The fitness tracker LeBron and Ronaldo swear is on sale with £60 off for Black Friday

Take control of your health and fitness for less (Picture: WHOOP/Getty/Metro)
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You might think you know your body inside out, but fitness trackers can reveal things you’d never notice on your own.From ECG heart readings and sleep cycles to stress levels and calories burned, a really good tracker can be a game-changer for your he