Resilience of the Hellenic navy seals assessed by heart rate variability during cognitive tasks

The interaction between high physical performance under extreme conditions in military and the simultaneous control of the cognitive executive functioning has been a subject of research in literature for the past few decades. Stroop test and Heart-rate variability (HRV), have been verified valuable clinical tools for the assessment of cerebral and autonomic/ cardiovascular stress responses respectively.

Thirty-four subjects were enrolled in this study. Of them, 18 were candidates under intense preparation for their enlistment in the Hellenic Navy SEALs (HN-SEALs) and 16 were healthy controls (HC). All subjects underwent stroop tasks, along with mental state and personality examination. HRV variables in time and frequency domains recordings were acquired, during each aforementioned cognitive testing procedure.

Our results showed that HNS's performance on both cognitive and emotion stroop tasks were equivalent to controls (p≥.054); however, HNS exhibited statistically significant lower levels of HRV in different time and frequency domain variables, compared to HC (ranged from p<.01 to p<.05). Finally, in a between group comparison of the psychometric tools, HNS had significantly higher somatization, anxiety and neuroticism than HC.

In conclusion, these findings indicate that HNS display flexibility in their autonomic regulation during cognitive and emotional tasks. This characteristic is closely related to problem solving or adaptability skills. Therefore, we support that HRV measurement turns out to be an invaluable tool for both scientific and clinical insights, promising to be an index regarding the psychophysiological resilience especially in the neurovisceral integration (NVI) model.