Effect of Combat Stress in the Psychophysiological Response of Elite and Non-Elite Soldiers

Heart Rate Variability in Military Pilots During Flight: A Scoping Review

INTRODUCTION

Piloting an aircraft is a complex multitasking activity that involves managing information in a nonautomatic way and generates a high workload (psychological, cognitive, and physical) for the pilot. The excess of these demands can result in decreased performance and may impair flight safety. Heart rate variability (HRV) has been used in recent studies as a method to investigate operator's workload in complex environments. This measure can assess the stress and recovery ability of the autonomic nervous system. However, a better understanding of flight influence on the pilot's autonomic modulation is necessary. Therefore, this scoping review aims to systematically map the studies related to changes in the autonomic modulation in military pilots during flight, in order to characterize their workload at different times and flight profiles.

MATERIALS AND METHODS

A literature search was conducted using MEDLINE (by PubMed), SCOPUS, and LILACS databases. Recent records (2002-2022) that analyzed HRV in military pilots during flight were included. Meanwhile, studies in which piloting activity was not performed were excluded. The study was conducted in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guideline extension for Scoping Reviews and the Updated Methodological Guidance for the Conduct of Scoping Reviews.

RESULTS

A total of 298 records were obtained, of which 19 were included in the scoping review. The studies analyzed flights performed in high- and low-performance aircrafts, helicopters, and flight simulators, using time domain, frequency domain, and nonlinear HRV indices. Real and simulated flights produced significant autonomic changes. Some flights elicited autonomic nervous system responses that persisted up to 5 h after landing. During real flight, the most sensitive indices for identifying variations in pilot workload were root mean square of successive differences between normal heartbeats, standard deviation of interbeat interval of normal sinus beat (SDNN), ratio of low-frequency to high-frequency power, and Poincaré plot standard deviation perpendicular to the line of identity (SD1), whereas the interbeat interval (RR), SDNN, SD1, and Poincaré plot standard deviation along the line of identity (SD2) were the most sensitive indices when comparing segments of simulated flight with different levels of difficulty.

CONCLUSIONS

This scoping review provided insight into the influence of flight on autonomic modulation in military pilots. Some key themes were highlighted: Increased sympathetic activity during flight, sensibility of different domains of HRV to flight demands, and autonomic changes during recovery time. Future research efforts may allow us to enhance the understanding of pilot's workload limits and to elucidate the optimal postflight recovery time.

An Examination of Subjective and Objective Measures of Stress in Tactical Populations: A Scoping Review

Persons working in tactical occupations are often exposed to high-stress situations. If this stress is to be measured, an understanding of the stress outcomes used in these occupations is needed. The aim of this review was to capture and critically appraise research investigating subjective and objective outcome measures of physiological stress in tactical occupations. Several literature databases (PubMed, EMBASE, EBsco) were searched using key search words and terms. Studies meeting inclusion criteria were critically evaluated and scored by two authors using the Joanne Briggs Institute (JBI) critical appraisal tool. Of 17,171 articles, 42 studies were retained. The Cohen's Kappa agreement between authors was 0.829 with a mean JBI Score of included studies of 8.1/9 ± 0.37 points. Multiple subjective and objective measures were assessed during a variety of high-stress tasks and environments across different occupations, including police officers, emergency service personnel, firefighters, and soldiers in the military. Common objective outcomes measures were heart rate, cortisol, and body temperature, and subjective measures were ratings of perceived exertion, and the Self Trait Anxiety Inventory. Often used in combination (i.e., subjective and objective), these outcome measures can be used to monitor stressors faced by tactical personnel undergoing on-the-job training.

Resting-state heart rate variability after stressful events as a measure of stress tolerance among elite performers

Introduction: A common trait of elite performers is their ability to perform well when stressed by strong emotions such as fear. Developing objective measures of stress response that reliably predict performance under stress could have far-reaching implications in selection and training of elite individuals and teams. Prior data suggests that (i) Heart rate and heart rate variability (HR/HRV) are associated with stress reaction, (ii) Higher basal sympathetic tone prior to stressful events is associated with higher performance, and (iii) Elite performers tend to exhibit greater increase in parasympathetic tone after a stressful event. Methods: The current study assesses the predictive utility of post-stressful event HR/HRV measures, an under-studied time point in HR/HRV research, in the context of military personnel selection. Specifically, we examined the relationship between a comprehensive set of HR/HRV measures and established questionnaires related to stress tolerance, experimental evaluation of executive function during stress induction, and ecologically valid selection assessment data from a week-long Special Operations Forces selection course (N = 30). Results: We found that post-stressful event HR/HRV measures generally had strong correlations with the neuroticism facet of the NEO personality inventory as well as the general and distress facets of the defensive reactivity questionnaire. HR/HRV measures correlated reliably with a change in executive function measured as a decrease in verbal fluency with exposure to a well-validated stressor. Finally, we observed a divergent pattern of correlation among elite and non-elite SOF candidates. Specifically, among elite candidates, parasympathetic nervous system (PNS) measures correlated positively and sympathetic nervous system (SNS) measures correlated negatively with evaluation of stress tolerance by experts and peers. This pattern was not present in non-elite candidates. Discussion: Our findings demonstrate that post-stressful event HR/HRV data provide an objective non-invasive method to measure the recovery and arousal state in direct reaction to the stressful event and can be used as metrics of stress tolerance that could enhance selection of elite individuals and teams.

PECULIARITIES OF FORMATION OF CADETS' PSYCHOLOGICAL RESILIENCE AND PHYSICAL READINESS FOR COMBAT STRESS

OBJECTIVE

The aim: To investigate the impact of special physical training sessions on the formation of cadets' psychological resilience and physical readiness for the stress factors of future professional and combat activities.

PATIENTS AND METHODS

Materials and methods: The research involved 96 cadets (men) in the 2nd training year of S. P. Koroliov Zhytomyr Military Institute (Ukraine) aged 18-20 years, who were divided into two groups: the experimental (E, n = 47) and the control (C, n = 49). The cadets of the E group studied according to the authors' program, and the C group cadets - according to the existing program. Cadets' psychological resilience was studied using psycho-diagnostic methods aimed at assessing their volitional qualities. Cadets' physical fitness was assessed by the tests of general and special physical training.

RESULTS

Results: It was found that the level of general physical training of the E and the C group cadets was significantly the same (p > 0.05) at the end of the research but in terms of special physical training and psychological readiness, the E group cadets had all indicators significantly (p < 0.05-0.001) better than those of the C group.

CONCLUSION

Conclusions: It has been proved that the special physical training sessions conducted according to the authors' program were more effective than the existing program in forming cadets' physical readiness and psychological resilience for stress factors of future professional and combat activities.

National vs. Non-National Soccer Referee: Physiological, Physical, and Psychological Characteristics

Purpose: The objectives of the present study were to analyze the relationship between psychological variables (self-esteem, anxiety and self-confidence) assessed before the competition and physical and physiological responses demonstrated during the competition in soccer referees and to compare these psychophysical and physiological responses by category (CAT; national and non-national). Method: A total of 153 soccer referees participated (age Mage = 23.2; SD = 4.8 years; experience Mage = 6.0; SD = 4.5 years) in the study. The CSAI-2 and Rosenberg questionnaires were conducted before the match, and match performance data were collected using GPS devices. Results: The results showed significant differences in self-esteem and self-confidence across CATs (p < .001; d > .84). The national referees had higher psychological and physical-physiological responses (mean and maximum heart rate) Some correlations were observed among the psychophysical and physiological responses, CAT and age, demonstrating that the age could explain up to 48.4% of the variance the referee CAT (p < .001) and this CAT could explain self-esteem, anxiety and self-confidence by up to 20% of the variance. Conclusions: national referees presented better psychological responses prior to the competition, and also obtained greater physical and physiological records, which could be translated into a better position on the pitch in conflicting plays in order to make a right and just decision.

Autonomic stress response of physiotherapy student in the different scenarios of an objective structured clinical examination

The aim of the present research was to analyse modifications in the autonomic stress response of Physiotherapy students undergoing a 12-scenario Objective Structured Clinical Evaluation (OSCE). A total of 86 last year students of the Physiotherapy bachelor's degree (27.29 years (SD = 6.66); 36 females and 50 males) randomly assigned were monitored during the complete OSCE to measure heart rate variability (HRV) in temporal, frequency, and non-linear domains. The HRV analysed showed a large anticipatory stress response of students maintained during the entire evaluation. The stress response varied regarding OSCE station complexity and demands and the highest sympathetic response was not found in higher emotional scenarios.The autonomic modulation monitoring allows teachers to design OSCE scenarios more adapted to the students, limiting the effect of the stress response to allow a better performance.

Comparison of Hemodynamic Brain Responses Between Big Wave Surfers and Non-big Wave Surfers During Affective Image Presentation

Background

Big wave surfers are extreme sports athletes who expose themselves to life-threatening risk when training and competing. Little is known about how and why extreme sports athletes choose to participate in their chosen sports. This exploratory study investigated potential neurophysiological and psychometric differences between big and non-big wave surfers.

Methods

Thirteen big wave surfers (BWS) and 10 non-big wave surfers (CON) viewed a series of images from the International Affective Picture System (IAPS) while undergoing brain functional magnetic resonance imaging (fMRI). The Fear Schedule Survey-III, Arnett Inventory of Sensation Seeking, Discrete Emotions Questionnaire, and Positive and Negative Affect Schedule were also completed.

Results

The BWS group demonstrated higher blood-oxygen level-dependent (BOLD) signal change in the insula, visual cortex, and periaqueductal gray, whereas the CON group displayed increased hypothalamus activation in response to high amplitude negative-valence (HAN) image presentation. Psychophysiological interaction (PPI) analyses found CON showed significant interactions between frontal and temporal cortical regions as well as between the hypothalamus and the insula, frontal, and temporal cortices during HAN image presentation that were not seen in BWS. No differences between groups were found in their responses to the questionnaires.

Conclusion

Our findings demonstrate significant differences in brain activation between BWS and CON in response to the presentation of HAN IAPS images, despite no significant differences in scores on psychometric questionnaires.

Psychomotor abilities of candidates for Polish Special Forces

Combat tasks involving special units often put a mental and physical strain on the soldiers. During the military operation, soldiers may struggle with multiple difficulties such as extreme physical effort, sleep deprivation, weather conditions, limited access to food and stress. These circumstances require a high level of cognitive ability (including psychomotor abilities) to overcome the physiological stress response and to be able to quickly and efficiently make decisions under stressful situations, especially in combat. The aim of the study was to assess the level of the psychomotor abilities of candidates for the Polish Special Forces. The study comprised 48 candidates for the Polish Special Forces (age: \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$30.06 \pm 2.87$$\end{document}30.06±2.87), 40 athletes (age: \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$27.93 \pm 3.91$$\end{document}27.93±3.91) and 40 non-athletes (age: 24). The study was performed using Test2Drive software. Four computer-based tests were used to assess the following psychomotor abilities: simple reaction time, choice reaction time, hand-eye coordination and two-dimensional visuomotor coordination/spatial orientation test (SPANT). The analysis demonstrated statistically significant differences in reaction time and motor time between the study groups. The shortest reaction time in each test was observed in athletes, while the shortest motor time was observed in soldiers. All the psychomotor tests, except for the number of correct answers in SPANT, demonstrated statistically significant differences between the studied groups. It was also found that military training had a positive effect on the motor time in every psychomotor test. As regards the reaction time, it was observed that the athletes were characterised with better reaction times than the special forces candidates. The study has confirmed that military training and sports training have a positive effect on the level of psychomotor abilities, especially motor time.

Analyzing the relationship between self-efficacy and impulsivity in amateur soccer referees

Soccer referees (SRs) are exposed to stressful situations during the competition that can affect decision-making, could be affected by impulsivity during the competition and therefore, require optimal psychological skills. The objective of this study was to ascertain and analyze the relationship between levels of impulsivity and self-efficacy of amateur SRs in the senior category. A total of 21 Spanish SRs participated in this study (age 23.57 ± 2.40 years and 7.81 ± 2.58 seasons of experience). Self-efficacy data were collected with the REFS questionnaire between 48 and 72 h before the competition. The impulsivity data were collected using the UPPS-P questionnaire 60 min before the start the competition. The results indicate that SRs with higher self-efficacy have lower levels of impulsivity, specifically in the dimensions of negative urgency (p < 0.01), positive urgency (p < 0.05), lack of premeditation (p < 0.001), and lack of perseverance (p < 0.001), as well as lower global impulsivity (p < 0.01). However, the SRs with the highest self-efficacy also obtained higher levels in the sensation seeking dimension (p < 0.05). In conclusion, the main finding of this study showed that self-efficacy is influenced by SR impulsivity prior to competition. These novel facts allow us to discover aspects related to decision-making in refereeing that can be trained to reach optimal levels.

Mass Casualty Incident: Do Tactical Tag Bracelets Improve Triage Performance by First Responders? A Randomized Controlled Mass Casualty Incident Simulation and Response of A French Gendarmerie Elite Unit

INTRODUCTION

Tactical triage replaces primary triage in the exclusion zone in mass murder or terrorist events to prioritize victims requiring life-saving interventions (LSIs) and/or rapid extraction in an environment with a lack of resources and under active threat. French gendarmerie tactical unit medical teams use triage bracelets during mass casualty incidents (MCIs). This study assessed the value of these bracelets in the tactical triage performance of nonhealthcare combat rescue operators in an MCI simulation.

OBJECTIVES

To compare triage performance with and without the use of bracelets based on categorization accuracy, LSIs, and time to end triage.

MATERIALS AND METHODS

Two groups of operators were randomly assigned to participate in an MCI simulation alone (10 simulated patients) with (intervention group) or without (control) bracelets. The primary outcome was triage performance assessed by the mass casualty triage performance assessment tools. The results were measured based on the LSI required, triage category, and time of completion of the task. Secondary outcomes were operator-perceived stress and self-efficacy.

RESULTS

Eleven operators (intervention group n = 5, control group n = 6) participated. Triage performance, based on a maximum score of 90, was better for the intervention group [72.200 (SD = 10.330) vs. 57.000 (SD = 12.961), P = .045]. Self-efficacy was increased after the simulation in the intervention group [45.00 47.2 (SD = 4.147) vs. 50.400 (SD = 5.505), P = .034)].

CONCLUSIONS

This is the first study to show the best triage performance among nonhealthcare combat rescuers using triage bracelets in an MCI simulation. The small sample size did not allow for external validity of the results. The initially calculated number of participants (N = 12) was not reached for operational reasons. The use of bracelets may have a place in the medico-organizational act of tactical triage during MCIs in exclusion zones. Further studies should be conducted to assess the value of triage bracelets by other first responders, including physician-nurse teams.

The Effect of Studying a Double Degree in the Psychophysiological Stress Response in the Bachelor's Thesis Defense

The aim of this research was to analyze the effect of studying a single or double degree in the psychophysiological stress response and academic performance of university students in their bachelor's thesis defense. We analyzed the autonomic stress response, cortical arousal, subjective distress perception, and the sense of objective and subjective academic fulfilment of 84 single-degree physiotherapy students and 26 double-degree sport sciences and physiotherapy students during their bachelor's thesis defense. The results showed that the bachelor's thesis defense was a stressful event for double-degree students, showing an activation of the sympathetic nervous system and presenting a higher autonomic habituation response for the double degree students compared to the single degree students. We found higher mean grades during the whole degree and higher grades in the written and oral bachelor's thesis academic achievements for single-degree students compared to double-degree students. No significant differences were found between single-degree and double-degree students in subjective distress perception and cortical arousal. No correlation was found between academic performance variables and subjective distress perception, cortical arousal, and autonomic modulation variables. We conclude that the bachelor's thesis defense produces a large anticipatory anxiety response in single-degree physiotherapy students and in double-degree sport sciences and physiotherapy students. Double-degree students showed higher levels of habituation and adaptability to the stressful event, with a better autonomic response. Academic achievements were significantly higher among single-degree students compared to the double-degree group.

New Training Program for the New Requirements of Combat of Tactical Athletes

Actual theaters of operations are complex contexts where soldiers must face different situations, such as symmetrical, asymmetrical, or close quarter combat. The requirements of the actual battlefield are different to the traditional conditioning military training. This new changing scenario produces an activation of the innate fight or flight defense mechanisms with large activations of the anaerobic metabolic pathways and the sympathetic autonomic nervous system. In these scenarios, the anaerobic, aerobic, and strength demands are so specific and the time to improve all training demands in the units is limited. We propose a new training periodization for the military population based on the latest research into the psychophysiological response of soldiers in actual theaters of operations (actual military missions) and actual civilian models of training and periodization to develop a specific, easy, and reliable periodization model for actual tactical athletes. This training intervention was developed in order to improve operational training according to the demands of actual theaters of operations, based on recent research in military and civilian populations. We tried to conduct a proposal that is easy to apply, with minimal use of material different to what could be found in a military base and that could be implemented in a short period of time.

Relationship between age, category and experience with the soccer referee's self-efficacy

Soccer referees (SRs) encounter stressful situations during competitions and sometimes even outside them, which may affect their decision making. Therefore, it is important that they possess or acquire optimal levels of self-efficacy, since it is related to less stress during competition, also guaranteeing sports performance and prevent sports abandonment. The objectives of this study were to characterize the profile, in terms of self-efficacy, of SRs depending on their category, age, and experience and to determine the relationship of these factors on SR self-efficacy. Two-hundred fifty-six Spanish referees participated in this study and Referee Self-Efficacy Scale was administered and completed. The results indicated that the SRs older than 25 years, of national category, and with experience greater than or equal to 8 years, have higher levels of self-efficacy than those with the least (p < .01). Likewise, moderate positive correlations were also observed between global self-efficacy and the category, age, and experience of the SRs. In conclusion, age, category and experience factors relate the self-efficacy of the SR, which can explain up to 17% of the variance, affecting decision-making and other decisive behaviors in the competition. These findings are of interest to delegations and referee committees seeking to implement psychological intervention programs to prevent burnout and abandonment of sports practice due to the consequences of low self-efficacy.

The effect of experience on the psychophysiological response and shooting performance under acute physical stress of soldiers

Present research studied the psychophysiological response and shooting performance taking into consideration the experience of the soldier after a physical stress protocol, which leaded to acute fatigue conditions. Sixty soldiers were divided into experienced and non-experienced groups to conduct a high-intensity interval training (HIIT) based on endurance type exercises (10 intervals of 40 m run at maximum intensity with 2 changes of direction and 45 s of recovery. Psychophysiological and shooting performance variables were measured before, during and after the HIIT protocol. Significant increases in heart rate, blood lactate, lower limbs strength, as well as a significant decrease in blood oxygen saturation and body temperature were found in both groups. Shooting performance was affected by experience and fatigue, being more accentuated in non-experienced. Present HIIT protocol elicited a similar psychophysiological response than in previously reported combat manoeuvres, thus proving to be an optimal stimuli approach/intervention for soldier's specific physical preparation.

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

OBJECTIVES

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.

METHODS

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.

RESULTS

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.

CONCLUSION

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.

Assessment of Resilience of the Hellenic Navy Seals by Electrodermal Activity during Cognitive Tasks

Stress resilience plays a key role in task performance during emergencies, especially in occupations like military special forces, with a routine consisting of unexpected events. Nevertheless, reliable and applicable measurements of resilience in predicting task performance in stressful conditions are still researched. This study aimed to explore the stress response in the Hellenic Navy SEALs (HN-SEALs), using a cognitive–physiological approach. Eighteen candidates under intense preparation for their enlistment in the HN-SEALs and 16 healthy controls (HCs) underwent Stroop tests, along with mental-state and personality examination. Simultaneously, electrodermal activity (EDA) was assessed during each one of cognitive testing procedures. Compared to healthy control values, multiple components of EDA values were found decreased (p < 0.05) in the HN-SEALs group. These results were associated with an increase in resilience level in the HN-SEALs group, since a restricted sympathetic reactivity according to the reduced EDA values was observed during the stressful cognitive testing. This is the first report providing physiological measurements of the sympathetic response of HN-SEALs to a stressful situation and suggests that EDA turns out to be a simple and objective tool of sympathetic activation and it may be used as a complementary index of resilience in HN-SEALs candidates.

Can anxiety in undergraduate students in a high-fidelity clinical simulation be predicted? A randomized, sham-controlled, blinded trial

INTRODUCTION

High-fidelity clinical simulation has implied a revolution in health science training. Despite its benefits, some drawbacks could hinder the learning process, especially the anxiety produced during such scenarios.

OBJECTIVES

The aim of the present work is to develop a predictive model capable of determining which students will present high levels of anxiety.

DESIGN

We performed a randomized, sham-controlled, blinded trial in which students were randomly assigned to four scenarios and played one of two possible roles.

METHODS

Before and after the simulation we assessed the anxiety level along with physiological and analytical parameters. The main analyzed outcome was an increase of ≥25% in anxiety compared with baseline.

RESULTS

The type of scenario or the role played had no effect on anxiety. The predictive model presented an Area Under the Receiver Operating Characteristics of 0.798 (95% CI: 0.69-0.90; p < 0.001), with age and systolic blood pressure being protective factors against anxiety.

CONCLUSIONS

Our results showed that the anxiety level developed during simulation could be predicted. The application of this predictive model when associated to appropriate techniques to deal with increased anxiety levels could improve the learning process of medical students during simulations.

Portable Biosensors for Psychophysiological Stress Monitoring of a Helicopter Crew

This study aims to analyze the psychophysiological stress response of a helicopter crew using portable biosensors, and to analyze the psychophysiological stress response differences of experienced and non-experienced crew members. We analyzed 27 participants (33.89 ± 5.93 years) divided into two different flight maneuvers: a crane rescue maneuver: 15 participants (three control and 12 military) and a low-altitude maneuver: 12 participants (five control and seven military). Anxiety, rating of perceived exertion, subjective perception of stress, heart rate, blood oxygen saturation, skin temperature, blood lactate, cortical arousal, autonomic modulation, leg and hand strength, leg flexibility, spirometry, urine, and short-term memory were analyzed before and after both helicopter flight maneuvers. The maneuvers produced a significant increase in stress and effort perception, state of anxiety, and sympathetic modulation, as well as a significant decrease in heart rate, blood oxygen saturation, leg and inspiratory muscle strength, and urine proteins. The use of biosensors showed how a crane rescue and low-altitude helicopter maneuvers produced an anticipatory anxiety response, showing an increased sympathetic autonomic modulation prior to the maneuvers, which was maintained during the maneuvers in both experienced and non-experienced participants. The crane rescue maneuver produced a higher maximal heart rate and decreased pulmonary capacity and strength than the low-altitude maneuver. The psychophysiological stress response was higher in the experienced than in non-experienced participants, but both presented an anticipatory stress response before the maneuver.

Effect of Stress on Autonomic and Cardiovascular Systems in Military Population: A Systematic Review

Stress is regulated by the autonomous nervous system, increasing the sympathetic modulation when a threat is perceived. A multifactorial response usually leads to significant behavioural modifications and alterations on homeostasis and physical and psychological status. Moreover, stress is an emotional response that can lead to psychosocial and psychophysiological adversity. Regarding military population, military operations and combat exposure are important stressors that influence acute and chronic stress response in soldiers, affecting their performance and health. A bibliographic search was carried out between April and May 2019, focusing on recent studies (2013–2019) that analysed psychophysiological response, stress, stress regulation, heart rate, heart rate variability, and posttraumatic stress disorder in military population. Autonomic and cardiovascular chronic stress seems to be modulated by experience and previous specific training of each military unit. Physical exercise, music embedded with binaural beat technology, bidirectional sensory motor rhythm training, heart rate variability biofeedback, and transcutaneous vagal nerve stimulation are the main techniques applied to balance stress and to recover body homeostasis. Since military population are usually exposed to multiple stressors, knowing previous training and experience, together with developing techniques to balance stress, is the main practical application in this field of study to balance autonomic and cardiovascular systems.

Airsoft: an efficient and motivating cardiovascular training choice

BACKGROUND

Obesity and sedentarism have reached pandemic levels, postulating World Health Organization physical exercise as an important key factor for the prevention and treatment. In order to find a motivating and effective physical activity, we conducted this research intending to analyze the physiological and mechanical demands of an airsoft game.

METHODS

Cardiovascular and mechanical activity were analyzed by heart rate monitors and GPS in 32 sedentary subjects (27.3±6.2 years; 26.3±7.9 BMI).

RESULTS

Participants performed moderate to vigorous aerobic intensity for 3 hours and 20 min of which 55.2% was between 60-70% of their maximal heart rate and 14.2% above 70% of it, turned into distance 9.5 km of which 91.5% was moderate and 8.5% vigorous intensity.

CONCLUSIONS

A single airsoft game performed by sedentary subject exceed the international recommendation of physical activity and weekly physical activity of US adults' citizens. This motivating and outdoor activity is an effective alternative to increase the population's physical activity levels.

Psychophysiological response in night and instrument helicopter flights

Instrument and night flights are sources of mishaps: they produce stressful contexts to aircrews in which operability can be affected. This study aimed to analyse the effect of night and instrument flights in cortical arousal, autonomic modulation, muscle strength, and stress perception. 23 people were analysed (8 helicopter pilots, 4 helicopter mechanics - Spanish Air Forces - and 11 controls) before and after instrument and night flight exposition. Lactate and perceived exertion rose after flights. Anxiety was higher in instrument than in night flights. Pilots had a higher sense of anxiety before a flight compared to mechanics, although mechanics experienced a higher raise of heart rate during flight, with lower heart rate variability. Breath capacity was affected in pilots. Cortical arousal was more affected in unexperienced than in experienced aircrew during flights. These data suggest differences in their previous training. Practitioner summary: Night and instrument helicopter flights produced a different psychophysiological response of aircrew. These results could help to design specific training for aircrew that usually face instrument and night manoeuvres. Specific training based on high-intensity interval training integrated with reverse periodisation could improve their preparation. Abbreviations: BMI: body mass index; BOS: blood oxygen saturation; BT: body temperature; CA: cognitive anxiety; CFFT: critical flicker fusion threshold; ES: effect size; FEV1: forced expiratory volume in 1 second; FVC: forced vital capacity; HF: high frequency; HR: heart rate; HRV: heart rate variability; HIS: isometric handgrip strength; LF: low frequency; NVG: night vision googles; PEF: peak expiratory flow; pNN50: proportion of differences between R-R intervals higher than 50 ms; RMSSD: square root of the mean of the sum of the squared differences between adjacent normal R-R intervals; RPE: rated of perceived exertion; SA: somatic anxiety; SC: self confidence; STAI: state trait anxiety inventory.

Psychophysiological Stress Response in an Underwater Evacuation Training

Background: This research aimed to analyze the psychophysiological stress response of air crews in an underwater evacuation training. Materials and Methods: We analyzed in 36 participants (39.06 ± 9.01 years) modifications in the rating of perceived exertion (RPE), subjective stress perception (SSP), heart rate (HR), blood oxygen saturation (BOS), cortical arousal (critical flicker fusion threshold, CFFT), heart rate variability (HRV), spirometry, isometric hand strength (IHS), and short-term memory (ST-M) before and after an underwater evacuation training. Results: The maneuver produced a significant (p ≤ 0.05) increase in the SSP, RPE, Mean HR and maximum HR (Max HR), and a decrease in minimum HR (Min HR) and HRV. Conclusion: An underwater evacuation training produced an increase in the sympathetic nervous system modulation, elevating the psychophysiological stress response of the air crews, not negatively affecting their cortical arousal.

Determining the psychophysiological responses of military aircrew when exposed to acute disorientation stimuli

INTRODUCTION

Exposure to enviromental flight conditions may impair performance and physical integrity, thus training in simulated environments it is a key factor. This research aimed to study the psychophysiological response, cortical arousal and autonomic modulation of pilots and medical aircrew personnel during disorientation exposure, considering gender, experience, flying hours and body mass index (BMI) as influencial variables.

METHODS

A total of 47 soldiers (37 men and 10 women, 22 medical aircrew personnel and 25 fighter pilots) of Spanish Air Forces faced 25 min of vestibular, proprioceptive and visual disorientation.

RESULTS

Disorientation exposure elicited an increased psychophysiological response, significant increases in isometric hand strength, cortical arousal, autonomic modulation, perceived stress and effort in both groups while a significant decrease in respiratory muscle capacity and blood oxygen saturation in the medical aircrew group were found. Cross-sectional analysis showed gender differences, males presented greater parasympathetic activity and strength. Larger BMI was associated with greater levels and perception of stress as well as lower cardiovascular performance and sympathetic modulation. Furthermore, experience, previous training and larger flying hours correlated with greater parasympathetic modulation.

CONCLUSION

Disorientation exposure produces an increase in cortical arousal and decrease in the parasympathetic nervous system either in pilots and medical aircrew personnel. In addition, medical aircrew personnel are less adapted to disorientation stimulus presenting significantly higher psychophysiological stress response, thus complementary physical training should be mandatory.

Psychophysiological anxiety response of a rescue helicopter crew in a crane rescue manoeuvre

Background

This research aimed to analyse the psychophysiological modifications of a rescuer helicopter crew in a crane rescue manoeuvre.

Methods

We analysed in eight participants (32.5±6.6 years) divided in four categories (pilot, mechanic, rescuer and control) with variables of anxiety, rating of perceived exertion (RPE), stress subjective perception (SSP), heart rate, blood oxygen saturation (BOS), skin temperature, blood lactate, cortical arousal, autonomic modulation, legs and hands strength, legs flexibility, spirometry, urine, and short-term memory before and after a helicopter crane rescue manoeuvre.

Results

The manoeuvre produced a significant (p≤0.05) increment in the RPE, SSP, anxiety, blood lactate and sympathetic modulation, and a decrease in BOS and pulmonary capacity.

Conclusion

A helicopter rescue crane manoeuvre produced an increase in the sympathetic nervous system modulation, increasing the psychophysiological response of the crew independently of their experience or role. This information allowed us to improve actual specific operative training in this population.

Autonomic and cortical response of soldiers in different combat scenarios

INTRODUCTION

The study of chronic and acute responses when exposed to extreme, aggressive and stressful environments, such as in combat environments, is becoming increasingly popular as such information leads to better optimisation of soldiers' physical and psychological performance, as well as mission effectiveness and efficiency. Due to internal complexity, uncertainty and variability of real combat scenarios, a specific approach to all possible types of military combat scenarios is necessary.

METHODS

Modifications in the autonomic modulation and cortical arousal before and after asymmetrical, symmetrical and close quarter combat simulations were analysed in 31 male professional veteran soldiers (age: 34.5±4.2 years) with between seven and 18 years of experience in their respective units, as well as experience in international missions in current conflict areas such as Lebanon, Afghanistan, Bosnia, Kosovo and Iraq.

RESULTS

The three combat situations produced a non-significant decrease in cortical arousal after combat simulations, presenting a trivial effect size in symmetrical and close quarter combat situations and a small effect size in asymmetrical situations. HR increased significantly in the three combat situations, and close quarter combat produced the highest sympathetic modulation of the three situations analysed.

CONCLUSION

Symmetrical, asymmetrical and close quarter combat situations produced an increase in sympathetic modulation, being highest in the close quarter combat situation, where actions are performed at a close distance and in closed spaces.

Multidisciplinary Analysis of Differences Between Finisher and Non-finisher Ultra-Endurance Mountain Athletes

Ultra-endurance races are one of the most physically and psychologically demanding sports, depending performance on several elements. The aims of the present study were (i) to analyze differences in selected psychophysiological parameters between finisher and non-finisher ultra-endurance mountain athletes, and (ii) to analyze modifications in psychophysiological parameters before and after an ultra-endurance mountain event. Selected psychophysiological variables were assessed in 46 finishers and 24 non-finishers in two over 100 km ultra-endurance races were examined. We found how an ultra-endurance mountain race produced dehydration, a decrease in systolic blood pressure, weight and leg strength muscle values, as well as an increase in heart rate and rate of perceived exertion values. Finishers presented lower systolic blood pressure, weight, body mass index, half marathon time and fluid intake before competition day compared to non-finishers. In addition, body mass index, pre-race hydration, and performance in lower distance races were predictors of performance in these ultra-endurance mountain races.

The Impact of Acute Stress Physiology on Skilled Motor Performance: Implications for Policing

Investigations of police performance during acutely stressful situations have primarily focused on higher-order cognitive processes like attention, affect or emotion and decision-making, and the behavioral outcomes of these processes, such as errors in lethal force. However, behavioral outcomes in policing must be understood as a combination of both higher-order processes and the physical execution of motor skills. What is missing from extant police literature is an understanding of how physiological responses to acute stress contribute to observed decrements in skilled motor performance at the neuromuscular level. The purpose of the current paper is to fill this knowledge gap in the following ways: (1) review scientific evidence for the physiological (i.e., autonomic, endocrine, and musculoskeletal) responses to acutely stressful exposures and their influence on skilled motor performance in both human and animal models, (2) review applied evidence on occupationally relevant stress physiology and observed motor decrements in performance among police, and (3) discuss the implications of stress physiology for police training and identify future directions for applied researchers. Evidence is compelling that skill decay is inevitable under high levels of acute stress; however, robust evidence-informed training practices can help mitigate this decay and contribute to officer safety.

Psychophysiological Patterns Related to Success in a Special Operation Selection Course

Actual theaters of operations require fast actions from special operations units with a high level of readiness and survival. Mission accomplishment depends on their psychological and physiological performance. The aim of the present study was to analyze: (1) the physical parameters related with success in a special operation selection course; and (2) the modifications of the psychological profile of recruits before and after a special operation selection course. Fifty-five male soldiers of the Spanish Army (25.1 ± 5.0 years, 1.8 ± 0.1 cm, 76.8 ± 7.9 kg, 24.4 ± 2.5 kg/m²) undertaking a 10-week special operation selection course performed a battery of physiological and psychological tests. Results showed how successful soldiers presented higher leg strength, anaerobic running performance, and cardiovascular response than non-successful soldiers. The psychological values of life engagement test, acceptance and action questionnaire, coping flexibility scale, and perceived stress scale did not present significant differences after the selection course. We can conclude that success in a special operation selection course was related to higher anaerobic and cardiovascular fitness. This special operation selection course did not modify the psychological profile of successful soldiers.

Psychophysiological modifications in an assault infantry manoeuvre using a chemical, biological, radiological and nuclear personal protective equipment

Introduction

The study of the psychophysiological response during combat actions has been poorly researched despite its importance for warfighter training and specific instruction. The aim of the present investigation was to analyse the effect of chemical, biological, radiological and nuclear personal protective equipment (PPE) on the psychophysiological response, mechanical and physical load and fine motor skills of professional soldiers in an endurance infantry manoeuvre.

Methods

16 soldiers conducted an assault manoeuvre with and without the PEE in separate days. We analysed before and after the manoeuvre the psychophysiological response, fine motor skills, shooting test accuracy and anxiety state.

Results

The use of PPE produced significantly higher (p<0.05) stress, fatigue, temperature, HR, somatic anxiety and time in middle and high HR zones and significantly lower values in speed average and maximum speed. These findings can be used to improve the training and specific instruction for professionals who require the use of PPE equipment.

Conclusion

The use of the PPE suit in an assault manoeuvre produces a decrease in the speed of movement, an increase in HR, body temperature, somatic anxiety and subjective perception of effort.

Effect of different combat jet manoeuvres in the psychophysiological response of professional pilots

Extreme limits of the human body could be reached in air combat. We analysed 29 fighter pilots before and after offensive and defensive manoeuvres on heart rate (HR), heart rate variability, leg and hand strength, spirometry, temperature, blood oxygen saturation (BOS), lactate, hydration (USG), cortical activation, memory and psychological variables. The defensive manoeuvre produced a significative decrease in forced vital capacity from spirometry and USG post flight, a moderate effect in the decrease in cognitive anxiety and an increase in leg strength. A significant increase in mean HR and an increase with a large effect size was reported for Stress Subjective Perception and Rating of Perceived Exertion in both manoeuvres. With this data we can conclude that high level of physical fitness and specific training programs should be applied to fighter pilots.

Evaluation of Central Fatigue by the Critical Flicker Fusion Threshold in Cyclists

Central fatigue related in sport stimuli was studied by Critical Flicker Fusion Threshold (CFFT) to know the influence of exercise on the central nervous system (CNS), but there is a lack of knowledge about the central or peripheral fatigue in endurance events. This study aimed to analyze changes in CFFT before and after the incremental cycle ergometer test as a means to assess the fatigue of the CNS. CFFT ascending and descending, the subjective criterion and sensory sensitivity were analysed in 8 professional male cyclists (72.1 ± 5.59 kg, 180.3 ± 6.43 cm, 17.4 ± 0.7 years) before and after a maximum incremental cycle ergometer test (start 50w increases 50w each 5 min). In this incremental test, the induced fatigue was probably more a peripheral phenomenon than one due to central nervous system fatigue, because sensory sensitivity did not significantly decrease. In conclusion, an incremental cycle ergometer test increased the cortical arousal and does not affect negatively the CNS of professional cyclists.

Psychophysiological response of different aircrew in normobaric hypoxia training

Hypoxia remains the most important hazard in high altitude flights, but there is still a need for deeper analysis of the effect of hypoxia exposition in the psychophysiological and cognitive functions. The aim of this study was to study the effect of hypoxia training in cortical arousal, autonomic modulation, muscle strength and cognitive function. We analysed 23 male aircrew personnel of the Spanish Army and Air Force (10 Helicopter Pilots, 7 Transport Aircrew, 3 Transport Pilots and 3 F-18 Fighter Pilots) before, during and after a normobaric hypoxia exposition. Hypoxia produced an increase in perceived stress and effort, a higher Heart Rate and a decreased function of breath muscles. Working memory and pattern recognition were impaired after hypoxia exposition. Significant differences were found in cognitive tests performance among aircrew groups, suggesting differences on their previous training. These results can improve specific training for better preparation of pilots and aircrews for hypoxic threats. Practitioner summary: Distinct aircrew preparation produces a different hypoxia exposition effect on psychophysiological response and cognitive functions. Hypoxia produced an increase in Heart Rate, a decreased function of breath muscles, being more negatively affected in Transport Pilots. Cognition abilities were impaired after hypoxia exposition, independently of the aircrew group.

Psychophysiological Monitorization in a Special Operation Selection Course

The present research aimed: i. to analyse the psychophysiological response of soldiers undertaking a special operation selection course; ii. to study the relationship between fat and muscle loss and the psychophysiological response of soldiers undertaking a special operation selection course. We analysed 46 professional soldiers from a special operations unit (25.1 ± 5.0 years, 1.8 ± 0.1 cm, 76.8 ± 7.9 kg, 24.4 ± 2.5 kg/m²) undertaking the last phase of their 10 weeks special operation selection course. Before and immediately after the exercise the following variables were assessed: Stress subjective perception, fatigue subjective perception, rating of perceived perception, cortical arousal, body temperature, blood oxygen saturation, spirometry, isometric hand strength, lower body muscular strength, urine, body composition, life engagement test, coping flexibility scale, acceptance and action questionnaire, perceived stress scale, anxiety state, visual analogue scale and differential aptitude test. A special operation selection course induced an intense stress and physical response as suggested by the psychophysiological changes with a significant (p < 0.05) increase in fatigue and stress subjective perception, blood oxygen saturation, Ph, cognitive impairment and motivation-loss. Moreover, decreased leg strength, peak expiratory flow, cortical arousal, body composition, body weight, fat and muscle mass, anxiety stress, alertness, sadness and tension decreased after the exercise. Regarding body composition, higher muscle mass loss participants were related to a higher cognitive impairment and similar psychophysiological response than lower fat mass loss participants.

Higher use of techniques studied and performance in melee combat produce a higher psychophysiological stress response

We aimed to analyse the effectiveness of an operative training in soldiers' psychophysiological and melee combat performance. Nineteen soldiers performed a 50-hr training for 10 weeks. After training, they were divided into two groups: higher performance group (HPG) and lower performance group (LPG), then they conducted a realistic melee simulation where psychophysiological response, task performance, and the utilization of techniques learned were measured. HPG presented a significantly (p < 0.05) higher heart rate, blood lactate, and jump height; a lower blood oxygen saturation, task performance mark, use of studied techniques than LPG after the simulation; and a higher low frequency/high frequency ratio of heart rate variability previous the simulation than LPG. Independent of performance and the use of studied techniques by the participants, the melee simulation produced an increase in fight or flight response, increasing rated of stress and perceived exertion, sympathetic modulation, and physiological response. A specific melee combat training program induced different modifications in psychophysiological and task performance depending on the level of studied technique used. HPG presented a significantly higher cardiovascular response than LPG and time perception, and memory presented no differences between groups; also HPG presented a significantly higher use of studied techniques.

Psychophysiological response of air mobile protection teams in an air accident manoeuvre

Different extreme contexts elicit a stress response on human body, specifically on combat produces an increase of sympathetic nervous system and a direct effect on the organic response. This research aimed to study the psychophysiological response of an air security force in a simulated air accident in a hostile area and its subsequent subterfuge to a safe area. We analyzed 13 soldiers (32.4 ± 8.0 years) from an air security force unit of the Spanish Air Force who were divided into three teams to conduct the manoeuvre. We analyzed before and after the manoeuvre psychological well-being scale, personal views survey, recovery-stress questionnaire (REST-52 Sport); heart rate variability, visual analogue scale, rated of perceived exertion, spirometry, hydration and hand strength were analyzed during the four days of the manoeuvre: This produced a significantly (p < .05) increase in sympathetic modulation, hand strength, dehydration status, general and specific stress from RESTQ-52. With this data we can conclude that an air accident manoeuvre of three nights and four days causes in the air mobile protection team a high sympathetic nervous system modulation, increases on muscle strength manifestations and stress and a dehydration status.

Effect of experience, equipment and fire actions in psychophysiological response and memory of soldiers in actual underground operations

The present study aimed to analyze the effect of underground operations on the psychophysiological and memory response of soldiers taking into consideration experience, the use of nocturne vision systems and previous combat actions on the psychophysiological response. Seventy participants were recruited and divided in four groups, three experimental groups with different experimental conditions, SNFV (Soldiers No-Fire Night-Vision), SFV (Soldiers Fire Night-Vision), SNFNV (Soldiers No-Fire No Night-Vision), and one control group, CNFV (Control No-Fire Night-Vision). We analyzed modifications in psychophysiological and memory response pre and post an underground operation. The underground operation produced a significant increase (p < 0.05) in blood lactate, blood oxygen saturation, rated perceived exertion, heart rate, cognitive and somatic anxiety and sympathetic modulation in all groups. Groups with higher stress values scored higher incorrect items in the memory post mission questionnaire. The higher psychophysiological activation correlated positively with cognitive impairment and lower memory. We concluded that an underground operation produced an increase in psychophysiological activation and a negative effect on memory, being modulated by previous training and experience. The lack of special equipment as night vision systems in underground operations induced similar stress response than prior combat actions, decreasing conciseness of time.

Use of Psychophysiological Portable Devices to Analyse Stress Response in Different Experienced Soldiers

Previous studies have shown that actuate stress have a negative effect on working memory, visio-spatial ability and symptoms of disassociation. We conducted the present research with the aim of to analyse the effect of experience and training in psychophysiological response, attention and memory of soldiers in combat. Variables of blood lactate, blood glucose, blood oxygen saturation, body temperature, heart rate, lower body muscular strength manifestation, autonomic modulation, cortical arousal, cognitive and somatic anxiety, and memory by a post mission questionnaire were analysed before and after a combat simulation in 49 soldiers of Spanish Army. Combat simulation produced a significant increase (p < 0.05) in blood lactate, blood glucose, blood oxygen saturation, rated perceived exertion, heart rate, cognitive and somatic anxiety. Significant increase in low frequency domain and significant decrease in high frequency domain of the heart rate variability was found in experienced and highly trained soldiers. The percentage of correct response in the post mission questionnaire indicated that elements better remembered were those related with soldier integrity and considered as a possible life threat, Significant differences in the post mission questionnaire by experience and training was also found. Correlation analysis showed that higher psychophysiological activation correlated positively with cognitive impairment and lower memory. As a conclusion, higher experienced soldiers presented higher physiological activation as well as cognitive and memory impairment than lower experienced soldier after a combat simulation and memory function was modulated by the stimulus nature.

Use of Portable Digital Devices to Analyze Autonomic Stress Response in Psychology Objective Structured Clinical Examination

The aim of the present study was to explore changes in the autonomic stress response of Psychology students in a Psychology Objective Structured Clinical Examination (OSCE) and their relationship with OSCE performance. Variables of autonomic modulation by the analysis of heart rate variability in temporal, frequency and non-linear domains, subjective perception of distress strait and academic performance were measured before and after the two different evaluations that composed the OSCE. A psychology objective structured clinical examination composed by two different evaluation scenarios produced a large anxiety anticipatory response, a habituation response in the first of the evaluation scenarios and a in the entire evaluation, and a no habituation response in the second evaluation scenario. Autonomic modulation parameters do not correlate with academic performance of students.

Psychophysiological response in parachute jumps, the effect of experience and type of jump

We aimed to analyse the effect of experience and type of parachute jump on the psychophysiological responses of jumpers. We analysed blood oxygen saturation, heart rate, blood glucose, lactate and creatinkinase, leg strength, isometric hand strength, cortical arousal, specific fine motor skills, self-confidence and cognition, and somatic and state anxiety, before and after four different parachute jumps: a sport parachute jump, a manual tactical parachute jump, tandem pilots, and tandem passengers. Independently of the parachute jump, the psychophysiological responses of experienced paratroopers were not affected by the jumps, except for an increase in anaerobic metabolism. Novice parachute jumpers presented a higher psychophysiological stress response than the experienced jumpers, together with a large anticipatory anxiety response before the jump; however, this decreased after the jump, although the high physiological activation was maintained. This information could be used by civil and military paratroopers' instructors to improve their training programmes.