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pumped from the heart to the
aorta. The diastolic pressure is
the lowest, produced when
resting between beats. Normal
blood pressure lies between
110-145 mmHg (systolic) and
70-90 mmHg (diastolic) – you
might see a figure of 120/80
(120 over 80).
Blood
55% plasma, for transporting
CO2, nutrients and hormones,
and 45% cells. Red cells
transport oxygen via
haemoglobin, and white cells
(leukocytes) fight infection.
Platelets are for clotting blood.
Heart Disease
Heart disease can be grouped
into 3 categories:
· Hypertensive—from high
blood pressure, working
the heart harder so it gets
enlarged (anxiety, etc.).
· Coronary, or Arteriosclerotic—
hardening of the arteries
through excessive calcium,
or cholesterol, which again
makes the heart work
harder (bad diet).
· Valvular or rheumatic—
where valves are unable to
open or close properly,
allowing back pressure to
build up (old age).
Adrenaline increases the speed
and force of the heart beat.
To reduce the risks of heart
disease, double your resting
pulse for at least 20 minutes 3
times a week.
Fatigue
It’s not so much the amount of sleep
you get, but when you get it that
counts, so fatigue is just as likely to
result from badly planned sequences
of work and rest. A surprising
amount (over 300) of bodily
functions depend on the cycle of day
and night—we have an internal
rhythm, which is modified by such
things. You naturally feel best when
they're all in concert, but the slippery
slope starts when they get out of
line. The best known
desynchronisation is jet lag, but it
also happens when you try to work
nights and sleep during the day—
bright light can fool your body into
thinking it's day when it's not. One
day for each time zone crossed is
required before sleep and waking
cycles get in tune with the new
location, and total internal
synchronisation takes longer
(kidneys may need up to 25 days).
Even the type of time zone change
can matter—6 hours westward
requires (for most people) about
four days to adjust—try 7 for going
the other way! This Eastward flying
compresses the body's rhythm and
does more damage than the
expanded days going west; North-
South travel appears to do no harm.
Symptoms of jet lag are tiredness,
faulty judgement, decreased
motivation and recent memory loss.
They're aggravated by alcohol,
smoking, high-altitude flight,
overeating and depression, as found
in a normal pilot's lifestyle.
In view of this, commercial pilots
have a maximum working day that is
intended to ensure they are rested
The two types of fatigue are acute
and chronic, the former being shortHuman
Factors 257
term, or more intense, and the latter
arising from more long-term effects,
like many episodes of acute fatigue.
Foods low in carbohydrate or high
in protein help fight fatigue,
especially "healthy" ones, like fruit or
yoghurt, or cereals, especially
granola. Coffee, of course, contains
caffeine, which keeps you awake (as
does tea), but too much can lead to
headaches and upset stomachs. Be
aware that it takes about 5 minutes
for caffeine to kick in, and people
who drink unleaded coffee
(decaffeinated) still report the
unpleasant side effects (the process
that removes the caffeine is allegedly
just as harmful in different ways).
Caffeine has a half-life of about 3
hours, and although it might not
stop you getting to sleep, it will
affect the quality of that sleep.
Sleep is actually a state of altered
consciousness, in which you don't
lose awareness of the external world,
as any mother will tell you. It is part
of a daily cycle which is actually 25
hours long – that is, the sleeping and
waking rhythm is about an hour
longer than the normal day of 24
hours, which itself is a mean figure
anyway (Moore-Ede, Sulzman &
Fuller, 1982). This is why flying West
is easier on the system than flying
East – the body's rhythm is extended
in the right direction.
It's worth noting that a shave is
about equal to 20 minutes of sleep,
in terms of refreshing you, and
washing your face or brushing your
teeth are also good ideas, as is
moving around for 5-10 minutes.
Types of Sleep
In a typical cycle of 90 minutes,
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