Sex-related differences in heart rate variability and static body stability in military personnel under stressful conditions

Abstract

The study of sex-related characteristics of the HRV status and static balance performance under stressful conditions in military personnel is extremely relevant in modern conditions, especially given the increasing number of women in the armed forces. This trend indicates the need for a more detailed study on the physiological characteristics of women and men in the military environment. An analysis of HRV enables the identification of delicate alterations in autonomic nervous system functioning that arise as a result of exposure to stressors (Dantas, et al., 2010; Draghici, 2016; Dantas, et al., 2018; Thomas et al., 2019; Geovanini, et al., 2020). Our study has a number of methodological characteristics that should be taken into account when interpreting the results. The sample of subjects was formed from among operational-level officers, which allows us to generalize the results obtained for this particular category of military personnel. Our results indicate the presence of sex differences in autonomic regulation in military persons, with most of them being statistically significant (p<0.05; p<0.01). Women demonstrate a reduced overall HRV and a greater dominance of the sympathetic nervous system compared to men, which may indicate an increased level of baseline stress in women or specifics of their adaptation to stressful conditions. Our results are consistent with the findings of Koenig et al. (2016) and Geovanini et al. (2020), who also found higher HRV in men. Research has indicated that stress can significantly influence HRV (Kim, 2018). Notably, periods of heightened stress are frequently linked to diminished parasympathetic nervous system activity, leading to reduced high-frequency HRV and increased low-frequency HRV. Neuroimaging research suggests that brain regions involved in stress appraisal, such as the ventromedial prefrontal cortex, may influence fluctuations in HRV. HRV is a complex physiological phenomenon shaped by a multitude of factors, including medical conditions, physical health, mental state, environmental influences, lifestyle habits, and genetic predispositions (Tiwari, 2021).