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

The anti-fatigue effect of phosphoserine, L-serine and a mixture of sodium phosphate and L-serine has been studied in rats. Phosphoserine orally administered induced a statistically significant anti-fatigue effect in rats of both sexes submitted to a training test by rotarod, with 14 sessions in 3 days. Furthermore, phosphoserine was utilized better than the mixture of sodium phosphate and L-serine, whereas L-serine alone induced no effect. Therefore the effect of phosphoserine seems to be due to the phosphoryl bond.
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PMID:Influence of phosphoserine on the performance of rats on the rotarod. 95 8

The electromyogram (EMG) is often used to study human muscle fatigue, but the changes in the electromyographic signals during muscle contraction are not well understood in relation to muscle metabolism. The 31P NMR spectroscopy is a semi-quantitative non-invasive method for studying the metabolic changes in human muscle. The aim of this study was to develop a method by which EMG and NMR spectroscopy measurements could be performed simultaneously. All measurements were performed in a whole body 1.5 Tesla NMR scanner. A calf muscle ergometer, designed for use in a whole body NMR scanner, was used. The subject had the left foot strapped to the ergometer. The anterior tibial EMG was recorded by bipolar surface electrodes. A surface coil was strapped to the anterior tibial muscle next to the EMG electrodes. Simultaneous measurements of surface EMG and surface coil 31P NMR spectroscopy were performed in the scanner during an isometric submaximal voluntary contraction until exhaustion, in 6 normal volunteers. Concentrations of phosphocreatine (PCr), inorganic phosphate (P(i)) and pH were analysed together with root mean square (RMS) and median frequency of the EMG. The fatiguing contractions (endured 5-13 min) produced a rapid decline in PCr and pH accompanied by a rapid rise in P(i). The RMS was approximately constant until the normalized PCr concentration declined below 0.6-0.7 and the pH declined below 6.75-6.85; exceeding these metabolic limits was associated with a rapidly increasing RMS value (2-3 times the previous level by exhaustion). The median frequency declined linearly with time and was found to be highly linearly correlated with the pH value (r = 0.82).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Simultaneous electromyography and 31P nuclear magnetic resonance spectroscopy--with application to muscle fatigue. 128 59

The force produced by muscles declines during prolonged activity and this decline arises largely from processes within the muscle. At a cellular level the reduced force could be caused by: (a) reduced intracellular calcium release during activity; (b) reduced sensitivity of the myofilaments to calcium; or (c) reduced maximal force development. Experiments involving intracellular calcium measurements in isolated single fibres show that all 3 of the above contribute to the decline of force during fatigue. Metabolic changes associated with fatigue are probably involved in each of the 3 factors. Thus the accumulation of phosphate and protons which occur during fatigue cause a reduction in calcium sensitivity and a decline in maximal force. The cause of the reduced intracellular calcium during contractions in fatigue is less clear. During prolonged tetani the conduction of the action potential in the T-tubules appears to fail leading to reduced intracellular calcium in the central part of the muscle fibre. However, during repeated tetani there is a uniform decline of intracellular calcium across the fibre and this remains one of the least understood processes which contribute to fatigue.
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PMID:Role of excitation-contraction coupling in muscle fatigue. 131 91

Fatigue during the 400-m sprint was studied by measuring muscle ATP, creatine phosphate (CP), lactate (M-La), and blood lactate (B-La) in six male runners before and after four experimental sprints (100, 200, 300, and 400 m). During the first 100 m, muscle CP decreased from 15.8 +/- 1.7 to 8.3 +/- 0.3 mmol/kg while M-La increased to 3.6 +/- 0.4 mmol/kg. After 200 m the CP had decreased to 6.5 +/- 0.5 mmol/kg and M-La had increased to 8.3 +/- 1.1 mmol/kg. At the end of the 400 meters, ATP and CP concentrations had decreased by 27% and 89%, respectively, and M-La had increased to 17.3 +/- 0.9 mmol/kg. It was concluded that after 200 m the speed of running decreased, although CP was not depleted and lactate concentration was not at maximum level. Complete fatigue occurred when CP stores were depleted and B-La and M-La attained an individual maximum.
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PMID:Fatigue and changes of ATP, creatine phosphate, and lactate during the 400-m sprint. 132 8

We evaluated the effects of diaphragmatic fatigue on muscle phosphatidylinositol phosphate (PIP) metabolism. Results revealed that the total PIP pool was 76% greater in fatigued rat diaphragms compared to controls, which suggests that fatigue was associated with inhibition of sarcolemmal membrane bound PIP hydrolysis.
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PMID:Effects of diaphragmatic fatigue on phosphoinositide hydrolysis. 132 75

Genetic endowment and proper training are the major factors contributing to athletic success in endurance and ultraendurance events. Proper nutrition, primarily adequate carbohydrate and fluid, prior to and during the event is also critical. Endurance athletes often utilize other nutritional substances or practices, often referred to as ergogenics, in attempts to obtain a competitive edge by enhancing energy utilization and delaying the onset of fatigue. Numerous nutritional ergogenics have been used in attempts to enhance endurance performance, but with several exceptions most have been shown to be ineffective, including bee pollen, L-carnitine, CoQ10, inosine, amino acids, alkaline salts, and vitamin E at sea level. Research findings are equivocal relative to the ergogenicity of caffeine, phosphate salts, and vitamin E at altitude. Loss of excess body fat, a nutritional practice, may be an effective ergogenic. Conversely, some agents such as alcohol may impair performance, an ergolytic effect. Additional research is necessary to support the efficacy of several nutritional ergogenics to enhance prolonged endurance performance, such as caffeine, phosphates, specific amino acids, and various commercial products. Such research should involve exercise tasks comparable in intensity and duration to that experienced in the marathon and similar endurance events.
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PMID:Ergogenic and ergolytic substances. 132 3

Major findings from our work on exposures and effects from organophosphate-containing pesticides in selected occupational and community patients and groups in Israel are reviewed as a basis for recommending control measures. The worker groups were pilots, ground-crews, and field workers; exposed nonworkers were adults and children living in kibbutzim with drift exposures, and household residents in houses treated by pest exterminators. In all groups, evidence of exposure-illness associations was found even though persons with acute poisoning were not seen. Complaints (headache, dizziness, fatigue, nausea, breathing problems, abdominal cramps, and tingling in extremities) were associated with within-normal depressions in cholinesterase activity. Whole blood and plasma cholinesterase activity were slightly more sensitive indicators of mixed exposure than red blood cell cholinesterase activity. High alkyl phosphate levels and symptoms were seen in individuals with within-normal limit depressions in cholinesterase activity. Complaints of weakness and tingling in hands and feet, together with low-grade changes in nerve conduction, suggest the possible influence of agents with a neurotoxic esterase-type activity independent of cholinesterase activity. Transient in-season neuropsychological changes in tests of mood status and performance were associated with exposure. Recommendations for exposure reduction include: accelerating the already declining use of pesticides in general, and organophosphates in particular; promoting the shift from more to less toxic organophosphates and other pesticides; and introducing rigid performance specifications for closed systems in loading and mixing at end-user sites. Dermal protection remains a problem. Cholinesterase activity levels and symptom interviews are useful for monitoring workers at risk, but alkyl phosphate levels are the definitive measure of exposure, surveys, investigations and surveillance.
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PMID:Health effects from exposure to organophosphate pesticides in workers and residents in Israel. 133 Sep 77

Muscular fatigue is manifested by a decline in force- or power-generating capacity and may be prominent in both submaximal and maximal contractions. Disturbances in muscle electrolytes play an important role in the development of muscular fatigue. Intense muscular contraction is accompanied by an increased muscle water content, distributed in both intracellular and extracellular spaces. This water influx will modify ionic changes in both compartments. Changes in muscle intracellular electrolyte concentrations with intense contraction may be summarised as including decreases in potassium (6 to 20%) and in creatine phosphate (up to 70 to 100%) and increases in lactate (more than 10-fold), sodium (2-fold) and small, variable increases in chloride. The net result of these intracellular ionic concentration changes with exercise will be a reduction in the intracellular strong ion difference, with a consequent marked rise in intracellular hydrogen ion concentration. This intracellular acidosis has been linked with fatigue via impairment of regulatory and contractile protein function, calcium regulation and metabolism. Potassium efflux from the contracting muscle cell dramatically decreases the intracellular to extracellular potassium ratio, leading to depolarisation of sarcolemmal and t-tubular membranes. Surprisingly little research has investigated the effects of intense exercise training on electrolyte regulation and fatigue.
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PMID:The roles of ionic processes in muscular fatigue during intense exercise. 137 45

Adenine nucleotide (AN) degradation has been shown to occur during intense exercise in the horse and in man, at or close to the point of fatigue. The aim of the study was to compare the concentrations of muscle inosine 5'-monophosphate (IMP) and plasma ammonia (NH3) during intense exercise with the concentrations of muscle and blood lactate. Seven trained thoroughbred horses were used in the study. Each exercised on a treadmill for periods of between 30 s and 150 s, at 11 and/or 12 m.s-1. Blood and muscle samples were taken and analysed for lactate and NH3 and adenosine 5'-triphosphate (ATP), phosphorylcreatine (PCr), IMP, creatine, lactate and glycerol-3-phosphate respectively. Horses showed varying degrees of AN degradation as indicated by plasma [NH3] and muscle [ATP] and [IMP]. Comparisons of [IMP] with muscle [lactate], and plasma [NH3] with that of blood [lactate] indicated a threshold to the start of AN degradation. This threshold corresponded to a lactate content of around 80 mmol.kg-1 dry muscle and 15 mmol.l-1 in blood. We discuss the mechanisms which have been proposed to account for AN degradation and suggest that IMP formation occurs as a result of a sudden rise in the concentration of adenosine 5'-diphosphate (ADP) and consequently the concentration of adenosine 5'-monophosphate. The data suggest a critical pH below which there may be a substantial reduction in the kinetics of ADP rephosphorylation provided by PCr resulting in an increase in [ADP], which is the stimulus to AN degradation during intense exercise.
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PMID:Adenine nucleotide degradation in the thoroughbred horse with increasing exercise duration. 139 58

The latissimus dorsi (LD) muscle is considered suitable to assist ventricular mechanical function in either cardiomyoplasty or extra-aortic-assist devices. Such application requires that this mixed-type skeletal muscle be transformed into a fatigue-resistant muscle, the adaptation of which can be elicited by chronic stimulation. In this study the LD muscles of dog and goat were subjected in situ to 12 wk of continuous electrical stimulation through intramuscular electrodes, and their myofibrillar and metabolic adaptations were compared. A gradual increase in the contraction rate of the muscle (in 10 wk from 30 to 80 contractions/min) caused the proportion of immunohistochemically identified type I fibers to increase in dog muscle from 30 to 74% and in goat muscle from 21 to 99%. Correspondingly, the anaerobic-glycolytic activity (fructose-6-phosphate kinase and lactate dehydrogenase activities) decreased by approximately 75% in both dog and goat muscles, whereas the oxidative capacity (fatty acid oxidation and citrate synthase activity) increased two- to threefold in goat LD muscle but remained unaltered in dog LD muscle. Muscular contents of high-energy phosphates and endogenous substrates were maintained, but the L-carnitine content decreased by 43% in both dog and goat. Our data further indicate that, for the monitoring of the metabolic adaptation of skeletal muscle, the ratio of activities of the oxidative and anaerobic-glycolytic pathways (e.g., citrate synthase to fructose-6-phosphate kinase activities) is a useful parameter in both dog and goat.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Differences in metabolic response of dog and goat latissimus dorsi muscle to chronic stimulation. 140 41


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