracker on your non-dominant hand, with the small oval at the bottom of the sensor pointed toward your thumb, and offers instructions for attaching the buckle to the strap. The video also shows how to adjust the band sizing by sliding the sensor toward or away from the buckle.

Fitting the buckle into the fabric below the sensor was a bit of a pain, but once I wrestled it into place, it only took me a minute to find the right fit. Once in place, you'll tell the app which wrist you want to use. It will then ask for your preferred sleep time and duration, then prompt you to enable automatic exercise tracking. Finally, it updates the Loop's firmware while providing a walkthrough of its various features.

(Credit: Andrew Gebhart)

Once setup is complete, you need to wear your device for a couple of days so it can learn about you and start populating the app with your collected data. Then the app's main page will show a diary of your data, along with the device’s battery life at the top. Tap the gear icon in the upper right to customize what the diary shows and how it’s sorted. Options include the highest and lowest heart rates of the day so far, sleep stats like your overnight recharge status and heart rate variability (HRV), and your cardio load status (a metric that indicates the cardiovascular effect of your training over time).

Tapping any item in your journal opens up more detailed stats, and tapping the device itself opens a settings menu where you can toggle various alerts or force a data sync. Back on the main page, you can hit the menu icon in the upper left to access other features and data. Go here to manually start a training session, see a calendar of your workout progress, and check your sleep data.

(Credit: Polar/PCMag)

This menu also lets you access the Polar Fitness Program, a premium service that offers training guidance for any sport tailored to your current skill and fitness level. Polar offers a 30-day free trial, after which it costs $8.99 per month. I tested the Polar Loop without the premium subscription.

Battery Life: A Week of Use Between Charges

Thanks to its screenless design, you shouldn't have to take the Loop off to charge very often. It lasted eight days in testing, matching the company’s estimates.

(Credit: Andrew Gebhart)

In terms of battery life, it outperforms most fitness trackers with a screen, including the Fitbit Charge 6. The Charge 6 lasted just three days in testing with the always-on display enabled, or 4.5 days with it disabled, falling short of Fitbit's one-week estimate.

The Whoop 5.0 outshines both the Loop and the Charge 6 on this front. It lasted 16.5 days and includes a portable battery pack that snaps onto the device for on-the-go recharging. With Whoop and its wireless charger, you essentially never need to take off your tracker.

That said, the Polar Loop's weeklong battery life is more than sufficient for most needs, especially given the price difference between it and the Whoop. You can plan to charge it once a week on a lazy afternoon. It roughly matches the seven-day battery life of our favorite smart ring, the Oura Ring 4.

Sleep: Detailed Insights Hidden in a Cluttered App

The Polar Loop tracks and charts the amount of sleep you get, the duration you spend in each sleep cycle, the regeneration of your slumber from REM cycles, and the solidity (the level of continuity weighed against interruption). Over a month of testing, it consistently provided an accurate and detailed breakdown of my sleep.

It uses this information to score your sleep as well, though I found the associated chart for this metric a little too simplistic to be helpful, despite its attractive color palette. Polar also grades your Energy Boost from sleep and your Recharge Level to help you understand how well you've recovered from recent training and stress.

(Credit: Polar/PCMag)

Oddly, Energy Boost and Recharge each have their own cards on the app's main journal page, and you need to scroll down to the section that shows sleep time to see the collected information on sleep cycles and your sleep score. Alternatively, you can find the same information via the menu button in the upper left, but I do wish the journal page were a little less cluttered.

Still, Polar provides an impressive amount of information, and its numbers matched those from comparable devices to a reasonable degree. I tested it for a couple of weeks while wearing the Whoop 5.0 on my other wrist, and then against the Apple Watch Ultra 3. Polar’s sleep times consistently aligned with the other trackers.

Sleep charts from the Polar Loop also showed similar ebbs and flows as Apple. The Apple Health app helpfully shows your sleep breakdown alongside key overnight health stats, such as respiration rate and heart rate. Polar measures both of those as well, but you need to find them on a different card in the journal, which again makes me wish the app were a little better organized. At the very least, I was able to find Polar’s data. Whoop makes it difficult to find minute details, instead highlighting prescriptive information like recommendations to improve sleep debt and efficiency.

Exercise Tracking: Reliable Metrics With Some False Starts

The basic version of the Polar app doesn’t offer much in the way of recommendations, but provides some basic takeaways under sleep, such as “prioritize a regular rhythm,” and cardio load feedback indicating how your current average training amount will affect your fitness level. Otherwise, it keeps to the basic stats. If you’re looking for holistic advice, Whoop offers plenty, as does the Fitbit Charge 6 with its Daily Readiness Score.

The Polar Loop offers a basic VO2 Max fitness test to show how well your body uses oxygen during intense exercise. It does not support the running performance and power tests available on more advanced Polar devices, such as the Grit X and other smartwatches.

I took the Loop's VO2 Max test three times. It can be tough to figure out how to start it, as you need to go to the menu in the upper left of the app and hit Start, then tab over to Testing. It takes the app a second to recognize and sync with the wearable when you first open up the menu.

For the test, the app asks you to lie down and relax for roughly five minutes. Once, I coughed during the process, and it asked me to restart. On the other two occasions, the app reported my fitness as Very Low, with a VO2Max score of 25 each time. A score of 26 to 31 qualifies as the next level, called just Low.

On both occasions, I ended up feeling a bit self-conscious during the process as I gradually became aware that my asthma was causing a slight wheeze. I suspect that had something to do with my score, but Polar doesn’t provide much detail on contributing factors.

Otherwise, the Polar Loop measures your activity throughout the day, estimating calories burned and steps taken. The step counts I saw were sometimes a few hundred off from the number shown by the Apple Watch Ultra 3, but both still generally reflected whether I had walked a lot or a little.

The calories burned numbers were wildly different between the two devices. I suspect Apple only shows the calories expended during activity, whereas Polar adds that number to the amount you naturally burn throughout the day. Polar is also pretty strict with its inactivity notifications, as I’d get them even late in the evening, when I was settling in to watch a video game or a TV show.

(Credit: Polar/PCMag)

When automatically tracking exercise, the Polar Loop tended to be a bit overreactive. I go to a personal trainer twice a week for high-intensity interval training (HIIT) sessions, and on a couple of occasions, Polar thought I had completed my activity and stopped measuring my exercise when I was simply taking one of the breathers customary of the format. When I wore it alongside the Whoop on the other wrist, Polar would produce the exercise results much more quickly, but its competitor never jumped the gun in the same way. Polar reliably started at least one automatic session for each of my gym trips, but sometimes missed the latter half of the session.

During these activities, Polar’s calculations for average heart rate and calories burned matched those from the Ultra 3 to a reasonable degree. Moreover, their charts of my workout heart rate showed similar rises and dips. However, during one workout, Polar showed an extreme spike of 198 beats per minute (bpm), whereas the Ultra 3 showed my max heart rate as 176bpm. Otherwise, the number consistently stayed within 3 to 5bpm of Apple’s. I’d call the one spike erroneous on Polar’s part, but a minor blip since it only happened once.

I manually tracked a 30-minute run with the Polar Loop on one wrist and the Apple Watch Ultra 3 on the other, and the two impressively stayed within 1 to 2bpm of each other throughout. Even when I sprinted at intervals, the Polar Loop kept up with my heart rate changes as quickly as the Ultra 3.

While the Polar Loop doesn’t have built-in location tracking, it can use your phone’s GPS to map manually tracked outdoor exercises. Otherwise, the Loop monitors pace, calories burned, and heart rate zones during outdoor running. The Ultra 3 and the Fitbit Charge 6 offer some additional running metrics you don't get with the Polar Loop or the Whoop, including cadence and stride length.

The Polar Loop occasionally got confused and automatically tracked a workout I had already started manually in the app, generating duplicate results. Moreover, every time you check the stats page, it asks you to assess the difficulty of your workout and how you felt afterwards. I didn’t see much difference in the advice based on my answers to these questions, so I found the extra step to get to the stats annoying.