The Fitbit Sense replaces the Ionic at the top end of the company’s family of fitness and health smart-watches and activity trackers. On top of every Fitbit fitness metric and a built-in GPS, it measures your stress levels, skin temperature, blood oxygen, electrodermal activity, ECG, and heart-rate variations.
Fitbit calls the Sense an “advanced health smartwatch”, and it’s on health that it beats other Fitbits such as the Versa 3, which launched at the same time but focuses more on core fitness features.
It’s a great smartwatch, only held back by a bad wrist strap and the fact that a few too many of the best health tracking features are held back for paying Fitbit Premium subscribers.
Design & build
The Fitbit Sense is a good-looking watch with a bright screen and a responsive user interface.
The main body is made of aluminium with a polished (medical-grade) stainless steel finish. This high-quality stainless steel ring is required to get some of the more advanced sensor readings. It’s also more durable; the medical-grade refers to its corrosion resistance.
It features a big 1.58in OLED display with a resolution of 336 x 336, which is bright, and easy to read even in direct sunlight.
The physical button found on the Versa 2 has been replaced with a new haptic sensor on the left edge – so there’s no physical button to push in, but instead a touch-sensitive area that vibrates a little to let you know your touch has been recognised.
Also new is the included swappable strap called the Infinity Band, and it takes a little getting used to. Instead of a classic watch strap, there’s a peg you push through the best hole for your fit, and then you close it through a loop.
This is my biggest gripe with the Sense: the band that it ships with just isn’t as secure as the old watch-buckle. I had it fall off my wrist within 24 hours, and when you consider it’s used in physical workouts, that isn’t good enough. I would seriously suggest you purchase one of the accessory straps that feature more robust buckles.
At least Fitbit has made swapping the bands much, much easier with the Sense. Changing the strap on the old Versa and Versa 2 was as fiddly as fiddly can get. This time, you just have to push a tab forwards and gently slide the strap off, and then click a new one in.
As for colours, the Sense is available in Graphite Stainless Steel with a Carbon band, or Soft Gold Stainless Steel and Lunar White band.
The Ionic, like the Fitbit Surge that it replaced, was marketed as a sports smartwatch. Sports was regarded as the pinnacle of the fitness tracker, but with the Sense Fitbit has pivoted away from sports to more of a focus on physical and mental health, as well as including all the expected fitness features.
Medical practitioners are increasingly warning that stress can be as dangerous as physical illness, contributing to high blood pressure, heart disease, obesity and diabetes. Fitbit has new tools in the Sense that can help identify stress, and therefore can potentially help you recognise and manage it.
Fitbit gives you a Stress Management Score that calculates how your body is responding to stress based on your heart rate, sleep, and activity level data.
It’s helped by a new Electrodermal Activity (EDA) sensor that measures changes in the resistance of the skin to a small, undetectable electric current in response to sweat secretion. EDA measures the intensity of emotion, not its state, so an increase in conductance can be caused by both positive and negative emotional states. You can log your mood (stressed, calm, etc) after the EDA scan.
Users can then see a graph of their EDA responses in the Fitbit app, which tracks trends over time.
Some ways of managing stress include increasing physical activity and mindfulness – to which end the Fitbit app includes a guided meditation feature. After your session is over, prompts in the mobile app let you reflect on how you feel and see if these have a positive effect on your stress levels.
You can set a weekly mindfulness goal, track daily mindful minutes and days, and see trends. The score ranges from 1-100, with higher scores indicating your body is showing fewer physical signs of stress. It’s paired with recommendations to better manage stress, such as breathing exercises.
Fitbit Premium members will get a detailed breakdown on how the score is calculated, which consists of over 10 biometric inputs, including exertion balance (impact of activity), responsiveness (heart rate, heart rate variability and electrodermal activity from the EDA Scan app), and sleep patterns (sleep quality). This will be a common theme as we go on, with some of the best tracking features in the Sense held back for subscribers.
There’s also a new skin temperature sensor, which can be used to indicate the onset of a fever or illness (can you think of any big ones going around?), as well as linking up with Fitbit’s existing health tracking for menstrual phases. This is done at night, when the Sense will measure your skin temperature variation to see trends, so it doesn’t display one-off readings.
It takes the Sense three nights to calculate your baseline skin temperature. You then see nightly average variation compared to that baseline temperature on the Temperature tile on the Today screen in the Fitbit app.
If your temperature is spiking or dropping compared to normal, this could be a sign of illness. Few of us use a thermometer every day, so it will be interesting to see if this works – though I’ll have to wait for an illness to report back on its worthiness.
SpO2, ECG & more
Like other Fitbit smartwatches, the Sense can measure your average SpO2 levels – the amount of oxygen in your blood. This data can be used to detect your breathing rate alongside how well blood is being transported throughout the body. Low levels of oxygen can result in serious symptoms such as hypoxemia.
Note that the Sense only tracks your oxygen saturation levels while you sleep, unlike the Apple Watch 6 or Withings ScanWatch, both of which can take a blood O2 reading in just 15 seconds at any time of day. Check out our full comparison between Fitbit and Apple Watch for more on how the two brands stack up.
An ECG sensor can assess your heart for atrial fibrillation (AFib), to detect common heart rhythm irregularities, but the ECG isn’t active yet – Fitbit says it will be added via an update in October, at which point you’ll be able to get a reading by opening the ECG app and placing your index finger and thumb on the opposite corners of the metal frame for 30 seconds.
An improved heart-rate sensor helps to drive another new feature: heart-rate notifications when it detects that your heart rate is above or below your normal threshold. This can be useful to detect bradycardia (a heart rate that is too slow) or tachycardia (a heart rate that is too fast).
Fitbit Premium subscribers can see their heart-rate variation (HRV), the time between each heartbeat. Again, this can indicate the onset of illness, as well as fatigue and stress. Premium subscribers also get a new Health Metrics dashboard that tracks your 7- and 30-day trends for metrics like heart-rate variation, breathing rate per minute, oxygen saturation, and skin temperature variation.
As I’ve said, beyond the new health tracking tech the Sense also has an impressive array of fitness features – indeed no other Fitbit has more than the Sense.
Of course, it tracks activities such as Steps, Distance, Floors Climbed, Active Minutes and Calories Burned.
The Active Minutes metric has been improved with the newer Active Zone Minutes (AZM) metric, and the Sense buzzes when you enter a new Heart-Rate Zone: Fat Burn, Cardio, or Peak. This gives you instant notice that you have reached a target zone, and whether you need to push harder in your workout or pull back. AZM was first seen on the Fitbit Charge 4, and has now been rolled out on most Fitbits.
The Sense can also give you real-time stats for over 20 exercise modes during your workouts. These can be set manually, or Fitbit’s SmartTrack tech can automatically recognize and record exercises such as running, cycling, swimming, treadmill, weights, yoga, and circuit training.
The Sense has GPS built-in, so you don’t need to lug your phone around with you on a run or bike ride. It also allows you, after outdoor exercise, to check your Workout Intensity Map in the Fitbit app to see your heart rate zones throughout your mapped route, plus distance and pace by kilometre or mile.
The watch also includes a 6-axis gyroscope to track strokes and laps while swimming. By contrast, the Versa 3 and most other Fitbits don’t include gyroscope but instead calculate laps for swimming based on distance.
The Sense, like all the latest Fitbits, offers advanced sleep tracking, showing the light, REM and deep sleep stages and scoring you on the quality of your sleep based on your sleeping heart rate, time spent awake, and time in sleep stages. You can also get a sleeping heart rate measurement, but this is yet another feature kept back for Fitbit Premium subscribers only.
Battery and charging
Fitbit claims the Sense has a battery life of 6+ days. I haven’t had the Sense that long, and will update this review when I’ve gone through a week of testing.
Of course, the battery life depends on your usage – using the GPS will burn through battery faster than without. Frustratingly I can’t find an on-screen battery indicator on the watch, although you can see it easily in the mobile app.
The Sense features a new charger type, which connects magnetically to the back of the Sense. I’d hoped it would connect any way round, but it fits in just one alignment. While I like the fact that it’s smaller than the chunky Versa charger, the fact that it lies awkwardly while charging is not so great.
It takes about two hours to fully charge from zero, though the company says that it takes just 12 minutes of charging to give you a day’s battery life.
Software & apps
While the Fitbit smartwatches are no match for Apple or Samsung when it comes to running a wide range of apps, they do at least handle notifications well. Alerts for calls, texts and calendar events are supported, along with apps such as WhatsApp, Gmail, and Facebook.
Also handy are silent alarms that buzz on your wrist, in theory without waking your bed partner – although if used with a metal strap I can confirm that the buzz can be audible to others. Smart Alarm is a setting that lets you wake up at the best time during your sleep cycle (during light sleep), up to half an hour earlier but no later than the time you set.
In terms of apps you get the obvious – timers, weather, and a calendar, but also a meditation app and Fitbit Pay for contactless payments.
Spotify, Pandora and Deezer are there for music control, and you can also download apps for services such as Uber, Spotify and airlines, along with other fitness and sport apps. There are still more apps on an Apple Watch, but the Sense will cover most of the essentials.
The Fitbit Sense also supports Amazon’s Alexa, with Google Assistant coming in “late 2020”. With Google in the process of buying Fitbit it’s an obvious addition, as are the Android-only features like sending quick replies and voice replies right from your wrist when your phone is nearby.
Price and availability
The Sense costs £299/$329. That makes it the most expensive Fitbit by some way – even the new Versa 3 is significantly less at £199/$229. Check out our Fitbit ranking to see which other models we recommend, or find the latest Fitbit deals if you want to save a little.
Still, it’s fairly typical pricing for a high-end smartwatch, and is still less than the latest Apple Watch or Samsung Galaxy Watch.
If you want to get similar health tracking for less – at the cost of access to many of the smart features – it’s worth considering the Withings ScanWatch, which offers even more comprehensive health features in a classic analogue watch design.
Otherwise, check out our rankings of the best smartwatches and best fitness trackers to see what else is out there.
As you’d expect, there’s also a range of straps and bands to go with the Sense. Accessory straps include woven and knit bands, silicon sports bands, and Horween leather bands. There’s even a range of Pendleton bands made from recycled plastic fibres.
And as I’ve already mentioned, to get the most out of the Fitbit Sense you’ll really need a Fitbit Premium subscription – for better or worse. If you’re knew to Premium you’ll get six months free with the Sense, but otherwise it will cost you £7.99/$9.99 per month.
The Sense adds a lot of new health features at the top-end of the Fitbit range. You could call it the hypochondriac’s smartwatch, it’s so full of warning signs, but there’s a lot here that will help indicate serious health problems that you will have the chance to improve.
Mindfulness might seem a little kooky to some and a concern for those with too much time on their hands, but there is no denying that stress can affect us all, and managing it will quickly bring not just mental but long-term physical health benefits.
If fitness is all you want an activity-tracking smartwatch for, then the cheaper Fitbit Versa 3 offers everything you’ll get in that respect with the Sense.
For all-round physical and mental health tracking, the Sense is the Fitbit with it all.