In the conclusion of the following paper about the Polar OH1 it says: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0217288 «The findings of the study shows that the Polar OH1 HR is in high agreement to the criterion measure ECG HR under moderate to high intensity physical activities. Therefore, when accurate HR measurements are required, Polar OH1 can be used in …