Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0015672 (fatigue)
 51,768 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In any situation where heat production as a result of physical exercise exceeds heat elimination from the body by radiation and convection, the body will depend on sweat secretion and evaporation for its thermoregulation. Sweat secretion will reach maximal levels at high energy expenditures in the heat but will be limited when exercising in the cold climate. Athletes and their coaches should understand some of the principles of thermoregulation in order to make an adequate decision about optimal fluid and carbohydrate replacement in a specific situation. In general it is advised that the carbohydrate content of rehydration drinks should be low (max 80 g l-1) when sweat loss is maximal, may be intermediate when both carbohydrate availability and moderate dehydration influence performance (up to 110 g l-1), and may be maximal (up to 160 g l-1) when the sweat loss is minimized and carbohydrate is the major determinant of the rate of fatigue development. Sodium should be added to rehydration drinks in order to maximize fluid and carbohydrate absorption. A range of electrolyte values for replacement of sweat induced losses, based on whole body wash down procedure is presented.
 ...
PMID:Heat--sweat--dehydration--rehydration: a praxis oriented approach. 189 60

We report a case of 47-year-old woman with an isolated deficiency of adrenocorticotropic hormone. She was admitted complaining of fatigue and frequent loss of consciousness. The patient developed severe hyponatremia (100 mEq/l) after five days of the admission. Her plasma renin activity and plasma aldosterone concentration were low though she was dehydrated. After the treatment of dehydration, plasma osmolality was low but high plasma antidiuretic hormone (ADH) level sustained. Both high urinary sodium excretion and low urinary aldosterone excretion still remained after one month of replacement therapy with prednisolone. But, glomerular filtration rate and a response of urinary volume to acute water loading were normalized. These results suggested that severe hyponatremia of the patient was caused by an inappropriate secretion of ADH and suppression of renin-aldosterone system. We consider the suppression of renin-aldosterone system was partially independent of an inappropriate secretion of ADH.
 ...
PMID:[Hyponatremia in isolated deficiency of adrenocorticotropic hormone: role of a decrease in aldosterone secretion independent of antidiuretic hormone excess]. 217 15

Metabolic fatigue is a characteristic muscle response to intense exercise that has outstripped the rate of ATP replacement. The accumulation of metabolic by-products, namely hydrogen ions and diprotonated phosphate, interferes with actin-myosin interaction, effectively preserving muscle ATP levels by preventing further ATP hydrolysis. Muscle force and metabolite concentrations return to normal in about 5 minutes. Less intense exercise causes a more subtle, non-metabolic fatigue due to a still-undefined disturbance of excitation-contraction coupling, which can last for several hours. In this type of fatigue, greater effort is required to generate submaximal forces. Endurance exercise is mainly limited by the size of muscle glycogen stores and how efficiently they are used. Endurance training permits an athlete to work aerobically at high rates, consuming a mixture of lipid and carbohydrate fuels. When muscle glycogen is used up, exercise can only continue at the relatively low rate supportable by lipid metabolism. Anaerobic exercise is also limited by subjective factors such as dyspnoea and muscle pain, which have objective determinants. Extremely prolonged exercise can lead to general collapse because of dehydration, hyperthermia, or hypoglycaemia. None of these factors explains the phenomenon of asthenia, a subjective sense of exhaustion that produces no objective impairment of physical performance. The metabolic myopathies are experiments of nature that promise to shed new light on the biochemical basis of muscle fatigue. This will require quantitative studies of the kind provided by topical magnetic resonance spectroscopy, correlating physiology and metabolism in vivo.
 ...
PMID:Muscle metabolism during fatigue and work. 226 24

To assess current weight loss practices in wrestlers, 63 college wrestlers and 368 high school wrestlers completed a questionnaire that examined the frequency and magnitude of weight loss, weight control methods, emotions associated with weight loss, dieting patterns, and preoccupation with food. Clear patterns emerged showing frequent, rapid, and large weight loss and regain cycles. Of the college wrestlers, 41% reported weight fluctuations of 5.0-9.1 kg each week of the season. For the high school wrestlers, 23% lost 2.7-4.5 kg weekly. In the college cohort, 35% lost 0.5-4.5 kg over 100 times in their life, and 22% had lost 5.0-9.1 kg between 21 and 50 times in their life. Of the high school wrestlers, 42% had already lost 5.0-9.1 kg 1-5 times in their life. A variety of aggressive methods wer used to lose weight including dehydration, food restriction, fasting, and, for a few, vomiting, laxatives, and diuretics. "Making weight" was associated with fatigue, anger, and anxiety. Thirty to forty percent of the wrestlers, at both the high school and college level, reported being preoccupied with food and eating out of control after a match. The tradition of "making weight" still appears to be integral to wrestling. The potential physiological, psychological, and health consequences of these practices merit further attention.
 ...
PMID:Patterns of weight loss and regain in wrestlers: has the tradition changed? 228 53

Repetitive lengthening contractions have been predicted as a mechanism causing injury, pain, and delayed soreness in the hyperactive masticatory muscle. This mechanism was examined by the mechanical lengthening of the contracted superficial masseter (SM) muscle in anesthetized rats. Repetitive stimulation of the left SM to tetanic tension was followed by mechanical lengthening, which stressed contracted muscle. The contralateral muscle was passively lengthened repetitively. Contractile tension in response to a varying frequency of stimulation was measured in pre- and post-lengthened SM muscles. A selective loss of force at all frequencies up to 100 Hz occurred in the muscles subjected to lengthening contractions. Low-frequency fatigue did not occur in SM muscles passively lengthened. All animals recovered without loss of weight or dehydration. They were killed at 24 or 72 h post-lengthening. The SM muscles were collected, and no significant differences were found in mean weight, length, or cross-sectional area when the right and left SM muscles were compared at 24 or 72 h. Two observers independently examined histological secretions of SM muscles and graded the localized inflammatory sites on a scale of 1-4. A non-parametric statistical test was used so that the inflammatory scale for each muscle could be ranked. There were significantly more injured sites in SM muscles subjected to lengthening contractions, compared with the lengthened (but relaxed) SM muscles. The SM muscles of anesthetized rats were internally injured by repetitive lengthening contractions, and they exhibited low-frequency fatigue. These findings support the hypothesis that repetitive lengthening contractions in the masticatory muscle could be a mechanism for the pain and dysfunction of masticatory muscles in humans with certain parafunctional habits.
 ...
PMID:Microtrauma to rat superficial masseter muscles following lengthening contractions. 239 86

Two cases of miliary tuberculosis with syndrome of inappropriate secretion of antidiuretic hormone (SIADH) were reported. Case 1. A 70-year-old woman suffering from general fatigue and appetite loss developed neck stiffness and stupor three days after admission. The chest X-ray film showed a miliary pattern in both lungs. The lumber puncture showed high pressure and increased leucocytes in the cerebrospinal fluid. Serum natrium concentration was 113 mEq/L. Tubercle bacilli were seen in the broncho-alveolar lavage fluid by the Ziehl-Nielsen staining. An improvement in electrolytes balance was produced by 2.5% NaCl and antituberculous treatment, then her mental function recovered. Case 2. A 71-year-old man was admitted with gastric ulcer. When he developed dry cough thirty days after admission, the chest X-ray film showed a miliary pattern in both lungs. Acute respiratory failure advanced concomitantly. Tubercle bacilli were seen in the sputum (Gaffky 5) by the Ziehl-Nielsen staining. Antituberculous treatment was started. Although the miliary shadow improved gradually, hyponatremia was rather progressing. The following values for serum constituents were determined: sodium, 118 mEq/L; antidiuretic hormone, 10.3 pg/ml. Antituberculous treatment and supplement of NaCl (10 g/day) improved serum natrium level. He had no mental disturbance in his clinical course. In both cases, thyroid, renal and adrenal function were normal. Systemic edema and dehydration did not exist at the state of hyponatremia, and it was very clear that laboratory data were compatible with SIADH criteria. Miliary tuberculosis is one of the least commonly recognized causes of SIADH.
 ...
PMID:[Two cases of miliary tuberculosis with SIADH]. 279 13

The concept that a specific level of central venous pressure (CVP) limits man's adjustment to heat stress has been debated. Evidence was presented that identifies a true limit of adjustment as being more related to factors affecting evaporative cooling, such as level of hydration, release of active vasodilation substance (AVS), and sweat gland fatigue. However, it was conceded that decreases in CVP and subsequent low-pressure baroreceptor activation modify cutaneous blood flow and subsequently reduce conductance of heat from the core to the periphery. It was suggested that CVP merely reflects a downstream pressure, which must be allowed to reach a pressure lower than that observed in the peripheral venous bed during active cutaneous vasodilation, to insure adequate venous return. However, a loss of evaporative cooling has been observed during prolonged progressive dehydration of subjects in the supine position, resulting in 3 to 4 percent loss of total body weight. This loss of evaporative cooling was not apparent when euhydration was maintained. As it was unlikely that CVP was reduced in these experiments in the supine position, it was concluded that CVP was not the limiting factor in man's adjustment to heat stress.
 ...
PMID:Is cardiac filling pressure the limiting factor in adjusting to heat stress? 375 Nov 35

The winter athlete has several potential tactics for sustaining body temperature in the face of severe cold. An increase in the intensity of physical activity may be counter-productive because of increased respiratory heat loss, increased air or water movement over the body surface, and a pumping of air or water beneath the clothing. Shivering can generate heat at a rate of 10 to 15 kJ/min, but it impairs skilled performance, while the resultant glycogen usage hastens the onset of fatigue and mental confusion. Non-shivering thermogenesis could arise in either brown adipose tissue or white fat. Brown adipose tissue generates heat by the action of free fatty acids in uncoupling mitochondrial electron transport, and by noradrenaline-induced membrane depolarisation and sodium pumping. The existence of brown adipose tissue in human adults is controversial, and although there are theoretical mechanisms of heat production in white fat, their contribution to the maintenance of body temperature is small. Acclimatisation to cold develops over the course of about 10 days, and in humans the primary change is an insulative, hypothermic type of response; this reflects the intermittent nature of most occupational and athletic exposures to cold. Nevertheless, with more sustained exposure to cold air or water, humans can apparently develop the humoral type of acclimatisation described in small mammals, with an increased output of noradrenaline and/or thyroxine. The associated mobilisation of free fatty acids suggests the possibility of using winter sport as a pleasant method of treating obesity. In men, a combination of moderate exercise and facial cooling induces a substantial fat loss over a 1- to 2-week period, with an associated ketonuria, proteinuria, and increase of body mass. Possible factors contributing to this fat loss include: (a) a small energy deficit; (b) the energy cost of synthesising new lean tissue; (c) energy loss through the storage and excretion of ketone bodies; (d) catecholamine-induced 'futile' metabolic cycles with increased resting metabolism; and (e) a specific reaction to cold dehydration. Current limitations for the clinical application of such treatment include uncertainty regarding optimal environmental conditions, concern over possible pathological reactions to cold, and suggestions of a less satisfactory fat mobilisation in female patients. Possible interactions between physical fitness and metabolic reactions to cold remain controversial.(ABSTRACT TRUNCATED AT 400 WORDS)
 ...
PMID:Adaptation to exercise in the cold. 388 60

The catabolism of bodily fuels provides the energy for muscular work. Work output can be limited by the size of fuel reserves, the rate of their catabolism, the build-up of by-products, or the neurologic activation of muscle. A substance that favorably affects a step that is normally limiting, and thus increases work output, can be considered an ergogenic aid. The maximal amount of muscular force generated during brief contractions can be acutely increased during hypnosis and with the ingestion of a placebo or psychomotor stimulant. This effect is most obvious in subjects under laboratory conditions and is less evident in athletes who are highly motivated prior to competition. Fatigue is associated with acidosis in the working musculature when attempts are made to maximize work output during a 4 to 15-minute period. Sodium bicarbonate ingestion may act to buffer the acid produced, provided that blood flow to the muscle is adequate. Prolonged intense exercise can be maintained for approximately two hours before carbohydrate stores become depleted. Carbohydrate feedings delay fatigue during prolonged exercise, especially in subjects who display a decline in blood glucose during exercise in the fasting state. Caffeine ingestion prior to an endurance bout has been reported to allow an individual to exercise somewhat more intensely than he or she would otherwise. Its effect may be mediated by augmenting fat metabolism or by altering the perception of effort. Amphetamines may act in a similar manner. Water ingestion during prolonged exercise that results in dehydration and hyperthermia can offset fluid losses and allow an individual to better maintain work output while substantially reducing the risk of heat-related injuries.
 ...
PMID:Ergogenic aids. 610 Aug 48

Eight physically trained subjects underwent three experimental conditions on separate occasions between 1400 and 1800 h. Two conditions acted as controls for a high-intensity exercise (HI) condition of treadmill running at 80% VO2 max for a total of 80 min. The rate of body heating was modelled in a no-exercise passive heating condition (PH), and the total exercise load was replicated in a low-intensity condition (LI) at 40% VO2 max for 160 min. LI produced no slow-wave sleep (SWS--stages 3 + 4 sleep) changes, but was the only condition to produce significant increases in sleep length and in non-rapid eye movement (REM) sleep (stages 1 + 2 + 3 + 4), and a significant decrease in sleep onset time. Although HI and PH produced similar SWS increases, these consisted of significant increases in stage 3 sleep for HI and in stage 4 sleep for PH. No REM sleep parameter was affected under any condition. Self-estimates of presleep tiredness produced no significant findings. It was concluded that a high and sustained rate of body heating for 1-2 h, particularly the inherent rapid rates of core temperature increase and of body dehydration, may trigger a SWS response, and that exercise may simply be a vehicle for these effects.
 ...
PMID:Exercise and sleep: body-heating effects. 684 96


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>