Recommendations are independently chosen by Reviewed’s editors. Purchases you make through our links may earn us a commission.
Despite being Reviewed’s fitness tracker expert, Fitbit’s unfortunately timed launch of the new Charge 4 caught me off guard. But the world of fitness tracking must march on, and it’s been a year and a half since Fitbit released the wildly popular Charge 3, which we deemed the best of our own test.
Luckily, social distancing does not exclude exercising outside, at least where I live, in the U.S. Virgin Islands. After I stalked FedEx to retrieve my review unit, I was stoked to put the Charge 4—now equipped with on-board GPS—through its paces in the great outdoors.
What’s new in the Fitbit Charge 4?
From the outside, startlingly little. I studied it side by side with my Fitbit Charge 3 and can’t see any visual differences at all, in the overall style, the display menus, or even the clock faces available for download. (The charge cables are interchangeable as well.) However, Fitbit also didn’t replace the stock inch-wide plastic strap, either—it’s stiff and cuff-like and gets sweaty during exercise, and is one of the only low points on the otherwise excellent Charge devices. My Charge 3 normally sports a woven fabric band, available on special edition models and for sale a la carte, which is infinitely more comfortable.
It’s what Fitbit put inside the Charge 4 that’s new and arguably improved: that GPS chip, capable of geolocating the wearer’s location using either the GPS and GLONASS satellite networks. This is a marked change for Fitbit, which had been relying on what it calls “connected GPS” in most of its devices to map and measure a wearer’s runs, bike rides, walks, or other outdoor distance-related activities using the GPS chip in the device’s linked smartphone. The upshot: With a Charge 4, users can now record location-based details of their outdoor workouts (and glimpse data, such as current pace or distance traveled while exercising) and not have to carry along a phone.
Other new fitness features include during-workout heart-rate zone alerts (to indicate how hard you’re working, based on your pulse rate) and an “Active Zone Minutes” measurement, which gives you “credit” for working hard and an additional metric to gauge how much exercise you get overall.
Fitbit also added a few software updates to the Charge 4, such as the ability to view limited sleep data on the display (you had to open the app before); a device sleep mode to dim the screen and mute notifications during the preset window you indicate you’re usually asleep; a Spotify app to allow users to control music playing on the connected smartphone from the wrist, and Fitbit Pay. (Those last two—Spotify and Fitbit Pay—were already available in the Fitbit Versa 2 smartwatch but I don’t personally use either app, so I didn’t test them in the Charge 4.)
What the Fitbit Charge 4 does well: almost everything
The great news: Like the appearance, the top-rated activity tracking of the Charge 3 is largely unchanged in the Charge 4, and a few updates that Fitbit made are worthy ones. The main Charge 4 ‘pros’ include:
Comprehensive fitness tracking: Like its predecessor, Charge 4 measures step count (albeit high, like most wrist-worn devices) and stairs climbed. It has dedicated exercise modes to record all sorts of workouts including runs, bike rides, swims, yoga, bootcamp and more, with the ability to add and select from six at a time on the device itself. It also has best-in-class automatic activity detection to record walks, runs, swims, bike rides, or other workout sessions of 10 minutes or longer, should you forget or prefer not to turn on an exercise mode. (The data for auto-recognized activities is less detailed, but what good is an activity tracker if it doesn’t give you “credit” for activity?) It also has optional reminders to move and hourly step goals to meet, as a means to get you off your butt over the course of the day. (I noticed mine didn’t seem to fire as regularly as I’d expect, but I also get up a lot anyway.)
New to the Charge 4, Fitbit created what it calls “Active Zone Minutes” (not unlike the “intensity minutes” metric that competitor Garmin has measured on its devices for years) as a way to quantify the intensity of the user’s exercise sessions. Per Fitbit, this metric is “based on your resting heart rate and age” and uses heart rate data and the amount of time spent in each Fitbit-determined heart rate zone during workouts to award “minutes,” with the goal of achieving 150 (or more) per week. On my first workout with the Charge 4, a 37-minute easy-effort four-mile run along the beach, I “earned” a whopping 73 zone minutes—and on a repeat of the same route, completed in 34 minutes (and therefore at a greater intensity) two days later, I earned just 65. My take: For people just getting into fitness or aiming to up their intensity, seeing their efforts thus quantified could be motivating—but also should be taken with a grain of salt.
Detailed sleep tracking: Fitbit’s sleep tracking is the best I’ve used (at least anecdotally and from a user-friendliness perspective), and the Charge 4 is no different. It appears to register my various brief awakenings during the night, as well as my unfortunate occasional early-morning insomnia. I found fascinating the additional sleep metrics, such as sleeping heart rate (if it’s lower than your awake resting heart rate, it’s a sign of restorative sleep), and the data collected from the Charge 4’s built-in SpO2 sensor, which shines a specific wavelength of red light through you skin and measures the reflection back as a way to approximate the oxygen saturation in your blood. If the sensor detects low oxygen saturation levels or a wide variation from high to low, it may indicate a condition such as sleep apnea—though it is not a diagnostic tool, it could be a sign to see your doctor.
Impressive GPS accuracy: I will admit: I didn’t have high hopes for the onboard GPS in the Charge 4. Historically, I’ve had a tough time getting even the connected GPS in other Fitbit devices to work very well—however, historically I’ve tested fitness devices in my former home of New York City, a tough environment for GPS in general, with the tall buildings, bridges, scaffolding, and park tree cover to interfere with the signals.
Now that I live in St. Croix in the U.S. Virgin Islands, where the tallest building is the air traffic control tower at the airport (and the second tallest is a distillation tower at a rum factory), overhead interference is a moot concern. Still, I took the Charge 4 to the most advantageous running spot possible: A mile-long stretch of wide-open beach.
Still, on the morning of the first run, I was under time constraints and (frankly) didn’t have the patience to wait around too long for GPS to connect. I scrolled and tapped my way into the Charge 4’s run mode and noted the little “connecting” indicator on-screen. Then I fired up my Garmin Forerunner 245, which connected in a second to the satellites. I gave the Charge 4 maybe another 20 or 30 seconds, them impatiently pressed start on the Garmin and the Fitbit and took off.
To my utter surprise, the Charge 4 measured the four-mile run near identically to the Garmin running watch. Which happened again on the second run, two days later, and I waited for “connected” that day, which still took longer than the instant Garmin, but only 10 to 15 seconds. My 17-mile-plus bike ride clocked in at 17.38 on the Garmin and 17.53 on the Fitbit—and as GPS is never perfect, I think a margin of 0.15 mile (one way or the other) over an exercise effort of 1 hour, 23 minutes is A-OK.
What the Fitbit Charge 4 doesn’t do so well: heart rate features and outdoor visibility
Of course, no device—even our category favorite—is perfect. There are few promises on which I don’t think the Charge 4 delivers. Namely:
Unreliable heart rate readings and flawed heart rate zones: Wrist-based heart rate is never going to be as good as heart rate readings taken from a chest strap monitor for the very reason that your wrist is further from your heart. That said, I’ve never had good luck with the on-board heart rate tracking of any Fitbits (in particular) for measuring exertion. The Charge 4, sadly, proved no different. Despite my steady pacing on both runs, the device registered patently false high readings—there is no possible way my heart rate spiked to 199 during those efforts. My actual max heart rate, which I had professionally measured, is 190. (As an aside, Fitbit thankfully allows you to set your own max in the app. If you are able to approximate yours, from, say, a reliable recording during an all-out effort, it’s better than using the preset formula of 220 minus your age, which produces a broad average.)
What’s more, the default setting during workouts is for the device to notify you when your heart rate enters certain heart-rate zones—this is, in fact, a much-touted new feature of the Charge 4. Of course, with those false high readings came a false alert saying I was in “peak” zone, and a hearty congratulations for my effort. (Which, to be frank, it’s not always a “good job” to work near your max.) It’s easy enough to turn these alerts off, which I did. I also turned on “lap” alerts for run workouts to vibrate every mile. (You may also choose to receive alerts for kilometers, minutes, or calories burned.)
Also, as a certified personal trainer and running coach, I’m not a fan of the way these zones are defined. Fitbit opted to offer four zones, labeled “below zones” (under 57% of max, which I had to calculate, as the zone thresholds are labeled in the app in beats per minute, or BPM), “fat burn” (57% to 72%), “cardio” (72% to 89%), and “peak” (89% to 100%). There is no one-size-fits-all standard for heart rate zone training, but most models use five zones. Fitbit allows you to add your own target zone (again based on BPM, not percentage of max, which annoyingly required me to do more math), which overlays, rather than nestles among, the four preset zones. Garmin, by comparison, divides its five zones as “warm up” (50% to 60% of max), “easy” (60% to 70%), “aerobic” (70% to 80%), “threshold” (80% to 90%), and “maximum” (90% to 100%)—and while these are designed for its target endurance-athlete audience, I believe they’re more useful to a general fitness person as well. Which brings up another point: The “fat burn” zone must die. While it is accurate that sustained effort in this moderately low zone will burn proportionately more fat than carbs, you will burn more overall calories in the “cardio” zone, including more overall fat! Takeaway: If you are looking to lose weight, you are much better off working harder (for your heart, too) than limiting your workouts to the “fat burn” zone.
Hard-to-read display: My biggest complaint (aside from the heart rate monitoring… and the uncomfortable stock band): It’s really hard to read the display in the sun, both because it’s too dim and because the screen itself is so small. This wouldn’t be a huge deal for a device generally used indoors or on walks, but the Charge 4 is touted for all its great “outdoor” functions, thanks to the built-in GPS. There really should be a brighter screen mode for use during activities, or even an always-on, which would drain the battery something fierce but sure would be nice on a run so you don’t have to wait that split-second for the screen to wake.
The bottom line on the Fitbit Charge 4
Given the nature of my job, I’m often asked, “Which fitness tracker should I get?” My answer is almost always, “That depends on what you want it to do.” For dedicated runners or triathletes, I recommended a GPS running watch (and you basically can’t go wrong with a Garmin). For tech geeks who want an extension of their phone on their wrist, I point them towards a smartwatch with fitness features, such as the Apple Watch or the Fitbit Versa 2.
For those who want a great all-around activity tracker, one that puts fitness at the forefront and encourages you to move more and offers detailed sleep and other health tracking, all for a reasonable price, the Fitbit Charge 4 is your winner.
Prices were accurate at the time this article was published but may change over time.