According to this paper, the Polar OH1 can be used instead of an ECG device for moderate and high intensity physical activities: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0217288 and eventually also for non-athletic research applications, what means, that the accuracy of the Polar OH1 is sufficient to replace an ECG device. A Polar OH1 paired to a Garmin watch can …