Assessing Garmin Stress Level Score Against Heart Rate Variability Measurements

Daily stressors elicit physiological and mental responses impacting health, cognition, and behavior. Accurately assessing stress responses in natural settings remains challenging despite extensive research, though wrist-worn devices have the potential to address this gap through remote data collection. The Garmin fitness tracker provides a stress score largely based on HRV which must be validated prior to use in research. This study aimed to assess the stress score given by the Garmin Vivosmart 4 against HR and HRV from ECG recordings derived by the Polar H10 chest strap. A pilot study of 29 participants was conducted, followed by power calculations and preregistration of the main study which included 60 participants. Data were collected simultaneously from both devices during a laboratory session of restful and mental-stress-inducing tasks. Garmins stress score, mean HR, SD2/SD1, and HF power exhibited significant differences between stress and rest conditions. Moreover, Garmins stress score correlated significantly with HR, RMSSD, and SD2/SD1. Our findings suggest that physiological responses to mental stress were influenced by sex and tonic HRV. The study suggests that the GSS is indicative of mental stress, with its accessibility and noninvasive nature promising widespread utilization in various research domains.