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The Joy of laziness.

Even we--two people who used to be dedicated long-distance runners--are no longer completely convinced that athletic exercise is healthy! In exercise, it does not hold true that "a lot helps a lot." Exercise, physical labor, and heavy exertion create an "emergency situation" for an organism, in which it reacts in the same way it does to other stressors. In order for our body to complete the exercise tasks we require of it, it must put the same mechanisms into motion that it does in any other stress situation. The adrenal glands secrete cortisol in order to prepare enough energy for the physical task. As a result, the blood sugar level rises. Stress hormones like adrenaline and noradrenaline increase the pulse and blood pressure in order to ensure adequate nutrition of the organism even with the increased exertion. Our breathing grows faster in order to pump more oxygen into the organism.

If the exertion, and the associated stress to the organism, is light and of relatively short duration, and if the organism has enough time to regenerate, then there is no damage to the body.

Endurance sports, on the other hand, create constant stress episodes and, in the long term, appear to cause changes in the way the organism regulates stress. If practiced with a focus on endurance and results, recreational sports appear to be as damaging as constant stress at work--a conclusion reached by Horst Meermann at the Max Planck Institute for Psychiatry in Munich [Germany]. The subjects of his study were older marathon runners (average age 55) who had been running marathons for at least 10 years and covered between 75 to 90 miles (120 and 150 km.) a week when in training. Blood tests showed that the continual intensive physical exertion led to an overproduction of the stress hormone cortisol in the runners' adrenal glands. The natural regulatory cycle, which is meant to prevent a constant production of the hormone, no longer functioned in these marathon runners.

Like a defective thermostat that cannot change its setting back to "normal" despite a rise in the room temperature, the reaction mechanism of marathon runners is so damaged that their high cortisol levels, elevated by the years of running, can no longer return to normal.

The release of cortisol is regulated by a reaction mechanism in the organism that works similarly to a heater's thermostat. During times of stress, a particular region of the brain releases the hormone CRH (corticotrophin-releasing hormone). This stimulates that production of another messenger substance, ACTH [adrenocorticotropic hormone], which causes the adrenal glands to release the stress hormone cortisol. The released cortisol restricts CRH production, thereby preventing further cortisol production. The cortisol turns itself off, protecting the body from damage. Under chronic stress, this regulatory mechanism is disabled. The result is a constant high level of cortisol in the blood.

Research has shown that constant stress affects the memory. The Max Planck Institute tests were also able to find this effect in long-distance runners, athletes who are under constant stress. In comparison to the older test subjects, they had significantly worse short-term memories. After half an hour, the physically active subjects included in the study were much worse at recalling new terms than were the inactive subjects.
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Title Annotation:exercise and health
Author:Axt, Peter; Axt-Gadermann, Michaela
Publication:Nutrition Health Review
Article Type:Reprint
Geographic Code:1USA
Date:Sep 22, 2004
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