The Metabolism Alteration Process Syndrome

Recent studies have shown that endurance overtraining could result from successive and cumulative alterations in metabolism, which become chronic during training. The onset of this process is a biochemical alteration in carbohydrate (saccharide) metabolism. During endurance exercises, the amount of saccharide chains from two blood glycoproteins (a2-macroglobulin and aI-acid glycoprotein) was found to have decreased, i.e. concentrations of these proteins remained unchanged but their quality changed. These saccharide chains were probably used for burning liver glycogen stores during exercise. This step was followed by alterations in lipid metabolism. The most relevant aspect of this step was that the mean chain length of blood fatty acid.~ decreased, i.e. ~e amount of fatty acids were found within th~ -~!2-~,.!?)!.~_Q.Y~m!!'!1).!;Q.l!14.!Y!Q1;:I.~S. ~~~::~ig~: peroxidation of blood lipoparticles occurred. For the final step of this overtraining process, it was found that these dysfunctions in carbohydrate/lipid metabolism led to the higher use of amino acids, which probably resulted from protein catabolism. The evolution of three protein concentrations (a.l-acid glycoprotein, a2-macroglobulin and 19G3) correlated with this amino acid concentration increase, suggesting a specific catabolism of these proteins. At this time only, overtraining was clinically diagnosed through conventional symptoms. Therefore, this process described successive alterations in exercise metabolism that shifted from the main energetic store.~ of exercise (carbohydrates and lipids) towards molecular pools (proteins) normally not substantially used for the energetic supply of skeletal muscles. Now, a general biochemical model of the overtraining process may be proposed which includes most of the previously identified metabolic hypotheses. training is a loss of perfomlance level despite the maintenance or increase of training load. IS] Nevertheless, a growing body of evidence suggests that various alterations in metabolism may appear during the overtraining process in endurance sports, and that there is a causal link between them.16] Most of the metabolic pathways have been tent.atively studied to highlight overtraining parameters, i.e. carboMany parameters have been tentatively used to detect overtraining in endurance sports such as: (i) skeletal muscle cell strucUlral damage;rll (ii) rest and exercise metabolism alterations;121 (iii) changes in immunological and/or hormonal response to training stress;131 and (iv) sympathetic and parasympathetic nervous systems expressions.f41 However, to date, the only reliable criteria for diagnosing over-