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Effects of intermittent recovery hypoxia on molecular, metabolic and neuromuscular responses: implications for optimizing swimmer training


Considering that the different approaches to exposure to hypoxia in combination with training promote distinct local and systemic responses that consequently specifically influence parameters that are associated with sports performance, the objective of the present project will be to investigate the acute effects of different combinations of intermittent hypoxia associated with training (THI; FiO2 = 13.5%), on molecular, metabolic and neuromuscular responses, as well as their implications for optimizing the training of swimmers. To contemplate the general objective of this project, three experiments with specific objectives will be carried out. The first will be performed on the Krogh ergometer using the unilateral knee extension exercise and will aim to compare the effects of different THI models on the expression of muscle proteins (inducible hypoxia factor, hexokinase, lactate dehydrogenase, citrate synthase, and phosphofructokinase) from biopsies performed before and after THI. Participants will be divided into two groups [Effort and recovery in hypoxia (EH: RH), Effort in hypoxia, and recovery in normoxia (EH: RN)]. Both groups (EH: RH and EH: RN) will make efforts with unilateral knee extension. The contralateral leg of both groups will be exercised and recovered in normoxia [EN: RN (control group)]. The second experiment will be carried out on the cycle ergometer and will aim to compare the effects of different THI on metabolic participation [aerobic and anaerobic (alactic and lactic)] and parameters of central and peripheral fatigue (twitch interpolation). In this experiment, participants will be submitted to efforts under the conditions of EH: RH, EH: RN and EN: RN. Finally, the third experiment will aim to investigate the effects of THI on metabolic participation, mechanical parameters and swimming performance. The swimmers will undergo three training sessions, each of which will address a combination of THI (EH: RH, EN: RH and EN: RN). To generate the different hypoxia conditions in swimming, a hypoxia-generating structure will be built that can be used in a conventional swimming pool at a substantially reduced cost compared to commercial models. The training sessions, in all experiments, will consist of ten efforts lasting approximately 30 seconds in intensity of "all-out", separated by 4 minutes of passive recovery. Additionally, the analysis of blood metabolites (metabolomics) will be carried out in experiments 1 and 3. The molecular responses (experiment 1), metabolic (experiments 1, 2 and 3), neuromuscular (experiment 2), mechanical parameters and the swimming performance (experiment 3) will be compared between situations using a mixed model, with fixed factors (ie, exposure condition and time of evaluation) and random (ie, participants). The effects of THI, before, during and after each training session will be compared using ANOVA Two-way analysis of variance, followed by Tukey's post hoc. The associations between changes in the variables of interest (metabolic, blood, muscle and fatigue metabolites) with the performances in the different experiments and with the doses of hypoxia, will be verified with the Pearson correction test. In all cases, the level of significance will be set at p <0.05. (AU)

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