Fitbit Flex 2 or Alta HR: which is right for you?
Fitbit knows the importance of keeping its fitness tracker line fresh. Earnings figures released earlier this week show that 84% of its revenue in the three months of this year came from new products. This includes the company’s flagship Charge 2 device, Alta HR and Flex 2. All three wearables bought welcome new additions, without breaking too much ground.
Essential reading: Choosing the right Fitbit tracker
The Flex 2 is an update to the San Francisco’s original Flex device released back in 2013. This is the company’s slimmest tracker yet and the only Fitbit device that is water resistant. Here’s how it stacks up against the Alta HR.
Fitbit Flex 2 or Alta HR: Design
The Flex 2 is 30% smaller than the original model and features a removable core unit along with interchangeable slim, classic fitness bands in seven colors. The tracker slots into bands, bangles and pendants so there are quite a few customisation options.

The core unit has a very small form-factor measuring 31.7 x 8.9 x 6.8 mm. Inside you will find a 3-axis accelerometer and vibration motor. A simple LED display uses 5 color-coded lights to show progress toward your daily goal, and keeps you connected with call and text notifications.
There are a number of design options to help you tailor the look to your liking. You can choose from a range of luxe, premium mirror-finish bangles in silver stainless steel, and 22k-plated gold or rose gold stainless steel, or elegant lariat-style necklaces in silver stainless steel or 22k-plated gold stainless steel.

The Alta HR looks very much like its much loved predecessor. Fitbit calls it the “world’s slimmest” wrist-worn tracker with a continuous heart rate sensor.
The gadget sports a discreet, slightly curved, touch-screen, OLED display with a 128 x 36 pixel resolution. It’ll automatically turn on or off based on your wrist movements. The screen shows your activity stats and the time, and can be personalized using a variety of portrait or landscape clock face options. Just like the Flex 2, you won’t find any buttons on the device, and this is because you don’t really need them. Simply tap on the sides of the display to navigate.
The Alta HR features a satin finish, stainless steel body, and a line of interchangeable bands so you can find the one to fit your personal style. You simply pop the bands on and off. There are a bunch of colors to choose from including black, blue-grey, fuchsia or coral. There are also two “special edition” rose gold and gun metal trackers as well as a selection of designer accessories.
Fitbit Flex 2 or Alta HR: Battery life and water resistance
Apart from the design, waterproofing is the biggest change to the Flex 2. This is Fitbit’s only swim-proof wristband so far. The device is water resistant up to 50 meters, whether you’re in the shower, pool or ocean, and it automatically tracks your pool swims including laps, duration and calories burned in the Fitbit app. Alta HR is only splash proof so don’t plan on going swimming with it.
![]() | Fitbit Alta HR | ![]() |
The Flex 2 can keep going for around 5 days, depending on use, settings, and other factors. Alta HR is good for up to a week before needing a top-up – an impressive feat considering the slimmed down factor and inclusion of a heart rate sensor.

Fitbit Flex 2 or Alta HR: Features
Flex 2 features are fairly standard and cover the basics. This means the tracker monitors your steps, distance, calories, active minutes and hourly activity. You will also get automatic exercise tracking for running, sports and aerobic workouts and personalised weekly exercise goals. To help you stay active throughout the day, Flex 2 sends Reminders to Move that encourage you to take 250 steps every hour.
At night, the tracker will monitor how long and how well you sleep, set a sleep goal and bedtime reminder to form good habits and wake you up gently with a silent alarm. Sleep mode kicks in from your movements which means, all you have to remember is to wear your tracker to bed. When you wake up, sync your tracker to see last night’s sleep stats on the dashboard.

The Alta HR covers all of this and throws a few more features into the mix. The most important difference is the Pure Pulse technology.
Fitbit’s stylish new tracker displays your real-time target heart rate zone, so you can optimize your workout sessions for fat burning, a fitness boost, or performance benefits. It will also monitor your resting heart rate in the morning. Outside of any specific ailment, a lower resting heart rate correlates very closely to a state of greater general fitness and health.
Alta HR also benefits from Fitbit’s new sleep features. ‘Sleep Stages’ uses accelerometer and heart rate data to more accurately estimate how long you spend in Light, Deep, and REM sleep stages each night. The other new sleep feature provides you with advice on ways to improve your kip time.
Where the Flex 2 has an edge over the Alta HR is in its ability to track swimming. Four strokes can be monitored: freestyle, breaststroke, backstroke and butterfly. To track your pace and distance, you need to enter the pool length in meters or yards into the Fitbit app before starting your swim. The device then automatically tracks the duration of your swim and the number of pool lengths you complete.
While you are limited to the vertically positioned LED display colour-coded lights on the Flex 2, the Alta HR has a 1.4 inch OLED display for showing workout data and progress towards your goals. For more detailed data, head over to the smartphone app. The app itself is beautifully designed, and is the same software used by all Fitbit trackers.
Both trackers will display notifications. When you get calls and texts, Flex 2 vibrates and flashes lights to let you know. Tap twice on the tracker to see progress against your Main Goal. The Alta will also show you calendar notifications and you will be able to see snippets of all information (such as who is calling or texting you), on the tracker’s display.
Fitbit Flex 2 or Alta HR: The bottom line
Both the Flex 2 and Alta HR feature small functionality improvements and big design improvements. Fitness tracker meets fashion is obviously a trend, and Fitbit is tapping into this. They bring a minimalist design, discreet form-factor and have the option of being customised for a smarter look.
In the case of Flex 2, waterproofing is the biggest functionality change. For Alta HR, its the heart rate tracking function. In terms of price, there is quite a big difference. The Alta HR typically sells for $80 more, nearly twice the price of its less sophisticated cousin.
![]() | Fitbit Flex 2 | ![]() |
If you are after a no hassle, discreet tracker that covers the basics, and has a comprehensive app to go along with it, the Flex 2 is a great option. This is also an option for swimmers as its Fitbit’s only device to offer waterproofing. If you are a bit more serious about your fitness and don’t mind spending a bit more, an activity tracker that sports a heart rate sensor is clearly the way to go.
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