https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6732081/ «Once all devices were on, they were asked to run at the following speeds on a treadmill (in mph): 4, 5, 6, 7, 8, and 9 for two min. ( 4 – 9 km / h ).» Reference device: Cardiac Sience ECG device Result: «The Polar H7 chest strap had the greatest agreement with …