Unit 1 - Concepts of Training and Conditioning

Page 1  
 - Introduction
Lesson Two – “Stress, Adaptation and Overload”

Readings: Selye Ancillary readings.

Competencies –

Upon completing this lesson, the student should be able to:

  1. Discuss Selye’s theory of stress
  2. Differentiate and discuss the three stages of the General Adaptation Syndrome as it relates to the overall concept of training and conditioning
  3. Discuss the 3 major training principles and how the relate to the GAS
  4. Develop examples that illustrate Selye’s theory of Stress and GAS

Lesson TWO – Stress, Adaptation, and Overload (June 4, 2006 - June 6, 2006)

Contents of Lesson 2:
Page 2 Back to Top
 - Overload and Stress

Activity StepsPrior to beginning this lesson, e-mail me your definition of STRESS and how you imagine stress affects the physiological response. (5 points).

Now that you have completed lesson 1 and have a basic understanding of some of the terminology, it is time to discuss further, the concept of OVERLOAD.  You have probably learned about the overload principle in other Kinesiology classes. This lesson is designed to help you understand the theoretical framework that is the basis of exercise as the stressor on the physiological systems and the overload principle as the mediator of the continuation of stress after adaptation. If you haven’t visited the ancillary page, now is the time to do so. To get to the ancillary page just click on the "ancillary" button on the left side of your screen. On the ancillary page you will find a link titled lesson 2: Selye’s theory of stress and GAS. The file is in Adobe Acrobat format, so make sure you have Acrobat Reader on your computer. Read the article carefully because this is the foundation for all physiological responses to stress, and this article begins to explain why the overload principle is incorporated as a physiological principle to training.

After reading the article on stress and the general adaptation syndrome (GAS), you should have a better understanding of stress and its relation to exercise and overload. In fact, we can now describe exercise as the all-encompassing stressor in any training regimen and overload as the mediator of GAS for the conditioning outcome. So, what are the important items you should have gleaned from the readings?

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 - Simplification of Selye

Stress response

The over simplified view of Selye’s theory states that stress raises the physiological function above baseline measures or out of its natural homeostatic state. Selye presented the first acceptable theory that all stress (psychological, physiological, or environmental) caused common physiological reactions. The physiological response to a stressor begins the process of adaptation. The diagram above graphically represents the physiological reaction to any stress. As adaptations occur, this reaction to a stressor is minimized. To gain the same physiological response as the first time stress is introduced, post adaptation stress must be increased. Selye further explains that the adaptation process could be delineated into three stages.

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 - Simplification of Selye (cont.)
Amazed The first stage of GAS is the alarm reaction stage. This is the immediate or acute response to a perceived stressor. Stage 1 of Selye’s theory deals with the flight or fight response associated with the sympathetic nervous system. In exercise, this response to the stressor is explained through the neurohormonal regulatory response to anticipatory stress and also to the acute response that immediately occurs with the first bout of exercise. The neurohormonal response begins with afferent excitation of the hypothalamus due to the perceived stress. This excitation of the hypothalamus begins a chain of events in both the neural pathways and hormonal pathways. The end product of these events is the physiological response to the perceived stress like an increase in heart rate.

Dog tugThe second stage of Selye’s theory is the stage of resistance. This stage refers to the chronic effects of stress. In terms of exercise as the stress stimulus, the end product of this stage is the true adaptation of the physiology. The resistant stage can be described as a sensitization to the stressor where physiological adaptations bring the body back into homeostasis alleviating the impact of the stressor. In the resistance stage the neurohormonal chain of events described in the first stage is lessened due to changes or adaptations in the physiology.

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 - Example Stage 1 and Stage 2 of Selye’s Theory
ExampleLets look at an example of the first two stages of Selye’s theory as they relate to exercise. The first example would be if you decided to begin to take the stairs instead of the elevator every morning at work. As you look at the stairs on the first day and decide to begin to take the first steps toward better fitness, the perception of stress or for a better term the anticipatory response causes a neural trigger that stimulates the hypothalamus. Your immediate physiological response to this stressor is an increase in heart rate and respirations rate. These increases in heart rate and respiration are due to an increase in sympathetic nervous system activity caused by the excitation of the hypothalamus.
  • This is described as the fight or flight response and illustrates Stage 1 of Selye’s theory. As you repeat this process each day, the perception or anticipation dissipates due to desensitization (you adapt to the perceptual stimulus and the neural trigger no longer stimulates the hypothalamus). In other words, after a week of taking the steps, you become accustomed to the sight of the stair case and realize that it is not a barrier for you.
  • An example that describes Stage 2 of Selye’s theory incorporates the exercise described in the first example. As you take the steps each day, the stressor of the activity is the increase in work required to move your body up the incline of stairs. Remember that work = force X distance. In the case of taking the stairs, work = body weight (the force) X the product of the vertical and horizontal incline (distance). As you repeatedly complete this activity over the course of several weeks, adaptations in one or more of the physiological systems will occur to resist the effects of the stressor. One physiological adaptation that might occur after weeks of taking the steps is the loss of body fat. That loss of body fat changes (decreases) your weight, which in turn decreases the work required moving your body up the steps (This is a simplistic example, actually more than one physiological system is affected). Selye observed that prolonged stress ultimately forces physiological accommodations (adaptations) to maintain a relative balance (homeostasis) in the presence of continued stress.
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 - Overload, Adaptation, and Maintenance

Computer MeltdownI have now explained Selye’s first two stages of GAS. Stage 2 of Selye’s theory is the more important of the two when we discuss training and conditioning for fitness. So, how does the overload principle act within the resistance stage (stage 2) as it applies to training and conditioning? Well, lets take the final statement on the preceding page: Prolonged stress ultimately forces physiological accommodations (adaptations) to maintain a relative balance (homeostasis) in the presence of continued stress. Remember that previously we describe exercise as the stressor, however we should be more specific and include the exercise load, or for a better term, the exercise volume as the true stressor. With this in mind, we can then assume from our stair example that once we have adapted to the exercise volume (distance traveled up the stairs), we again reach physiological homeostasis. Once we have reached physiological homeostasis, no further adaptations will occur and the current exercise volume is no longer a stressor. If we maintain the same exercise volume for the rest of our life, we will remain in the same state of fitness after the full adaptation process. Therefore, without increasing the exercise volume (overload) we will remain in a homeostatic state (maintenance). So, to improve upon our fitness levels, whether it is health related or sports specific, we need to overcome the homeostasis that is reached after physiological adaptations occur. To overcome the homeostasis achieved through adaptation, we then need to increase the exercise volume. We define each increase in exercise volume as overload. Notice, we have now developed a simplistic training program: overload-adaptation-
……and so on. Before we leave this page, I want to point out an interesting point (to me anyway):

  • Notice that the out come of our simplistic training program is always homeostasis. If we were to define this program in the terms of training and conditioning, the training portion of the program is overload and adaptation while the conditioning portion of the program is homeostasis. Don’t you find it humorous that we describe conditioning as homeostasis?
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 - Reversibility and Selye’s Theory

Military climb Up to this point, we have yet to describe the third stage of GAS, which is the stage of exhaustion. One item that should have given you an “ahah” moment, if you read the Selye paper, was that the outcome of the exhaustion stage in Selye’s theory is illness and death. The exhaustion stage is when stress persists with enough intensity (overload) that the individual will reach a point beyond which adaptations are no longer possible and physiological function will suffer. In other words, if stress persists long enough or with a great enough intensity, the individual begins to experience a decline in performance (over-training). This means that we have to be conscious and understand that exercise volume in the form of overload may react in a negative fashion and cause a detriment to performance (over-training). An extreme example of exercise volume and over-training comes from a true experience. I met a young man, several years ago, which was training for the Tenneco Marathon (Houston). When I asked him about his training volume, he stated that he was running about 300 miles per week (now that is a training volume). His actual training method was to rise at 2:00 am and go for a 15 mile run, followed by breakfast a rest period of reading or watching TV, then at 9:00 am go for a 5 mile run followed by a snack, classes at the university, then 4:00 PM a running protocol that totaled 10 miles, followed by dinner, some reading, and at 9:00 PM he would go and jog a light 10 to 12 miles at a slower pace. Oh, and on Saturday or Sunday he would run 30 miles continuously. If you haven’t figured it out yet, his “stress” far exceeded his ability to adapt. His physiological symptoms to the stress were sleeplessness, lethargy, some pulmonary problems, and his marathon time had increased by 22 minutes (he was getting slower). Why do I give this example? Throughout this course, we will discuss the overload principle as it pertains to the training of specific physiological systems. You should ask yourself as you complete each lesson, “what factors may increase the possibility to over-training in this physiological system”.

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 - Completion

Finish line Now that you have completed this lesson, please e-mail me (Dr. Eldridge) a revised definition of stress and describe how your definition has evolved since the completion of the lecture and study guide (5 points).

You have just completed the final lesson of the first unit. You should now have an understanding of the basic principles and terminology used within the context of training and conditioning. You should also have a better understanding of stress and adaptation as described by Selye. If you have any questions concerning these two lessons, please ask your questions in class before the test..

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