Heart Rate Variability and Accelerometry as Classification Tools for Monitoring Perceived Stress Levels—A Pilot Study on Firefighters

Abstract

Chronic stress is the main cause of health problems in high-risk jobs. Wearable sensors can become an ecologically valid method of stress level assessment in real-life applications. We sought to determine a non-invasive technique for objective stress monitoring. Data were collected from firefighters during 24-h shifts using sensor belts equipped with a dry-lead electrocardiograph (ECG) and a three-axial accelerometer. Levels of stress experienced during fire incidents were evaluated via a brief self-assessment questionnaire. Types of physical activity were distinguished basing on accelerometer readings, and heart rate variability (HRV) time series were segmented accordingly into corresponding fragments. Those segments were classified as stress/no-stress conditions. Receiver Operating Characteristic (ROC) analysis showed true positive classification as stress condition for 15% of incidents (while maintaining almost zero False Positive Rate), which parallels the amount of truly stressful incidents reported in the questionnaires. These results show a firm correspondence between the perceived stress level and physiological data. Psychophysiological measurements are reliable indicators of stress even in ecological settings and appear promising for chronic stress monitoring in high-risk jobs, such as firefighting.

Monitoring stress and allostatic load in first responders and tactical operators using heart rate variability: a systematic review

“…Both no differences [ 33 – 36 ] and decreases [ 37 ] in HRV were observed in on-duty work periods compared to off-duty work periods. Twelve studies compared HRV responses to different working shift types, conditions and tasks to evaluate their similarity [ 2 , 33 , 34 , 37 – 45 ]. On-duty firefighter incidents yielded lower HRV than non-incidents that were matched for similar physical activity [ 45 ].…”

“…Twelve studies compared HRV responses to different working shift types, conditions and tasks to evaluate their similarity [ 2 , 33 , 34 , 37 – 45 ]. On-duty firefighter incidents yielded lower HRV than non-incidents that were matched for similar physical activity [ 45 ]. Resting HRV was similar during comparable work shifts across a 24 h period [ 34 , 43 , 44 ] except in early morning shifts (3:15 am to 5:15 am compared to 5:00 am to 7:00 am) in which increases in tiredness complaints and a reduction in sleep quality occurred [ 43 ].…”

Gait Analysis under Spatial Navigation Task in Elderly People—A Pilot Study

“…In order to conduct the research in the ecological conditions, we developed an innovative procedure to investigate SN in the real building and equipped the participants with wearable sensors, previously developed by our team [ 40 ], to measure gait parameters while navigating. The goal of the present study was twofold: to develop a new procedure to examine spatial navigation ability in the real environment and to identify gait indicators, collected while navigating that would allow for the most accurate assignment of the participants to the proper category (young or elderly).…”

Evaluation of Functionality of Warning System in Smart Protective Clothing for Firefighters

“…Its level may be also evaluated on a basis of measurements of physiological parameters [ 8 ]. Among the physiological parameters, special attention was paid to the variability of the heart rate as a marker of stress in the human body [ 8 , 9 , 10 , 11 ]. Both mental and physical activity increases the heart rate.…”