Analysis of heart rate variability during emergency flight simulator missions in fighter pilots.

INTRODUCTION: Managing emergency situations in different simulated flight segments can entail a workload that could affect the performance of military pilots. The aim was to analyse the modifications in neurovegetative balance (using HR variability, HRV) of professional fighter pilots attending learning/training sessions on emergency situations in a flight simulator. METHODS: A total of 18 pilots from the Spanish Air and Space Force were included. HRV was recorded simultaneously during diverse simulated emergency situations in three different flight segments: take-off, in-flight and landing. RESULTS: The comparison between take-off and in-flight revealed a statistically significant increase (p<0.05) in percentage of consecutive RR intervals that differ by more than 50 ms from each other (pNN50), root mean square of the successive differences (rMSSD), standard desviation 1 and 2 (SD1 and SD2), and a statistically significant decrease (p<0.000) in stress score (SS) and in the sympathetic to parasympathetic ratio (S:PS). Between flight and landing, a statistically significant increase (p<0.05) in mean HR, minimum HR, maximum HR, SS and S:PS was shown, while experiencing a significant decrease (p<0.000) in pNN50, rMSSD and SD2. Finally, between take-off and landing, the variables which showed significant changes (p<0.05), with these changes being a significant increase, were mean HR, minimum HR, maximum HR, rMSSD, SD1 and SD2. SS and S:PS ratios showed a statistically significant decrease (p<0.000). CONCLUSIONS: An emergency situation in a flight simulator manoeuvre produced an anticipatory anxiety response in pilots, demonstrated by low HRV, which increased during the flight segment and decreased during the landing segment of the flight.Trial registration number NCT04487899.

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.

Effects of Hypoxia on Selected Psychophysiological Stress Responses of Military Aircrew.

There is a lack of information on the psychophysiological response of pilots under hypoxic conditions. The study of the physiological, psychological, cardiorespiratory, neurological, behavioural, sensory, and cognitive symptoms that may appear during training in hypobaric chambers is essential to optimize the training processes of aircrew members. Thus, the present study is aimed at analyzing the psychophysiological responses of aircrew members in an incremental hypoxia training protocol. Psychophysiological responses of 44 aircrew members (34 males and 10 females) in an incremental hypoxia training protocol (3 minutes at 0 meters, 8 minutes at 5,000 meters, and maximum time at 7500 meters) were measured. Results suggested that the incremental hypoxia training protocol did not affect cortical arousal and handgrip strength; however, it increased the sympathetic tone, perceived stress, perceived effort, and heart rate and decreased forced expiratory volume and blood oxygen saturation. Thus, we concluded that acute hypoxic hypobaric exposure leads to decreased parasympathetic tone, blood oxygen saturation, and maximal spirometry values, without negatively affecting handgrip strength and cortical arousal. This information will lead to find specific training systems that meet the real needs of aircrew.

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.

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.

Could academic experience modulate psychophysiological stress response of biomedical sciences students in laboratory?

The aim of the present research was to analyse the subjective and objective psychophysiological stress response of experienced and non-experienced Pharmacy and Biotechnology students in laboratory practices. We analysed in 82 Pharmacy and Biotechnology degree students divided into two groups (non-experienced: n: 53; experienced: n: 29) the autonomic stress response by the analysis of heart rate variability (HRV) before, during and after and distress perception before and after a laboratory practice. Results showed how students in both groups presented a large anticipatory anxiety response at the beginning of the practise (low HRV values). During the entire laboratory practice, non-experienced students showed a maintained sympathetic modulation while experienced students presented a higher parasympathetic modulation (high HRV values) consistent with a habituation process. Laboratory practise performed by Pharmacy and Biotechnology students produced an anticipatory anxiety response independently of their experience, but, non-experienced students showed a lower habituation response in both subjective and objective stress records than experienced students at the end of the laboratory practice.

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 α-tocopherol megadoses on hematologic parameters and antioxidant capacity of rats in an ultraendurance probe.

This study was aimed to analyze the effect of two different megadoses of α-tocopherol (vit E) in the antioxidant activity and red and white blood series of Wistar rats after a 180-min ultraendurance probe. Three groups of 10 rats were analyzed; VEAG: acute administration of a megadoses of 5,000 IU/kg of vit E the day before the probe; VECG: chronic administration of 1,000 IU/kg/day of vit E for 6 days before the probe; CG: placebo administration. VEAG presented white cells, red blood cells, hematocrit, hemoglobin values significantly higher than CG and VECG (p < 0.05). The mean corpuscular hemoglobin and lymphocytes concentrations were significantly higher in the VECG than in the other two groups (p < 0.05). Similarly, VEAG presented a significantly higher vit E blood concentration than VECG and CG (p < 0.05), and VECG than CG (p < 0.05). Finally, we found a significantly positive correlation between trolox equivalent antioxidant capacity (TEAC) and red blood cells concentration (r = 0.374) and a significantly inverse correlation between TEAC and blood lactate concentration (r = -0.365). Our findings suggest that acute vit E megadoses could protect against transitory sport anemia symptoms and increase the white blood cell count in comparison with the chronic dose and control groups after an ultraendurance probe.

Enzymatic production of dietary nucleotides from low-soluble purine bases by an efficient, thermostable and alkali-tolerant biocatalyst.

Traditionally, enzymatic synthesis of nucleoside-5'-monophosphates (5'-NMPs) using low water-soluble purine bases has been described as less efficient due to their low solubility in aqueous media. The use of enzymes from extremophiles, such as thermophiles or alkaliphiles, offers the potential to increase solubilisation of these bases by employing high temperatures or alkaline pH. This study describes the cloning, expression and purification of hypoxanthine-guanine-xanthine phosphoribosyltransferase from Thermus thermophilus (TtHGXPRT). Biochemical characterization indicates TtHGXPRT as a homotetramer with excellent activity and stability across a broad range of temperatures (50-90°C) and ionic strengths (0-500mMNaCl), but it also reveals an unusually high activity and stability under alkaline conditions (pH range 8-11). In order to explore the potential of TtHGXPRT as an industrial biocatalyst, enzymatic production of several dietary 5'-NMPs, such as 5'-GMP and 5'-IMP, was carried out at high concentrations of guanine and hypoxanthine.

Use of Biotechnology Devices to Analyse Fatigue Process in Swimming Training.

The aim of the present research was to analyze the acute psycho-physiological response during a high intensity interval training (HIIT) session of trained swimmers. We analyzed blood lactate concentration, heart rate, heart rate variability (HRV), arms isometric strength, rating of perceived exertion (RPE) and cortical arousal before and after a HIIT session in 14 trained swimmers (16.2 ± 2.6 years 169.1 ± 10.2 cm 61.3 ± 9.9 kg). HIIT session consisted in: 4 × 10 m tethered swimming resting 90 s between sets, 3 min rest, 16 × 25 m maximum speed swimming resting 30 s between sets. Blood lactate concentration, cortical arousal, and rating of perceived exertion significantly increased (p < 0.05) after HIIT. HRV parameters significantly decreased after HIIT, showing an increase in sympathetic nervous system modulation. Results obtained showed the high impact of HIIT sessions on the swimmer's organism, which may be the cause of adaptation in this low volume training sessions.

The effects of intermittent hypoxia training on hematological and aerobic performance in triathletes.

The aim of the present research was to analyze modifications on hematological and aerobic performance parameters after a 7-week intermittent hypoxia training (IHT) program. Eighteen male trained triathletes were divided in two groups: an intermittent hypoxia training group (IHTG: n: 9; 26.0 ± 6.7 years; 173.3 ± 5.9 cm; 66.4 ± 5.9 kg; VO2max: 59.5 ± 5.0 ml/kg/min) that conducted a normoxic training plus an IHT and a control group (CG: n: 9; 29.3 ± 6.8 years; 174.9 ± 4.6 cm; 59.7 ± 6.8 kg; VO2max: 58.9 ± 4.5 ml/kg/min) that performed only a normoxic training. Training process was standardized across the two groups. The IHT program consisted of two 60-min sessions per week at intensities over the anaerobic threshold and atmospheric conditions between 14.5 and 15% FiO2. Before and after the 7-week training, aerobic performance in an incremental running test and hematological parameters were analyzed. After this training program, the IHTG showed higher hemoglobin and erythrocytes (p < 0.05) values than in the CG. In terms of physiological and performance variables, between the two groups no changes were found. The addition of an IHT program to normoxic training caused an improvement in hematological parameters but aerobic performance and physiological variables compared to similar training under normoxic conditions did not increase.

Short-term periodized aerobic training does not attenuate strength capacity or jump performance in recreational endurance athletes.

The purpose of this study was to investigate the effects of three different distributions of aerobic training on the isokinetic strength and vertical jump performance [SJ, CMJ and Abalakov (ABA)] in thirty middle-aged endurance athletes (38.7 ± 9.8 yrs; 174.7 ± 6.5 cm; 72.0 ± 9.8 kg). Three zones of training were required to quantify volume of training: Zone 1, low-intensity-training < VT1; Zone 2, threshold-training, between VT1 and VT2; and Zone 3, high-intensity-training > VT2. The INC group (n = 10) began training in the Zone 1 and then gradually built up training in Zone 2 and Zone 3, thereby increasing the intensity of aerobic activity over the 4-week training period. The CON group (n = 10) performed the same activity every week in Zones 1, 2 and 3. The FRE group followed a free distribution of endurance training loads (n = 10). The results showed significant decreases in peak torque knee extension 30° (p < 0.05) in CON group and significant decreases (p < 0.05) in ABA in FRE group. Results provide a physiological basis to support several performance studies that consistently indicate 5 d·wk(-1) endurance training does not impair strength development over the short term. In conclusion, variations in volume and intensity in training groups did not interfere with isokinetic strength and vertical jump performance.

Efectos agudos en el sistema nervioso central después de realizar una contrarreloj simulada en ciclistas cadetes / Acute effect on central nervous system after a simulated trial in cadets cyclists

Objetivos. El origen de la fatiga en el deporte ha sido ampliamente estudiado; a pesar de ello, no se conoce exactamente su funcionamiento. Una de las causas de la disminución de rendimiento en los deportistas es la fatiga del sistema nervioso central (SNC). El presente trabajo de investigación pretende estudiar los cambios en los umbrales Flicker Fusion (UFF) antes y después de realizar una contrarreloj simulada de 30 minutos en cicloergómetro, como medio para valorar la fatiga del SNC en un grupo de ciclistas entrenados de categoría cadete. Método. Se analizó a siete sujetos varones (62,6±4,11 kg, 172,8±7,94 cm, 14,7±0,8 años, 13,4±3,53% grasa, 21,0±1,83 kg/m2, consumo máximo de oxígeno [ml/kg/min] 63,2±5,13, consumo máximo de oxígeno [l]: 4,1±0,5). Se realizó una prueba de 30 minutos máximo en cicloergómetro. Previamente al test y al finalizar este, se realizaron las mediciones del UFF ascendente, el UFF descendente, el criterio subjetivo y la sensibilidad sensorial. Cada sujeto realizó el test de UFF en tres ocasiones, obteniéndose un valor promedio de ellos. Resultados. Los resultados muestran un aumento de la activación cortical después de la realización de la contrarreloj, por lo tanto, no se muestran signos de fatiga del SNC, ya que los resultados de sensibilidad sensorial aumentaron (pre: 30,1±4,3 Hz; pos: 32,4±6,3 Hz). Estos resultados coinciden con otros estudios en los que se realizaron esfuerzos de naturaleza similar. Conclusión. Una prueba máxima de 30 minutos en cicloergómetro no parece que genere fatiga en el SNC, medida con el sistema Flicker Fusion en ciclistas de la categoría cadete al no disminuir los UFF(AU)

Objectives. The study of origin of fatigue in sport has been extensively studied, it still does not know exactly how it works. One of the causes of decreased performance in athletes is fatigue in central nervous system (CNS). The present research aims to study changes in Flicker Fusion Threshold before and after a 30 minutes trial on a cycle ergometer, as a means to assess the CNS fatigue in a group of trained cyclists cadet. Method. Seven male subjects were analyzed (62.6 ± 4.11 kg, 172.8 ± 7.94 cm, 14.7 ± 0.8 years, 13.4 ± 3.53% fat, 21.0 ± 1.83 kg/m2, VO2max [ml/kg/min] 63.2 ± 5.13, VO2max [l]: 4.1 ± 0.5). They performed a 30 minutes maximum cycle ergometer trial. Prior to this trial and at the end, we measured following variables: Flicker fusion threshold ascending, Flicker fusion threshold descending, subjective criteria and sensory sensitivity. Each subject performed the test three times, Flicker Fusion Threshold obtaining an average value of them. Results. The results show increased cortical activation after the 30 minutes trial, therefore do not show signs of fatigue of the CNS, since the results of sensory sensitivity increased (pre: 30.1 ± 4.3 Hz; Post: 32.4 ± 6.3 Hz). These results are similar with other studies in which subject realized efforts with similar nature. Conclusion. It has been shown as 30 minutes trial on a cycle ergometer does not seem to generate fatigue in the CNS measured with Flicker Fusion system in cyclist of cadet category, because did not decrease the Flicker Fusion Threshold(AU)