ABSTRACT
This longitudinal study examines the growth of psychological characteristics and adaptation of physiological markers of stress during a six-month assessment and selection course for U.S. Navy SEALs. Resilience, hardiness, and grit instruments were used to evaluate the psychological characteristics. Blood samples were taken to determine physiological markers related to stress adaptation; specifically, evaluating DHEA, DHEA-to-cortisol ratio, BDNF, NPY, and cortisol. Data was collected at four timepoints throughout the assessment and selection course from 353 students over three classes. Results indicated that resilience and hardiness grow after an initial decline, DHEA and DHEA-to-cortisol increased suggesting physiological adaptation. However, psychological and physiological markers do not exhibit the same growth patterns for participants in the course. This study enhances the understanding of psychological growth and physiological adaptation in a high-stress environment over an extended duration.
Subject(s)
Resilience, Psychological , Seals, Earless , Animals , Humans , Hydrocortisone , Dehydroepiandrosterone , Longitudinal Studies , Biomarkers , Stress, Psychological/psychologyABSTRACT
Military operational stress is known to increase adrenal hormones and inflammatory cytokines, while decreasing hormones associated with the anabolic milieu and neuroendocrine system. Less is known about the role of extracellular vesicles (EVs), a form of cell-to-cell communication, in military operational stress and their relationship to circulating hormones. The purpose of this study was to characterize the neuroendocrine, cytokine, and EV response to an intense. 24-h selection course known as the Naval Special Warfare (NSW) Screener and identify associations between EVs and cytokines. Blood samples were collected the morning of and following the NSW Screener in 29 men (18-26 yr). Samples were analyzed for concentrations of cortisol, insulin-like growth factor I (IGF-I), neuropeptide-Y (NPY), brain-derived neurotrophic factor (BDNF), α-klotho, tumor necrosis factor-α (TNFα), and interleukins (IL) -1ß, -6, and -10. EVs stained with markers associated with exosomes (CD63), microvesicles (VAMP3), and apoptotic bodies (THSD1) were characterized using imaging flow cytometry and vesicle flow cytometry. The selection event induced significant changes in circulating BDNF (-43.2%), IGF-I (-24.6%), TNFα (+17.7%), and IL-6 (+13.6%) accompanied by increases in intensities of THSD1+ and VAMP3+ EVs (all P < 0.05). Higher concentrations of IL-1ß and IL-10 were positively associated with THSD1+ EVs (P < 0.05). Military operational stress altered the EV profile. Surface markers associated with apoptotic bodies were positively correlated with an inflammatory response. Future studies should consider a multiomics assessment of EV cargo to discern canonical pathways that may be mediated by EVs during military stress.
Subject(s)
Extracellular Vesicles , Insulin-Like Growth Factor I , Adolescent , Adult , Biomarkers/metabolism , Brain-Derived Neurotrophic Factor/metabolism , Cytokines/metabolism , Extracellular Vesicles/metabolism , Extracellular Vesicles/pathology , Hormones/metabolism , Humans , Insulin-Like Growth Factor I/metabolism , Interleukin-1beta , Male , Neurosecretory Systems/metabolism , Tumor Necrosis Factor-alpha/metabolism , Vesicle-Associated Membrane Protein 3/metabolism , Young AdultABSTRACT
This research examines resilience from both cognitive and physiological perspectives and the relative importance of resilience for progression within an extremely physical training environment for 116 individuals. Our study provides a unique contribution as an examination of the combined effects of psychological and physiological resilience in the success of individuals in the first phase of a military special operations training course, the Navy's Basic Underwater Demolition/SEAL (BUD/S) course. Our study used the Connor-Davidson Resilience Scale (CD-RISC) for the psychological assessment and a blood sample to measure the concentrations of cortisol, DHEA and BDNF, each associated with stress adaptation and neuronal integrity. Our contributions include: heeding the call for more extensive research for resilience, examining physiological markers as predictors in training situations, combining psychological and physiological resilience into a single metric to assess resilience, and providing empirical support for the vital role of resilience in both stamina and persistence in training. Our findings indicate that both psychological and physiological resilience can be important predictors of persistence individually, but combining the measures provides a more holistic view to predict the success of an individual in this intensive training program. The present study has implications not only for the military community, but also for those individuals seeking elite performance in a broad array of fields, like professional athletes, CEO's, and emergency response workers.
