The Charge 4 has added a new metric called Active Zone Minutes, which uses your heart rate zones to determine the intensity of your workout. Like the Charge 3, it's also hard to see the screen in direct sunlight.

The only time the lag really bothered me was while I was running and wanted to quickly glance at my stats without taking my eyes off the road. The touchscreen isn't as responsive and it takes a few seconds to light up when you raise your arm to wake the screen, but I eventually got where I wanted to go. Instead, you control the Charge 4 with a combination of the touchscreen and by pressing the left side of the tracker to navigate settings.

, and it also does away with physical buttons. The screen can only display in black and white, but I like that it's nearly half the size of a traditional smartwatch, such as the , the new version doesn't look much different - it's just the tiniest bit bulkier on your wrist. The $150 Charge 4 (£130, AU$230) is a tracker I will happily wear 24/7 thanks to its sleek, understated design.

There are plenty of great wearables for athletes, like the Garmin Forerunner 945 and Suunto 3, that have way more fitness chops than the Charge 4, but they're not the most fashionable. Shorter battery life than the Fitbit Charge 3

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