Fitbit’s proprietary PurePure heart rate technology on the Ionic employed an optical sensor array that used multiple wavelengths of light to filter out motion artifacts, enabling more accurate calorie burn and BPM tracking during high-intensity workouts and weight lifting sessions. The wrist-based sensor tracked heart rate zones (fat burn, cardio, peak) continuously, helping athletes optimise their training intensity. Combined with the Run Detect feature, which automatically paused activity tracking if the user stopped, it created a more streamlined experience. Regular runners and gym enthusiasts who want to investigate alternative health-oriented smartwatches from major tech brands can browse the Donysterling.co.uk store, which gives further perspective on the category.