Gene/Protein Disease Symptom Drug Enzyme Compound
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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 electrically evoked isometric and isokinetic properties of the triceps surae have been studied in 11 healthy male subjects. The results showed that the time to peak tension (TPT) and half relaxation time (1/2 RT) of the maximal twitch were 110 +/- 11 ms and 82 +/- 11 ms respectively, and the peak rates of rise of contraction (delta P50, delta P200) and relaxation (delta PR50, delta PR200) at 50 and 200 Hz were 0.36 +/- 0.07, 0.48 +/- 0.08 and 1.27 +/- 0.33, 1.25 +/- 0.27% Po ms-1 respectively. The decline in force during a fatigue test was significantly (P less than 0.02) associated with the decrease in maximal relaxation rate (r = 0.79). The TPT was significantly (P less than 0.05) and inversely related to delta P50 and delta P200. The mean angle specific torque-velocity relationship for the 11 subjects was adequately described by the empirical exponential equation of the form: V = 16.5 (e-P/30.8-e-84.3/30.8) where V = velocity (rads s-1) and P = torque (Nm). The only significant association found between the isometric and isokinetic properties of the muscle was between delta PR200 and the torque expressed at a given velocity of 4 rads s-1. This lack of association between the two variables is difficult to explain with certainty but it is suggested that it may be due to the differential effects of Ca2+ release and uptake and cross-bridge turnover rate in the two situations.
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PMID:Electrically evoked isometric and isokinetic properties of the triceps surae in young male subjects. 322 74

The electrically evoked isometric properties of the triceps surae have been studied in young (22 yr) and elderly (69 yr) men and women. The results show that the triceps surae of elderly subjects had an increased time to peak tension (TPT) of the twitch, a lower specific tension (force/cross section area), and showed a greater relative force loss when subjected to a standard "fatigue" test procedure than young triceps surae. The respective figures for TPT, specific tension, and fatigue index (FI) were 147 +/- 15 ms (male), 143 +/- 8 ms (female), 19.5 N/cm2 and 0.52 +/- 0.16 (male), 0.37 +/- 0.09 (female) in the elderly, compared with 118 +/- 14 ms (male), 132 +/- 11 ms (female), 32.9 N/cm2 and 0.67 +/- 0.11 (male), 0.62 +/- 0.09 (female) in their younger counterparts. The peak rates of rise (delta P50, delta P200) and relaxation (delta PR50, delta PR200) of tetani at 50 Hz and 200 Hz were slower (p less than 0.05) in the elderly group. The delta P50 and delta P200 were inversely associated (r = 0.76 and -0.50 respectively) with TPT, and the half relaxation time (1/2RT) of the maximal twitch was related to delta PR50 (r = 0.53). The decrease of tetanus relaxation rate during the 2 min fatigue test (delta PRF) was greater in the elderly than the young and was positively associated (r = 0.74) with FI. It is concluded that elderly muscle is weaker, more slowly contracting and fatigable than that of the young. However, it is suggested that the reduced specific tension and enhanced fatiguability of the elderly may in part be due respectively to the inadequacies of our estimates of the effective cross-sectional area CSA) of contractile tissue in the lower leg and the influence of blood flow which may be compromised during a 2 min test.
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PMID:Mechanical properties of young and elderly human muscle. 346 6

Subjects were instructed to modify their N100-P200 component of VEP (in Cz recording) within selected time window. The aim was to increase the number of VEPs for which the amplitude of segment in question exceeded the definite threshold. The success in task performance suggests several modifications of the to-be-conditioned segment through different mechanisms. Of our 26 subjects, 14 were able to modify their VEPs according to the task demands. However, the latter subjects could be divided into 2 groups on the basis of the rate of increase in the number of correct responses under conditioning. Subjects which did not succeed in task performance could be also classed into 2 groups: one group with statistically negligible changes and the other decreasing the number of correct responses. ANOVA has shown significant distinctions in task performance for the groups with different levels of self-estimation of tiredness after experiment and different personal strategies. The success in task performance is likely to be dependent on the values of Eysenck questionnaire scales and topography of alpha activity.
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PMID:[The conditioning of the N100-P200 component of the human visual evoked potential by using biofeedback]. 854 Feb 51

The VEPs to checkerboard-flashes were recorded from Cz in 32 healthy adult volunteers (14 men, 18 women) under biofeedback conditions. The subjects were instructed to modify N100-P200 component in such a way that the amplitude of the segment within selected time-window from the beginning of the sample to its main positive peak exceeded the definite threshold. Each subject solved the task by means of individual combination of voltage and temporal regulation with the prevalence of the latter. Shifts of the latencies both of N100 and P200 were involved in VEP modifications. Four groups of subjects were distinguished by their success in task performance which depended on the strategy and level of self-estimated tiredness. The latency of N300 (out of the chosen time-sample) was longer for the subjects which were successful in increasing the number of "correct" responses. Differences in VEP components depended on the strategy types, levels of self-estimated tiredness, and sex on the subjects.
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PMID:[Changes in the components of the human visual evoked potential during conditioning using biological feedback]. 875 50

Pethidine (meperidine) is a compound with both local anaesthetic and opioid agonist properties. We have in a recent study demonstrated that pethidine could be an interesting alternative to prilocaine in arthroscopy with local anaesthetic technique. Therefore, we investigated, in a controlled randomized double-blind study, the effect of three doses of pethidine compared with a standard local anaesthetic, in patients subjected to arthroscopic knee joint surgery. Ten patients in each group received 50 mg (P50), 100 mg (P100), 200 mg (P200) of pethidine or prilocaine (5 mg/ml) + adrenaline (4 mg/ml) (PC), injected intra-articularly (i.a.) before surgery. We measured pain intensity and discomfort during arthroscopy and pain intensity at rest and at movement, nausea and tiredness for 3 days post-operatively at regular intervals using the VAS-technique. We also measured the concentration of pethidine and its demethylated metabolite, norpethidine, in plasma by collecting blood samples at 20, 40, 60, 80, 140 and 200 min following injection, and in synovial fluid which was collected through the arthroscope at the start and the end of the surgery. It was found that significantly more patients in the P50 group (n = 6) needed general anaesthesia due to intense pain than those in the P100 group (n = 1), P200 group (n = 0) or the PC group (n = 1). The PC group required significantly more analgesics and had a significantly higher calculated total sum of pain scores at movement post-operatively, than the other three groups. The P200 group more often reported tiredness post-operatively than the other three groups. We conclude that 100 or 200 mg pethidine i.a. produces satisfactory anaesthesia for surgery. There was a rapid transfer of pethidine from synovial fluid to plasma, resulting in plasma levels earlier reported to produce centrally mediated effects, such as analgesia and tiredness. We found much higher concentrations of norpethidine in the synovial fluid than in plasma, suggesting a local demethylation in the knee joint tissues. This site of drug oxidation has not earlier been demonstrated neither in vitro nor in vivo. The results suggest that pethidine given i.a. in the dose range of 50 to 200 mg results in analgesia due to both peripheral and central mechanisms. The significant systemic uptake of pethidine can cause unwanted side-effects.
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PMID:A comparison of 50, 100 and 200 mg of intra-articular pethidine during knee joint surgery, a controlled study with evidence for local demethylation to norpethidine. 1020 35

This study investigated the psychophysiological effects of sleep deprivation on auditory event-related potentials (AERPs) and their relationship with psychological parameters. Twenty-four subjects remained awake for 37 h under continuous surveillance. In the mornings and the evenings of 2 consecutive study days, AERPs were recorded and 4 self-rated scales (sleepiness, fatigue, anxiety, and mood) were quantified. The latencies of P300 and N200 were significantly prolonged (p < 0.001) and their amplitudes decreased (p < 0.05) as a consequence of sleep deprivation. However, the only significant change in N100 and P200 was an increase in the P200 amplitude (p < 0.05). The increase in the latencies of P300 and N200 were correlated with increased sleepiness (p < 0.05), and the increase in P200 amplitude was correlated with negative mood, anxiety, and fatigue (p < 0.05). Although the changes in P300 and N200 induced by sleep deprivation are due to sleepiness, which may slow cognitive processing and decrease the efficiency of mental processing, the increase in P200 may be related with increased anxiety, negative mood, and fatigue.
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PMID:Auditory event-related potentials and psychological changes during sleep deprivation. 1517 12

This study investigated behavioral responses to and auditory event-related potential (ERP) correlates of mental fatigue caused by mobile three-dimensional (3D) viewing. Twenty-six participants (14 women) performed a selective attention task in which they were asked to respond to the sounds presented at the attended side while ignoring sounds at the ignored side before and after mobile 3D viewing. Considering different individual susceptibilities to 3D, participants' subjective fatigue data were used to categorize them into two groups: fatigued and unfatigued. The amplitudes of d-ERP components were defined as differences in amplitudes between time-locked brain oscillations of the attended and ignored sounds, and these values were used to calculate the degree to which spatial selective attention was impaired by 3D mental fatigue. The fatigued group showed significantly longer response times after mobile 3D viewing compared to before the viewing. However, response accuracy did not significantly change between the two conditions, implying that the participants used a behavioral strategy to cope with their performance accuracy decrement by increasing their response times. No significant differences were observed for the unfatigued group. Analysis of covariance revealed group differences with significant and trends toward significant decreases in the d-P200 and d-late positive potential (LPP) amplitudes at the occipital electrodes of the fatigued and unfatigued groups. Our findings indicate that mentally fatigued participants did not effectively block out distractors in their information processing mechanism, providing support for the hypothesis that 3D mental fatigue impairs spatial selective attention and is characterized by changes in d-P200 and d-LPP amplitudes.
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PMID:Effect of mental fatigue caused by mobile 3D viewing on selective attention: an ERP study. 2519 5

A single-trial extraction of a visual evoked potential (VEP) signal based on the partial least-squares (PLS) regression method has been proposed in this paper. This paper has focused on the extraction and estimation of the latencies of P100, P200, P300, N75, and N135 in the artificial electroencephalograph (EEG) signal. The real EEG signal obtained from the hospital was only concentrated on the P100. The performance of the PLS has been evaluated mainly on the basis of latency error rate of the peaks for the artificial EEG signal, and the mean peak detection and standard deviation for the real EEG signal. The simulation results show that the proposed PLS algorithm is capable of reconstructing the EEG signal into its desired shape of the ideal VEP. For P100, the proposed PLS algorithm is able to provide comparable results to the generalized eigenvalue decomposition (GEVD) algorithm, which alters (prewhitens) the EEG input signal using the prestimulation EEG signal. It has also shown better performance for later peaks (P200 and P300). The PLS outperformed not only in positive peaks but also in N75. In P100, the PLS was comparable with the GEVD although N135 was better estimated by GEVD. The proposed PLS algorithm is comparable to GEVD given that PLS does not alter the EEG input signal. The PLS algorithm gives the best estimate to multitrial ensemble averaging. This research offers benefits such as avoiding patient's fatigue during VEP test measurement in the hospital, in BCI applications and in EEG-fMRI integration.
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PMID:Single-Trial Visual Evoked Potential Extraction Using Partial Least-Squares-Based Approach. 2537 49

The purpose of the current study was to determine the effects of three different pulse durations (200, 350, and 500 microseconds [P200, P350, and P500, respectively]) on oxygen uptake (VO2), cycling performance, and energy expenditure (EE) percentage of fatigue of the knee extensor muscle group immediately and 48 to 72 h after cycling in persons with spinal cord injury (SCI). A convenience sample of 10 individuals with motor complete SCI participated in a repeated-measures design using a functional electrical stimulation (FES) cycle ergometer over a 3 wk period. There was no difference among the three FES protocols on relative VO2 or cycling EE. Delta EE between exercise and rest was 42% greater in both P500 and P350 compared with P200 (p = 0.07), whereas recovery VO2 was 23% greater in P350 compared with P200 (p = 0.03). There was no difference in the outcomes of the three pulse durations on muscle fatigue. Knee extensor torque significantly decreased immediately after (p < 0.001) and 48 to 72 h after (p < 0.001) FES leg cycling. Lengthening pulse duration did not affect submaximal or relative VO2 or EE, total EE, and time to fatigue. Greater recovery VO2 and delta EE were noted in P350 and P500 compared with P200. An acute bout of FES leg cycling resulted in torque reduction that did not fully recover 48 to 72 h after cycling.
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PMID:Effect of adjusting pulse durations of functional electrical stimulation cycling on energy expenditure and fatigue after spinal cord injury. 2580 53