Adaptation under Extreme Environmental Conditions

• Published date: 01 May 1970
• DOI: 10.1177/000271627038900103
• Author: George E. Ruff
• Date: 01 May 1970
• Subject Matter: Articles

Adaptation under Extreme Environmental Conditions
By GEORGE E. RUFF
ABSTRACT: Living systems tend to maintain in equilibrium
variables associated with their continued existence. Environ-
mental conditions which force these variables beyond their
normal ranges produce stress within the system. Feedback
mechanisms then seek to restore equilibrium. Stress arises
from overloads or underloads of energy and information, as
well as from inputs which have threatening implications.
The process of adapting to stress depends partly on the nature
of the stress-producing agent and partly on the mechanisms
available to the system. Exposure to heat, for example,
involves dilation of blood vessels, reduction of body activity,
and sweating to reduce body heat. At the same time, the
system undergoes neurophysiological and endocrine changes
which are found in many other types of stress. When the
system is subjected to extreme environmental conditions for
an extended period of time, adaptive responses may become
increasingly costly. A possible outcome is one of the "dis-
eases of adaptation" described by Selye. Eventually, adap-
tive mechanisms may fail and the system may collapse.
The stress encountered by most individuals arises from the
symbolic, rather than the physical, aspects of their environ-
ment.
Among the exceptions are groups such as antarctic
explorers, mountain-climbers, prisoners of war, and crews of
space vehicles. Although problems arise under these condi-
tions, most studies of men under stress reveal a remarkable
capacity for adaptation to extreme environments.
George E. Ruff, M.D., Philadelphia, Pennsylvania, is Professor of Psychiatry, School
of Medicine, University of Pennsylvania. While chief of the Stress and Fatigue Section
of the Air Force’s Aerospace Medical Laboratory, he carried out research on stress in
Air Force operations, isolation, confinement, and crew-selection. He was in charge of
psychiatric evaluation and psychological testing of the first group of astronauts, and
subsequently participated in a study of stress imposed on the astronauts during Project
Mercury. Dr. Ruff’s current research deals with the psychophysiology of stress and
with medical education.
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T HE process of adaptation to ex- past experience, inputs which do not
treme environmental conditions can
disturb one system may require strenu-
be conceptualized by viewing each indi-
ous adaptive changes in another.
vidual or group as a system with inputs
An example of adaptation to an ex-
and outputs of energy and information.
treme environment can be provided by
Energy inputs come from the physical
an acceleration experiment, in which
environment-for example, intakes of
gravitational force is applied by a hu-
oxygen, food, or pathogenic bacteria.
man centrifuge. If the subject is re-
&dquo;Information&dquo; is conveyed by energy
quired to do a continuous tracking task,
which has been organized in such a way
his performance remains normal at low
that it can be coded and decoded.
&dquo;g&dquo; levels. If the rate of information
input is increased, the tracking output
will increase
INPUTS, OUTPUTS,
to a
AND ADAPTATION
maximum, then de-
crease if the information overload ex-
Each system maintains in equilibrium
ceeds the subject’s adaptive capacity.
the variables associated with its con-
If the information input is maintained
tinued existence.
These variables are
at an optimal level, and the energy
confined within limited ranges by feed-
input is varied by increasing gravita-
back mechanisms. Inputs which force
tional stress, circulation becomes im-
them beyond their normal range produce
paired and compensatory adjustments
stress within the system. Adjustments
must be made. These include cardiac
made to restore equilibrium constitute
output and secretion of noradrenaline,
the process of adaptation, which in-
which causes peripheral blood vessels to
volves reorganization of the system to
contract and redistributes blood to more
prevent failure of subsystems required
critical areas. As the subject struggles
for survival.
harder to carry out his task, perform-
Changes in the environment may re-
ance not only may remain normal, but
quire adaptive efforts by presenting the
may improve. But when the gravita-
system with overloads or underloads of
tional load becomes too great, cerebral
energy or information.
Examples of
circulation fails, performance decreases,
energy overloads are excesses of heat,
and the subject may black out.
pressure, sound, or radiation.
Under-
The effect of the implications of this
loads include lack of vitamins, water,
environmental change can be demon-
...