[ASGMAG.COM] AMERICAN SURVIVAL GUIDE 17“ASTHEDEGREEOFDEHYDRATION
PROGRESSES,URINEOUTPUTWILLDROP
ANDCONFUSIONANDFATIGUEWORSEN.A
PERSONWHOISSEVERELYDEHYDRATED
WILLEVENTUALLYDEVELOPPURPLE
FINGERNAILS.”weight, while children are about 65 percent and
infants closer to 75 percent. Water is a critical
component of all of the body’s metabolic
processes.
Minimum water intake varies greatly de-
pending upon weight, environment, exertion,
nutritional state, and genetics. Most people
will tolerate a 3 percent to 4 percent decrease
in total body water fairly well. A 5 percent to
8 percent decrease will precipitate signifi cant
symptoms. More than 10 percent results in
serious impairment, while loss of 15 percent to
25 percent of total body water is usually fatal.
SYMPTOMS OF DEHYDRATION
The initial symptoms of mild dehydration are
fatigue and dizziness. These effects are com-
pounded by other insults like food and sleep
deprivation. Early dehydration also tends to
cause headache, decreased appetite, and a
general grouchiness.
As the degree of dehydration progresses,
urine output will drop, and confusion and
fatigue worsen. A person who is severely
dehydrated will eventually develop purple
fingernails. Once the water loss becomes
critical an imbalance in sodium will typically
precipitate seizures.
In a hostile environment a total body
water loss as low as one to two percent can
potentially result in demonstrable cognitive
impairment. As dehydration is a function of
stress, exertion, and environment this can be
insidious. While it is typically presumed that
dehydration is a major concern in hot climates,
failure to drink adequately in arctic areas can
be just as dangerous.
Diarrhea and vomiting make these problems
exponentially worse. While fluid replacement
drinks offer some theoretical benefit, con-
sumption of excessively sugary or salty foods
can exacerbate the problem. Oral rehydration
will reverse the effects of mild dehydration
rapidly.
SLEEP DEPRIVATION
There is an entire discipline of medicine
dedicated to studying sleep, but we still don’t
understand it well. Different people have
different sleep requirements, but getting inad-
equate sleep over time results in a cumulative
sleep debt. This is not something that you can
really train for.
There are four recognized stages of sleep.
These four stages comprise a sleep cycle that
typically lasts 90 to 110 minutes. Each stage
lasts between 5 and 15 minutes. This four-
‹ Below: It doesn’t take
the zombie apocalypse
to create a survival
situation. An auto
accident or even an
injury while on a long
run can unexpectedly
test your survival skills.stage cycle repeats over and over throughout the night.
Stage 1 is light and easily aroused. This is the phase wherein you might experience those
hypnic jerks or the sensation of falling.
Stage 2 sleep is a deeper sleep state wherein everything calms down. Your body temperature
drops a bit and heart rate decreases.
Stage 3 non-REM sleep is the good stuff. This is the most restorative phase of sleep. It can be
difficult to arouse people from Stage 3 sleep. This is the type of sleep that spawns sleepwalk-
ing, sleep talking, bedwetting, and night terrors. Stage 3 non-REM sleep involves the release of
human growth hormone and several restorative processes for the immune system.
REM, or Rapid Eye Movement, sleep makes up about a quarter of your sleep cycle but is nec-
essary for cementing memory and rejuvenating the body. Awakening is easier from REM sleep
than from Stage 3 non-REM sleep but can result in a more pronounced sense of grogginess
afterward. REM sleep is when we dream.THE PRACTICAL EFFECTS OF SLEEP DEPRIVATION
The initial manifestations of a sleep deficit are yawning, fatigue, irritability and moodiness.
With a cumulative sleep deficit comes a depressed mood, forgetfulness, an inability to concen-
trate and a lack of motivation. As REM sleep is required to cement memories, a sleep deficit can
result in difficulty learning new concepts. Eventually the sleep-deprived person becomes clumsy
and can develop an increased appetite.
Sleep deprivation is an easy and safe way to increase stress in a training environment, so the
military makes widespread use of it. On two occasions when I was a soldier, I went four days
without sleep. In both cases I began to hallucinate. Once a sleep deficit is properly repaid, the
sundry negative symptoms of sleep deprivation should abate.
When significantly deprived of sleep, the body compensates by stealing brief periods of micro-