Background
Military exercises generate high levels of stress to simulate combat, providing a
unique opportunity to examine cognitive and physiologic responses of normal humans
to acute stress.
Methods
Cognitive and physiologic markers of stress were evaluated before, during, and after
an intense training exercise conducted for 53 hours in the heat. Cognitive performance,
mood, physical activity, sleep, body composition, hydration, and saliva cortisol,
testosterone, and melatonin were assessed. Volunteers were 31 male U.S. Army officers
from an elite unit, aged 31.6 ± .4 years.
Results
Wrist activity monitors documented that soldiers slept only 3.0 ± .3 hours during
the exercise and were active throughout. Volunteers lost 4.1 ± .2 kg (p < .001) of weight, predominately water (3.1 ± .3 L) (p < .001). Substantial degradation in cognitive function, assessed with computerized
tests, occurred. Vigilance, reaction time, attention, memory, and reasoning were impaired
(p < .001). Mood, including vigor (p < .001), fatigue (p < .001), confusion (p < .001), depression (p < .001), and tension (p < .002), assessed by questionnaire, deteriorated. The highest cortisol and testosterone
levels were observed before the exercise.
Conclusions
This study quantifies the overwhelmingly adverse impact of multiple stressors on cognitive
performance, mood, and physiologic parameters, during a continuous but brief military
exercise conducted by highly motivated, well-trained officers.
Key words
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Article info
Publication history
Published online: January 11, 2005
Accepted:
November 9,
2004
Received in revised form:
November 4,
2004
Received:
August 6,
2004
Identification
Copyright
© 2005 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.
