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

Changes in motor evoked potential (MEP) amplitude, post-MEP silent period duration, and interpolated twitch torque were measured using transcranial magnetic (TMS) and electrical (TES) stimulation during a 20% maximum voluntary contraction of the elbow flexors sustained to exhaustion. TMS- and TES-induced MEP amplitude increased progressively over the contraction period up until the point of exhaustion. The TMS-induced silent period was prolonged only during the second half of the contraction period, the time course being different from that of the MEP responses, whereas the TES-induced silent period did not change. The findings indicate that corticomotor excitability increases during a sustained submaximal voluntary contraction and that, as fatigue develops, there is a progressive buildup of intracortical inhibition. This may represent a mechanism whereby corticomotor output is maintained at an appropriate level to preserve optimal motor unit firing frequencies during a fatiguing contraction.
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PMID:Changes in corticomotor excitation and inhibition during prolonged submaximal muscle contractions. 927 Jun 73

Lisa Capaldini, a physician who treats HIV-positive patients in San Francisco, discusses the multiple causes of fatigue. HIV-related fatigue is easy to overlook because it is attributed to be a normal part of HIV disease and begins slowly, worsening over time. It is important for HIV-positive patients and their doctors to maintain a fatigue inventory every few months to chronicle and compare energy levels to previous periods. For most patients, the cause of fatigue can be identified and treated. Fatigue can be categorized into several types, including: physical, psychological, morning, depression, and hypogonadism. Physical fatigue, usually evident after performing a specific activity, may be caused by anemia, chronic diarrhea or pain, or malaise from HIV treatments. Psychological fatigue can be divided into two categories: motivational, no will to do anything because the activities no longer are pleasurable (termed anhedonia), and mental, classified as diminished attention span, inability to concentrate, or difficulty calculating. Morning fatigue is evidenced by waking up tired and remaining tired, signaling a possible symptom of depression. Hypogonadism, caused by low levels of androgens and/or other sex hormones, produces a listless, depressed mood, and trouble concentrating. Treatment for hypogonadism differs for men and women, but consists of measuring androgens and restoring them to an adequate level with testosterone replacement. Testosterone replacement is available in an intramuscular shot, Testoderm and Androderm patches, or gels. Testosterone therapy for women requires the interaction of a primary physician who is familiar with hormone replacement therapy. Capaldini recommends CBCs, testosterone levels, DHEA levels, chemistry panels, and echocardiograms to diagnose fatigue.
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PMID:Fatigue and HIV: interview with Lisa Capaldini, M.D. Interview by John S. James. 1136 45

Several epidemiological studies have demonstrated a gradual decrease of serum testosterone with aging in men. A considerable number of men will experience hypogonadal androgen levels, defined by the normal range for young men. Thus, in addition to the long-standing use of androgen replacement therapy in the classical forms of primary and secondary hypogonadism, age-associated testosterone deficiency has led to considerable developments in application modes for testosterone. Since oral preparations of testosterone are ineffective, due to the first-pass effect of the liver, or, in case of 17 alpha-alkylation, cause hepatotoxicity, intramuscular injection of long-acting esters, such as testosterone enanthate, have been the mainstay of testosterone therapy. However, the large fluctuations of serum testosterone levels cause unsatisfactory shifts of mood and sexual function in some men; combined with the frequent injections, this delivery mode is thus far from being ideal. In contrast, the transdermal testosterone patches are characterized by favorable pharmacokinetic behavior and have proven to be an effective mode of delivery. Safety data over 10 years indicate no negative effect on the prostate. Nevertheless, the scrotal testosterone patch system is hampered by the application site, which is not easily accepted by many subjects; the non-scrotal patch has a high rate of skin irritations. In view of the drawbacks of the currently available preparations, the most recent developments in testosterone supplementation appear to be highly promising agents. Androgen, which has been available in the United States since mid-2000, will be introduced this year in most European markets as Testogel, a hydroalcoholic gel containing 1% testosterone. Doses of 50-100 mg gel applied once daily on the skin deliver sufficient amounts of testosterone to restore normal hormonal values and to correct the signs and symptoms of hypogonadism. The gel has shown to be very effective and successful in American patients, who have benefited from its availability for almost 3 years. Furthermore, in phase II and III clinical studies, the intramuscular injection of 1000 mg testosterone undecanoate every 12-15 weeks has led to extremely stable serum testosterone levels for a prolonged period of time and has resulted in excellent efficacy. It is very likely in the future that these products will be the mainstay of testosterone supplementation. Whereas the indication for testosterone substitution for men with classical forms of hypogonadism is unequivocal, the use of testosterone in men with age-associated hypogonadism is less uniformly accepted. Yet, the few studies addressing this question indicate that men with testosterone serum levels below the lower normal limit for young adult men and with lack of energy, libido, depressed mood and osteoporosis may benefit from testosterone supplementation. However, it should be kept in mind that the experience documented in studies is limited. Nevertheless, serious side-effects, especially in regard to the prostate, did not occur, with the longest study extending over 3 years.
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PMID:Testosterone supplementation: what and how to give. 1462

First we tested the reliability of two new field tests of core stability (plank to fatigue test [PFT] and front abdominal power test [FAPT]), as well as established measures of core stability (isokinetic trunk extension and flexion strength [TES and TFS] and work [TEW and TFW]) over 3 days in 8 young men and women (24.0 +/- 3.1 years). The TES, TFS, TFW, and FAPT were highly reliable, TEW was moderately reliable, and PFT were unreliable for use during a single testing session. Next, we determined if age, weight, and the data from the reliable field test (FAPT) were predictive of TES, TEW, TFS, and TFW in 50 young men and women (19.0 +/- 1.2 years). The FAPT was the only significant predictor of TES and TEW in young women, explaining 16 and 15% of the variance in trunk performance, respectively. Weight was the only significant predictor of TFS and TFW in young women, explaining 28 and 14% of the variance in trunk performance, respectively. In young men, weight was the only significant predictor of TES, TEW, TFS, and TFW, and explained 27, 35, 42, and 33%, respectively, of the variance in trunk performance. In conclusion, the ability of weight and the FAPT to predict TES, TEW, TFS, and TFW was more frequent in young men than women. Additionally, because the FAPT requires few pieces of equipment, is fast to administer, and predicts isokinetic TES and TEW in young women, it can be used to provide a field-based estimate of isokinetic TES and TEW in women without history of back or lower-extremity injury.
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PMID:Age, weight, and the front abdominal power test as predictors of isokinetic trunk strength and work in young men and women. 1938 85

CB1 receptor is highly expressed in cerebral structures related to motor control, such as motor cortex, basal ganglia and cerebellum. In the spinal cord, the expression of CB1 receptors has also been observed in ventral motor neurons, interneurons and primary afferents, i.e., in the cells that may be part of the circuits involved in motor control. It is known that the antagonist/inverse agonist of CB1 receptors Rimonabant penetrates the blood-brain barrier and produces a broad range of central psychoactive effects in humans. Based on the occurrence of central effects in humans treated with Rimonabant and on the location of CB1 receptors, we hypothesized that the application of Rimonabant can also affect the motor system. We tested the effects of a single dose of 20mg of Rimonabant on the excitability of motor cortex and of spinal motor neurons in order to detect a possible drug action on motor system at cortical and spinal levels. For this purpose we use classical protocols of transcranial magnetic and electrical stimulation (TMS and TES). Single and paired pulse TMS and TES were used to assess a number of parameters of cortical inhibition and cortical excitability as well as of the excitability of spinal motor neurons. We demonstrated that a single oral dose of 20mg of Rimonabant can increase motor system excitability at cortical and spinal levels. This opens new avenues to test the CB1R antagonists/inverse agonists for the treatment of a number of neurological dysfunctions in which can be useful to increase the excitability levels of motor system. Virtually all the disorders characterized by a reduced output of the motor cortex can be included in the list of the disorders that can be treated using CB1 antagonists/reverse agonists (e.g. stroke, traumatic brain injury, spinal cord injury, multiple sclerosis, fatigue syndromes, parkinsonisms, etc.).
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PMID:CB1 receptor antagonism/inverse agonism increases motor system excitability in humans. 2157 7