Fatigue: Is It a Stress or a Strain? Is fatigue an injury to the
human body from which we need time to recover? Or is fatigue just being
tired or over tired, for which a good night’s sleep is the common
remedy?
That is the question: is fatigue just a stress on the body
and mind and as such something from which the body and mind can bounce
back without any damage? Or is fatigue rather something more insidious
than just a stress? Is it possible that fatigue is actually a strain,
that is to say, an injury, some kind of damage to the body and mind? If
fatigue is an injury to the body and mind, and overstress resulting in a
strain, does the the body and mind need time to heal back to health
from this injury?
Does repeated stress lead to more damaging
strain? Can the road to recovery from the strain of fatigue to the body
and mind be a lot longer than just one good night’s sleep?
I am a
professional international pilot of 40 plus years, twenty in the US
Navy, much of it on carriers with extended hours, much of it at night
and twenty at a global package delivery airline, much of it in
international operations and much of it at night. I have a degree in
liberal arts and a degree in metallurgical engineering. I have no degree
in sleep-ology, so any sheep skin focused stickler can stop reading
right here.
But I am a human being who has spent many nights and
days working multiple shift hours far in excess of any reasonable eight
or ten hour schedule, over tired, falling asleep at the switch as the
saying goes from fatigue, but trying to do a good job, a necessary job
and trying to have a life outside of work at the same time. The one
thing that I have noticed is that recovery from fatigue seems to take
much more time than just one good night’s sleep. So I began to wonder
why? Was I injured and needing to heal? But where was the injury, how
can I feel it and how can I measure it? How much time did I need for
full physiological recovery of my body and my mind? Was I required to
sacrifice the health of my body and my mind for some jobs? If so, how am
I being separately compensated for both the work I do and the
sacrificing of the health of my body and my mind?
Well again, I
didn’t study physiology in college, but I did receive a reasonably good
education in flight physiology during these past 40 years and I have
read most of what the fatigue and sleep experts have written in industry
literature. It is all good, many studies, great work by some fine
people. And I didn't study labor relations and compensation, but I did
recognize that there are two issues to working at night and working
extended hours repeatedly, the issue of compensation for the work and
compensation for the hours past any reasonable shift.
But even
then I often come away with more questions fatigue than answers. What
is the pineal gland anyway and how does it work? Does the brain need
oxygen and sugar to function? Why does worry have the same affect as
caffeine? Why is a hot shower so refreshing when tired? Why do kids fall
asleep when tired where ever they sit down? Why do older folks struggle
often with sleep? Why do I feel so tired on weekend layovers that I
just want to relax and do nothing stressful, just recover and hope for
restful sleep? Why does fatigue knock your brain out like a light switch
turning off, even when you are not lying down in bed? How does it know
to do that? What else do we not know about fatigue?
So, in my
curiosity I harkened back to my university days studying metallurgy. I
remembered that we studied the physical relationship between stress and
strain on a metal sample and on samples of wood, plastic, ceramics and
other material. Stress is the force that is applied to the metal sample
and strain is the amount of deformation that occurred to the sample
piece as a result of the stress.
What we found was that for the
most part, metals deform elastically under lower levels of stress and
essentially return to their original shape, size and strength. This
means that the stress is borne by the material and it springs back into
its original being.
In physiology terms, we might say that one all
nighter isn’t so bad; just get a good night’s sleep and you will bounce
back, good as new and be ready to go just fine. Probably all true,
especially so for lab studies.
Now back to the metal samples. As
we continue to add stress to the metal samples, somewhere down the line
we get strain that is no longer elastic. The sample now begins to
deform. It is still strong and has some of its original strength, but it
has become bent, stretched and weakened. The stress that was put on
the sample past the elastic strain point damaged the sample. It is
deformed plastically, that is, it will no longer spring back into it’s
original size, shape and strength. Moreover, if the stress is
continually applied, not only does the strain become a deformation in
size, shape and strength, the sample will eventually break, fail and
just come apart, often with a very loud bang.
Now, back to
the human physiology story. Again I am not an expert, but I wondered if
the human body and mind did not react in a similar manner, that is to
say, that the body and mind can take some stress, some sleeplessness,
and bounce back elastically with just a good night’s sleep.
But
what happens to the human body and mind when the stress of sleeplessness
is applied continuously, and applied over the ability to take this
stress undamaged? Can the stress eventually cause a strain, that is,
damage to the body and mind, damage that one good night’s sleep is
insufficient time in which to recover? Can we over stress the body and
mind with fatigue? Can fatigue be damage that affects the body and mind
such that it is injured and needs time to recover from the injury?
I
don’t know the answers to all of these questions. But I believe that
these questions need to be asked. Is fatigue more of a strain at some
point that just a stress? Can we do injury to our bodies and minds by
stressing them with fatigue to the point that they are damaged in some
manner and no longer function well? Can this damage be such that one
good night’s sleep is insufficient in which to recover? Have we broken
something that needs mending? Have we injured something in ourselves
which needs recovery?
Is fatigue more of a strain than a stress?