Validity of the Polar H10 for Continuous Measures of Heart Rate and Heart Rate Synchrony Analysis

Heart rate (HR), a non-invasive indicator of physiological arousal and autonomic nervous system engagement, is widely used in cognitive and affective sciences to monitor individual responses and interpersonal synchrony in dynamic emotional and social contexts. Recent advances in wearable sensors have enabled researchers to assess HR synchrony in ecologically valid settings. In this study, we replicate prior validations of the Polar H10 chest strap for individual HR measurement and extend these findings by evaluating its validity for measuring HR synchrony between individuals. Dyads completed a previously validated experimental task designed to elicit HR fluctuations while jointly attending to emotionally evocative, 5-min audiovisual stimuli. First, we observed high correspondence (Pearson's r > 0.99) between the Polar H10 and a gold-standard ECG system in measuring individuals' HR, both at the aggregate and moment-to-moment levels, thus confirming and extending prior findings. Second, we found high correspondence (Pearson's r > 0.95) between the two systems in quantifying dyadic HR synchrony using multiple analytical approaches. These results support the use of the Polar H10 as a low-cost, easy-to-use, and reliable tool for both individual and dyadic HR measurement. This represents an important step toward establishing its applicability in real-world settings where traditional ECG systems are impractical.