The General Adaptation Syndrome

A theory formulated by Dr. Hans Selye is sometimes called stress theory, but more commonly the General Adaptation Syndrome (GAS). GAS provides a framework from which most exercise programs and training cycles can be designed. Dr. Selye’s clinical observations with humans and experiments with mice and rats led him to propose a three stage process employed by any living organism when adapting to a stimulus that tends to disrupt its normal functional state (homeostasis). The disrupting stimulus is called a stressor and may be beneficial (e.g., exercise) or harmful (e.g., germs). GAS proposes that when any stressor, such as physical trauma, infection, heat, or fright, is imposed on a living organism, the organism’s initial response results in a decrease in its ability to cope with additional stressors. This is called the shock or alarm stage of GAS. For example, if you are exposed to a flu virus your ability to cope with exercise is greatly reduced.

However, as time passes after the stressor exposure your body should make internal adjustments that result in adaptations, so that future exposure to the original stressor in particular, and to other stressors in general, will be less disrupting to homeostasis. Reversal of the shock phase is termed counter-shock, and it leads to the resistance phase of GAS. The effect of adaptation to a given stressor on your body’s ability to cope with other stressors is called cross-resistance. This is why a person who stays in shape through regular exercise can better withstand the pressures of work or the common cold.

If multiple stressors are imposed on your body, counter-shock may not occur, or the resistance phase may deteriorate into the third or exhaustion stage of GAS. The possible negative effects of multiple stressors are referred to as cross sensitization. Failure to recover from the shock phase, or the exhaustion phase of GAS, may also occur from a single very potent stressor or exposure to a given stressor for a prolonged period of time. Heavy physical exercise day after day for many weeks will probably result in over-training, which is a manifestation of the exhaustion phase of GAS.

The phasic structure of Dr. Selye’s adaptation theory is the basis for the concept of variation and training cycles for both general exercise and specialized conditioning for athletes at all competitive levels. An additional and very important concept of GAS is that of the body’s specific and non specific responses to stressors. The concept is that no matter what type of exercise, or what stressor in general, is imposed on your body, a non specific response will also occur. Non-specific responses affect your body as a whole through the nervous system and hormonal and other biochemical processes. The ultimate concept for you to grasp is that all stressors of whatever type result in essentially the same non-specific effects in addition to their own specific effects.

A burned finger elicits a specific response to guard against infection and repair damaged tissue, plus a non specific response. A strenuous workout results in specific bodily adaptations and the same non specific responses that were caused by the burned finger, or the pressure at work, or the term paper due next week. Since non specific stressor responses are additive. The exhaustion phase of GAS may result as a cumulative effect of many seemingly minor stressors.

Thus, in planning your exercise program, it is prudent to consider the other stressors in your daily life, as well as during special periods of abnormal pressure and commitments. World class athletes in a number of countries are monitored regularly for signs of excess stress. Typically, their blood and urine parameters and resting heart rate and blood pressure are monitored. You can suspect excess stress if you experience loss of appetite, weight loss, sleep disorders, gastrointestinal ulcers, a lack of, or decrement in, training progress, or just a general feeling of constant fatigue and ill health.

The fastest and only real cure for this problem, if indeed it is a manifestation of the exhaustion phase of adaptation, is to decrease the level of stressors acting on your body. Maybe you need to take a vacation, reduce the intensity and duration of your exercise program, or cut back on other activities; whatever you can manage at the time.

Application of GAS

An application of the above theory to exercise program planning indicates that:

  1. Exercise programs should start gradually to ease through the shock or initial alarm phase of GAS, and then slowly, over a period of weeks, intensify to the desired level.  An initial decrease in your strength or physical feeling may occur.  This is the alarm stage of GAS.
  2. The content, intensity, and duration of workouts should not remain constant, since the body could rapidly adapt to a constant stressor level and improvement would stop.
  3. Occasional breaks or layoffs from your regular exercise program are needed to reduce and change stressor inputs to your body and thus to avoid the exhaustion phase of GAS.  Typical periods to apply these three concepts are one or two weeks for an initial phase of training (or so called re-adaptation after a layoff), six to ten weeks for the major portion of a training cycle, and one or two weeks for a break or, better still, a change to some other physical activities resulting in what is referred to as active rest.  GAS is cyclical and fluctuating in nature and by training in a similar manner you can expect to make greater gains over longer periods.

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