Introduction: Military operations, especially combat, expose individuals to multiple stressors, including sleep loss, food deprivation, and sustained physical activity. Civilians, such as woodland firefighters, disaster victims, and relief workers, are also exposed to such environments. Our laboratory developed a brief, intense, laboratory-based simulation of a multistressor environment which included sleep loss, continuous physical activity, and food deprivation.
Methods: During this sustained operations (SUSOPS) scenario, and a control period, cognitive performance and mood were measured in 13 volunteers. The scenario included road marches, battle drills, and land navigation. Physical activity and sleep were assessed with actigraphs.
Results: Significant decrements in visual vigilance, choice reaction time, and matching-to-sample, a test of short-term memory, were observed. Marksmanship was stable and physical activity significantly increased. Mood states assessed by the Profile of Mood States (POMS: Tension, Depression, Anger, Vigor, Fatigue and Confusion) also significantly deteriorated.
Discussion: Cognitive function declined more extensively and rapidly than physical performance. Decrements in cognitive performance were comparable to those in a field study conducted for an equivalent period of time in uncontrolled conditions. This demonstrates that decrements in cognitive function and increased physical activity, similar to those in highly stressful field environments, can be duplicated under controlled conditions. The simulated SUSOPS scenario is an appropriate paradigm for assessment of adverse effects of military and civilian multistressor environments on human performance, physiology, and interventions designed to mitigate them.