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Revista Brasileira de Medicina do Esporte
On-line version ISSN 1806-9940
SILVEIRA, Leonardo R. et al. Metabolic regulation and production of oxygen reactive species during muscule contraction: effect of glycogen on intracellular redox state. Rev Bras Med Esporte [online]. 2008, vol.14, n.1, pp. 57-63. ISSN 1806-9940. http://dx.doi.org/10.1590/S1517-86922008000100011.
Fatigue is closely related to the depletion of glycogen in the skeletal muscle during prolonged exercise. Under this condition, the production of oxygen reactive species (ROS) is substantially increased. It has been shown that dietary supplementation of carbohydrate or antioxidant attenuates muscle fatigue during contraction. This suggests that glycogen availability and/or elevated ROS production plays an important role on muscle fatigue development during prolonged muscle activity. Although the mechanism is still unknown, we propose that elevated muscle glycogen availability may lead to a high activity of hexose monophosphate pathway, increasing the NADPH and glutathione concentration in the skeletal muscle tissue. Elevated antioxidant capacity would increase the muscle redox balance during muscle contraction, improving performance. In this process, the glucose-fatty acid cycle may be important to increase lipid oxidation and consequently decrease glycogen utilization during prolonged activity. In addition, an elevated ROS production could reduce the activity of key metabolic enzymes including aconitase and a-ketoglutarate dehydrogenase, decreasing the oxidative energy production in the skeletal muscle during prolonged activity.
Keywords : fatigue; antioxidants; metabolism; skeletal muscle; prolonged exercise.