Background: Usage of wrist-worn activity monitors has rapidly increased in recent years, and these devices are being used by both fitness enthusiasts and in clinical populations. We, therefore, assessed the test-retest reliability of the Polar Vantage M (PVM) watch when measuring heart rate (HR) during various treadmill exercise intensities.
Methods: HR was measured every 30 s (simultaneous electrocardiography (ECG) and PVM). Test-retest reliability was determined using an intraclass correlation coefficient (ICC) with 95% confidence intervals (CIs). Standard error of measurement (SEM) and smallest real difference (SRD) were used to determine measurement variability.
Results: A total of 29 participants completed the trials. ICC values for PVM during stages 1, 2 and 5 demonstrated good to excellent test-retest reliability (0.78, 0.78 and 0.92; 95% CI (0.54-0.90, 0.54-0.9, 0.79-0.97)). For PVM during stages 0 (rest), 3 and 4, the ICC values indicated poor to good reliability (0.42, 0.68 and 0.58; 95% CI (-0.27-0.73, 0.32-0.85, 0.14-0.80)).
Conclusion: This study identified that the test-retest reliability of the PVM was comparable at low and high exercise intensities; however, it revealed a poor to good test-retest reliability at moderate intensities. The PVM should not be used in a clinical setting where monitoring of an accurate HR is crucial to the patients' safety.
Keywords: aerobic exercise; heart rate response; monitoring; photoplethysmography; smart wristband; wearable device; wearable technology.