fatigue

fatigue,

in engineering, microscopic cracking of materials, especially metals, after repeated applications of stress. Fissures may be formed within pieces of metal during their manufacture when, while cooling from the molten state, they shrink and tensile stresses arise. Once a crack has started it spreads under repeated stress until the metal ruptures. Examples of fatigue are found in steel rails, beams, and girders. Metallic fatigue resulted in the catastrophes encountered by many of the Liberty ships built during World Wars I and II and the crashes of a number of the earliest jet aircraft constructed. Materials used in construction are tested for fatigue strength, or endurance limit, by being subjected mechanically to cyclic applications of stress. Steel parts are sometimes treated by shot blasting to increase their fatigue resistance.

fatigue,

in physiology, inability to perform reasonable and necessary physical or mental activity. Muscle fatigue, for example, results when the contractile properties of muscle are reduced, and continued exertion is impossible unless the muscle is allowed to rest. In muscle tissue, the depletion of glycogenglycogen
, starchlike polysaccharide (see carbohydrate) that is found in the liver and muscles of humans and the higher animals and in the cells of the lower animals. Chemically it is a highly branched condensation polymer of glucose; it is readily hydrolyzed to glucose.
..... Click the link for more information. (stored glucose), a source of energy for muscle cells, and the accumulation of lactic acidlactic acid,
CH₃CHOHCO₂H, a colorless liquid organic acid. It is miscible with water or ethanol. Lactic acid is a fermentation product of lactose (milk sugar); it is present in sour milk, koumiss, leban, yogurt, and cottage cheese.
..... Click the link for more information. , which is produced through the breakdown of glucose, was long thought to the cause of muscle fatigue, but it is now known that the lactic acid produced is used as an energy source as well. A new explanation of muscle fatigue suggests that it is related to the control of the flow of the calcium ions in muscle. The release of those ions causes muscle contraction, while their storage causes relaxation. After prolonged exercise, the channels that control calcium flow become leaky, diminishing the muscle cells ability to contract. In the normal body the damaged channels are repaired after a period of rest. There are some persons in whom fatigue is a chronic state that does not necessarily result from activity or exertion. In some instances this abnormal fatigue may be associated with systemic disorders such as anemia, a deficiency of protein or oxygen in the blood, addiction to drugs, increased or decreased function of the endocrine glands, or kidney disease in which there is a large accumulation of waste products. If excessive fatigue occurs over a prolonged period, exhaustion (marked loss of vital and nervous power) may result. In most persons with chronic fatigue, however, the condition seems to be associated with bipolar disorder. Thorough medical and psychiatric examination may be required.

Fatigue

the altered physical and mental state that results from exertion and causes a temporary reduction of human or animal operating capacity. The subjective sensation of fatigue is called tiredness.

Dynamics. The body’s operativeness is a dynamic process that includes several phases: activation, or mobilization for action; the initial reaction, representing the process of quantitative equilibration; overcompensation, or the search for an appropriate decision; compensation, or the maintenance of a level of efficiency adequate to the demands of the activity engaged in; and undercompensation, decompensation, and breakdown—that is, the gradual exhaustion of the body’s reserves and loss of operating capacity. Fatigue commonly occurs—beginning at the stage of undercompensation and persisting through the phases that follow—when the physiological reserves are considerably reduced and the body shifts to less energy-efficient types of reactions. One such reaction is the maintenance of the rate of blood flow by means of an increased heart rate rather than the more efficient reaction whereby the stroke volume is increased; another one is the activation of a greater number of motor units to effect a motor reaction when the power of contraction of individual muscle fibers is reduced—that is, when the alternating sequence of muscular contraction and relaxation is disrupted.

The initial stages of fatigue in man are marked by the reduced effectiveness of his activity; in other words, greater expenditures of physiological and psychic energy are required to perform the same work, and consequently work productivity declines. The effect of fatigue is, first of all, to impair the stability of the autonomic functions, the force and rapidity of muscular contraction, the regulation of bodily functions, and the formation and inhibition of the conditioned reflexes. As a result, the tempo of operation is slowed down; there is impairment of the rhythm, precision, and coordination of movements, and a greater expenditure of energy is needed for the performance of a given action. The thresholds of the sensory systems are raised, readily accessible stereotypic forms become dominant in the decision-making process, and there is loss of capacity to focus and transfer attention. Fatigue is generally accompanied by an increase in the number of errors and by a change in the type of errors made. Quantitative errors predominate in the initial phases, and qualitative errors in the later ones.

The overall development of fatigue can be described as impairment of the body’s ability to respond adequately to the demands placed on it by a particular activity. The response is inadequate in this case by failing to satisfy the following three criteria: optimal quality and coordination of the specific reactions underlying the activity, a bodily response that both quantitatively and qualitatively corresponds to the demands of the task at hand, and minimal expenditure of the physiological reserves.

Work may cease altogether when fatigue is pronounced. The subjective signs of fatigue in man are disagreeable sensations in the muscles and joints involved in the task and, when the body is in a static position, pain and numbness in the muscles of the back, abdomen, and neck, pain in the front and back of the head (especially in sensory and mental fatigue), loss of ability to concentrate, and easy distractibility; at first there is a slight increase in the individual’s contacts with others in the immediate environment, followed by a sharp reduction of such contacts; and finally, an unconscious drive to take longer and more frequent work breaks is observed in human subjects.

Men and animals share several common mechanisms that are characteristic of fatigue—namely, those associated with biochemical changes at the cellular level and with impairment of the conditioned reflexes. On the other hand, several fundamental differences have been identified in the dynamics as well as in the structural mechanisms of human fatigue—these being determined and regulated by the motivation, the goals, and the social nature of human activity. One such difference is the absence of clear-cut phases in the development of fatigue in animals; rather, the latter show a steady decrease in the quantitative indicators of fatigue and a less pronounced modification of performance. Furthermore, fatigue in animals is virtually unaffected by volition.

As a dynamic process, fatigue reflects the nature of the activity engaged in, and particularly its intensity, duration, and tempo. With optimal intensity, fatigue sets in later; with an increase or decrease of such optimal intensity, the onset of fatigue is accelerated. Fatigue develops rapidly when the individual is engaged in monotonous or static activity or is subjected to sensory deprivation—for example, when performing the same operation over an extended period during which a limited range of movements is required. Such monotonous activity as the narrowly specialized work performed on the assembly line results in lowered attention, diminished motivation, and the rapid onset of fatigue. This is especially true of static activity, when work is performed in a fixedly tense position, or when there is limited exposure to such stimuli as acoustic or light signals that convey information about the work environment. The work environment includes such major external factors as the microclimate, and particularly the air’s temperature, humidity, rate of movement, composition, and content of chemical impurities, as well as noise, vibration, and intensity.

Other factors in the development of fatigue are the individual’s state of health and physical condition; if these are satisfactory, they not only build up greater physiological reserves but also help activate the bodily functions more rapidly and contribute to their operational effectiveness. The time at which fatigue sets in and the rate at which it develops also depend on such individual psychological traits as the subject’s level of anxiety and volitional qualities, including persistence; these qualities, which may be called the parameters of activation, include those functional characteristics of human beings that enable them to realize their potential in a specific activity. For example, attention is an activation parameter that stimulates the efficient operation of memory; another example is a high level of volition, which makes it possible to maintain the required level of activity in spite of marked tiredness. The higher mental faculties, which shape the individual’s ideals and world outlook, play the main role.

Types. Depending on the type of work performed, fatigue may be mental or physical, with corresponding variations in the metabolic indicators—for example, changes in body temperature or in the bioelectric potentials. It has been found that physical and mental fatigue have a common base; thus the classification system that is commonly used has identified the nervous system, which directs human activity, as the primary site of fatigue. A distinction is made between sensory fatigue (including its varieties, such as the perceptual and the informational) and effector fatigue. In addition, there is the separate category of generalized fatigue. Any such classification, however, rests on an underlying physiological theory.

Sensory fatigue results from prolonged or intensive exposure to a stimulus, such as light or a loud noise, which causes a primary change in the sensory systems—a change that begins in the receptor and terminates in the cortical ending of the analyzer. Perceptual fatigue, chiefly localized in the cortical ending of the analyzer, is associated with loss of ability to detect a signal, as in the case of a high degree of interference, a low-intensity signal, or poor differentiability. Informational fatigue arises from an insufficiency of information or from information overload, when the greatest load falls on the dynamics of transaction between the nerve centers. This transactional process consists of a formation of the temporary connections between the various components of the central nervous system and an activation of the associative connections by means of which the objective environment is correctly perceived.

Effector fatigue results from the changes that take place chiefly in the sections of the central nervous system where motor activity originates. Mental fatigue arises from the changes produced by one of the following intensive operations: (1) reproductive activity that involves the mere processing of information according to hard-and-fast rules, such as counting or classifying; (2) productive activity, including data reduction, judgment-making, conceptualizing, and drawing conclusions; and (3) heuristic activity, or creative activity that is governed by individually determined implicit algorithms. Since all the changes mentioned above are usually found in combination, one may speak of generalized fatigue as a condition associated with all working activity, while distinguishing those cases in which impairment of the central nervous system is most pronounced.

Theories. Of the many theories on fatigue, those that have a purely historical interest include the “toxicity” theory of the German scientist E. Pfluger (1872), the “exhaustion” theory of M. Schiff (1868, Switzerland), and the “metabolic” theory of the Englishman A. Hill (1929). The two leading sets of theories generally accepted today are concerned with the changes that take place in the nerve centers. According to one such group of theories, fatigue is linked to hypoxia (that is, a deficiency of oxygen), impairment of the homeostatic control mechanisms, and especially changes in the metabolic mediators and in the chemical processes of excitation. Proponents of the second set of theories reject the association of fatigue with the operation of any single mechanism. In their view, fatigue may be determined by a number of factors or combinations thereof, ranging from inadequate blood circulation in the case of local muscular fatigue to protective inhibition in the case of general fatigue—namely, the structural changes effected in the homeostatic regulatory system by the higher divisions of the central nervous system.

Major contributions to modern theories of fatigue were made by I. M. Sechenov, I. P. Pavlov, N. E. Vvedenskii, A. A. Ukhtomskii, and L. A. Orbeli. Orbeli, for example, associated fatigue with the breakdown of the autonomic nervous system’s function of adaptotrophic regulation. Other Soviet physiologists who have made studies of fatigue include G. V. Fol’bort and S. A. Kosilov. Recent investigations have revealed a set of fine mechanisms associated with fatigue; these are the mechanisms involved in the impairment of the metabolism of high-energy compounds, decrease in the activity of the oxidizing enzymes, and changes in the hypothalamic function of endocrine regulation. For example, it was found that the functioning of the adrenal gland is lowered, the secretion of corticotropin by the pituitary gland is reduced, and there is an initial increase and subsequent decrease in the activity of the islands of Langerhans. The result is an increase of incompletely oxidized products and hyperglycemia, which in turn cause secondary changes to take place in the afferent impulse function, followed by an even greater disruption of homeostasis and a breakdown in the balance between autonomic and motor reactions.

In its initial stages, fatigue has a beneficial effect on the body’s resistance, contributing to the body’s more rapid and complete marshaling of its reserves and compensatory functions as well as mastery and reinforcement of skills. Pronounced fatigue, on the other hand, has the negative effect of reducing productivity, and it may lead directly to the prepathological phase of a breakdown; in the absence of proper rest, it may cause pathological exhaustion. Extreme fatigue may result in neuroses and vascular diseases.

Means of control. Fatigue can be prevented and controlled by introducing sound work and rest routines, improving the work environment, implementing biotechnological recommendations with respect to workplace organization and the arrangement of control panels or consoles, and adopting a rational system of distribution of human and mechanical operations. A major weapon in combating fatigue is work training, which makes it possible to develop optimal functional systems whereby work is performed at the prescribed rate with minimal expenditure of physiological reserves; at the same time, such systems ensure the reinforcement of skills and provide correctly planned pauses and work breaks.

Emotion and motivation are important factors in any activity. The more powerful the motivation, the later fatigue sets in, particularly when the motivation has high social significance and is competitive in nature. This type of motivation arouses interest in and a creative attitude toward one’s work. Positive emotions enhance the worker’s adaptation to an even rhythm of work, prolong optimal efficiency, and serve to more fully activate the body’s physiological reserves.

REFERENCES

Vinogradov, M. I. Fiziologiia trudovykh protsessov. Moscow, 1966.
Marchenko, E. N., I. S. Kandror, and L. S. Rozanov. “K voprosu o printsipakh klassifikatsii rabot po stepeni tiazhesti, vrednosti i opasnosti.” Gigiena truda i professional’nye zabolevaniia,” 1972, no. 3.
Vvedenie v ergonomiku. Edited by V. P. Zinchenko. Moscow, 1974.
Rozenblat, V. V. Problema utomleniia. Moscow, 1975.
Donskaia, L. V. Dvigatel’naia deiatel’nost’ cheloveka v usloviiakh mekhanizirovannogo proizvodstva. Leningrad, 1975.
Cameron, C. “A Theory of Fatigue.” Ergonomics, 1973, vol. 16, pp. 633–48.
Symposium on Fatigue. London, 1953.
Bugard, P. “La Fatigue.” Physiologie, psychologie et médecine sociale. Paris, 1960.

V. I. MEDVEDEV

Fatigue

the change in the mechanical and physical properties of a material induced by stresses and strains that vary cyclically over time. The change in the condition of a material subject to fatigue alters the material’s mechanical properties, macrostructure, microstructure, and substructure. The changes occur in stages and are dependent on the original properties, the type of stressed state, the history of loading, and the effect of the environment. Irreversible phenomena, characterized as fatigue damage, occur at some stage and lower the breaking strength of the material. Microcracks first form within the structural components of materials and along the boundaries of their junctions, for example, the grains of a polycrystalline metal, the fibers and matrix of composites, and the molecular chains of polymers. In later stages these grow into microcracks or lead to the final failure of a structural member or a specimen undergoing mechanical testing.

The fatigue process may be described quantitatively by the relationship between the cumulative damage and the number of cycles or the duration of the loading with respect to the magnitude of the cyclic stress or strain. The corresponding relationship between the number of cycles and the stages of damage, including the onset of cracks or the final failure, is called a stress-endurance, or endurance-limit, curve and is the primary characteristic of fatigue in materials.

The accumulation of cyclic damage reflects the strain in a material as a macroscopically and microscopically inhomogeneous medium (for metals, as a polycrystalline conglomerate; for polymers, as a conglomerate of molecular chains; and for composites, as a regular structure consisting of a matrix and fibers). This process in the field of a uniformly stressed state, for example, simple tension and compression, may be described by a mechanical model in which the sections create an inhomogeneous strain in the structural components of the material; the inhomogeneity is characterized by probability distributions for the values of the microstrains and microstresses, including residual values.

A cyclic load on such inhomogeneous structures produces irreversible elastoplastic and viscoelastic strains in the most highly stressed structural sections, which accumulate as the number of cycles and the amount of time under cyclic loading are increased. These increase up to critical values characteristic of the material and the environment in which the material is located, resulting in the onset of macroscopic cracks as the limiting state of the first stage of fatigue failure. The kinetics of the change of state of the material at this stage is manifested submicroscopically (by a change in the density of dislocations and in the concentration of vacancies), microscopically (by the formation of slip lines, extrusions, and intrusions on the free surface of microstresses), and mechanically (by changes in hardness, the parameters of the elastoplastic hysteresis loop, the cyclic elastic modulus, and such ma-crophysical properties as density and the electrical, magnetic, and acoustic resistances).

Figure 1. Stress-endurance curves in the region of high-cycle fatigue

In the second stage of fatigue failure, the accumulated damage may be evaluated by the rate of growth of macrocracks and by the decreased resistance to failure (quasi-brittle or brittle fracture), which depends on the change in the material’s static strength, including the fracture toughness characteristics as critical values of the stress intensities at the edge of a fatigue crack.

Stress-endurance curves in the region of high-cycle fatigue (where the number of cycles at failure is over 10⁵) are caused by repeated elastic strains; they are plotted in amplitudes (or maximum stresses) of the cycle with logarithmic (log σ and log N) or semilogarithmic (σ and log N) coordinates (Figure 1). Depending on the characteristics of the material, the ambient temperature during testing, and the physical and chemical activity of the environment, stress-endurance curves may have either an asymptotic character (curve 1) or a continuously decreasing character with a convexity turned toward the origin of coordinates (curve 2). The value of the stress amplitudes σ_–1, which are the asymptotes in curves of the first kind, is called the endurance limit of the material; the value of the stress amplitudes

(σ_–1) N_f

for which failure occurs with the number of cycles N_f along a curve of the second kind, is called the fatigue strength. Type 1 curves are typical of materials having very stable structures and for very low temperatures; type 2 curves apply to materials having less stable structures, to higher temperatures, and to active environments.

Figure 2. Typical stress-endurance curve in the region of low-cycle fatigue

Curves in the region of low-cycle fatigue (where the number of cycles at failure is 10⁴ or less) resulting from repeated plastic strains are plotted in amplitudes of these strains with logarithmic coordinates log ∊_af and log N (Figure 2).

REFERENCES

Konstruktsionnye materialy, vol. 3, Moscow, 1965. Pages 382–90.
Forrest, P. Ustalost’ metallov. Moscow, 1968. (Translated from English.)
Serensen, S. V. Soprotivlenie materialov ustalostnomu i khrupkomurazrusheniiu. Moscow, 1975.

S. V. SERENSEN

fatigue

[fə′tēg] (electronics) The decrease of efficiency of a luminescent or light-sensitive material as a result of excitation. (mechanics) Failure of a material by cracking resulting from repeated or cyclic stress. (physiology) Exhaustion of strength or reduced capacity to respond to stimulation following a period of activity.

fatigue

The progressive structural change occurring in a localized area of a metal subjected to conditions of repeated cyclic stresses and strains considerably below the ultimate tensile strength; may result in cracks or complete fracture.

fatigue

Typical fatigue curve showing how the number of repetitions of the load and its magnitude affect the specimen and the point where the failure can take place.i. The process leading to failure of metals under the repeated action of a cycle of stress. Failure depends upon the mean stress, the range of stress, and the number of cycles. If the stress is decreased, the material can withstand a greatly increased number of repetitions before failure. This is demonstrated by the typical fatigue curve in the illustration, usually called an S-n curve. The length of time before failure is called the fatigue life. See also fatigue life.
ii. The state of the human organism after exposure to any type of physical or psychological stress (e.g., pilot fatigue).
fatigue index An arbitrary scale of airframe life, normally terminating at 100, but it can be extended.
fatigue life The minimum life of a component, or the entire aircraft, in term of the number of hours or number of operating/load cycles before which the component (or aircraft) is designed to function without fatigue failure. Also known as the technical life.

fatigue

1. Physiol the temporary inability of an organ or part to respond to a stimulus because of overactivity 2. Mechanics the progressive cracking of a material subjected to alternating stresses, esp vibrations

fatigue

Fatigue

Definition

Fatigue is physical and/or mental exhaustion that can be triggered by stress, medication, overwork, or mental and physical illness or disease.

Description

Everyone experiences fatigue occasionally. It is the body's way of signaling its need for rest and sleep. But when fatigue becomes a persistent feeling of tiredness or exhaustion that goes beyond normal sleepiness, it is usually a sign that something more serious is amiss.Physically, fatigue is characterized by a profound lack of energy, feelings of muscle weakness, and slowed movements or central nervous system reactions. Fatigue can also trigger serious mental exhaustion. Persistent fatigue can cause a lack of mental clarity (or feeling of mental "fuzziness"), difficulty concentrating, and in some cases, memory loss.

Causes and symptoms

Fatigue may be the result of one or more environmental causes such as inadequate rest, improper diet, work and home stressors, or poor physical conditioning, or one symptom of a chronic medical condition or disease process in the body. Heart disease, low blood pressure, diabetes, end-stage renal disease, iron-deficiency anemia, narcolepsy, and cancer can cause long-term, ongoing fatigue symptoms. Acute illnesses such as viral and bacterial infections can also trigger temporary feelings of exhaustion. In addition, mental disorders such as depression can also cause fatigue.A number of medications, including antihistamines, antibiotics, and blood pressure medications, may cause drowsiness as a side-effect. Individuals already suffering from fatigue who are prescribed one of these medications may wish to check with their healthcare provider about alternative treatments.Extreme fatigue which persists, unabated, for at least six months, is not the result of a diagnosed disease or illness, and is characterized by flu-like symptoms such as swollen lymph nodes, sore throat, and muscle weakness and/or pain may indicate a diagnosis of chronic fatigue syndrome. Chronic fatigue syndrome (sometimes called chronic fatigue immune deficiency syndrome), is a debilitating illness that causes overwhelming exhaustion and a constellation of neurological and immunological symptoms. Between 1.5 and 2 million Americans are estimated to suffer from the disorder.

Diagnosis

Because fatigue is a symptom of a number of different disorders, diseases, and lifestyle choices, diagnosis may be difficult. A thorough examination and patient history by a qualified healthcare provider is the first step in determining the cause of the fatigue. A physician can rule out physical conditions and diseases that feature fatigue as a symptom, and can also determine if prescription drugs, poor dietary habits, work environment, or other external stressors could be triggering the exhaustion. Several diagnostic tests may also be required to rule out common physical causes of exhaustion, such as blood tests to check for iron-deficiency anemia.Diagnosis of chronic fatigue syndrome is significantly more difficult. Because there is no specific biological marker or conclusive blood test to check for the disorder, healthcare providers must rely on the patient's presentation and severity of symptoms to make a diagnosis. In many cases, individuals with chronic fatigue syndrome go through a battery of invasive diagnostic tests and several years of consultation with medical professionals before receiving a correct diagnosis.

Treatment

Conventional medicine recommends the dietary and lifestyle changes outlined above as a first line of defense against fatigue. Individuals who experience occasional fatigue symptoms may benefit from short term use of caffeine-containing central nervous stimulants, which make people more alert, less drowsy, and improve coordination. However, these should be prescribed with extreme caution, as overuse of the drug can lead to serious sleep disorders, like insomnia.Another reason to avoid extended use of caffeine is its associated withdrawal symptoms. People who use large amounts of caffeine over long periods build up a tolerance to it. When that happens, they have to use more and more caffeine to get the same effects. Heavy caffeine use can also lead to dependence. If an individual stops using caffeine abruptly, withdrawal symptoms may occur, including headache, fatigue, drowsiness, yawning, irritability, restlessness, vomiting, or runny nose. These symptoms can go on for as long as a week.

Alternative treatment

The treatment of fatigue depends on its direct cause, but there are several commonly prescribed treatments for non-specific fatigue, including dietary and lifestyle changes, the use of essential oils and herbal therapies, deep breathing exercises, traditional Chinese medicine, and color therapy.

Dietary changes

Inadequate or inappropriate nutritional intake can cause fatigue symptoms. To maintain an adequate energy supply and promote overall physical well-being, individuals should eat a balanced diet and observe the following nutritional guidelines:

Drinking plenty of water. Individuals should try to drink 9 to 12 glasses of water a day. Dehydration can reduce blood volume, which leads to feelings of fatigue.
Eating iron-rich foods (i.e., liver, raisins, spinach, apricots). Iron enables the blood to transport oxygen throughout the tissues, organs, and muscles, and diminished oxygenation of the blood can result in fatigue.
Avoiding high-fat meals and snacks. High fat foods take longer to digest, reducing blood flow to the brain, heart, and rest of the body while blood flow is increased to the stomach.
Eating unrefined carbohydrates and proteins together for sustained energy.
Balancing proteins. Limiting protein to 15-20 grams per meal and two snacks of 15 grams is recommended, but not getting enough protein adds to fatigue. Pregnant or breastfeeding women should get more protein.
Getting the recommended daily allowance of B complex vitamins (specifically, pantothenic acid, folic acid, thiamine, and vitamin B₁₂). Deficiencies in these vitamins can trigger fatigue.
Getting the recommended daily allowance of selenium, riboflavin, and niacin. These are all essential nutritional elements in metabolizing food energy.
Controlling portions. Individuals should only eat when they're hungry, and stop when they're full. An overstuffed stomach can cause short-term fatigue, and individuals who are overweight are much more likely to regularly experience fatigue symptoms.

Lifestyle changes

Lifestyle factors such as a high-stress job, erratic work hours, lack of social or family support, or erratic sleep patterns can all cause prolonged fatigue. If stress is an issue, a number of relaxation therapies and techniques are available to help alleviate tension, including massage, yoga, aromatherapy, hydrotherapy, progressive relaxation exercises, meditation, and guided imagery. Some individuals may also benefit from individual or family counseling or psychotherapy sessions to work through stress-related fatigue that is a result of family or social issues.Maintaining healthy sleep patterns is critical to proper rest. Having a set "bedtime" helps to keep sleep on schedule. A calm and restful sleeping environment is also important to healthy sleep. Above all, the bedroom should be quiet and comfortable, away from loud noises and with adequate window treatments to keep sunlight and streetlights out. Removing distractions from the bedroom such as televisions and telephones can also be helpful.

Essential oils

Aromatherapists, hydrotherapists, and other holistic healthcare providers may recommend the use of essential oils of rosemary (Rosmarinus officinalis), eucalyptus blue gum (Eucalyptus globulus), peppermint, (Mentha x piperata), or scots pine oil (Pinus sylvestris) to stimulate the nervous system and reduce fatigue. These oils can be added to bathwater or massage oil as a topical application. Citrus oils such as lemon, orange, grapefruit, and lime have a similar effect, and can be added to a steam bath or vaporizer for inhalation.

Herbal remedies

Herbal remedies that act as circulatory stimulants can offset the symptoms of fatigue in some individuals. An herbalist may recommend an infusion of ginger (Zingiber officinale) root or treatment with cayenne (Capsicum annuum), balmony (Chelone glabra), damiana (Turnera diffusa), ginseng (Panax ginseng), or rosemary (Rosmarinus officinalis) to treat ongoing fatigue.An infusion is prepared by mixing the herb with boiling water, steeping it for several minutes, and then removing the herb from the infusion before drinking. A strainer, tea ball, or infuser can be used to immerse loose herb in the boiling water before steeping and separating it. A second method of infusion is to mix the loose herbal preparation with cold water first, bringing the mixture to a boil in a pan or teapot, and then separating the tea from the infusion with a strainer before drinking.Caffeine-containing central nervous system stimulants such as tea (Camellia senensis) and cola (Cola nitida) can provide temporary, short-term relief of fatigue symptoms. However, long-term use of caffeine can cause restlessness, irritability, and other unwanted side effects, and in some cases may actually work to increase fatigue after the stimulating effects of the caffeine wear off. To avoid these problems, caffeine intake should be limited to 300 mg or less a day (the equivalent of 4-8 cups of brewed, hot tea).

Traditional chinese medicine

Chinese medicine regards fatigue as a blockage or misalignment of qi, or energy flow, inside the human body. The practitioner of Chinese medicine chooses acupuncture and/or herbal therapy to rebalance the entire system. The Chinese formula Minot Bupleurum soup (or Xiao Chia Hu Tang) has been used for nearly 2,000 years for the type of chronic fatigue that comes after the flu. In this condition, the person has low-grade fever, nausea, and fatigue. There are other formulas that are helpful in other cases. Acupuncture involves the placement of a series of thin needles into the skin at targeted locations on the body known as acupoints in order to harmonize the energy flow within the human body.

Deep breathing exercises

Individuals under stress often experience fast, shallow breathing. This type of breathing, known as chest breathing, can lead to shortness of breath, increased muscle tension, inadequate oxygenation of blood, and fatigue. Breathing exercises can both improve respiratory function and relieve stress and fatigue.Deep breathing exercises are best performed while laying flat on the back on a hard surface, usually the floor. The knees are bent, and the body (particularly the mouth, nose, and face) is relaxed. One hand should be placed on the chest and one on the abdomen to monitor breathing technique. With proper breathing techniques, the abdomen will rise further than the chest. The individual takes a series of long, deep breaths through the nose, attempting to raise the abdomen instead of the chest. Air is exhaled through the relaxed mouth. Deep breathing can be continued for up to 20 minutes. After the exercise is complete, the individual checks again for body tension and relaxation. Once deep breathing techniques have been mastered, an individual can use deep breathing at any time or place as a quick method of relieving tension and preventing fatigue.

Color therapy

Color therapy, also known as chromatherapy, is based on the premise that certain colors are infused with healing energies. The therapy uses the seven colors of the rainbow to promote balance and healing in the mind and body. Red promotes energy, empowerment, and stimulation. Physically, it is thought to improve circulation and stimulate red blood cell production. Red is associated with the seventh chakra, located at the root; or base of spine. In yoga, the chakras are specific spiritual energy centers of the body.Therapeutic color can be administered in a number of ways. Practitioners of Ayurvedic, or traditional Indian medicine, wrap their patients in colored cloth chosen for its therapeutic hue. Individuals suffering from fatigue would be wrapped in reds and oranges chosen for their uplifting and energizing properties. Patients may also be bathed in light from a color filtered light source to enhance the healing effects of the treatment.Individuals may also be treated with color-infused water. This is achieved by placing translucent red colored paper or colored plastic wrap over and around a glass of water and placing the glass in direct sunlight so the water can soak up the healing properties and vibrations of the color. Environmental color sources may also be used to promote feelings of stimulation and energy. Red wall and window treatments, furniture, clothing, and even food may be recommended for their energizing healing properties.Color therapy can be used in conjunction with both hydrotherapy and aromatherapy to heighten the therapeutic effect. Spas and holistic healthcare providers may recommend red color baths or soaks, which combine the benefits of a warm or hot water soak with energizing essential oils and the fatigue-fighting effects of bright red hues used in color therapy.

Prognosis

Fatigue related to a chronic disease or condition may last indefinitely, but can be alleviated to a degree through some of the treatment options outlined here. Exhaustion that can be linked to environmental stressors is usually easily alleviated when those stressors are dealt with properly.There is no known cure for chronic fatigue syndrome, but steps can be taken to lessen symptoms and improve quality of life for these individuals while researchers continue to seek a cure.

Prevention

Many of the treatments outlined above are also recommended to prevent the onset of fatigue. Getting adequate rest and maintaining a consistent bedtime schedule are the most effective ways to combat fatigue. A balanced diet and moderate exercise program are also important to maintaining a consistent energy level.

Resources

Books

Davis, Martha, et al. The Relaxation & Stress Reduction Workbook. 4th ed. Oakland, CA: New Harbinger Publications, Inc., 1995.Hoffman, David. The Complete Illustrated Herbal. New York: Barnes & Noble Books, 1999.

Key terms

Aromatherapy — The therapeutic use of plantderived, aromatic essential oils to promote physical and psychological well-being.Guided imagery — The use of relaxation and mental visualization to improve mood and/or physical well-being.Hydrotherapy — Hydrotherapy, or water therapy, is use of water (hot, cold, steam, or ice) to relieve discomfort and promote physical well-being.

fatigue

[fah-tēg´] 1. loss of the ability of a muscle to respond to stimuli.2. a nursing diagnosis accepted by the North American Nursing Diagnosis Association, defined as an overwhelming sustained exhaustion and decreased capacity for physical and mental work at the usual level. Fatigue is a normal reaction to intense physical exertion, emotional strain, or lack of rest. When it is not relieved by rest, it may have a more serious origin; it may be a symptom of poor physical condition, a specific disease or oncoming disease, or severe emotional stress. Sometimes fatigue is psychological in origin. Tiredness and a loss of interest in one's work may actually result from boredom with the daily routine. If one is certain that there is nothing wrong physically, steps should be taken to vary the daily round, to seek new and more active ways to spend leisure time, perhaps to revive old interests that have been neglected. See also activity intolerance.caregiver role fatigue excessive fatigue of a caregiver" >caregiver caused by the neglect of his or her personal needs due to the demands of physical and emotional care of someone else.vocal fatigue phonasthenia.

fa·tigue

(fă-tēg'), 1. That state, following a period of mental or bodily activity, characterized by a lessened capacity or motivation for work and reduced efficiency of accomplishment, usually accompanied by a feeling of weariness, sleepiness, irritability, or loss of ambition; may also supervene when, from any cause, energy expenditure outstrips restorative processes and may be confined to a single organ. 2. Sensation of boredom and lassitude due to absence of stimulation, monotony, or lack of interest in one's surroundings. [Fr., fr. L. fatigo, to tire]

fa·tigue

ponophobia, kopophobia.

fatigue

(fə-tēg′)n.1. Physical or mental weariness resulting from effort or activity.2. Physiology The decreased capacity or complete inability of an organism, organ, or part to function normally because of excessive stimulation or prolonged exertion.3. The weakening or failure of a material, such as metal or wood, resulting from prolonged stress.v. fa·tigued, fa·tiguing, fa·tigues v.tr.1. To tire out; exhaust.2. To create fatigue in (a metal or other material).v.intr. To be or become tired.

fatigue

Medtalk A state of mental and/or physical exhaustion, which is often understood to be unusual for the affected person. See Chronic fatigue, Driver fatigue, Nightshift fatigue, Taste fatigue.

fa·tigue

(fă-tēg') 1. That state, following a period of mental or bodily activity, characterized by a lessened capacity for work and reduced efficiency of accomplishment, usually accompanied by a feeling of weariness, sleepiness, or irritability; may also supervene when, from any cause, energy expenditure outstrips restorative processes and may be confined to a single organ. 2. Sensation of boredom and lassitude due to absence of stimulation, monotony, or lack of interest in one's surroundings. [Fr., fr. L. fatigo, to tire]

fatigue

Physical or mental tiredness. Physical fatigue is due to accumulation in the muscles of the breakdown products of fuel consumption and energy production (metabolism). Mental fatigue is usually the result of boredom, FRUSTRATION, ANXIETY, over-long concentration on a single task or dislike of a particular activity. Fatigue commonly involves both kinds.

fatigue

exhaustion in muscles resulting from exertion or over-stimulation following a period of activity.

fa·tigue

(fă-tēg') That state, following a period of mental or bodily activity, characterized by a lessened capacity or motivation for work and reduced efficiency of accomplishment, usually accompanied by a feeling of weariness, sleepiness, irritability, or loss of ambition. [Fr., fr. L. fatigo, to tire]

Patient discussion about fatigue

Q. What can cause chronic fatigue? For the last few weeks I’ve been having this strange fatigue, I sleep 12-14 hours at night (I used to sleep 6-7 hours), and I’m tired all day long. It really bothers me. What can is be? A. Wow, there are so many…to give you a taste- here is a list. I guess some of them you can rule out pretty easily through checking your habits and other symptoms (if you have any):
http://www.wrongdiagnosis.com/symptoms/fatigue/common.htm

Q. I suffer of lack in energy lately, any advice? I’m 35, usually a strong guy but for the past 3 weeks I’ve been sleeping all day, doing nothing while awake, having no energy to do anything. Any one know a reason or what should I do?A. Have you tried changing your diet? You may lack of vitamins or other essential materials that can cause drowsiness. Try eating vegetables and fruits. Force yourself to do a daily walk, 25 minutes, that’s all. and could be you got an infection that will take some time…

Q. How do you know when your tiredness is a chronic health symptom? Sometimes I'm just overwhelmingly tired and need to lay down for awhile. Then I feel better but then I haven't accomplished a lot. At least after I rest I am able to do things again. What is Chronic Fatigue all about?A. Wow! Good question!
I tell you what- here is a very good site I use all the time. You enter a symptom and it gives you all the illnesses that have the symptom. Then you enter another symptom you have and it narrows the list.
I already entered fatigue for you:
http://www.healthline.com/symptomsearch?addterm=Fatigue
and here is a site about chronic fatigue syndrome that you can look for differences:
http://www.idph.state.il.us/about/womenshealth/factsheets/cfsyndrome.htm

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Patient discussion about fatigue

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Synonyms for fatigue

noun tiredness

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noun khakis

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verb tire

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noun the condition of being extremely tired

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verb to diminish the strength and energy of

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noun temporary loss of strength and energy resulting from hard physical or mental work

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noun used of materials (especially metals) in a weakened state caused by long stress

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noun (always used with a modifier) boredom resulting from overexposure to something

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noun labor of a nonmilitary kind done by soldiers (cleaning or digging or draining or so on)

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verb lose interest or become bored with something or somebody

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verb exhaust or get tired through overuse or great strain or stress