Fatigue Management

The benefits of naps can be offset by lengthy periods of drowsiness due to sleep
inertia. However, these post-nap ‘hangover’ effects can be minimised by
timing naps to coincide with the peaks in the circadian cycle. Avoid napping
during the circadian trough or circadian lull if you may need to be quickly
alert. Naps are usually more effective in the late afternoon or late evening;
although, daylight morning naps are of benefit, particularly after a night
without sleep. One-hour naps are useful for reducing the frequency and
duration of microsleeps.
Some research indicates that during periods of chronic sleep loss, naps taken
late at night (2200 to 2400 hours) help to maintain performance, while naps
taken in the early morning (0400 to 0600 hours) help to recover performance
(but the latter are likely to cause significant sleep inertia). Afternoon naps
tend to contain proportionally more Stage four sleep. If possible, naps should
be taken in quiet surrounds. A nap in the corner of a busy command post, or
alongside a supply route, is likely to reduce the recuperative value of sleep
because sleep will be disrupted by noise and activity. Even if the soldier does
not momentarily awaken, research has shown that noise and surrounding
activity will cause cortical arousals in the subconscious brain that fragment
the wave patterns and stages of the sleep cycle. The result is disturbed and,
hence, ineffectual sleep.
... to experience all the unusual forms of sleep, one has to
join the Army. We have slept on the ground, with a rock for
a pillow and the stars for blankets. We have also slept in
mud with torrential rain for eiderdown. ... I am blessed in
a very special way - I can sleep under any circumstances. I
have slept under the one blanket and a couple of inches of
snow. I have also slept in the back of a three-ton truck,
driven at twenty miles per hour across country at night,
with the lights out.
X61400, ‘On Sleep',
Khaki and Green, 1943
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