Scientific studies at the Swiss Federal Institute of Sport Magglingen SFISM: Scientific study of the Swiss Federal Institute of Sport Magglingen SFISM with a cheap ECG device: Schiller Medilog AR12 Plus Holter Recorder $1700: Scientific studies performed at the Cleveland Clinic in Ohio with an expensive ECG device: refurbished on ebay $ 6’990: https://journals.lww.com/acsm-msse/Fulltext/2017/08000/Variable_Accuracy_of_Wearable_Heart_Rate_Monitors.22.aspx https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6732081/ …