According to our own little experience, it is the paper: Accuracy of commercially available heart rate monitors in athletes: a prospective study: https://pubmed.ncbi.nlm.nih.gov/31555543/ Variable Accuracy of Wearable Heart Rate Monitors during Aerobic Exercise https://pubmed.ncbi.nlm.nih.gov/28709155/ https://pubmed.ncbi.nlm.nih.gov/31004219/ showed a signal quality of 99.6 of the Polar H10 chest strap for sporting activites. But since the paper of …