Evaluation of the Validity and Lateral Differences of Ring-Type Wearable Sensors for Heart Rate and Heart Rate Variability Monitoring Under Multiple Conditions

Ring-type wearable sensors are increasingly used for continuous monitoring of heart rate (HR) and heart rate variability (HRV); however, evidence regarding their measurement validity and potential lateral differences remains limited. This study aimed to evaluate (1) the validity of HR and HRV obtained from ring-type photoplethysmography (PPG) sensors under multiple activity conditions (Experiment 1), and (2) the presence of lateral differences in autonomic indices when worn on the left versus right hand (Experiment 2). In Experiment 1, HR and HRV indices from the ring sensor were compared with those from a Holter electrocardiogram (ECG) and a wrist device during rest, low activity, and moderate activity. Mixed-model analysis revealed significant differences in very low frequency (VLF) power between the left- and right-hand rings (p = 0.001). Additionally, significant interactions between device side and measurement condition were observed for HR and low-frequency (LF) components, indicating that lateral differences were condition-dependent. In Experiment 2, participants wore two ring sensors simultaneously to assess left–right discrepancies under rest and exercise conditions. The SDPP index showed a significant difference (p = 0.017), with mean values differing between Rest and Exercise, demonstrating condition-related variability but limited systematic lateral bias. Overall, ring-type wearable sensors demonstrated high validity for HR and acceptable performance for selected HRV metrics during rest and low-activity states. While some condition-dependent lateral differences emerged for specific HRV parameters, the practical impact on overall measurement performance remained modest. These findings support the utility of ring-type wearable devices for autonomic monitoring while highlighting the importance of considering activity level and side–condition interactions.