Chapter

7

Stress

An Introduction to Stress							123
The Stress Model . . . . . . . . . . . . . . . . . .	. .	. .	. .	. .	.	.	124
Arousal and Performance . . . . . . . . . . . . . .	. .	. .	. .	. .	. .		.124
Stress Reaction and the General Adaption Syndrome (GAS)							125
Stress Factors (Stressors) . . . . . . . . . . . . . . .	. .	. .	. .	. .	.	.	127
Physiological Stress Factors							128
External Physiological Factors . . . . . . . . . . . . .	. .	. .	. .	. .	.	.	128
Internal Physiological Factors							131
Cognitive Stress Factors/Stressors . . . . . . . . . . . .	. .	. .	. .	. .	.	.	132
Non-professional Personal Factors/Stressors . . . . . . . .	. .	. .	. .	. .	.	.	132
Stress Table . . . . . . . . . . . . . . . . . . . .	. .	. .	. .	. .	.	.	133
Imaginary Stress (Anxiety) . . . . . . . . . . . . . .	. .	. .	. .	. .	. .		.134
Organizational Stress . . . . . . . . . . . . . . . .	. .	. .	. .	. .	. .		.134
Stress Effects							135
Coping with Stress on the Flight Deck							137
Stress Management Away from the Flight Deck . . . . . .	. .	. .	. .	. .	. .		.138
Stress Summary . . . . . . . . . . . . . . . . . .	. .	. .	. .	. .	. .		.139
Questions . . . . . . . . . . . . . . . . . . . .	. .	. .	. .	. .	. .		.140
Answers . . . . . . . . . . . . . . . . . . . . .	. .	. .	. .	. .	.	.	144

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7 Stress

Stress 7

122

Stress 7

An Introduction to Stress

Stress is commonly defined as the body’s responses to the demands placed upon it. Perception plays a very large role in the degree of stress suffered and this is discussed in detail later in this chapter (The Stress Model). Anything that causes stress is known as a stress factor or stressor.

It is hard to measure stress in biological terms, though the strain produced by many physical and mental stressors can be measured in terms of alteration in blood pressure, pulse rate, weight, change in efficiency and so on.

The body constantly strives to maintain physiological equilibrium (homeostasis) in spite of varying external conditions and it contains numerous mechanisms to keep the status quo. For example, as body heat increases, sweat is produced which, by the cooling effect of evaporation, cools the body in an attempt to return it to its normal temperature. As soon as outside conditions either put strain upon these homeostatic mechanisms or are so extreme as to nullify them, physical stress takes place.

Mental stress, however, is much harder to measure, except in special laboratory experiments.

Whereas stress is a natural requirement of life, too much stress is harmful. Animals are designed to cope with their environment and if all forms of external stimulation are removed they tend to pine away and even die. Experiments on volunteers kept for a considerable period of time in a stimulus-free environment have shown that they tend to regress to an infantile stage and may not return to normal for a considerable time. Thus it can be said that a certain amount of stress is of fundamental importance in keeping us aware and vigilant, whereas too much stress will degrade the performance of both body and mind.

We are all different and the stress level caused by a particular stressor will differ from one individual to another. The level will largely depend on the person’s inborn and learnt characteristics.

Stress is cumulative. If a pilot is experiencing a minor irritation or stress, his/her stress level will increase disproportionately if another stressor is added, even though the original situation may have been resolved. Thus if a pilot, having had an argument with a colleague on the ground, then flies and encounters a problem on the flight deck, his/her stress level will rise to a higher level than that if the argument had not taken place.

Experience helps ward off stress. The successful completion of a stressful task will reduce the amount of stress experienced when a similar situation arises in the future.

In everyday life too little stimulation may lead to mental unrest. The active man, who retires from work, frequently becomes bored and irritable; in some cases he may fail to adjust and so develop a chronic illness.

A reasonable level of stress in our life is beneficial but a high stress level is associated with unpleasant psychological and physiological responses such as:

•Sweating.

•Dry mouth.

•Difficulty in breathing.

•Increased heart rate.

•Anxiety/apprehension.

•Fatigue.

•Fear.

Stress 7

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7 Stress

The Stress Model

Stress arises from the evaluation individuals make of the demands which they perceive to be placed upon them and the ability they perceive they have to cope with the demand. It is the person’s evaluation of the demands imposed rather than the actual demands which will be used in his evaluation of the difficulty of the task. Equally it is the perception of ability rather than actual ability that determines the amount of stress.

Stress 7

Figure 7.1 A model of stress and coping

From Figure 7.1 it will be appreciated that the feedback mechanism is of great importance in determining the amount of stress experienced on subsequent performances of the task. Successful completion of a perceived difficult task will both reduce the perceived demand and increase the perceived ability thus changing the original evaluation and reducing the stress and vice versa.

One of the features of stress is that an event which causes high stress in one individual may not have the same effect on another. It is also a fact that something which is stressful for an individual on one occasion may not be stressful at another time. Stress is subjective.

Arousal and Performance

Arousal can be defined as “the measure of the human being’s readiness to respond”. The relationship between arousal and performance is shown in Figure 7.2.

At low arousal levels, such as just after waking or during extreme fatigue, the attentional mechanism is not very active, processing of sensory information is slow and the nervous system

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