https://www.tandfonline.com/doi/full/10.1080/17461391.2021.2023656 Heart rate and energy expenditure were measured using the Polar H10 and Metamax 3B: respectively (reference measures) as well as with the 3 wrist-worn devices during 5 different activities (sitting, walking, running, resistance exercises and cycling). The Apple Watch 6 displayed the highest level of accuracy for heart rate measurement with a coefficient of variation …