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

Muscle fatigue, defined as a decreased force generating capacity, develops gradually during exercise and is distinct from exhaustion, which occurs when the required force or exercise intensity can no longer be maintained. We have reviewed several biochemical and ionic changes reported to occur in exercising muscle, and analysed the possible effects these changes may have on the electrical and contractile properties of the muscle. There is no evidence that substrate depletion can account for the decreased force generating capacity, but this factor may be important for the rate of energy turnover and be a major determinant for endurance. Increased concentration of inorganic phosphate and hydrogen ions will depress the force generating capacity, but since fatigue can develop gradually without accumulation of these ions they can only be important when aerobic ATP production is insufficient to support the contractions. Evidence is presented showing that a disturbed balance of K+ alone might cause depolarisation block at high stimulation frequencies, but extracellular K+ accumulation does not increase gradually during prolonged dynamic or static exercise, and is therefore not closely related to fatigue. The repeated release of Ca2+ from the sarcoplasmic reticulum (SR) during muscular activity is suggested of Ca2+ by the mitochondria, increasing with stimulation frequency and duration and possibly also deteriorating mitochondrial function. We therefore speculate that decreased Ca2+ availability for release from SR might contribute to a gradual decline in force generating capacity during all types of exercise.
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PMID:Biochemical correlates of fatigue. A brief review. 328 52

Poliomyelitis has almost been eradicated world-wide, but during the last decades polio survivors have noted new problems: late effects of polio and post-polio. In Denmark, 7-8000 polio survivors are disabled by poliomyelitis. Late effects of polio, defined as onset of new symptoms decades after the acute poliomyelitis, include fatigue and overuse muskuloskeletal problems. Post-polio is a sub-category of the late effects of polio and related to impaired neuro-muscular function with unexpected onset, which is not caused by the patient's age. Post-polio is a clinical diagnosis and cannot be verified by a definitive test. The dysfunction of the muscles is caused by loss of motor neurones and reduced neuromuscular reserve capacity, in combination with a disturbed balance between the ongoing reinnervation and denervation at the expense of the reinnervation. Many polio survivors suffering from late effects of polio have a need for multidisciplinary rehabilitation, physiotherapy, reconstruction of orthosis, social counselling, modifications to the home and individual aids.
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PMID:[Sequelae after polio--a review]. 965 30