Physiological Decrements During Sustained Military Operational Stress

Abstract

Missions conducted by the U.S. Military during combat involve a multitude of operational stressors that can cause deterioration in physical and military performance of soldiers. Physiological consequences of sustained operational stress include decrements in anabolic hormones, skeletal muscle mass, and loss of bone mineral density. The objective of this review is to examine the current literature and provide commanders with information on the physical and physiological decrements in soldiers conducting sustained operations. The intent is that this will provide commanders with insight on how to plan for missions to incorporate possible countermeasures to enhance or sustain warfighter performance.

Evaluation of occupational physical load during 6-month international crisis management operation

“…Consequently, these stressors may lead to degraded performance and increased risk for illnesses and task or mission failure [2,7]. Internal or external threats in a military environment may lead to acute stress modifying the function of the autonomic nervous system that may be indirectly evaluated by studying metabolic and neuroendocrine responses such as vagal activity of the heart and catabolic (e.g., cortisol) or anabolic biomarkers (e.g., testosterone, insulin-like growth factor-1) [2,8]. An increase in the concentration of catabolic hormones and stressful situations per se may activate immune function [8].…”

“…Military tasks are often performed with extra loads and protective equipment such as body armor, which increase the energy expenditure of such activities [1,[3][4][5][6]. In addition to physical strain, negative energy balance, sustained readiness and sleep deprivation, high ambient temperature, altitude and environmental toxins may all separately or in combination disturb homeostasis of the body and thus, increase stress of soldiers [1,2,7]. Consequently, these stressors may lead to degraded performance and increased risk for illnesses and task or mission failure [2,7].…”

“…Many of the operational military duties have been characterized as prolonged, low intensity physical activity (PA) intermittent by shorter bouts of higher intensity activities [1,2]. Military tasks are often performed with extra loads and protective equipment such as body armor, which increase the energy expenditure of such activities [1,[3][4][5][6].…”

“…In addition to physical strain, negative energy balance, sustained readiness and sleep deprivation, high ambient temperature, altitude and environmental toxins may all separately or in combination disturb homeostasis of the body and thus, increase stress of soldiers [1,2,7]. Consequently, these stressors may lead to degraded performance and increased risk for illnesses and task or mission failure [2,7]. Internal or external threats in a military environment may lead to acute stress modifying the function of the autonomic nervous system that may be indirectly evaluated by studying metabolic and neuroendocrine responses such as vagal activity of the heart and catabolic (e.g., cortisol) or anabolic biomarkers (e.g., testosterone, insulin-like growth factor-1) [2,8].…”

Active and passive heat stress similarly compromise tolerance to a simulated hemorrhagic challenge

“…This workload was selected for two reasons: 1) it is a similar intensity to that commonly occurring during routine military foot/reconnaissance patrols (3,23), and 2) it is a workload that can be maintained for sufficient period of time in relatively nontrained subjects to achieve the desired increases in core temperature. While it may be insightful to identify the combined influence of heat stress and exercise at substantially higher (or even maximal) intensities on LBNP tolerance, the subjects may not have been able to tolerate the workload for a sufficient duration to achieve the required increases in core temperature.…”