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Health Tech: Fitbit Flex [REVIEW]

After using the Fitbit Flex for a month we are ready to provide our verdict.

In a previous review of the Fitbit One we concluded that we loved the feature list, but really wanted the Fitbit One to be supplied with a bracelet akin to that advertised as being provided with the Fitbit Flex. The last month has provided us with the chance to trial the Fitbit Flex and see if the Fitbit Flex package is the better of the two main Fitbit wearable fitness tracking options.

The first things we noted on receipt of the Fitbit Flex was that the tracking unit is substantially smaller than the Fitbit One although, in order to achieve this more compact form factor the Fitbit Flex loses the in-built altimeter and interactive display. Despite these feature loses the Fitbit Flex still provides the following functionality:

Steps taken

The built-in accelerometer counts the number of changes in acceleration resulting from your feet impacting with the ground during walking/running etc.

Distance travelled

The number of steps taken is used along with your height information from your Fitbit account profile information to calculate the distance travelled. For more accurate calculation you have the option to input your walking and running stride lengths on the Fitbit website.

Calories burned

The time between steps or step rate (e.g. Steps per minute) is used along with your age, weight and height information is used to calculate the number of calories burned, based on scientific studies.

Active minutes

The number of active minutes is calculated as the time spent with a step rate (e.g. steps per minute) greater than a non-user configurable pre-set limit, based on scientific studies.

Hours slept

Tapping the Fitbit Flex a number of times in close succession switches it between active and sleep modes. During sleep mode the Fitbit Flex uses the accelerometer to analyse sleep based movement equating this to quality of sleep.

Quality of sleep

The basic scientific logic behind sleep quality tracking is that during quality (deep sleep) you move less, with increased movement inferring restless sleep.

The trial of the Fitbit Flex has left us in turmoil as the Fitbit Flex and Fitbit One both have positives and negatives leaving the comparison between the two devices more unclear than we had expected.

Although the Fitbit One had left us longing for the permanently wearable wrist band we have been left missing the clip-on housing of the Fitbit One in some circumstances, although the main thing we have been left longing for is the interactivity of the Fitbit One‘s screen (see our Fitbit One review).

Although the Fitbit Flex provides progress information via 5 led lights identifying progress in 20% steps of your chosen goal, the Fitbit One screen cycles between logged information displaying the specific number of steps, distance travelled, calories burned and floors climbed. Being provided with the specific numbers and being able to check any of the statistics provides a more interactive feel.

As with the Fitbit One, initial setup of the Fitbit Flex is fast and simple requiring the USB Bluetooth dongle and/or USB charging cable to be plugged into a computer with an internet connection, or a mobile device (iPhone, Android or Windows Phone) with the official Fitbit app installed.

Once setup we found the Bluetooth connection between the Fitbit Flex and mobile apps to be more reliable than that of the Fitbit One which is also the experience of other Fitbit users we interviewed.

Although the Fitbit Flex electronic unit is black, Fitbit offer wristbands in black, slate, violet, lime, pink, teal, tangerine, navy, red and blue.

As with the rest of the Fitbit wearable fitness tracker range the Fitbit Flex is Water-resistant meaning that you can even keep it on in the shower although we wouldn’t suggest you try swimming in it as it is water-resistant and not water-proof.


Although the Fitbit Flex provides a permanently wearable wrist band, we prefer the functionality of the Fitbit One, as we miss the interactive display and the ability to live track multiple statistics without the need to check a mobile or web based app.

Both the Fitbit Flex and Fitbit One provide an affordable 24/7 wearable fitness tracking option, but with the recent announcement of the Fitbit Charge, Fitbit Charge HR and Fitbit Surge we are looking forward to the next generation of Fitbit wearable fitness trackers with the look and feel of the Fitbit Flex and the functionality of the Fitbit One.

One think that is missing from all know Fitbit future offerings is the ability to have a tracker device with both the clip on option from the Fitbit One and the wrist band wearable option of the Fitbit Flex and next generation devices (Fitbit Charge, Fitbit Charge HR and Fitbit Surge). We think this would be a nice differentiator for Fitbit as none of the competition offer this wearablility option that we are aware of. Let us know if you know different.