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Although everyone knows fatigue personally, it is a difficult concept to define. For muscular fatigue, one must know the aspect of performance affected. The most obvious demonstrations are decreased maximal force and slowed muscular answer. Fatigue can have a central origin, by reducing cognitive performance or lowering excitation of motoneurons. Various mediators are in question (serotonin, moduline, dopamine). The fatiguing muscular contractions are accompanied by reduced discharges of motoneurons. The neuromuscular junction does not seem to be in question. Cold reduces muscular power, whereas a hot environment limits exercise by a central mechanism, which starts the normal behavioural response to stop the exercise. Fatigue can also be the consequence of overtraining. In the periphery, the electric activity of the membrane's surface is the first possible sign of failure, which explains high-frequency fatigue: the accumulation of potassium outside the cell blocks the sodic channels to block the potentials of action or slow down their propagation. With fatigue, less calcium is released and limits the number of attached actin-myosin bridges connections of actin-myosin. The slowing down of the muscular answer represents a deterioration of the function of actin-myosin bridges. On the metabolic level, the most-often evoked changes are reduced pH and increased intracellular lactate level. However, these variations cannot all describe fatigue, since patients with Mc Ardle disease do not exhibit these variations but very quickly experience tiredness. In fact, an association of small metabolic intracellular variations could explain tiredness. The fast fibres are larger than slow fibres; their metabolic needs are higher and they are thus more sensitive to tiredness. The half time of recovery is within approximately 1 min: normal values of force and power are recovered after 5 to 10 min. During endurance activities, the limiting factors are glycogen reserves and levels of oxidative enzymes. On the whole, mechanisms of fatigue must be explored to completely understand the governing phenomena.
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http://dx.doi.org/10.1016/j.annrmp.2006.04.021 | DOI Listing |
BMC Sports Sci Med Rehabil
March 2025
Department of Physical Education and Sport, Faculty of Sport Sciences, Gazi University, Ankara, Turkey.
Background: The final event in modern pentathlon, the laser run, determines the final ranking, and it is not known whether the athletes' heart rates (HRs) and success rates during the shooting in the laser run are affected by environmental conditions. Although heart rate (HR) affects shooting performance, exercise-induced muscle fatigue accompanying increased HR can affect shooting speed and accuracy. The aims of this research were (a) to compare the HRs of pentathletes before and after fatigue, (b) to compare the shooting performance of pentathletes in the field vs.
View Article and Find Full Text PDFMult Scler Relat Disord
March 2025
Department of Physiotherapy, School of Health Sciences, University of Thessaly, 3rd km Old National Road Lamia, Lamia, 35100 Athens, Greece. Electronic address:
Background: It is a fact that Multiple Sclerosis is a neurodegenerative disease with severe symptoms that make everyday life of patients difficult as it progresses. There are several types of treatments aimed at limiting and delaying the onset of its symptoms. Hippotherapy being an innovative method of intervention, supported by several studies on its positive effects on various neurological disorders, is now under the microscope with the aim of testing its impact on the clinical picture and the functioning of people suffering from Multiple Sclerosis.
View Article and Find Full Text PDFEur J Appl Physiol
March 2025
Research and Development, The Nutraceutical Alliance Inc, Guelph, ON, L8N 3Z5, Canada.
During high-intensity exercise a lactic-acidosis occurs with raised myoplasmic and plasma concentrations of lactate and protons ([lactate], [H] or pH). We critically evaluate whether this causes/contributes to fatigue during human exercise. Increases of [lactate] per se (to 25 mM in plasma, 50 mM intracellularly) exert little detrimental effect on muscle performance while ingestion/infusion of lactate can be ergogenic.
View Article and Find Full Text PDFDysphagia
March 2025
Fonoaudiología. Facultad de Ciencias de la Salud, Universidad Arturo Prat, Iquique, Chile.
Swallowing is a complex neuromuscular process involving the coordination of anatomical structures in the central and peripheral nervous systems. The posture of the head and neck plays a critical role in the biomechanics of swallowing, especially in populations with dysphagia. This systematic review aims to explore the impact of head-neck posture on swallowing kinematics and muscle activation, providing a multidisciplinary perspective for optimizing dysphagia management.
View Article and Find Full Text PDFAnn Behav Med
January 2025
Department of Health Sciences, Section of Nursing Science, University of Groningen, University Medical Center Groningen, 9713 GZ Groningen, The Netherlands.
Background: Fatigue is a prevalent and debilitating symptom among kidney transplant candidates (KTCs), significantly affecting their quality of life and overall well-being. Its complexity necessitates a comprehensive approach to manage fatigue in this population.
Purpose: To explore the effectiveness of nonpharmacological interventions in reducing fatigue in KTCs.
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