Cambios hormonales en soldados aclimatados durante una marcha en gran altitud con esquí de montaña / Hormonal changes in acclimatized soldiers during a march at a high altitude with mountain skis

Background: The aim of the present study is to identify the physiological impact of acute exposure to high altitudes on special acclimatized troops of the Chilean Army. Twenty-nine soldiers carried out a nocturnal winter march on mountain skis at an initial altitude of 2,800 m and up to 3,640 m. Two separate blood measurements were taken. The first one was taken the day before the march (Pre-sample) and the second one just after returning to the base camp (Post-sample). All subjects had been acclimatized prior to the study. For hypothesis comparison purposes, the normality of the distribution was tested using the Shapiro-Wilk test. To determine if there were significant differences between the Pre and Post tests, a paired-samples Student t-test was applied for the variables with a normal distribution, and the Wilcoxon test was applied for the variables without a normal distribution. In all cases, a level of significance of 95% (p<0.05) was taken into consideration. Results: Exposure of acclimatized troops to altitudes of 2,800 m to 3,640 m has an impact on the endocrine parameters and on the reduction of cortisol (p<0.01), total testosterone (p<0.0001), free testosterone (p<0.0001) and the free testosterone-cortisol ratio (p<0.01). Likewise, an increase in total leukocytes (p<0.0001), neutrophils (p<0.0001), monocytes (p<0.0001) and basophils (p<0.001), as well as a decrease of eosinophils (p<0.0001) and lymphocytes (p<0.01), was observed. No hematological changes were detected. Conclusions: Endocrine changes were observed during high-altitude winter marches on mountain skis carried out by accli-matized Special Operation Troops, resulting in decreased cortisol and free and total testosterone levels. A stress condition due to the high altitudes also affected the anabolic/catabolic environment, which manifested as a significant decrease in the free testosterone/cortisol ratio. No hematological changes were identified. Marked changes were observed in some white cell series

Introducción: El objetivo del presente estudio es identificar el impacto fisiológico (con especial atención a los parámetros endocrinos y hematológicos) de la exposición aguda a gran altitud (GA) en tropas especiales aclimatadas del Ejército de Chile. Veintinueve soldados llevaron a cabo una marcha nocturna con esquí de montaña invernal a una GA de 2.800 m. hasta 3.640 m. Se tomaron dos muestras de sangre. La primera muestra fue tomada el día antes de la marcha (Pretest) y la segunda muestra justo después al regresar al campamento base Post test (a los 2.800 m). Todos los sujetos se encontraban aclimatados antes del estudio. Para cada análisis se testeo la normalidad de las distribuciones empleando el test de Shapiro-Wilk. Se calculó el promedio y la desviación estándar para cada medición. Para determinar si existían diferencias significativas entre el pre y post test se aplicó la prueba de t-Student pareada para las variables con distribución normal y el test de Wilcoxon para las variables que no tenían distribución normal. En todos los casos se consideró un nivel de confianza de 95% (valor p < 0,05). Resultados: La exposición de las tropas aclimatadas a GA tiene un impacto en los parámetros endocrinos y en la reducción de cortisol (p <0,01), testosterona total (p <0,0001), testosterona libre (p <0,0001) y el ratio testosterona libre-cortisol (p <0.01). Asimismo, se observaron un aumento de leucocitos (p <0,0001), neutrófilos (p <0,0001), monocitos (p <0,0001) y basófilos (p <0,001), así como una decrease de eosinófilos (p <0,0001) y linfocitos (p < 0.01). No se observaron cambios en la serie roja. Conclusiones: La marcha invernal nocturna con esquí de montaña en GA para tropas de operaciones especiales aclimatadas presento cambios endocrinos con disminución del cortisol, testosterona libre y total. Una condición de estrés por la marcha en GA también afectó al ambiente anabólico/catabólico, lo que se ve reflejado en una disminución significativa en el cociente testosterona libre/cortisol. No se observaron cambios hematológicos. Se observaron cambios significativos en algunas células de la serie blanca

Efectos hormonales y hematológicos en una marcha invernal de baja altitud en militares chilenos / Hormonal and hematological effects in a low-altitude winter march in chilean military

Introducción: Las exposiciones intermitentes a gran altitud tienen efectos agudos sobre algunos marcadores biológicos, como la testosterona, pero no así en baja altitud. Dado que el entrenamiento de soldados debería ir asociado a tareas militares específicas, adquiere gran importancia valorar los cambios fisiológicos que puedan producirse en determinadas circunstancias (como la altitud) pero durante la realización de actividades propias de las unidades militares. Objetivo: Identificar los cambios hematológicos y en las hormonas Testosterona Libre (TL), Testosterona Total (TT ) y Cortisol en una marcha nocturna a baja altitud en soldados de operaciones en montaña. Metodología: 32 Militares masculinos (26,3 ± 4,50 años, 75,1 ± 7,6 kg) realizaron una marcha invernal nocturna con equipo y un desnivel entre los 902 y 1648 m. Se obtuvieron muestras de sangre antes y después de la marcha y se midió TL, TT, cortisol y hemograma: hematíes (Hmt), hemoglobina (Hb), hematocrito (Htto) y volumen corpuscular medio (VCM). Resultados: Se produjo un descenso significativo de los valores de TL y TT sin cambios en el cortisol plasmático. También se observó un descenso en las cifras de Hmt, Hb, Htto y VCM. Conclusión: Una marcha invernal con equipo de combate, en baja altitud y con un desnivel de 746 m, produce un descenso significativo de los valores plasmáticos de Testosterona (libre y total) en soldados de una unidad de operaciones en montaña. No se observan cambios en los valores de cortisol. Se detecta una reducción significativa de hematíes, hemoglobina, hematocrito y VCM que podrían deberse a un efecto de hemodilución

Introduction: Intermittent exposures at high altitude have acute effects on some biological markers, such as testosterone, but not at low altitude. Since the training of soldiers should carry out specific military activities, is very important to asses physiological changes that can occur in particular circumstances (such as altitude) but during the performance of the activities of the military units. Objective: To identify the hematological changes and the hormones Free Testosterone (TL), Total Testosterone (TT ) and Cortisol during a nocturnal march at low altitude in soldiers of mountain operations. Methodology: 32 male military (26.3 ± 4.50 years, 75.1 ± 7.6 kg) performed a nocturnal winter march with equipment between 902 and 1648 m of altitude. Blood samples were obtained before and after the march, and TL, TT, cortisol and blood count were measured: red blood cells (Hmt), hemoglobin (Hb), hematocrit (Htto) and mean corpuscular volume (MCV ). Results: There was a significant decrease in TL and TT values without changes in plasmatic cortisol. A reduction in the values of Hmt, Hb, Htto and VCM has also been observed. Conclusion: A winter march with combat equipment, at low altitude and with a unevenness of 746 m, produces a significant decrease in the plasma values of Testosterone (free and total) in soldiers of mountain operations. No changes in cortisol values are observed. A significant reduction of red blood cells, hemoglobin, hematocrit and MCV is detected, which could be due to a hemodilution effect

Impact of Hypothermic Stress During Special Operations Training of Chilean Military Forces.

Introduction: The Chilean Army considers processes that can optimize physical capacities for responding to the impact of situations and given stressors. The study of the effect of hypothermia as a stressor agent (HSA) and its relationship with cardiovascular, hematological, anthropometric, endocrine, and immunological parameters has not been fully addressed experimentally in military populations. Objective: To identify the endocrine, hematological, cardiovascular, and immunological changes caused by HSA and to associate these variables with body composition and physical fitness in the military special operation courses of the Chilean Army. Materials and Methods: Forty-two male subjects were exposed to remain in cold water (10.6 °C) in the context of regular military operations training, the longest time of exposure was determined by individual volitional limits. The measurements were taken in pre-hypothermia conditions, then 2 d later under acute hypothermia condition, and finally during the course period of lesser physical and psychological stressors where the baseline measurements were taken. The statistical analysis consisted of testing normality of the distribution through the Shapiro-Wilk test, assessing the equality of variances through the Levene test, and variance analysis by applying the ANOVA test (analysis of variance). The Bonferroni test was used for multiple comparison correction and the Pearson test for correlations between two variables. The level of significance was of p < 0.05. Results: The main finding of this study is that HSA has a significant impact at the cardiovascular level and produces an increment in the cell population of the immune and hematologic systems. Significant hormonal changes were observed: ACTH (r = 0.50, p < 0.002), cortisol (r = 0.32, p < 0.03), free testosterone (r = 0.13, p < 0.002), total testosterone r = 0.31, p < 0.002), and anthropometrics (r = -0.51, p < 0.05). However, there is no significant correlation between physical fitness and HAS. Conclusions: All subjects experienced hypothermia stress elicited by immersion in cold water. This was evidenced by the decrease in core temperature as well as cardiovascular, endocrine, anthropometric, and immunological changes. Individual differences exist between subjects and their resistance to hypothermia in cold water. These differences are not explained by the physical fitness profile but rather respond to a greater body adiposity index and minor changes in the adrenocorticotropic hormone and cortisol hormone. An acute hypothermia stress condition also affects the anabolic/catabolic environment. Finally, HSA produces an increase in the cell population of the immune system. The authors believe that this study allows to standardize HSA exposure times during regular military operations training by identifying the physiological impacts under this extreme environment. At present, the availability of intra-abdominal temperature measurement apparatus with capsule thermometers raises the interest of corroborating the findings of the current study through the use of such measuring devices. Likewise, an interesting line of research for the future would be to compare the HSA against a psychological evaluation with the purpose of identifying the stress management mechanisms among subjects of these characteristics and include heart rate variability measurements as an indicator of sympathetic stress.