Method comparison of a ring-based PPG device and a chest-strap monitor for heart rate and heart rate variability in shooting athletes

Abstract Introduction: Ring-based photoplethysmography (PPG) devices are increasingly used in athlete monitoring, but evidence remains limited for precision-sport settings and finger-worn form factors. This study examined the agreement between a ring-based PPG device and a chest-strap monitor for heart rate (HR) and time-domain heart rate variability (HRV) metrics in shooting athletes. Methods: Sixty-four shooting athletes completed a 10-min seated recording initiated within 5 min after a routine scored training session. RingConn Gen2 and Polar H10 signals were acquired simultaneously using synchronized timestamps, refined by cross-correlation, and analyzed in 90-s windows after excluding the first and last 30 s. HR, the standard deviation of normal-to-normal intervals (SDNN), and the root mean square of successive differences (RMSSD) were derived from inter-beat intervals. Agreement was summarized using correlation and Bland-Altman analysis. Because multiple windows were nested within participants, window-level results are interpreted descriptively. Results: Agreement was very high for HR (; mean bias -0.42 bpm; 95% limits of agreement: -0.74 to -0.09 bpm), high for SDNN (; mean bias 1.25 ms; 95% limits of agreement: -3.83 to 6.33 ms), and high for RMSSD (; mean bias 1.62 ms; 95% limits of agreement: -10.08 to 13.34 ms). Discussion: Under seated, low-motion post-exercise recovery conditions, the ring-based device tracked HR and time-domain HRV metrics closely to the chest-strap monitor. These findings support the use of finger-based PPG for this specific measurement context, while broader application to daily training, movement-rich tasks, or competition settings requires further validation.