The Fitbit Charge 4 has a more angular design than the Fitbit Luxe, with a plastic case rather than stainless steel (Image credit: Fitbit) Both Charge devices will use a similar-size wristband, so Charge 3 owners who want to upgrade but like their old band will be able to easily swap them. All you have to do is press a button on the underside of the strap where it connects to the device. The only things I’d be concerned about is that, first, Active Zone Minutes as a concept is a lot less simple to comprehend than a step count. And, second, that those extra time credits for activities in your cardio and peak zones might encourage people to indulge in too much high-intensity exercise at the expense of lower intensity exercise when a balance between the two is what you want to aim for.

The Fitbit Charge 5's screen is about the same size, but is a full color AMOLED, with crisp graphics and animations. It looks very much like that of the Fitbit Luxe, and may indeed be the same unit. It's a huge upgrade, and one that brings the Charge series in line with rival device from the likes of Xiaomi and Amazfit. Fitbit Charge 5 vs Fitbit Charge 4: Features Smartwatch featuresThe Fitbit Charge 4's interface is intuitive, with only the touchscreen and a discrete button on the left-hand edge as controls. Tap the button or raise your wrist to wake the screen, then swipe right to access the device's various menus and settings.

With a battery life of up to 7 days—and up to 5 hours when using GPS—Fitbit Charge 4 lets you do more with less charging. Varies with use and other factors. Fitbit Pay Charge 4 automatically syncs to most popular iOS and Android devices to show your stats, trends and progress on your Fitbit dashboard. Mobile App After four days of wearing the Charge 4, plus two half-hour runs using GPS, the Charge 4’s battery life was down to 24 percent. Fitbit Charge 4 review: Verdict The Charge 5 has lots more health and fitness tools to offer, though – including an EDA (electrodermal activity) sensor, as seen on the Fitbit Sense. This uses your skin's conductivity to assess physiological changes brought about by stress. The Fitbit app then helps you understand the factors that affect your stress levels, and take steps to manage it.

Fitbit Charge 5 review: Performance

Fitbit has also brought its Smart Wake feature to the Charge 4; the company says it uses machine learning to know the best time to rouse you from your slumber, a feature my toddler has perfected without the assistance of advanced algorithms. Fitbit Charge 4: Spotify controls Extra silicone, fabric and leather bands for both watches are available to buy separately, but bear in mind that they use different fittings, so you can't use Charge 4 bands with a Charge 5, or vice versa. Display