Print
Email
Save
Definition
Fatigue may be defined as a subjective state in which one feels tired or exhausted, and in which the capacity for normal work or activity is reduced. There is, however, no commonly accepted definition of fatigue when it is considered in the context of health and illness. This lack of definition results from the fact that a person's experience of fatigue depends on a variety of factors. These factors include culture, personality, the physical environment (light, noise, vibration), availability of social support through networks of family members and friends, the nature of a particular fatiguing disease or disorder, and the type and duration of work or exercise. The experience of fatigue associated with disease will be different for someone who is clinically depressed, is socially isolated, and is out of shape, as compared to another person who is not depressed, has many friends, and is aerobically fit.
Description
Fatigue is sometimes characterized as normal or abnormal. For example, the feeling of tiredness or even exhaustion after exercising is a normal response and is relieved by resting; many people report that the experience of ordinary tiredness after exercise is pleasant. Moreover, this type of fatigue is called "acute" since the onset is sudden and the desired activity level returns after resting. On the other hand, there is fatigue that is not perceived as ordinary, that may develop insidiously over time, is unpleasant or seriously distressing, and is not resolved by rest. This kind of fatigue is abnormal and is called "chronic."
Some researchers regard fatigue as a defense mechanism that promotes the effective regulation of energy expenditures. According to this theory, when people feel tired they take steps to avoid further stress (physical or emotional) by resting or by avoiding the stressor. They are then conserving energy. Since chronic fatigue is not normal, however, it is a common symptom of some mental disorders, a variety of physical diseases with known etiologies (causes), and medical conditions that have no biological markers although they have recognizable syndromes (patterns of symptoms and signs).
Fatigue is sometimes described as being primary or secondary. Primary fatigue is a symptom of a disease or mental disorder, and may be part of a cluster of such symptoms as pain, fever, or nausea. As the disease or disorder progresses, however, the fatigue may be intensified by the patient's worsening condition, by the other disease symptoms, or by the surgical or medical treatment given to the patient. This subsequent fatigue is called secondary.
 |
Author Info: Tanja Bekhuis PhD, Rosalyn Carson-Dewitt MD, The Gale Group Inc., Gale, Detroit, Gale Encyclopedia of Neurological Disorders, 2005 |
Related Learning Centers |
 |
 |
 |
Advertise | Terms of Use | Privacy Policy