Don't waste your time using this app. I am a medical student and BodyBuilding athlete and owner of Polar H10, I know ECG reading well, I perform ECGs with professional 12-lead machines. Trust me, it is not the best App available, not recommended for several reasons, including an incorrect and not very usable graphic reading of the path without usable File output. It's not correct to mention the competition here but... good things pay off. I'm just saying this.