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

The relationship between elevated plasma ammonia (NH3) levels, fatigue development and muscle metabolism were examined in horses during a submaximal fatigue test. Eight Quarter Horse mares were intravenously infused prior to exercise with either sodium acetate (control) or ammonium acetate (AMINF), and exercised to fatigue on an 11% grade treadmill, carrying 27 kg of lead. Time to fatigue was not different (P greater than 0.05) between groups. Intramuscular NH3 and lactate increased (P less than 0.001) during exercise; however, the treatment did not (P greater than 0.05) affect either. A treatment by exercise interaction (P less than 0.01) occurred for plasma NH3. The reciprocal relationship between changes in plasma and intramuscular alanine (ala) and glutamate (glu) indicated activation of the glucose-alanine cycle. Plasma glutamine (gln) increased (P less than 0.001) during exercise; however intramuscular gln was not (P greater than 0.05) altered. The excretion of urea-N was depressed as a result of exercise while the orotic acid/creatinine ratio did not (P greater than 0.05) change. The amino acids and urinary metabolites were not (P greater than 0.05) affected by treatment. These results did not show any metabolic evidence for a role of increased plasma NH3 levels in fatigue development. However this study did provide insight into other aspects of nitrogen metabolism during exercise in the horse.
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PMID:Metabolic responses to ammonium acetate infusion in exercising horses. 168 73

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

1. Heptaminol stopped or delayed the progressive decline in tension which characterizes the phenomenon of fatigue in frog isolated twitch muscle fibre. 2. Heptaminol had no action on the sodium, potassium and calcium voltage-dependent ionic conductances. 3. The hypothesis of an action via an internal alkalinization was tested by comparison with the action of NH4Cl. Both substances increased the tension. 4. The action of heptaminol was suppressed in sodium-free (TRIS) solution or in the presence of amiloride while the action of NH4Cl was always observed. 5. These results could be explained by a stimulation of the Na/H antiport by heptaminol.
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PMID:Action of heptaminol hydrochloride on contractile properties in frog isolated twitch muscle fibre. 172 30

Six thoroughbred horses exercised on a motorised treadmill on two separate occasions at a speed of 11 or 12 m.s-1 for up to 2 min. 4 h prior to exercise each horse was given a 21 test solution of sodium bicarbonate (NaHCO3; 0.6 g.kg-1 body mass) or a control solution of water by nasogastric intubation, the order of administration of the two solutions was randomised. Blood samples (n = 15) were obtained before and during the 4 h after intubation, during exercise and for 30 min after exercise. NaHCO3 ingestion resulted in changes in pre-exercise acid-base status. The changes in blood lactate and base excess with exercise were greater after NaHCO3 administration; after 1 min of exercise in the case of lactate (P less than 0.05) and immediately after exercise in the case of base excess (P less than 0.05). Plasma ammonia levels were lower during (P less than 0.05) and immediately after (P less than 0.05) exercise following NaHCO3 ingestion. The peak change in plasma ammonia with exercise was also lower after NaHCO3 ingestion (P less than 0.05). Following exercise after NaHCO3 ingestion, five horses demonstrated lower muscle adenosine 5-triphosphate loss (P less than 0.05) and inosine 5-monophosphate formation (P = 0.05) and higher glycerol 3-phosphate formation (P less than 0.05). There is evidence to suggest that metabolic alkalosis may delay the onset of fatigue by decreasing the extent of adenine nucleotide loss during high-intensity exercise.
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PMID:The influence of metabolic alkalosis upon exercise metabolism in the thoroughbred horse. 174 3

The nutritional considerations of the ultraendurance athlete center around proper caloric and nutrient intake during training as well as adequate energy and fluid replacement during competition to maintain optimal performance. Energy needs of ultraendurance athletes during training vary widely, depending upon duration, intensity, and type of exercise training. These athletes may train several hours daily, thus risking inadequate caloric intake that can lead to chronic fatigue, weight loss, and impaired physical performance. It is not known whether protein needs are increased in ultraendurance athletes as a result of extended exercise training. Additionally, micronutrient needs may be altered for these athletes while dietary intake is generally over the RDA because of high caloric intake. Prior to competition, ultraendurance athletes should consider glycogen supercompensation and a prerace meal eaten 4 hrs before as a means of improving performance. Carbohydrate feedings during prolonged exercise can significantly affect performance. During events lasting over several hours, sodium sweat losses and/or the consumption of sodium-free fluids may precipitate hyponatremia.
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PMID:Nutritional considerations for ultraendurance performance. 184 90

It has been postulated that the staircase response of skeletal muscle is effected by Ca2+-dependent phosphorylation of myosin light chains. Dantrolene inhibits calcium release from the sarcoplasmic reticulum, so treatment with dantrolene should prolong the time required to reach the peak of the staircase response. Furthermore, since it has been postulated that Ca2+ release is attenuated by fatigue, there should be similarities between the staircase of fatigued muscle and staircase in the presence of dantrolene. The left gastrocnemius muscle of anesthetized rats was isolated in situ and connected to an isometric transducer. In the control condition, developed tension increased for approximately 10 s with repetitive stimulation at 10 Hz. The time to reach the peak of staircase was prolonged after a 5 min period of stimulation at 10 Hz or after injection of dantrolene sodium (0.8 mg.kg-1 IV). Other similarities between the dantrolene treated group and the fatigue group include the following: contraction time was shorter in fatigue (12.8 +/- 0.8 ms) and with dantrolene (14.7 +/- 1.3 ms) than in the controls (16.4 +/- 1 ms), and half-relaxation time increased from 5 s (10.8 +/- 9 ms) to 15 s (13.8 +/- 0.8 ms) of staircase in the control but did not increase at this time in the dantrolene or fatigue groups. This study demonstrates that both fatigue and a reduction in Ca2+ release from sarcoplasmic reticulum will prolong the time required to reach the peak of staircase.
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PMID:Skeletal muscle staircase response with fatigue or dantrolene sodium. 184 39

The aim of the present study was to follow local potassium homeostasis during and after exhaustive contractions. Eight subjects performed static handgrip with their right forearm at 10%, 25% and 40% maximal voluntary contraction. Blood flow (venous occlusion plethysmography) and the venous effluent plasma potassium concentration were followed during the contractions and during a 60-min recovery period. Electromyography was registered during exercise (frequency analysis). With all three protocols the blood flow increased significantly during the contractions and the same was true of the effluent plasma potassium concentrations. In the recovery period blood flow and the venous effluent plasma potassium concentration returned to base values within 30 min following 40% maximal voluntary contraction while following 10% and 25% maximal voluntary contraction, venous effluent plasma potassium concentration was still significantly below resting values one hour after the exercise had ceased, indicating a long-lasting uptake of potassium from the blood into the muscles. In line with this a significant potassium deficit was still seen after 1 hour of recovery following 10% and 25% maximal voluntary contraction. It is concluded that the recovery of potassium homeostasis following prolonged low-intensity contractions is a slow process. This may be due to either sequestration of potassium in other tissues with a subsequent slow release and/or insufficient sodium/potassium pump activation. The contraction induced potassium loss may play a major role in muscle performance since it may impair mechanical force production, and it is hypothesized that this may be the origin of low-frequency fatigue.
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PMID:Potassium homeostasis during and following exhaustive submaximal static handgrip contractions. 187 66

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.
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PMID:Heat--sweat--dehydration--rehydration: a praxis oriented approach. 189 60

Fifty-two patients with moderate or severe infections associated with internal medicine were treated with imipenem/cilastatin sodium (IPM/CS) and the efficacy and the safety of this drug were evaluated. There were 20 patients with pneumonia, 10 with acute exacerbation of chronic respiratory tract infections, 9 with sepsis, 2 with pyothorax, 3 with intraabdominal infection, 2 with urinary tract infection, 1 with pulmonary abscess, 1 with infective endocarditis, 4 with fever of unknown origin. Forty-four patients were evaluable for the efficacy. Clinical efficacies were excellent in 12 patients, good in 26, fair in 3 and poor in 3. The overall clinical efficacy was 86.4%. The efficacy rate was 63.6% in patients previously treated and 93.9% in patients previously untreated with other antibiotics. Bacteriologically, Staphylococcus aureus (8 strains), Streptococcus pneumoniae (5), Streptococcus pyogenes (1), other Gram-positive coccus (1), Klebsiella pneumoniae (8), Haemophilus influenzae (4), Pseudomonas aeruginosa (3), Serratia marcescens (3), Escherichia coli (3), Branhamella catarrhalis (1), Citrobacter freundii (1), Klebsiella oxytoca (1), Enterobacter sp. (1), and Peptostreptococcus sp. (1) were eradicated. P. aeruginosa (3) and Acinetobacter sp. (1) decreased. S. aureus (1), S. epidermidis (1), P. aeruginosa (5), and S. marcescens (1) persisted or appeared. The eradication rate was 83.7%. Six patients showed adverse reactions including general fatigue 1, epigastralgia 1, eruption 1, eosinophilia 1 and elevation of S-GOT 2. But all of the adverse reactions were mild or slight, and transient. These findings indicate that IPM/CS is a useful and safe drug against bacterial infections in internal medicine.
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PMID:[Clinical evaluation of imipenem/cilastatin sodium in the internal medicine]. 192 Aug 13

In fatigued muscles the T-system is swollen; thus the action potential may fail to travel along the T-system or the T-tubule terminal cisternae signal may fail to bring about TC Ca2+ release. This would lead to a decrease in the number of myofibrils activated and in force development, but if fatigue is the result of a generalized process, all the myofibrils would be affected equally leading to a lower activation of all of them. We have investigated this possibility in isolated twitch muscle fibres by giving them repetitive tetanic stimulations until fatigue developed. The behaviour of myofibrils was followed with cinemicrophotography. Before fatigue, no lack of shortening of myofibrils could be found. During fatigue groups of myofibrils became wavy. When exposed to caffeine, the wavy myofibrils disappeared and tension similar to the control developed. The tension-caffeine concentration relationship was shifted to the left after development of fatigue. In low Na+ solution fatigue developed faster and after reintroducing normal Ringer, tension recovered substantially. K-contractures were smaller during fatigue. These results indicate that in this type of fatigue, a step in the EC coupling chain of events is involved in its development.
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PMID:Differential activation of myofibrils during fatigue in phasic skeletal muscle cells. 830 Aug 50


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