You've probably seen Fitbit and Apple share stories about how their smartwatches have saved lives. Anecdotes about users who discovered heart irregularities or finally started taking their health seriously after using their products. As companies continue to stuff their smartwatches with tech once reserved for doctors’ offices, wearables are finding their place as comprehensive health trackers. The race now is to see who can figure out what the next trendy metric will be and how to interpret that data.
With its new $330 Sense smartwatch, Fitbit is hoping you’ll want a sensor that measures your body’s reaction to stress, as well as other things like skin temperature and blood oxygen. The device also introduces a new buttonless design but otherwise doesn’t look all that different from the company’s previous smartwatches. Still, the Fitbit Sense is the company’s stab at what it calls an “advanced health” device and it’s chock full of features to help it meet that promise. It can feel overwhelming when confronted with all the new data, but the Sense lays the groundwork for a future when all this information will be put to good use.
Hardware and UI changes
One of the big changes Fitbit made here was to get rid of physical buttons completely. Instead, there’s a groove on the left side that the company has referred to as both a button and a solid state sensor. You’ll have to cover this inch-wide groove completely with your finger to trigger a “press.” You can set a long press to trigger an action like launching Alexa or tracking a workout, while a shorter tap will take you to the main watch face or wake up the screen.
It took me a while to get the hang of this. The lack of a real button makes it hard to know if I've successfully triggered the sensor. There's some haptic feedback, but this only became more reliable after I realized it’s better to use the side of my thumb rather than the middle, and apply some force to trigger the sensor.
Because Fitbit has done away with buttons, it also tweaked the navigation to be more swipe-heavy. Now, when you swipe right, you'll go back a page, while swiping up and down on the home page brings up your notifications and widgets, respectively. As before, swiping left shows the apps on your watch.
You can also customize the widgets drawer to show your favorite tools. I added things like food and water logging, along with the weather and some fitness metrics. I had to scroll all the way down to the bottom of this page when I wanted to track my calorie intake, which is where Fitbit places that widget by default. You can reorder these by tapping the Manage button at the bottom of this screen, then long pressing each widget to move it. Within specific widgets, though, you still can’t reorder each field so you can’t move calories burned above distance in Core Stats, for example.
While the new navigation feels intuitive, it's also a little sluggish and finicky. Not every swipe registers, and sometimes when I swiped left, the watch would think I tapped on the screen instead, and take me to an app I didn't want to launch. I had to learn to be very deliberate with my gestures.
It’s otherwise a very good-looking device. I like the shiny aluminum and stainless steel case, and the new sharper AMOLED screen is lovely and bright. I still prefer circular watch faces to the Fitbit’s rounded square shape, but the Sense still manages to look classy (if a little like an Apple Watch, only squatter in shape). Plus, at 45.9 grams with the band, it’s lighter than the Galaxy Watch 3, which weighs 48.2 grams without its strap. The smallest Apple Watch Series 6 is still the lightest, though, with the aluminum model weighing just 30.5 grams.
EDA and stress tracking
Aside from the changes to Fitbit’s interface and design, the Sense also adds features like an electrodermal activity (EDA) sensor and skin temperature monitoring. EDA is also known as galvanic skin response, and it looks for changes in your skin that may be caused by stress. You can manually conduct a scan using the on-watch app and select Quick Scan for a two-minute session or Guided Sessions for something more meditative.
During one of my quick scans, I sat still and covered the watch face with my palm, making sure my skin was in contact with the case. The watch vibrated to indicate the session was starting and I closed my eyes and waited for the two minutes to pass. At the beginning, my mind was still swirling from a stressful encounter, but I managed to calm down after a bit.
When the time was up, the Sense vibrated to let me know I could remove my palm. I’ll admit that on earlier attempts I lost patience and peeked at the screen to see how long more I had to sit still, and the Sense rightfully paused the session when I moved my hand. After the scan, the watch showed that I had four “changes” or “responses” during the first half of the scan, and none in the latter portion. I can’t really tell how good or bad that is, but it seems to track with my experience of feeling more frustrated at the start of the session and calmer toward the end. According to Fitbit, each “response” is a small change in the sweat level of my skin, though that still doesn’t help me gauge my performance. I got between 12 and 15 responses in subsequent tests after workouts, so a smaller number seems to be better.
While it was validating to see the watch agree that I was feeling troubled, a manual scan doesn’t feel like the best implementation of this tool. When I’m stressed, my first instinct isn’t to go to an EDA app on my watch -- it’s to fix whatever is causing my anxiety. The guided sessions might be helpful if you frequently lose sleep over the million things running through your mind at night, perhaps, but a better use of the EDA tool might be all-day tracking. Then, the Sense can gently remind me to take a walk to calm down the same way it tells me to get up to move if I’ve been idle too long. For now, though, the watch only tracks EDA when you ask it to, which might be a good thing for battery life.
Fitbit uses this data to assign you a Stress Management score, which also considers your heart rate, sleep and activity levels. Results range from 0 to 100, with higher numbers indicating “fewer physical signs of stress.” So far, despite a very stressful week, I’ve gotten a score of 89, which makes me proud but doesn’t feel accurate considering the amount of panicking I’ve done about my various deadlines.
With Fitbit Premium, you’ll get a bit more insight as to what contributed to your score, like your sleep patterns or physical activity. A deeper look at the app told me my score was dragged down by two nights of poor sleep, but boosted by several days of workouts.
I’ve only been using the Sense for a few days, though, so things might change. In which case, there’s always the Mindfulness tile in the Fitbit mobile app, which lets users set targets for the number of minutes a day they dedicate to their mental health. This tile also offers activities like “Learn Self Compassion” and “Spread Loving Kindness” in addition to guided breathing sessions to help you feel better. If you’ve ever used any mindfulness app like Aura, Calm or Headspace, these guides will seem familiar -- they’re audio files that tell you what to think about, though Fitbit’s tutorials also remind you to open the EDA app on the Sense.
Blood oxygen and skin temperature
Fitbit has been embedding blood oxygen sensors in its smartwatches for years, but it only enabled them through a software update this year. With the Sense, it introduces a new SpO2 watch face that will cycle between showing your blood oxygen saturation level, heart rate, floors climbed and steps taken. The watch measures your nightly average SpO2 percentage if you wear the watch to bed, and my result ranging between the 95th and 97th percentile was in line with what Samsung’s Galaxy Watch 3 showed.
Blood oxygen is a nice metric to keep an eye on, but it’s only really useful in detecting anomalies that could signal other underlying health issues. Since I didn’t have an irregularity during my review window, I can’t vouch for the long-term performance, but knowing it’s there offers some peace of mind.
Compared to Apple and Samsung, which track your SpO2 when you launch the tool, Fitbit will only monitor your blood oxygen levels when you’re asleep. A company spokesperson said this is because the Sense takes five minutes to measure your SpO2, and no one wants to sit still that long. Plus, the company said nighttime is when your body is most likely to show variations from your baseline levels, and that your blood oxygen doesn’t tend to change much during the day.
Fitbit adopts a similar philosophy with the new skin temperature tracking. You’ll need to have worn the Sense to bed for three nights before the watch can deliver reports on your baseline temperature as well as variations. If you want to continue to track your skin temperature after getting the baseline reading, you’ll have to keep wearing the Sense to bed, which could be annoying for some people (myself included).
If you do, though, the Sense has the potential to help catch when you have a fever, as well as detect the start of a menstrual cycle. After my third night, Fitbit reported no overall changes, which isn’t surprising since it’s the first result. (You’ll need the three evenings of data before it delivers the first report.) While it doesn’t give you a reading of your actual skin temperature, the Sense can tell you how it fluctuated as you slept, and it was interesting to see how I grew warmer as I fell deeper into sleep, then cooler again. Though this data isn’t immediately useful, I could see it alerting me to the onset of fever or an illness.
Heart rate, workouts and sleep tracking
Thankfully, you don’t have to be asleep for the Sense to monitor your heart rate. It constantly keeps an eye on your pulse to warn you of any irregularities, similar to other Fitbit products, and the Apple Watch, too. The device makes use of Fitbit’s new heart rate sensor and algorithm to see if your pulse is too high or low, based on your age and resting heart rate. Again, my heart rate hasn’t fallen outside what Fitbit determined to be my normal range, but this could help someone detect potentially fatal conditions.
The constant heart-rate monitoring also helps Fitbit better understand what sleep zones you’re in, making it a more insightful bedtime tracker than Apple’s devices with watchOS 7. The latter only tells you how long you were asleep based on your movement, while Fitbit will use your pulse to figure out if you’re in REM or deep sleep, for example. The Galaxy Watch 3 also does this and I’ve found it to offer similar data to the Sense, though Fitbit’s watch is slightly more comfortable to wear to bed.
Apart from keeping tabs on your health, the Sense can also help with your workouts. Its built-in GPS accurately measures your runs, walks, hikes or bike rides without your phone, and reports your distance and pace after you’re done. It took about 40 seconds for the Sense to lock onto a signal before my first run, but just 10 seconds when I tried again the next day in an area farther away from scaffolding and skyscrapers. That’s not terrible; in fact, it’s similar to the Galaxy Watch 3. Even so, the Sense lags the Apple Watch Series 5, which barely pauses to connect to GPS. (I was not able to test the Series 6 before this review was published, but as far as we know the GPS sensor on the Apple Watch hasn’t been updated.)
Like other Fitbit watches, the Sense can track a wide variety of activities, like yoga, circuit training, golf, martial arts and tennis. It’ll add up the amount of time you spent in heart-rate zones like fat burning, cardio or peak, then assign you points based on your age and resting pulse rate. These Active Zone Minutes were introduced with the Charge 4 tracker this year, and according to World Health Organization and American Heart Association guidelines, most people should strive to get 150 points a week.
Fitbit will also evaluate your cardio fitness, which is an estimate of your maximum oxygen uptake during intense exercise or VO2Max, and give you a score. While these numbers are mostly useful to athletes, they still provide reassurance that you’re not abnormal.
Fitbit Premium and other smartwatch features
It’s nice that the Sense is able to track so many different health metrics, but if you want to see more information or track your performance over time, you’ll have to spring for Fitbit Premium. It costs $9.99 a month and brings features like seven-day and 30-day trends for heart rate variability, SpO2, breathing rate, skin temperature changes and other metrics. Premium also unlocks the detailed breakdown into what affected your stress score and deeper details into your temperature changes throughout the night, as well as additional workout content and guided meditations.
I’m not a fan of requiring someone who bought your product to pay more each month to access their data, but at least the information Fitbit provides for free is meaningful. I also wish I didn’t have to keep wearing the Sense to bed to get continued reports on my breathing rate, heart rate variability, skin temperature and oxygen saturation.
Fitbit appears to have reconsidered its approach shortly before this review was published and is now going to allow users to access their longer-term health metrics for free. Eventually, anyway. The company issued a statement saying:
“We are making the Health Metrics Dashboard available first to Premium users as part of the perk of being a Premium member, and because we know our Premium users are interested in receiving additional data and insights about their health and wellness. Given today’s environment, we know advanced health metrics are a valuable addition to help anyone discover important trends about their wellbeing and are looking at ways to roll this out to Fitbit users with compatible (or supporting) devices more broadly in the coming months.”
Most other things about the Sense are typical of a Fitbit smartwatch: You get notifications from your phone when it’s nearby, and you can dictate replies to messages (if you’re using an Android device). You can also control your smart home gadgets with Alexa on your wrist, or play your favorite Spotify playlists and log your calorie or water intake, to name a few examples. I prefer Samsung’s Tizen OS for many of these features, as it generally offers more options, but Fitbit’s OS should be adequate for most people.
Performance and battery life
Fitbit doesn’t share information about the processors in its smartwatches, but whatever they used in the Sense could use an upgrade. The watch takes what feels like forever to launch apps like Today or Spotify. What’s more, the Sense crashed a few times during my first few hours with it. After I learned to be very deliberate with the device, I’ve grown accustomed to the delay, but in general Samsung and Apple watches are faster.
The Sense does beat its main competition on battery life, though -- it lasted about two and a half days before hitting 25 percent and warning me (through a phone alert and an email) that it was low on juice. That’s with the always-on display enabled, two nights of sleep tracking plus three brief workouts and one 40-minute yoga session. I expect GPS will also drain the battery, while disabling the always-on display should get you some hours back. That’s better than the Apple Watch Series 6 (based on our experience with the Series 5, since Apple gives similar estimates for both) and the Galaxy Watch 3, which might get you into a second day with always-on screens enabled. But generally they give up after one and a half.
As if all these features weren’t enough, Fitbit also said more new stuff would be coming to the Sense later this year, including an FDA-cleared ECG tool, Google Assistant support and spoken replies from Alexa and the Google Assistant through the watch’s speaker. There’s so much the Sense can measure that it almost feels overwhelming, but mostly I’m impressed by what the watch can do.
The majority of the health-tracking features work well and provide useful insights, and while I don’t like that you’ll need to subscribe to the Premium service for some extras, the free data is at least useful. I wish the Sense were faster and its OS more powerful. Still, at $330 it’s cheaper than the new Apple Watch Series 6 and the Galaxy Watch 3 while offering more health-tracking features. If you don’t need this slew of tools or don’t plan to wear a watch to bed, the cheaper Versa 2 is probably good enough, but for what it offers the Sense feels fairly priced.
Update (at 1:17pm ET on Sept. 22): This review was updated with Fitbit’s statement and change in approach regarding health metrics access being limited to Premium users. Since this hasn’t rolled out to free users yet, the score was not affected. A previous version of this article also said you can’t reorder widgets in the drawer below the home screen. This has been edited to clarify that you can move the widgets around but not the order of items within them.