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

1. We have examined the interaction between aerobic exercise and lipid-lowering drugs in a crossover study of 16 healthy normolipidaemic volunteers who each received 21 days' treatment with bezafibrate (400 mg), fluvastatin (40 mg), and placebo, in random order. 2. Fluvastatin treatment reduced pre-exercise total cholesterol (TC) by 23% (P < 0.0001), low-density lipoprotein cholesterol (LDL-C) by 33% (P < 0.0001), and plasma triglycerides by 11%, compared with pre-treatment values. Bezafibrate reduced TC by 11% (P < 0.01); LDL-C by 9%; and plasma triglycerides by 40% (P < 0.01), compared with pre-treatment values. 3. During exercise, in comparison with placebo, and fluvastatin treatment, respectively, bezafibrate significantly reduced mean fat oxidation: 31% vs 39%, P = 0.035, 31% vs 39%, P = 0.002, plasma free fatty acid (FFA) availability, e.g. after 90 min of exercise: (t90) 520 vs 662 mumol 1(-1), P = 0.054, 520 vs 725 mumol 1(-1), P = 0.016, and plasma levels of glycerol (t90): 59 vs 74 mumol 1(-1), P = 0.037, 59 vs 73 mumol 1(-1), P = 0.016. Fluvastatin had no impact on fat metabolism in comparison with placebo. 4. Reduced plasma FFA concentration and lower fat oxidation during prolonged exercise on bezafibrate treatment may be due to an inhibition of hepatic acetyl coenzyme A carboxylase, resulting in reduced FFA release from adipose tissue. 5. The possibility that impaired fat metabolism on fibrates could induce premature fatigue during exercise of moderate duration and intensity should be examined in hyperlipidaemic patients.
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PMID:A comparison of the effects of fluvastatin and bezafibrate on exercise metabolism: a placebo-controlled study in healthy normolipidaemic subjects. 873 78

The effect of the intramuscular injection of bupivacaine hydrochloride on selected morphological characteristics and contractile properties of adult rat extensor digitorum longus muscle was studied. Recovery of normal fiber size was already present 30 days after bupivacaine injection and at 90 days after injection, values of the normalized twitch tension (mN/mg of tissue) and of the fatigue index approached those measured in control muscle, whereas the normalized tetanic tension remained 57% of control. At 7-30 days postinjection, twitch force was decreased by reducing [Ca2+]zero (substituted by Mg2+) or adding Co2+ (5 mmol/L-1). By contrast potentiation of the twitch was recorded in the presence of Cd2+ (2 mmol/L-1). Glycerol treatment only reduced, but did not eliminate twitches developed by muscles 7 days after injection. Present results emphasize the importance of the recovery process in the loss of the susceptibility of the contractile responses to extracellular calcium in bupivacaine-injected muscles. These data may be of interest in the evaluation of functional aspects of muscles in which injections of viral vector or autologous myoblasts have been performed.
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PMID:External calcium dependence of extensor digitorum longus muscle contractility during bupivacaine-induced regeneration. 875 65

Hormonal and metabolic responses to electrically induced dynamic exercise were investigated in eight healthy young men with afferent neural influence from the legs blocked by epidural anesthesia (25 ml of 2% lidocaine) at L3-L4. This caused cutaneous sensory anesthesia below T8-T9 and complete paralysis of the legs. Cycling increased oxygen uptake to 1.90 +/- 0.13 (SE) l/min, and fatigue developed after 22.7 +/- 2.7 min. Compared with voluntary exercise at the same oxygen uptake and heart rate, concentrations of blood and muscle lactate (musculus vastus lateralis) as well as plasma potassium increased more while muscle glycogen decreased more during electrically induced exercise. Hepatic glucose production always rose during exercise. However, during involuntary exercise with sensory blockade, it did not match the rise in peripheral glucose uptake and plasma glucose decreased (P < 0.05). Plasma glycerol increased less in electrically induced vs. voluntary exercise, and free fatty acids and beta-hydroxybutyrate decreased only during electrically induced exercise. Epinephrine, growth hormone, adrenocorticotropic hormone, and cortisol levels were higher during involuntary vs. voluntary exercise (P < 0.05). In conclusion, neural and humoral mechanisms exert redundant control with regard to responses of catecholamines and pituitary hormones (growth hormone and adrenocorticotropic hormone). In contrast, neural input from motor centers and feedback from working muscle are important for glucose production and lipolysis during exercise in humans. Humoral feedback is apparently not sufficient to trigger normal mobilization of extramuscular fuel stores.
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PMID:Hormonal and metabolic responses to electrically induced cycling during epidural anesthesia in humans. 880 25

Previous studies have demonstrated that full recovery from weight loss may take months or years. The present investigation examined short-term recovery (5 wks "post") of physical performance (muscular strength, muscular power, vertical jump), body composition, metabolic hormones (testosterone, luteinizing hormone, sex hormone binding globulin, insulin-like growth factor-1, triiodothyronine, thyroxine, thyroid binding globulin, and thyroid-stimulating hormone) and metabolic markers (transferrin, ferritin, prealbumin, glycerol, nonesterified fatty acids, high-density lipoproteins, and lactate) in 10 healthy young men after an 8-week Army course with an energy deficit (1000 kcal/d) and loss of body mass (-12%). Subjects ate ad libitum after the course ended ("post"). Body composition was determined by dual-energy X-ray absorptiometry; strength from a simulated power clean, power from body mass and jump height, and metabolic hormones were measured in morning-fasted blood by radioimmunoassay. With the exception of transferrin and glycerol, all study parameters were significantly (p<.05) altered by the training course. At 5 weeks post fat-free mass along with all physical performance measures returned to initial levels; however, fat mass had significantly (p<.05) increased over initial levels. Also, with the exception of lactate, all measured hormones and markers were close to initial levels and within normal ranges. Reported complications during recovery included sleep irregularities, diarrhea, loss of motivation and feelings of fatigue. While the long range effect of this energy deprivation experience is uncertain, these data do suggest that severe weight loss does not result in lasting alterations of the contractile and metabolic properties of skeletal muscle in young, lean, healthy men.
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PMID:Physical performance and metabolic recovery among lean, healthy men following a prolonged energy deficit. 929 70

This study examined functional, biochemical, and morphological characteristics of skeletal muscle in nine multiple sclerosis (MS) patients and eight healthy controls in an effort to ascertain whether intramuscular adaptations could account for excessive fatigue in this disease. Analyses of biopsies of the tibialis anterior muscle showed that there were fewer type I fibers (66 +/- 6 vs. 76 +/- 6%), and that fibers of all types were smaller (average downward arrow26%) and had lower succinic dehydrogenase (SDH; average downward arrow40%) and SDH/alpha-glycerol-phosphate dehydrogenase (GPDH) but not GPDH activities in MS vs. control subjects, suggesting that muscle in this disease is smaller and relies more on anaerobic than aerobic-oxidative energy supply than does muscle of healthy individuals. Maximal voluntary isometric force for dorsiflexion was associated with both average fiber cross-sectional area (r = 0.71, P = 0.005) and muscle fat-free cross-sectional area by magnetic resonance imaging (r = 0.80, P < 0. 001). Physical activity, assessed by accelerometer, was associated with average fiber SDH/GPDH (r = 0.78, P = 0.008). There was a tendency for symptomatic fatigue to be inversely associated with average fiber SDH activity (r = -0.57, P = 0.068). The results of this study suggest that the inherent characteristics of skeletal muscle fibers per se and of skeletal muscle as a whole are altered in the direction of disuse in MS. They also suggest that changes in skeletal muscle in MS may significantly affect function.
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PMID:Strength, skeletal muscle composition, and enzyme activity in multiple sclerosis. 939 Sep 73

Feeding a high-carbohydrate (CHO) diet and administration of alkalinizing agents have both been shown to improve performance in high-intensity exercise. The effect of these treatments in combination was investigated in the present study. Six healthy male subjects exercised to exhaustion on an electrically braked cycle ergometer at a power output equivalent to 100% of their maximum oxygen uptake (VO2,max) on four separate occasions. Each subject consumed either a diet with the same composition as his normal diet (termed the experimental normal (N) diet; 54 +/- 7% CHO, 13 +/- 2% protein, 33 +/- 7% fat) or a high-CHO diet (81 +/- 2% CHO, 13 +/- 2% protein, 6 +/- 1% fat) that had the same energy and protein content for the 3 days prior to the exercise tests. Subjects then ingested either a placebo (CaCO3) or trisodium citrate (0.3 g (kg body mass)-1) 3 h before exercise. Time to fatigue was not different between experimental conditions. Consumption of the high-CHO diet had no effect on blood acid-base status, but the ingestion of sodium citrate induced a mild metabolic alkalosis after both the N diet and the high-CHO diet. This alkalinizing effect was also evident after exercise, since blood pH, plasma bicarbonate and blood base excess were higher (P < 0.05) after the ingestion of sodium citrate than under the placebo conditions. The changes in blood lactate, pyruvate and glucose and plasma glycerol after exercise were similar for all experimental conditions. Blood lactate, glucose and pyruvate and plasma glycerol concentrations increased from resting values (P < 0.01) following exercise but this increase was similar under all experimental conditions. These data demonstrate that when the energy and protein content of the diets is the same, exercise capacity and the metabolic response to intense exercise are similar following consumption either of a high-CHO diet or a more normal diet. Acute ingestion of sodium citrate prior to exercise resulted in a reduction in post-exercise acidosis despite a blood lactate concentration that was similar to that observed after the ingestion of a placebo, but did not affect exercise performance under the conditions of this study.
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PMID:The effect of sodium citrate ingestion on the metabolic response to intense exercise following diet manipulation in man. 941 35

T-tubules of skeletal muscle fibres easily transform into large vacuoles under the influence of various factors. These include osmotic shock produced by the efflux of small molecular weight molecules (e.g. glycerol), hypertonic shock, muscle fatigue and muscle damage. In most cases, vacuolation is reversible but the molecular mechanisms involved are not clear. Also, the functional role of reversible vacuolation has not been established. However, three possibilities may be considered. (1) Redistribution of ions and water between the cytoplasm and the extracellular space comprised by the T-system. Thus, the formation of large vacuoles may be a mechanisms for rapid osmoregulation that corresponds to regulated volume decrease in other types of cell. However, in our hands, inhibitors of various pathways that participate in volume regulation had no effect on reversible vacuolation. (2) Resealing of mechanical damage of the plasma membrane. This is usually accompanied by the development near the damaged membrane of numerous vacuoles which we have observed by confocal microscopy and use of a hydrophobic dye (RH414), to arise in part from T-tubules. (3) By confocal microscopy, it has also been shown that extracellular fluorescein dextran (Mr = 10,000), and both plasmid DNA (pUC18) and sonicated high molecular weight DNA stained with YOYO, enter vacuoles derived from T-tubules. This finding may indicate that reversible vacuolation, in the absence of membrane damage, could provide a pathway from the extracellular environment to the cytoplasm that is additional or complimentary to endocytosis; it may also be particularly relevant to the ability of muscle to be transfected by the direct injection of DNA. These several observations strongly indicate that the function of the T-system in skeletal muscle fibers is not restricted to excitation-contraction coupling.
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PMID:[Functional role of vacuolization of the T-system of skeletal muscle fibers]. 950 35

This study examined the efficacy of glycerol and water hyperhydration (1 h before exercise) on tolerance and cardiovascular strain during uncompensable exercise-heat stress. The approach was to determine whether 1-h preexercise hyperhydration (29.1 ml H2O/kg lean body mass with or without 1.2 g/kg lean body mass of glycerol) provided a physiological advantage over euhydration. Eight heat-acclimated men completed three trials (control euhydration before exercise, and glycerol and water hyperhydrations) consisting of treadmill exercise-heat stress (ratio of evaporative heat loss required to maximal capacity of climate = 416). During exercise ( approximately 55% maximal O2 uptake), there was no difference between glycerol and water hyperhydration methods for increasing (P < 0.05) total body water. Glycerol hyperhydration endurance time (33. 8 +/- 3.0 min) was longer (P < 0.05) than for control (29.5 +/- 3.5 min), but was not different (P > 0.05) from that of water hyperhydration (31.3 +/- 3.1 min). Hyperhydration did not alter (P > 0.05) core temperature, whole body sweating rate, cardiac output, blood pressure, total peripheral resistance, or core temperature tolerance. Exhaustion from heat strain occurred at similar core and skin temperatures and heart rates in each trial. Symptoms at exhaustion included syncope and ataxia, fatigue, dyspnea, and muscle cramps (n = 11, 10, 2, and 1 cases, respectively). We conclude that 1-h preexercise glycerol hyperhydration provides no meaningful physiological advantage over water hyperhydration and that hyperhydration per se only provides the advantage (over euhydration) of delaying hypohydration during uncompensble exercise-heat stress.
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PMID:Hyperhydration: tolerance and cardiovascular effects during uncompensable exercise-heat stress. 960 77

The manufacturer claims that using the Access Fat Conversion Activity Bar increases fat utilisation, which would have a glycogen-sparing effect and delay the onset of fatigue from endurance exercise. This claim was tested using seven trained distance runners who performed two trials of treadmill running at 73% of VO2max to exhaustion. In a counterbalanced design, subjects ingested either one Access Bar with water or water only prior to treadmill running. Times to exhaustion for the control and Access treatment trials were 104.6 +/- 24.9 min and 93.9 +/- 21.4 min, respectively, and were not significantly different (p > .05). Differences between trials were not observed for the respiratory exchange ratio, blood lactate or glucose concentrations, plasma glycerol concentration, or perceived exertion. Based on results from this study, it was concluded that the Access Bar does not affect fat or carbohydrate utilisation and does not improve exercise endurance.
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PMID:Effect of a sports food bar on fat utilisation and exercise duration. 961 69

We have investigated the potential for the human brain to use lipid fuels during acute hypoglycemia. Nine healthy male subjects underwent hyperinsulinemic (1.5 mU/kg x min) stepped hypoglycemic clamps on two occasions, infusing Intralipid (20%) and heparin (0.1 U/kg x min) on one occasion only (ILH), with an identical study without infusion of ILH acting as a control. Five subjects also underwent euglycemic clamping with Intralipid/heparin infusion. During hypoglycemia, ILH raised circulating levels of nonesterified fatty acids, glycerol, and beta-hydroxybutyrate, although the latter did not rise until after the onset of counterregulation. With ILH, epinephrine responses [area under the curve (AUC), 127.9 +/- 31.7 vs. 175.1 +/- 27.4 nmol/L x 180 min; P = 0.03] and GH responses (AUC, 260 +/- 91 vs. 1009 +/- 150, P < 0.01) were reduced and delayed (glucose thresholds, 2.8 +/- 0.04 vs. 3.0 +/- 0.1 mmol/L; P = 0.04), with a trend toward reduced cortisol responses. Similarly, hypoglycemic symptom scores were diminished during ILH (AUC, 647 +/- 162 vs. 1222 +/- 874; P = 0.03). However, there was no significant effect on the deterioration in four-choice reaction time, one measure of cognitive deterioration [glucose thresholds, 2.6 +/- 0.1 vs. 2.7 +/- 0.1 mmol/L, ILH vs. control (P = 0.75); AUC, 1420 +/- 710 vs. 2250 +/- 1080 ms/min (P = 0.59)]. During euglycemic clamping with Intralipid/heparin infusion studies, there was no rise in hormones, four-choice reaction time, or symptoms other than hunger and tiredness. Both nonesterified fatty acids and glycerol can penetrate the mammalian brain and be metabolized. Raised levels were able to reduce neurohumoral responses to hypoglycemia, but could not protect cognitive function. This suggests that regional differences exist in human brain metabolism between glucose-sensing and cognitive areas of brain, which may be important in the understanding of the mechanisms of glucose sensing and in the genesis of hypoglycemia unawareness in insulin-dependent diabetes.
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PMID:Reduced counterregulation during hypoglycemia with raised circulating nonglucose lipid substrates: evidence for regional differences in metabolic capacity in the human brain? 970 75


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