Fatigue Management

With frequent food, how long can you go without sleep? You
can manage a third night without sleep and maybe a
fourth, with all the symptoms getting worse, with attention
harder and harder to command, with more and more
activity necessary to keep you awake...
Psychology for the Fighting Man
YANK: The Army Weekly, 3 Sep 1943
Sleep is perhaps the major cyclic event in our lives, and it ranks with food and
water as crucial to health and survival. Common sense tells us that sleep
helps to restore mind and body. It is clear that sleep is essential if soldiers are
to maintain operational efficiency.
No human being knows how sweet sleep is but a soldier.
J.S. Mosby
War Reminiscences, 1887
Although sleep is a feature in our lives, there remains a great deal of
uncertainty about why we sleep, how sleep occurs and what actually happens
during sleep. Sleep is not a state of inactivity as many would think. Rather,
sleep is associated with complex and highly organised activities in the body
and the brain. In fact, many aspects of our physiology are busier during sleep
than when we are awake (for example, the secretion of several hormones) and
show remarkably stable patterns of activity. At the same time, sleep inhibits
some systems and abilities, inducing a disconnection from the outside world,
whereby sensory input is blocked or suppressed to such an extent that we
become temporarily blind and deaf.
A definition of sleep. The unconscious state regularly and naturally
assumed by man. Sleep is characterised by an almost complete absence of
outward movement and reduced sensory awareness. During sleep, both
mental and physical recuperation take place. Sleep shows a complex,
highly organised pattern of diverse physiological variables.
Stages of Sleep
Recordings of electrical waves in the brains of sleeping humans show five
quite distinct stages of sleep, extending from light sleep to progressively
deeper sleep. These different stages are associated with brain waves of
different characteristics as shown in Figure 1.
2