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)

Workload is an important factor related to perception of physical fatigue. Because a person engaged in physical activity eventually leading to painful exhaustion is in a pay-off situation, the paradigm of signal detection might be applicable to the perception of differences in load. Two male track and field athletes, aged 22 and 24 yr., participated in two experiments. In Exp. 1 difference threshold were determined with 25%, 50%, 60%, 65% and 70% of VO2 max as basic loads on a bicycle ergometer. Results showed a decreasing k over increasing work loads, contrary to Weber's law. In Exp. 2 a non-parametric signal detection procedure was used, with 25%, 40%, 50% and 60% of VO2 max as noise levels and a signal intensity of 1.5 watt in every condition. A chi 2 test for a 2-factor design showed only an effect of noise level. The converging results of both experiments led to the conclusion of a relative increasing sensitivity across increasing work loads. The main goal for future research will be to develop the signal detection method as a framework for research on fatigue.
 ...
PMID:Physical fatigue and the perception of differences in load: a signal detection approach. 67 33

On the basis of the study of cardiovascular, respiratory, nervous and motor systems of crewmembers (60 people) who made prolonged aircraft flights (over 10 hours) two types of physiological reactions have been defined. One type includes emotional reactions to short-term complications in the flight, and the other involves fatigue and relative exhaustion of the functional systems as a result of strenuous work and adverse flight effects. It has been demonstrated that the dynamic medical control is an important addition to the preflight and interflight physical examinations of the flying personnel.
 ...
PMID:[Dynamic medical control over the members of the flight crews in the process of long flights]. 71 68

Sixteen men and 16 women volunteer college students were tested for elbow flexion fatigue curve production on the Orthotron, an isokinetic testing device. Maximal voluntary contractions were obtained repeatedly, each contraction taking approximately 2 seconds to complete, with minimal (500 msec) intertrial rest, to exhaustion. To provide a basis for plotting the isokinetic fatigue curve, the degradation of torque values from initial to final contractions, was expressed as percentage of contraction time. Results obtained following statistical analysis of the data indicated that the isokinetic fatigue curve is: (1) curvilinear; (2) independent of sex differences; and (3) a function of initial strength. Moreover, it was found that the use of 50% of initial strength to denote fatigue in repetitive rhythmic isokinetic work has merit as a conservative estimate.
 ...
PMID:Fatigue curves of isokinetic contractions. 72 38

The present study was designed to investigate the effects of exercise to exhaustion on different components of visual capacity: visual field, and coincidence/anticipation capacity. 16 male subjects were first familiarized with the three visual tests, one day before being submitted to a prefatigue visual test. Metabolic fatigue was induced by working to exhaustion on a bicycle ergometer. Once fatigued, all subjects undertook the visual tests. Pre- and post-fatigue visual measurements were not significantly different. The results demonstrated the independence between metabolic fatigue and visual capacity.
 ...
PMID:Influence of imposed metabolic fatigue on visual capacity components. 74 14

Alterations in metabolism of catecholamines were studied in sportsmen after development of acute fatigue as a result of the test physical loading. Three types of the alterations were characterized on the basis of differences in excretion with urine of free and sulphate-bound adrenaline, noradrenaline, of their precursors DOPA and dopamine as well as acid metabolites (vanillyl mandelic acid). The first type of the alterations in catecholamines metabolism comprized the cases, when excretion of catecholamines, their precursors and metabolites did not increase; this appears to relate to the partial exhaustion of hormones and peripheric mediators of sympathoadrenal system. The second type was characterized by decreased excretion of the substances studied, by development of the "perversed" reactions due to modifications in the regulatory system, which led to the inhibition of the system instead of its stimulation. The third type was manifested as the hyperfunction of the system. The increased synthesis of catecholamines during the hyperfunction suggests that this process serves as a compensatory reaction to their preceding elevated secretion; the phenomenon appears to depend on the increased secretion of the newly formed catecholamines. Excretion of catecholamines and their precursors was decreased for a long time after development of chronic fatigue in the resting state and the increase in excretion of the substances studied was not observed after physical loading.
 ...
PMID:[Catecholamines, their precursors and metabolites in human fatigue after exertion]. 88 3

The objectives of this study were to describe in greater detail the initial rise and spontaneous decline in acute hypoxic pulmonary vasoconstriction and to investigate a number of mechanisms that could have caused this secondary vasodilation. With the onset of isocapnic hypoxia (Pao2 of 28, 44, or 56 mmHg), pulmonary vascular resistances increased to maximum values at 3 min and then spontaneously declined toward control values. Pulmonary perfusion pressures rose to maxima at approximately 4 min and then also declined. During severe hypoxic exposures (Pao2 of 30-37 mmHg) this secondary vasodilation was found not to be due to beta-adrenergic-induced vasodilation, withdrawal of alpha-adrenergic-induced vasoconstriction, vasodilation caused by a sustained increase in pulmonary blood flow, fatigue of the vascular smooth muscle contractile mechanism, or release of vasodilatory prostaglandins. It is suggested that the decline in hypoxic pulmonary vasoconstriction may be due to an exhaustion of a chemical mediator, release of a pulmonary vasodilator agent, or myogenic stress relaxation.
 ...
PMID:Nonsustained pulmonary vasoconstriction during acute hypoxia in anesthetized dogs. 111 41

This study was undertaken to determine the effects of O2-enriched gases on performance. Nine trained subjects ran to exhaustion on the treadmill on five different occasions breathing one of a range of hyperoxic gas mixtures--20%, 40%, 60%, 80%, or 100% O2. Each subject worked at a workload determined to be 110% of that necessary to elicit his maximum O2 uptake. The exercise bouts were scheduled one week apart to minimize the effects of training and fatigue. The subjects were given no cues as to the mixtures being breathed or to their running times. The parameters measured included running time, minute ventilation, and heart rate. The results indicate that the maximum performance time increases significantly as the O2 fraction of the gas is increased. Contrary to other published literature, 100% O2 increases performance significantly over 60% O2. Ventilation at any point in time is decreased when breathing hyperoxic mixtures. This decrease appears to be more a function of breathing frequency than of tidal volume. Terminal heart rates are not significantly different regardless of the O2 fraction of the inspired gas.
 ...
PMID:Effects of hyperoxic gas mixtures on exercise tolerance in man. 114 52

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)
 ...
PMID:Simultaneous electromyography and 31P nuclear magnetic resonance spectroscopy--with application to muscle fatigue. 128 59

Shi-Quan-Da-Bu-Tang (Ten Significant Tonic Decoction), or SQT (Juzentaihoto, TJ-48) was formulated by Taiping Hui-Min Ju (Public Welfare Pharmacy Bureau) in Chinese Song Dynasty in AD 1200. It is prepared by extracting a mixture of ten medical herbs (Rehmannia glutinosa, Paeonia lactiflora, Liqusticum wallichii, Angelica sinesis, Glycyrrhiza uralensis, Poria cocos, Atractylodes macrocephala, Panax ginseng. Astragalus membranaceus and Cinnamomum cassia) that tone the blood and vital energy, and strengthen health and immunity. This potent and popular prescription has traditionally been used against anemia, anorexia, extreme exhaustion, fatigue, kidney and spleen insufficiency and general weakness, particularly after illness. In order to restore immunity in cancer patients, potentiate the therapeutic effect and ameliorate adverse toxicity of anticancer agents, 116 Chinese herbal formularies (Kampo) have been screened and evaluated. Fifteen compounds were found to have such actions. Among these, SQT was selected as the most effective as a potent biological response modifier. During the last eight years, animal models and clinical studies have revealed that SQT demonstrates extremely low toxicity (LD50 > 15 g/kg op murine), self-regulatory and synergistic actions of its components in immunomodulatory and immunopotentiating effects (by stimulating hemopoietic factors and interleukins production in association with NK cells, etc.), potentiates therapeutic activity in chemotherapy (mitomycin, cisplatin, cyclophosphamide and fluorouracil) and radiotherapy, inhibits the recurrence of malignancies, prolongs survival, as well as ameliorate and/or prevents adverse toxicities (GI disturbances such as anorexia, nausea, vomiting, hematotoxicity, immunosuppression, leukopenia, thrombocytopenia, anemia and nephropathy, etc.) of many anticancer drugs. The application and mechanistic studies of SQT in future development have potential importance in basic and clinical research of the traditional Chinese therapeutic approach of "toning the blood and strengthening Qi (vital energy)" in cancer immunotherapy.
 ...
PMID:Shi-quan-da-bu-tang (ten significant tonic decoction), SQT. A potent Chinese biological response modifier in cancer immunotherapy, potentiation and detoxification of anticancer drugs. 129 61

The burnout syndrome denotes a constellation of physical fatigue, emotional exhaustion, and cognitive weariness resulting from chronic stress. Although it overlaps considerably with chronic fatigue as defined in internal medicine, its links with physical illness have not been systematically investigated. This exploratory study, conducted among 104 male workers free from cardiovascular disease (CVD), tested the association between burnout and two of its common concomitants--tension and listlessness--and cardiovascular risk factors. After ruling out five possible confounders (age, relative weight, smoking, alcohol use, and sports activity), the authors found that scores on burnout plus tension (tense-burnout) were associated with somatic complaints, cholesterol, glucose, triglycerides, uric acid, and, marginally, with ECG abnormalities. Workers scoring high on tense-burnout also had a significantly higher low density lipoprotein (LDL) level. Conversely, scores on burnout plus listlessness were significantly associated with glucose and negatively with diastolic blood pressure. The findings warrant further study of burnout as a predictor of cardiovascular morbidity and mortality.
 ...
PMID:Burnout and risk factors for cardiovascular diseases. 139 14


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