Background Investigations of β-alanine supplementation shows effects on metabolic (aerobic and anaerobic) participation and performance on swimming by a possible blood acidosis buffering. Considering this background, the objective of the present study was to analyze the effects of β-alanine supplementation on metabolic contribution and performance during 400-m swim. Methods Thirteen competitive swimmers underwent a 6-week, double-blind placebo-controlled study, ingesting 4.8 g.day− 1 of β-alanine or placebo. Before and after the supplementation period, the total anaerobic contribution (TAn) and 30-s all-out tethered swimming effort (30TS) were assessed. Anaerobic alactic (AnAl) and lactic energy (AnLa) was assumed as the fast component of excess post-exercise oxygen consumption and net blood lactate accumulation during exercise (∆[La−]), respectively. Aerobic contribution (Aer) was determined by the difference between total energy demand and TAn. In addition to conventional statistical analysis (Repeated measures ANOVA; p > 0.05), a Bayesian repeated measures ANOVA was used to evidence the effect probability (BFincl). Results No differences and effects were found between groups, indicating no supplementation effects. Repeated measures ANOVA, with confirmation of effect, was indicate reduce in ∆Lactate (p: 0.001; BFincl: 25.02); absolute AnLa (p: 0.002; BFincl: 12.61), fatigue index (p > 0.001; BFincl: 63.25) and total anaerobic participation (p: 0.008; BFincl: 4.89). Conclusions Thus, the results demonstrated that all changes presented were evidenced as a result of exposure to the training period and β-alanine supplementation doesn’t affect metabolic contribution and performance during 400-m freestyle.

Neuromuscular fatigue evaluation is widely performed on different muscles through the conventional protocol using maximum voluntary contraction (MVC) with electrical stimuli in the analyzed muscle. In an attempt to use this protocol on elbow extensor musculature, previous studies and pilot studies showed co-contraction effects from antagonist musculature during muscular stimulations. The aim of this study was to propose a new neuromuscular fatigue protocol evaluation on elbow extensor musculature. Twenty participants preformed exercises to induce central (CenFat) and peripheral fatigue (PerFat). Neuromuscular fatigue was evaluated on knee extensor muscles by a conventional protocol that provides Twitch Superimposed (TS K) and Twitch Potentiated (TP K), central and peripheral parameters respectively. For elbow extensor muscles, the protocol used sustained submaximal contraction at 10, 20, 30, 40, and 50% of MVC. The neuromuscular fatigue in upper limbs was identified by Twitch Potentiated (TP E) and multiple Twitch Superimposed (TS E) parameters. Using the relationship between MVC (%) and evoked force, the proposed protocol used several TS E to provide slope, y-intercept and R 2. It is proposed that slope, R 2 , and y-intercept change may indicate peripheral fatigue and the identified relationship between y-intercept and R 2 may indicate central fatigue or both peripheral and central fatigue. The results were compared using the non-parametric analyzes of Friedmann and Wilcoxon and their possible correlations were verified by the Spearmann test (significance level set at p < 0.05). After PerFat a decrease in TP E (57.1%, p < 0.001) was found but not in any TS E , indicating only peripheral fatigue in upper limbs. After CenFat a decrease in TP E (21.4%, p: 0.008) and TP K (20.9%, p < 0.001) were found but not in TS K , indicating peripheral fatigue in upper and lower limbs but not central fatigue. A non-significant increase of 15.3% after CenFat and a statistical reduction (80.1%, p: 0.001) after PerFat were found by slope. Despite R 2 showing differences after both exercises (p < 0.05), it showed a recovery behavior after CenFat (p: 0.016). Although PerFat provided only peripheral fatigue, CenFat did not provide central fatigue. Considering the procedural limitations of CenFat, parameters resulting from the proposed protocol are sensitive to neuromuscular alteration, however, further studies are required.

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AgradecimentosPrimeiramente a minha família por sempre estar próxima mesmo quando alguns quilômetros nos separavam. Agradeço meu pai Edson e minha mãe Sandra pela paciência ao longo desses dois anos e por sempre me apoiarem nas minhas escolhas, a minha irmã por continuar sendo minha inspiração. Meus avós, tios e primos pelo apoio e credibilidade.Ao Prof. Dr. Marcelo Papoti por ter me aceitado como mestrando, e ter depositado a confiança necessária para que pudesse cumprir meus objetivos.A todos os meus parceiros do grupo de estudos em ciências fisiológicas e exercício (GECIFEX): sempre alegrarem o ambiente de trabalho além de ajudar de alguma forma para as coletas. Agradecimento especial para minha amiga Tarine Arruda que compartilhou comigo quatro anos de graduação, um ano de trabalho com natação e mais dois anos de mestrado, que nossa amizade perdure para sempre.Aos meus amigos que, mesmo com a distância e falta de tempo, de alguma forma partilharam da minha companhia durante estes dois anos: Ana Flávia Chiaranda, Igor Fassoli, Larissa Almeida, Camila Cintra, Jonatas Cursiol e James Héricles.A todos os meus calouros e amigos que participaram das avaliações. Ao Grupo de Estudos em Desempenho Físico e Treinamento Esportivo (GEDEFITE)por me receber calorosamente todas as manhãs quando eu ia avaliar algum participante na academia.A todos os professores e funcionários da EEFERP que me se disponibilizaram e/ou ajudaram de alguma forma. Palavras-chave: Fadiga neuromuscular; Twitch Interpolation; Extensão de cotovelo; Ciência do esporte; tríceps braquial. ABSTRACT Norberto MS. Validity of a specific protocol for neuromuscular fatigue analysis of the elbow extensor musculature [dissertation]. Ribeirão Preto: Universidade de São Paulo, Escola de Educação Física e Esporte de Ribeirão Preto; 2018.Muscular electrostimulation is a strategy used to investigate neuromuscular fatigue. However, this technique is poorly applied in the elbow extensor muscles due to the limitations of biomechanics (acting of synergistic muscles), neural (influence of neural reflex) and physiological (easiness to achieve post-activation and fatigue states of potentiation). Therefore,

An amendment to this paper has been published and can be accessed via the original article.

BACKGROUND: Metformin has shown potential to improve metabolic efficiency in short-intense efforts, prolonged-continuous efforts and recovery after supramaximal effort (i.e., phosphocreatine resynthesis). Metformin administration may be beneficial for high-intensity interval training session. The aim of the present study was to investigate the acute metformin administration effects on performance, rating of perceived exertion (RPE), blood lactate, blood glucose and neuromuscular parameters related to a swimming series of high-intensity.METHODS: A double-blind, cross-over, randomized and placebo-controlled study was carried out. Seven healthy swimmers ingested MET (500mg) or placebo capsule on different days and performed a typical glycolytic session of high-intensity (i.e., lactate production objective). Bout time, RPE, neuromuscular parameters, blood lactate and glucose were analyzed. Cohen’s d analysis with inference based on magnitude was adopted (confidence interval set at 90%).RESULTS: There was an improvement in the performance of the second effort (72/28/0). Blood glucose during the series presented possible effects for decrease (96/3/1, 78/21/0, 93/6/1 after the 4th, 6th and 8th effort respectively) followed by a possible increase effect at the end of the series (1/6/93).Blood lactate showed a similar behavior of a possible decrease during the series (94/5/1, 60/40/0, 90/9/1 after the 4th, 6th and 8th effort respectively), followed by a possible increase effect at the end of the series (1/5/94). It was evidenced a possible increase effect on voluntary activation for lower limbs (91/8/1) without characterization of central and peripheral fatigue.CONCLUSION: Metformin alters physiological parameters during and after maximal intermittent efforts in swimming without enhancement on performance.