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THE LAW OF STRESS
Robert A. Dato, Ph.D., NCPsyA

To fully understand the modern use of the term "stress", it is necessary and instructive to review the evolution of the stress concept. The first scientific study of stress was conducted by Galileo Galilei (1633), who observed that rods pulled in tension had a strength proportional to their cross-sectional areas. By studying springs, Robert Hooke (1679) discovered the Law of Elasticity, which states that, within the elastic limits of a body, force is proportional to extension. Over a century later, another stress pioneer, Thomas Young (1807), developed Young's Modulus of Elasticity, a constant which denotes the stiffness of a material within its elastic limits, It was not until the 19th century that a French mathematician, Augustin Cauchy (1822), coined the terms "stress" and "strain," defining stress as the pressure per unit area and strain as the ratio of the increase or decrease in the length of an object to its original length.

In the 20th century, the stress concept entered the field of the biological sciences. Walter Cannon (1915) conducted physiological research which resulted in his describing the stress response as a "fight or flight response." The General Adaptation Syndrome was discovered by a Canadian endocrinologist, Hans Selye (1936), who began the current trend to describe pressures with the term "stressors" and the biological response as "stress." He defined biological stress as the sum of nonspecific changes in the body caused by function or damage.

As this brief review of the evolution of the stress concept indicates, physical scientists use "stress" to indicate a force, pressure, or stimulus, whereas biological scientists use "stress" to indicate a change or response. The opposite use of the term by these two groups is unfortunate because it confuses the meaning of the concept for the scientific community as well as the general public.

What will be proposed here is a natural and universal law that both scientists and the public may find more memorable and useful than the myriad of stress definitions available today. The LAW OF STRESS states that STRESS IS THE DIFFERENCE BETWEEN PRESSURE AND ADAPTABILITY OF ANY KIND. In formula form, STRESS = PRESSURE - ADAPTABILITY, or S = P - A. This law clearly implies that stress is unadaptability. We have here a further evolution of the stress concept because it is presented as a function of the interaction of two key variables, and also provides us with a guide to stress management by advancing from an event model ("response") to a need/skill model ("unadaptability").

THE EVOLUTION OF THE STRESS CONCEPT

THE LAW OF STRESS IN VISUAL FORM
S = P - A

HIGH     PRESSURE     LOW

Stress = Pressure - Adaptability

MATHEMATlCAL ASPECTS OF THE LAW OF STRESS

The Law of Stress is a general law applying to inorganic as well as organic structures, including their biological and psychological systems. This Law states that stress is the difference between pressure and adaptability. It may be summarized as: Stress = Pressure -Adaptability, and may be condensed to: S = P-A.

The Stress Function forms the boundary between the areas of stress and adaptability for any given amount of pressure. Visual representation of the Law is presented below in order to provide a view of how stress, adaptability, and pressure vary with one another. Since stress is identical mathematically with unadaptability, the Stress Function is constructed of two variables, stress (y) and pressure (x). Additional components of the Function include: a Constant of Elasticity (k), an Exponent of Elasticity (e), and an Exponent of Plasticity (p). EL designates the Elastic Limit of the Function.

© 1978 Dr. Robert Dato, Dato Leadership Institute
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