Cardiac biosignal in confined nuclear submarine patrol: Heart rate variability a marker of adaptation

Extreme and unusual, and isolated and confined environments (EUE/ICE) are characterized by unique sensory stimulation. They are known to adversely affect human psychology and physiology, and threaten the outcome of spatial, polar, or submarine missions. This exploratory study evaluates the negative impact of a submarine patrol on the psychological and sensory performances according to heart rate variability (HRV). Nineteen submariners were classified into high parasympathetic activity (HPa) and low parasympathetic activity (LPa) groups using their pre-patrol parasympathetic level. The impacts of the mission on emotional health, interoception and exteroception were evaluated at baseline, twice during the patrol, and once at recovery one month later. Emotional health was assessed using the scale of positive and negative experience (SPANE) questionnaire. Interoception and exteroception were evaluated using other questionnaires and sensorial assessments, respectively. In all cases, no significant inter-group difference was found for emotional health. Exteroceptive and interoceptive functioning was better among the HPa group compared to the LPa group, both during the patrol and at recovery. HRV measures for the HPa group indicated a more adaptable profile, marked by greater cardiac vagal tone during the patrol and at recovery. Our results are the first to highlight the impact of physiological differences in HRV profile on adaptability in an ecological constraint environment. Such research would open perspectives for submariners’ preparation, but also the design of countermeasures that bring us closer to Mars.