Combat sports have always been important in the worldwide sport context. In order to provide fairer disputes, athletes are grouped into weight classes. Therefore, the majority of athletes significantly reduce their weight a few prior to competitions in order to gain competitive advantage. To reduce such a large amount of weight in such a short period of time, athletes use aggressive procedures such as reduced food intake and increased training volume and intensity. This practice can affect several variables related to health, being the suppression of the immune system on of the most common health-related issues of rapid weight loss. Several studies indicate that glutamine is an amino acid essential for the proper functioning of the immune system. Leukocytes use glutamine at high rates as energy substrate and as a precursor of nucleotide synthesis. It is well known that acute physical exercise causes a reduction in plasma glutamine concentration. In addition, studies have shown that both dietary restriction and increased training load can reduce plasma glutamine. This reduction may hamper the activity of some cells of the immune system, which may lead athletes to be more susceptible to oportunists infections. In fact, several reports indicate that there is an increased incidence of upper respiratory tract infections a few days after rapid weight loss. Therefore, we hypothesized that athletes who quickly reduce weight have a major chronic reduction of plasma glutamine so that immunosuppression could be explained, at least in part, by the reduction of plasma glutamine. Accordingly, we also believe that chronic supplementation of glutamine will be able to prevent the decrease in glutaminemia and minimize the impact of rapid weight loss on the immune system.Based on this, the aim of this work is to verify the impact of rapid weight loss on selected variables of the immune response and its relation to plasma glutamine. Also, this study aims to test the ability of chronic glutamine supplementation to counteract the putative decrease in plasa glutamine and in the immune cells activity.METHODSAbout 80 male combat athletes aged between 18 and 30 years will take part in this double-blinded, placebo controlled, randomized, parallel-group trial. The athletes will initially be non-ramdomicly divided in two groups: those who lose weight before competing (mean reduction of 5% to10% of body weight; n=60) and those who do not lose weight before competing (mean reduction of less than 2% of body weight; n=20). Then, the 60 athletes who lose weight will be randomly distributed into three different groups: 1) group supplemented with glutamine, 2) isonitrogenous placebo group and 3) isocaloric placebo group. The athletes who do not lose weight (i.e., the control group) will be necessary for controlling the effects of stress of competition on the analyzed parameters. All athletes will undergo a venous blood collection for determining the concentration of glutamine, total protein, cortisol, and selected parameters of the immune system parameters. Additionaly, they will be assessed for skinfold thickness, food intake and frequency of symptons and signals of infections. All analysi will take place 21 days before the competition, one day before the competition and five days after the competition. Supplementation period will be of 10 consecutive days, starting 5 days before the competition and ending 5 days after the competition. In addition to descriptive analysis, will be conducted proc -mixed models analysis. different models of the covariance matrix for the choice that best fits the data set will be tested, according to Schwarz's Bayesian criteria. If main effects of group, time or interaction are found, post-hoc tests with Tukey-Kraemer adjustment for multiple comparisons will be used. The significance level is 5%.
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