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

The TMS 32010 system for a real-time muscle fatigue monitor is described; it is based on mean frequency shift in the electromyographic signal (EMG). The mean frequency of the EMG is obtained, in real time, from its power spectrum, with a 2 Hz resolution. This is made possible by combining novel hardware and software.
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PMID:A real-time FFT analyser for monitoring muscle fatigue. 177 Aug 5

Twenty-five freshly extracted maxillary first premolars were divided equally among five modalities for rebuilding structurally compromised premolars. These modalities were: (A) buccal stainless steel Parapost/amalgam core, (B) palatal stainless steel parapost/amalgam core, (C) two stainless steel Paraposts/amalgam core, (D) two regular Link Plus TMS single-shear Minim pins/amalgam core, and (E) palatal cast gold post and core. Load fatigue was used as the testing protocol, using a 5.2-kg load applied at 72 cycles per minute. Each tooth was prepared with a 1.0-mm ferrule, and an upper limit of 250,000 load cycles was set for the testing. Two failures were exhibited, (1) preliminary failure which involved a crack in the luting cement layer, and (2) catastrophic failure wherein the core and crown separated from the root section. Statistical analysis using Kruskal-Wallis test showed three subsets (P < or = .05). The subset with the highest number of load cycles to failure contained the palatal stainless steel post/amalgam core, two stainless steel Paraposts/amalgam core, and palatal cast gold post and core.
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PMID:Load fatigue of five restoration modalities in structurally compromised premolars. 1034 88

This study examined whether muscle fatigue alters the facilitatory effect of motor imagery on corticospinal excitability. We aimed to determine if post-exercise depression of potentials evoked magnetically from the motor cortex is associated with alterations in internally generated movement plans. In experiment 1, motor-evoked potentials (MEPs) were recorded from two right hand and two right forearm muscles, at rest and during motor imagery of a maximal handgrip contraction, in eight neurologically normal subjects, before and after a 2-min maximal voluntary handgrip contraction. Resting MEP amplitude was facilitated by motor imagery in three of the four muscles, but consistently only in two. Motor imagery also reduced the trial-to-trial variability of resting MEPs. Following the exercise, resting MEP amplitude was depressed reliably in only one muscle engaged in the task, although two other muscles exhibited some depression. Motor imagery MEPs were smaller after exercise, but the degree of facilitation compared to the rest MEP was unchanged. In experiment 2, TMS intensity was increased after exercise-induced MEP depression so that the MEP amplitude matched the pre-exercise baseline. The amplitude of the MEP facilitated with motor imagery was not altered by MEP depression, nor was it increased when the TMS intensity was increased. These results suggest, at least with a simple motor task, that while post-exercise depression reduces corticospinal excitability, it does not appear to significantly affect the strength of the input to the motor cortex from those areas of the brain responsible for the storage and generation of internal representations of movement.
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PMID:Facilitation of cortically evoked potentials with motor imagery during post-exercise depression of corticospinal excitability. 1550 93

Previous studies have shown that the motor evoked potential (MEP) amplitude increases as force declines during a fatiguing muscle contraction, indicating that there is an increase in corticomotor excitability. In spite of this there is a progressive reduction in voluntary motor drive, as shown by an increase in the interpolated twitch force as fatigue develops. The aim of this study was to determine whether, by further increasing corticomotor excitability using a paired-pulse rTMS protocol designed to induce I-wave facilitation (iTMS), force loss during a sustained voluntary contraction could be reduced. We designed a cross-over study incorporating a 15-min period of iTMS (ISI 1.5 ms; 0.2 Hz; approximately AMT), following which MEP amplitude (first dorsal interosseous muscle) increased to 194 +/- 38% of baseline (P < 0.05), compared to a control period of stimulation that did not increase MEP amplitude (single-pulse TMS; 0.2 Hz; approximately 1.2 AMT). Eight right-handed healthy subjects received both iTMS and control stimulation, in a randomized order, a week apart. We measured percentage force loss at the end of a 10-s maximum right hand key-pinch task, and compared force loss before and after stimulation. There was an improvement in task performance following iTMS, with a reduction in force loss compared to pre-stimulation baseline (11.3 +/- 2.0 vs. 17.6 +/- 2.4%; post vs. pre; P < 0.05). There was no significant difference in force loss before and after control stimulation. The results indicate that by increasing corticomotor excitability using paired-pulse rTMS at trans-synaptic intervals, maximum voluntary force can be sustained at a higher level during a brief fatiguing maximal voluntary contraction.
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PMID:Paired-pulse rTMS at trans-synaptic intervals increases corticomotor excitability and reduces the rate of force loss during a fatiguing exercise of the hand. 1678 55

It is unknown whether changes in corticomotor excitability follow prolonged exercise in healthy humans. Furthermore, the role of supraspinal fatigue in decrements of force production and voluntary activation following prolonged exercise has not been established. This study investigated peripheral and central fatigue after a marathon (42.2 km) on a treadmill. Isometric ankle dorsiflexion force and electromyographic responses of the tibialis anterior in response to magnetic stimulation of the peroneal nerve (PNMS) and the motor cortex (TMS) were measured before, immediately after, 4 and 24 h post-marathon (MAR) in nine volunteers (mean +/- s.d. completion time, 208 +/- 22 min). Maximal voluntary contraction decreased by 18 +/- 7% immediately after MAR (P = 0.009) and remained significantly decreased after 4 h. The amplitude of the evoked response to TMS, but not to PNMS, was depressed immediately post-MAR by 57 +/- 25% (P = 0.04). Potentiated resting twitch force was reduced in response to both TMS and PNMS post-MAR (71 +/- 8 and 35 +/- 2% decrease, P = 0.035 and 0.037, respectively), and voluntary activation was reduced to 61.9 +/- 18% immediately post-MAR (P < 0.05). All measures had returned to baseline values after 24 h. These results suggest that fatigue was attributable to both a disturbance of the contractile apparatus within the muscle and submaximal output from the motor cortex.
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PMID:Corticomotor excitability contributes to neuromuscular fatigue following marathon running in man. 1744 40

Cortical excitability changes induced by tDCS and revealed by TMS, are increasingly being used as an index of neuronal plasticity in the human cortex. The aim of this paper is to summarize the partially adverse effects of 567 tDCS sessions over motor and non-motor cortical areas (occipital, temporal, parietal) from the last 2 years, on work performed in our laboratories. One-hundred and two of our subjects who participated in our tDCS studies completed a questionnaire. The questionnaire contained rating scales regarding the presence and severity of headache, difficulties in concentrating, acute mood changes, visual perceptual changes and any discomforting sensation like pain, tingling, itching or burning under the electrodes, during and after tDCS. Participants were healthy subjects (75.5%), migraine patients (8.8%), post-stroke patients (5.9%) and tinnitus patients (9.8%). During tDCS a mild tingling sensation was the most common reported adverse effect (70.6%), moderate fatigue was felt by 35.3% of the subjects, whereas a light itching sensation under the stimulation electrodes occurred in 30.4% of cases. After tDCS headache (11.8%), nausea (2.9%) and insomnia (0.98%) were reported, but fairly infrequently. In addition, the incidence of the itching sensation (p=0.02) and the intensity of tingling sensation (p=0.02) were significantly higher during tDCS in the group of the healthy subjects, in comparison to patients; whereas the occurrence of headache was significantly higher in the patient group (p=0.03) after the stimulation. Our results suggest that tDCS applied to motor and non-motor areas according to the present tDCS safety guidelines, is associated with relatively minor adverse effects in healthy humans and patients with varying neurological disorders.
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PMID:Safety aspects of transcranial direct current stimulation concerning healthy subjects and patients. 1745 83

During fatiguing exercise corticomotor excitability increases as force declines, which may serve to increase motor output to the exercising muscle, but paradoxically at the same time there is an increase in silent period (SP) duration which is thought to represent a build-up of intracortical inhibition. Paired-pulse TMS at long interstimulus intervals can also be used to derive an index of long-interval cortical inhibition (LICI), however this has not yet been investigated in fatigue. Our aim was to measure LICI during and after a fatiguing exercise and determine if the changes in the index of LICI parallel the changes in SP duration. To do this, we used single and paired-pulse TMS to measure motor evoked potential (MEP) amplitude, LICI and SP duration during, and for 10 min after, a 10-min intermittent maximal fatiguing exercise of the index finger, designed to fatigue the first dorsal interosseous (FDI) muscle (force after 10-min of exercise 64 +/- 7% of baseline, P < 0.05). Single-pulse MEP amplitude and SP duration were increased during fatiguing exercise (minute 10; 179 +/- 24% and 128 +/- 9% of baseline, respectively, P < 0.05), in contrast the measure of LICI was reduced compared to baseline (minute 10; 0.45 +/- 0.17 vs. baseline; 0.70 +/- 0.10, P < 0.05). These results suggest that SP duration and LICI may reflect processes occurring in different neuronal populations. The increased SP duration may correspond to processes of central fatigue in centres 'upstream' of primary motor cortex (M1), whereas the decrease in LICI, together with increased MEP amplitude, are consistent with an increase in M1 output during fatigue that may serve to compensate for reduced central drive.
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PMID:Differential changes in long-interval intracortical inhibition and silent period duration during fatiguing hand exercise. 1746 23

Twenty-four Angus x Hereford crossbred steers (247 kg BW; SE = 2.4 kg) were used in a completely random design to evaluate the effect of energy source and level with or without antibiotic administration on measures of immune function. Steers were fed 1 of 3 dietary treatments: a 70% concentrate diet ad libitum (70AL), a 30% concentrate diet ad libitum (30AL), and a 70% concentrate diet offered in an amount calculated to provide NE(g) intake equal to the 30AL treatment (70RES). Half the steers in each dietary treatment received a s.c. injection of tilmicosin phosphate (ANTI; 1 mL/30 kg of BW); the other half received an equal volume of saline s.c. (SAL). Steers were offered the treatment diets for 28 d before and were administered the ANTI or SAL injections 2 d before indwelling catheters were placed in the jugular vein and 2.0 microg/kg of BW of Escherichia coli lipopolysaccharide (LPS) was administered i.v. Blood serum was collected at 30-min intervals from -2 to 6 h and at 8, 12, 24, 48, and 72 h relative to the LPS challenge. Increased energy intake (70AL) increased (P < or = 0.04) DMI, ADG, and rectal temperature (RT) after the challenge compared with the 70RES treatment. The 30AL treatment increased the maximum concentrations and area under the response curve of the proinflammatory cytokines (PIC) interferon-gamma, tumor necrosis factor-alpha, and IL-6 (P < or = 0.05) compared with the average of the 70AL and 70RES treatments. Decreased energy intake (70RES vs. 70AL) increased IL-6 (P < or = 0.003) but did not significantly increase interferon-gamma and tumor necrosis factor-alpha (P > or = 0.14) after LPS administration. Tilmicosin administration decreased the time to attain maximal RT (P = 0.01) by 1 h without altering the peak RT (P = 0.85), and tilmicosin interacted with energy intake to increase prechallenge PIC in 70RES vs. 70AL (P < or = 0.05). Results indicate that increased PIC response, presumably resulting from a combination of decreased energy intake and from direct effects of roughage, may be a mode of action for the slight decrease in morbidity that often occurs when newly received, stressed calves are fed roughage-based receiving diets. Tilmicosin phosphate might have immunomodulatory capacity beyond its direct effects on pathogenic bacteria, and these effects could interact with dietary energy intake in cattle.
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PMID:Effects of dietary energy source and level and injection of tilmicosin phosphate on immune function in lipopolysaccharide-challenged beef steers. 1840 86

Saccadic eye movements are driven by motor commands that are continuously modified so that errors created by eye muscle fatigue, injury, or-in humans-wearing spectacles can be corrected. It is possible to rapidly adapt saccades in the laboratory by introducing a discrepancy between the intended and actual saccadic target. Neurophysiological and lesion studies in the non-human primate as well as neuroimaging and patient studies in humans have demonstrated that the oculomotor vermis (lobules VI and VII of the posterior cerebellum) is critical for saccadic adaptation. We studied the effect of transiently disrupting the function of posterior cerebellum with repetitive transcranial magnetic stimulation (rTMS) on the ability of healthy human subjects to adapt saccadic eye movements. rTMS significantly impaired the adaptation of the amplitude of saccades, without modulating saccadic amplitude or variability in baseline conditions. Moreover, increasing the intensity of rTMS produced a larger impairment in the ability to adapt saccadic size. These results provide direct evidence for the role of the posterior cerebellum in man and further evidence that TMS can modulate cerebellar function.
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PMID:Disruption of saccadic adaptation with repetitive transcranial magnetic stimulation of the posterior cerebellum in humans. 2066 54

We assessed for the first time the long-term maintenance of repetitive transcranial magnetic stimulation (rTMS)-induced analgesia in patients with chronic widespread pain due to fibromyalgia. Forty consecutive patients were randomly assigned, in a double-blind fashion, to 2 groups: one receiving active rTMS (n=20) and the other, sham stimulation (n=20), applied to the left primary motor cortex. The stimulation protocol consisted of 14 sessions: an "induction phase" of 5 daily sessions followed by a "maintenance phase" of 3 sessions a week apart, 3 sessions a fortnight apart, and 3 sessions a month apart. The primary outcome was average pain intensity over the last 24 hours, measured before each stimulation from day 1 to week 21 and at week 25 (1 month after the last stimulation). Other outcomes measured included quality of life, mood and anxiety, and several parameters of motor cortical excitability. Thirty patients completed the study (14 in the sham stimulation group and 16 in the active stimulation group). Active rTMS significantly reduced pain intensity from day 5 to week 25. These analgesic effects were associated with a long-term improvement in items related to quality of life (including fatigue, morning tiredness, general activity, walking, and sleep) and were directly correlated with changes in intracortical inhibition. In conclusion, these results suggest that TMS may be a valuable and safe new therapeutic option in patients with fibromyalgia.
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PMID:Long-term maintenance of the analgesic effects of transcranial magnetic stimulation in fibromyalgia. 2145 Apr 3


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