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Query: UMLS:C0015672 (fatigue)
 51,768 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Acute diaphragmatic fatigue has been experimentally shown to occur in normal healthy subjects and in patients with chronic obstructive pulmonary disease by asking them to modify their pattern of breathing or to breathe against high inspiratory resistances. During the expulsive period of labor women are asked periodically to make strong expulsive efforts and to sustain them isometrically for many seconds; this is likely to produce "natural" diaphragmatic fatigue. To investigate whether this was the case, six women were studied in the delivery room from the moment of the rupture of the amnion until delivery of the infant occurred. The development of diaphragmatic fatigue was assessed both by measuring the static maximal inspiratory pressure (MIP) and by analyzing the electromyographic power spectrum of the diaphragm (H/L ratio). The majority of contractions were concentrated in the expulsive period of labor. MIP, recorded in the supine position, significantly decreased from 103.2 +/- 17.2 cm H2O (at the beginning of the expulsive period) to 73.8 +/- 10.1 cm H2O (after the delivery). The H/L ratio fell progressively during the expulsive period; after the delivery, it was 59.2 +/- 15.7% of the value recorded at the beginning of the expulsive period. This study demonstrates that (1) the diaphragm is active in the expulsive efforts during labor and (2) the tension developed and the time each contraction is maintained may lead to the development of diaphragmatic fatigue. Therefore, we provide evidence of acute diaphragmatic fatigue in a natural condition.
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PMID:Evidence of acute diaphragmatic fatigue in a "natural" condition. The diaphragm during labor. 144 75

Brain serotonin (5-hydroxytryptamine, 5-HT) has been suggested to be involved in central fatigue during prolonged exercise. Changes in the ratio of plasma free tryptophan (free Trp) to branched-chain amino acids (BCAA) are associated with altered brain 5-HT synthesis. The purposes of this study were to describe systematically the effects of prolonged exercise on changes in plasma free Trp and BCAA and to examine the effects of carbohydrate (CHO) feedings on these same variables. Eight well-trained men [VO2max = 57.8 (SE 4.1) ml kg-1 min-1] cycled for up to 255 min at a power output corresponding to VO2 at lactate threshold (approximately 68% VO2max) on three occasions separated by at least 1 week. Subjects drank 5 ml kg-1 body wt-1 of either a water placebo, or a liquid beverage containing a moderate (6% CHO) or high (12% CHO) concentration of carbohydrate beginning at min 14 of exercise and every 30 min thereafter. Exercise time to fatigue was shorter in subjects receiving placebo [190 (SE 4) min] as compared to 6% CHO [235 (SE 10) min] and 12% CHO [234 (SE 9) min] (P < 0.05). Glucose and insulin decreased in the placebo group, and free Trp, free-Trp/BCAA, and free fatty acids increased approximately five- to sevenfold (P < 0.05). These changes were attenuated in a dose-related manner by the carbohydrate drinks.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effects of carbohydrate feedings on plasma free tryptophan and branched-chain amino acids during prolonged cycling. 148 39

The rate of metabolic heat production during prolonged exercise may be increased to 15-20 times that at rest. Evaporation of sweat secreted onto the skin can effectively limit the rise in body temperature which would otherwise occur, but results in the loss of water and electrolytes from the body. Dehydration and an increased thermal load can accelerate the onset of fatigue during exercise. The available evidence supports the idea that ingestion of fluids during prolonged exercise can improve performance. Heart rate and rectal temperature will generally be lower, and plasma volume will be better maintained when fluids are given. There is, however, no general agreement on the optimum formulation nor on the frequency or volume of drinking that is most appropriate. In practice, the ideal solution will depend on a number of factors, including the duration and intensity of the exercise, the environmental conditions and the characteristics of the individual. The variation between individuals is, however, large and the optimum strategy can only be established by subjective experience.
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PMID:Fluid balance and exercise. 148 52

A 15-year-old girl who drank excessive amounts of water while walking in the desert on a warm day, is reported. Due to complaints of fatigue and headache she was treated with more fluids and had a generalized seizure. On admission her sodium level was 125 meq/l and serum muscle enzymes were increased. Hyponatremia due to exertion and dilution is well established and may be more common than thought. It can present as a generalized seizure and with rhabdomyolysis. This case illustrates the danger of overzealous water replacement, especially without adequate replacement of salts. When water discipline is in force this possibility should be considered in patients presenting after prolonged, strenuous exercise or marching.
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PMID:[Dilutional hyponatremia and convulsions after strenuous exercise]. 159 97

Two of three members (a 29-year-old man [case 1] and a 26-year-old woman [case 2]) of a tourist party to the tropics (Mali) developed a high fever (less than or equal to 40 degrees C), headache, cough, weight loss (less than or equal to 5 kg) and tiredness 3-4 weeks after returning to Germany. In case 1, acute schistosomiasis was tentatively diagnosed as the cause because he reported an attack of dermatitis after exposure to fresh water in an endemic schistosomiasis region and had marked eosinophilia (2118/microliters; 28%) on admission. Serological tests were positive (ELISA with adult antigen, O.D. 0.65 [normal less than 0.15]; with egg antigen O.D. 1.73 [normal less than 0.30], antibody titre in the immunofluorescence test 1:320 [normal less than 1:80]) supported the diagnosis and it was confirmed by demonstrating the parasite, Schistosoma mansoni, in stool but not urine. Findings in case 2 were similar. The third member of the group [case 3], a 58-year-old woman, was symptom-free, but tests revealed schistosomiasis. All three patients were treated with a single dose of Praziquantel (40 mg/kg). A second course of praziquantel (single dose of 40 mg/kg as well as 20 mg/kg three times daily for 3 days) became necessary in case 1, while in case 3 a further single dose of 40 mg/kg was given to ensure a parasite-free state. A follow-up scheme is suggested: clinical examination with white cell and differential counts 1, 3, 6 and 12 months after treatment; three stool and/or urine examinations 3, 6 and 12 months after treatment.
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PMID:[Acute schistosomiasis in travellers to the tropics]. 160 Aug 68

Intense exercise (i.e.; above 60% VO2max) can be maintained for prolonged periods provided sufficient carbohydrate is available for energy and the heat generated from muscle metabolism does not cause excessive hyperthermia and/or dehydration due to sweating. It is clear that people should ingest carbohydrate during prolonged exercise (i.e.; longer than 1-2 h), which causes fatigue because of an inadequate supply of blood glucose and that fluids should also be ingested in an attempt to offset dehydration and reduce hyperthermia. Ingestion of approximately 30-60 g of carbohydrate (i.e.; glucose, sucrose, or starch) during each hour of exercise will generally be sufficient to maintain blood glucose oxidation late in exercise and delay fatigue. Since the average rates of gastric emptying and intestinal absorption can reach 1 l.h-1 for water and solutions containing up to 8% carbohydrate, exercising people can be supplemented with both carbohydrate and fluids at relatively high rates (over 60 g.h-1 of carbohydrate and 1 l.h-1 of fluid). Therefore, when sweat rate is not high (i.e.; less than 1 l.h-1), the addition of carbohydrate to fluids, and vice versa, does not prevent adequate supplementation of each, especially if large volumes are consumed to keep the stomach somewhat full and thus increase gastric emptying. Therefore, in most situations there are no trade-offs between fluid and carbohydrate.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Carbohydrate and fluid ingestion during exercise: are there trade-offs? 160 39

Respiratory training of premature infants was performed to determine whether improved respiratory muscle strength and/or endurance would result. Twenty-two premature infants were randomized into control and training groups for 2 wk, using inspiratory flow-resistive loads for training (75 cm H2O.L-1.s in wk 1 and 90 cm H2O.L-1.s in wk 2). Respiratory endurance was assessed by the time interval required for the development of a 5-torr rise in transcutaneous CO2 tension during the hypoventilation induced by loaded breathing, using a moderately severe resistive load (250 cm H2O.L-1.s at 1 L.min-1). Respiratory strength was assessed by the maximum negative airway pressure generated during occluded breaths, a pressure-time integral, and an effort index. Results revealed that respiratory muscle endurance, which was not initially different between control and trained groups, increased significantly after 2 wk in the trained group by 137% (median value, p less than 0.05), whereas it remained unchanged in the control group (-24%). The trained group of infants also showed a significant decrease in baseline breathing frequency between the initial and final measurements taken 2 wk apart when compared with controls (p less than 0.05) and a lesser increase in inspiratory time with loading in the final measurement as compared with the initial value (p less than 0.05). There was no significant difference between the control and trained groups in initial or subsequent measures of respiratory muscle strength. Inspiratory flow-resistive load training appears to improve the respiratory endurance of premature infants in whom respiratory muscle fatigue has been described to play a role in the development of respiratory failure.
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PMID:The effects of respiratory training with inspiratory flow resistive loads in premature infants. 163 24

Classic studies conducted in the 1920s and 1930s established that the consumption of a high carbohydrate (CHO) diet before exercise and the ingestion of glucose during exercise delayed the onset of fatigue, in part by preventing the development of hypoglycaemia. For the next 30 to 40 years, however, interest in CHO ingestion during exercise waned. Indeed, it was not until the reintroduction of the muscle biopsy technique into exercise physiology in the 1960s that a series of studies on CHO utilisation during exercise appeared. Investigations by Scandinavian physiologists showed that muscle glycogen depletion during prolonged exercise coincided with the development of fatigue. Despite this finding, attempts to delay fatigue during prolonged exercise focused principally on techniques that would increase muscle glycogen storage before exercise. The possibility that CHO ingestion during exercise might also delay the development of muscle glycogen depletion and hence, at least potentially, fatigue, was not extensively investigated. This, in part, can be explained by the popular belief that water replacement to prevent dehydration and hyperthermia was of greater importance than CHO replacement during prolonged exercise. This position was strengthened by studies in the early 1970s which showed that the ingestion of CHO solutions delayed gastric emptying compared with water, and might therefore exacerbate dehydration. As a result, athletes were actively discouraged from ingesting even mildly concentrated (greater than 5 g/100ml) CHO solutions during exercise. Only in the early 1980s, when commercial interest in the sale of CHO products to athletes was aroused, did exercise physiologists again begin to study the effects of CHO ingestion during exercise. These studies soon established that CHO ingestion during prolonged exercise could delay fatigue; this finding added urgency to the search for the optimum CHO type for ingestion during exercise. Whereas in the earlier studies, estimates of CHO oxidation were made using respiratory gas exchange measurements, investigations since the early 1970s have employed stable 13C and radioactive 14C isotope techniques to determine the amount of ingested CHO that is oxidised during exercise. Most of the early interest was in glucose ingestion during exercise. These studies showed that significant quantities of ingested glucose can be oxidised during exercise. Peak rates of glucose oxidation occur approximately 75 to 90 minutes after ingestion and are unaffected by the time of glucose ingestion during exercise. Rates of oxidation also appear not to be influenced to a major extent by the use of different feeding schedules.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Oxidation of carbohydrate ingested during prolonged endurance exercise. 164 41

Felodipine is a dihydropyridine that blocks the slow entry channel for calcium. It is highly vascular selective and reduces blood pressure (BP) by dilatation of peripheral arterioles. It reduces BP in mild, moderate, and severe hypertension, and the fall in BP depends upon the initial level. It has been compared with a variety of other drugs as monotherapy or as add-on therapy. In these studies, felodipine (10-40 mg/day) has caused a similar or greater fall in BP and a similar or greater percentage of patients have achieved a diastolic BP less than or equal to 90 mm Hg. The plain tablet of felodipine needs to be given twice a day but an extended-release form can be given once daily. Some patients respond to 5 mg/day and most patients respond to a daily dose of 20 mg or less. The adverse effects are few except for a constellation of symptoms related to the vasodilator ability of the drug. These include palpitations, flushing, fatigue, dizziness, and headaches. These occur, if at all, usually within the first 2 weeks and diminish as the drug is continued. They can be limited by starting on a small dose of felodipine (5 mg/day). People who have these adverse effects usually have a good response to the drug. Another adverse effect, which is the most frequent reason for drug withdrawal, is ankle edema. This is more common on the higher doses of the drug. It is due to dilatation of the precapillary resistance vessels rather than sodium and water retention. Felodipine is a useful and effective antihypertensive drug and can be used as monotherapy or added to other antihypertensive drugs. It is effective in people with all grades of hypertension.
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PMID:A review of the antihypertensive effects of felodipine alone or in combination. 169 35

A spherical organism 9-10 microns in diameter, seen in three outbreaks of diarrhea in Southeast Asia and the United States during the past 2 years, bore characteristics of a cyanobacterium when observed in formalin-preserved stool specimens and by electron microscopy. Organisms in freshly passed stool specimens showed an internal morula of lipid-containing globules. In fresh water, the morula divided into two sausage-shaped structures resembling the sporocysts of an isosporid coccidian. After 7 months, the organisms had not developed the crescentic sporozoites seen in the Coccidia but had begun to multiply slowly in culture. It was impossible to stain the internal structures of the organisms because the outer cyst wall ruptured during desiccation, releasing the contents of the cysts. The organisms were readily identified by their intense blue autofluorescence under UV light, but they were also recognizable by bright-field microscopy and by a modified acid-fast stain. Almost all infected persons suffered intermittent diarrhea for 2-3 weeks and many emphasized a feeling of intense fatigue during the course of their illness.
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PMID:Morphologic and staining characteristics of a cyanobacterium-like organism associated with diarrhea. 171 53


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