Effects of Transcranial Direct Current Stimulation on Psychophysiological Responses to Maximal Incremental Exercise Test in Recreational Endurance Runners.

Previous studies have suggested that transcranial direct current stimulation (tDCS) might improve exercise performance and alter psychophysiological responses to exercise. However, it is presently unknown whether this simple technique has similar (or greater) effects on running performance. The purpose of this study was, therefore, to test the hypothesis that, compared with sham and cathodal tDCS, anodal tDCS applied over the M1 region would attenuate perception of effort, improve affective valence, and enhance exercise tolerance, regardless of changes in physiological responses, during maximal incremental exercise. In a double-blind, randomized, counterbalanced design, 13 healthy recreational endurance runners, aged 20-42 years, volunteered to participate in this study. On three separate occasions, the subjects performed an incremental ramp exercise test from rest to volitional exhaustion on a motor-driven treadmill following 20-min of brain stimulation with either placebo tDCS (sham) or real tDCS (cathodal and anodal). Breath-by-breath pulmonary gas exchange and ventilation and indices of muscle hemodynamics and oxygenation were collected continuously during the ramp exercise test. Ratings of perceived exertion (RPE) and affective valence in response to the ramp exercise test were also measured. Compared with sham, neither anodal tDCS nor cathodal tDCS altered the physiological responses to exercise (P > 0.05). Similarly, RPE and affective responses during the incremental ramp exercise test did not differ between the three experimental conditions at any time (P > 0.05). The exercise tolerance was also not significantly different following brain stimulation with either sham (533 ± 46 s) or real tDCS (anodal tDCS: 530 ± 44 s, and cathodal tDCS: 537 ± 40 s; P > 0.05). These results demonstrate that acute tDCS applied over the M1 region did not alter physiological responses, perceived exertion, affective valence, or exercise performance in recreational endurance runners.

Improving Cycling Performance: Transcranial Direct Current Stimulation Increases Time to Exhaustion in Cycling.

The central nervous system seems to have an important role in fatigue and exercise tolerance. Novel noninvasive techniques of neuromodulation can provide insights on the relationship between brain function and exercise performance. The purpose of this study was to determine the effects of transcranial direct current stimulation (tDCS) on physical performance and physiological and perceptual variables with regard to fatigue and exercise tolerance. Eleven physically active subjects participated in an incremental test on a cycle simulator to define peak power output. During 3 visits, the subjects experienced 3 stimulation conditions (anodal, cathodal, or sham tDCS-with an interval of at least 48 h between conditions) in a randomized, counterbalanced order to measure the effects of tDCS on time to exhaustion at 80% of peak power. Stimulation was administered before each test over 13 min at a current intensity of 2.0 mA. In each session, the Brunel Mood State questionnaire was given twice: after stimulation and after the time-to-exhaustion test. Further, during the tests, the electromyographic activity of the vastus lateralis and rectus femoris muscles, perceived exertion, and heart rate were recorded. RM-ANOVA showed that the subjects performed better during anodal primary motor cortex stimulation (491 ± 100 s) compared with cathodal stimulation (443 ± 11 s) and sham (407 ± 69 s). No significant difference was observed between the cathodal and sham conditions. The effect sizes confirmed the greater effect of anodal M1 tDCS (anodal x cathodal = 0.47; anodal x sham = 0.77; and cathodal x sham = 0.29). Magnitude-based inference suggested the anodal condition to be positive versus the cathodal and sham conditions. There were no differences among the three stimulation conditions in RPE (p = 0.07) or heart rate (p = 0.73). However, as hypothesized, RM- ANOVA revealed a main effect of time for the two variables (RPE and HR: p < 0.001). EMG activity also did not differ during the test accross the different conditions. We conclude that anodal tDCS increases exercise tolerance in a cycling-based, constant-load exercise test, performed at 80% of peak power. Performance was enhanced in the absence of changes in physiological and perceptual variables.

Performance during a 20-km cycling time-trial after caffeine ingestion.

BACKGROUND: The objective of this study was to analyze the effect of caffeine ingestion on the performance and physiological variables associated with fatigue in 20-km cycling time trials. METHODS: In a double-blind placebo-controlled crossover study, 13 male cyclists (26 ± 10 y, 71 ± 9 kg, 176 ± 6 cm) were randomized into 2 groups and received caffeine (CAF) capsules (6 mg.kg(-1)) or placebo (PLA) 60 min before performing 20-km time trials. Distance, speed, power, rpm, rating of perceived exertion (RPE), electromyography (EMG) of the quadriceps muscles and heart rate (HR) were continuously measured during the tests. In addition, BRUMS questionnaire was applied before and after the tests. RESULTS: Significant interactions were found in power and speed (P = 0.001), which were significantly higher at the end of the test (final 2 km) after CAF condition. A main effect of time (P = 0.001) was observed for RPE and HR, which increased linearly until the end of exercise in both conditions. The time taken to complete the test was similar in both conditions (PLA = 2191 ± 158 s vs. CAF = 2181 ± 194 s, P = 0.61). No significant differences between CAF and PLA conditions were identified for speed, power, rpm, RPE, EMG, HR, and BRUMS (P > 0.05). CONCLUSION: The results suggest that caffeine intake 60 min before 20-km time trials has no effect on the performance or physiological responses of cyclists.

EMG spectral analysis of incremental exercise in cyclists and non-cyclists using Fourier and Wavelet transforms / Análise espectral do sinal emg de exercício incremental em ciclistas e não ciclistas usando as transformadas de Fourier e Wavelet

The aim of this study was to compare the electromyographic indices of fatigue (slope of median frequency) calculated with the fast Fourier transform (FFT) and wavelet transform (WT) in trained and untrained individuals during cycle exercise. A second objective was to compare the variance of the spectral parameters (median frequency - MF) obtained by the FFT and WT during exercise. Twelve cyclists and non-cyclists performed a maximal incremental test to determine the peak power (Wp) and electromyographic activity of the vastus lateralis (VL), rectus femoris (RF), biceps femoris (BF), semitendinous (ST) and tibialis anterior (TA). Mean values of median frequency, determined by the FFT and WT, were used for the spectral analysis of the electromyographic signals of the studied muscles. The analyzed parameters were obtained for each time period corresponding to 0, 25, 50, 75, and 100% of total duration of the maximal incremental test. No statistically significant differences were found in the values of MF and electromyographic indices of fatigue between the two techniques (FT and WT) both in the cyclists and non-cyclists group (P>0.05). Regarding the MF variance, statistically significant differences were found in all analyzed muscles, as well as in different time periods, both in the cyclists and non-cyclists groups when comparing the FFT and WT techniques (P<0.05). The WT seems to be more adequate to dynamic tasks, since it does not require the signal to be quasi-stationary, unlike the limitation imposed upon the use of the FFT.

O objetivo deste estudo foi comparar índices de fadiga eletromiográfica (inclinação da frequência mediana), calculado com a transformada rápida de Fourier (FFT) e transformada de wavelet (WT) em indivíduos treinados e não treinados durante o exercício de ciclismo. Um segundo objetivo foi o de comparar a variância dos parâmetros espectrais (frequência mediana - MF), obtidos por FFT e WT durante o exercício. Doze ciclistas e doze não ciclistas realizaram um teste incremental máximo, para determinar a potência pico (Wp) e atividade eletromiográfica do vasto lateral (VL), reto femoral (RF), bíceps femoral (BF), semitendíneo (ST) e tibial anterior (TA). Os valores médios da frequência mediana determinados pelo FFT e WT, foram utilizados para a análise espectral dos sinais eletromiográficos dos músculos estudados. Os parâmetros avaliados foram obtidos para cada período de tempo correspondente a 0, 25, 50, 75 e 100% da duração total do teste incremental máximo. Nenhuma diferença estatisticamente significativa foi encontrada nos valores da MF e índices eletromiográficos de fadiga entre as duas técnicas utilizadas (FT e WT), em ambos os grupos, ciclistas e não ciclistas (P> 0,05). Quanto à variância da MF, as diferenças estatisticamente significativas foram encontradas em todos os músculos analisados, bem como em diferentes períodos de tempo, tanto nos ciclistas quanto nos não ciclistas, quando se compara as técnicas FFT e WT (P <0,05). A WT parece ser mais adequada para tarefas dinâmicas, uma vez que não requer que o sinal a ser quase estacionário, ao contrário da limitação imposta ao uso da FFT.

Relação entre variabilidade da frequência cardíaca e aumento no desempenho físico em jogadores de futebol / The correlation between heart rate variability and improvement in soccer player's physical performance

O objetivo deste estudo foi analisar se a variabilidade da frequência cardíaca (VFC) analisada no período inicial da pré-temporada de futebol apresenta relação com a melhora do desempenho físico ao longo deste período. Dez jogadores de futebol fizeram parte da amostra. O desempenho foi analisado através dos seguintes testes: Yo-Yo Intermittent Recovery Test Level 1 (Yo-Yo IR1), sprint de 30 m e salto vertical, aplicados antes e após seis semanas da pré-temporada. As medidas de VFC foram realizadas em repouso, na posição supina, durante dez minutos. O teste de Spearman foi usado para investigar as possíveis relações entre VFC e melhora no desempenho e o teste T de Student para verificar as mudanças no desempenho e na VFC. A inferência prática baseada em magnitudes (analise qualitativa) foi aplicada para verificar as chances dos valores encontrados serem positivos, irrelevantes e negativos. Houve melhora significante do desempenho para o Yo-Yo IR1 (P< 0,001) e Sprint de 30 m (P< 0,001). A análise qualitativa revelou que a mudança do desempenho no Yo-Yo IR1 foi "muito provavelmente positiva", para o Sprint de 30 m foi "quase certamente positiva" e para o salto vertical foi "inconclusiva". Houve forte correlação entre um índice parassimpático da VFC e a variação no desempenho [r = 0,85; P = 0,003 (IC95% =0,49 - 0,97)]. Em conclusão, esse estudo mostrou uma correlação forte entre índices parassimpáticos da VFC analisados antes do treinamento, com a melhora do desempenho no Yo-Yo IR1 durante a pré-temporada em atletas de futebol.

The aim of this study was to analyze whether the heart rate variability (HRV), assessed at the beginning of a soccer preseason, reveals a correlation with the improvement of physical performance over this training period. Ten soccer players took part in the study. Their performance was evaluated by the following tests: the Yo-Yo intermittent recovery test, Level 1(Yo-Yo IR1); the 30-m sprint time, and the vertical jump; all were conducted before and after six weeks of pre-season. The HRV measurements were performed at rest in the supine position for ten minutes. The Spearman Rank Correlation test was used to investigate any possible relationship between HRV and improvements in performance, while the Student's t-test verified the changes in both performance and HRV. The Magnitude-Based Inferences approach (qualitative analysis) was applied to verify the possibilities of the observed values being positive, negative or inconclusive. There were significant improvements in Yo-Yo IR1 performance (P< 0.001) and in the 30-m sprint time (P< 0.001). The qualitative analysis revealed that the differences in Yo-Yo IR1 performance were very likely positive, were almost certainly positive for the sprint, but were inconclusive for the vertical jump. There was a strong correlation between one parasympathetic index and the change in performance [r = 0.85 P = 0.003 (IC95% = 0.49 - 0.97)]. In conclusion, this study revealed a strong correlation between parasympathetic indices of HRV (analyzed before the training) with the performance improvement in Yo-Yo IR1 in football athletes during pre-season.

A avaliação da produtividade em pesquisa na Educação Física: reflexões sobre algumas limitações dos indicadores bibliométricos / The assessment of productivity in research in Physical Education: reflections on some limitations of bibliometric indicators / Evaluación de la productividad en la investigación en Educación Física: reflexiones sobre ciertas limitaciones del indicadores bibliométricos

Nosso objetivo foi analisar as limitações da avaliação bibliométrica baseada no uso da citação; e refletir sobre a influência desta forma de avaliação da produção de conhecimento na área da Educação Física, especialmente na pós-graduação. Fizemos uma descrição das principais limitações dos indicadores (fator de impacto e índice h) utilizados no Brasil para avaliação da produção de pesquisa. Revistas e pesquisadores podem estar mudando seu comportamento para aumentar seu impacto no sistema de avaliação, com consequências como o distanciamento entre o que é produzido na área de conhecimento e sua relevância social e acadêmica. As formas de avaliação precisam ser (re)pensadas de forma mais profícua, quanto aos seus efeitos sobre a qualidade das publicações científicas. Consideramos fundamental um maior envolvimento por parte da comunidade acadêmica e científica, em discussões sobre as consequências que o uso desses indicadores baseados em citação pode trazer para a área da Educação Física.

The aim was examine the limitations of bibliometric evaluation based on citation, and discuss the influence of this form of assessment of knowledge production in Physical Education, especially in post-graduate programs. Thus, we made a description of the main limitations of the bibliometric indicators (impact factor and h-index) used in Brazil to assess the production in research. Journals and researchers may be changing their behavior to increase their impact/score in the evaluation system, with consequences like the gap between what is produced in the area of Physical Education and its academic and social relevance. We consider that the forms of assessment need to be (re)designed as well as the quality of scientific publications more productively considered. We believe it is crucial a greater involvement of the academic and scientific community in discussions about the consequences of using these citation-based indicators to the area of Physical Education.

Nuestro objetivo fue analizar las limitaciones de la evaluación bibliométrica basadas en el uso de la citación y reflexionar sobre la influencia de este tipo de evaluación de la producción de conocimiento en el área de Educación Física, sobre todo en la posgrado. Describimos las principales limitaciones de los indicadores (factor de impacto y índice h) utilizados en Brasil para evaluar la investigación cientifica. Revistas y investigadores pueden cambiar su comportamiento para incrementar su impacto en el sistema de evaluación, con consecuencias como la brecha entre lo conocimiento producido en la área y su relevancia social y académica. Las formas de evaluación deben ser (re)pensadas, por sus efectos sobre la calidad de las publicaciones. Consideramos que es esencial una mayor participación de la comunidad académica y científica en los debates sobre las consecuencias que el uso de estos indicadores bibliométricos pueden aportar al área de Educación Física.

A estimulação transcraniana por corrente contínua como recurso ergogênico: uma nova perspectiva no meio esportivo / Transcranial direct current stimulation as an ergogenic aid: a new perspective in sport

Nas duas últimas décadas tem-se verificado um considerável aumento no interesse de um grande número de pesquisadores em investigar o potencial de diferentes recursos ergogênicos que possam contribuir na melhoria do desempenho físico de atletas de diferentes modalidades. Grande parte dos estudos tem focado os mecanismos subjacentes ao desenvolvimento da fadiga, pelo fato de que este fenômeno complexo é considerado um fator limitante do desempenho esportivo. Sendo assim, recursos ergogênicos que são eficientes em protelar o desenvolvimento da fadiga podem melhorar o desempenho esportivo. Apesar de haver muitas discussões sobre a fadiga, sua causa exata ainda é um assunto controverso. Apesar disso, tem sido sugerido que mecanismos corticais podem estar envolvidos e que estudos sobre a modulação de regiões cerebrais específicas podem trazer respostas valiosas para entender melhor este fenômeno. Atualmente, a estimulação transcraniana por corrente contínua (ETCC) vem sendo utilizada como uma ferramenta não invasiva capaz de modular a excitabilidade de regiões específicas do córtex cerebral. Dados preliminares têm demonstrado que a ETCC anódica é capaz de aumentar a excitabilidade do córtex motor por até uma hora após sua aplicação, e também aumentar o tempo até em exercício isométrico até à exaustão. Estes dados sugerem ser provável que a ETCC possa ser utilizada como uma ferramenta em pesquisas sobre mecanismos envolvidos no desenvolvimento da fadiga e, talvez, como um possível recurso ergogênico para atletas.

The last two decades has followed an increase in interest from a large number of researchers interested in investigating the ergogenic potential of different resources that might assist in improving the physical performance of athletes in different sports. Most studies have focused on the mechanisms underlying the development of fatigue as this complex phenomenon is a limiting factor in sports performance. Thus, ergogenic resources that are effective in delaying the development of fatigue may improve athletic performance. Despite many discussions about fatigue, its exact cause is still a controversial subject. However, it has been suggested that cortical mechanisms may be involved and studies that have tried to modulate specific brain regions can provide valuable answers to better understand this phenomenon. Currently, (tDCS) has been used as a noninvasive tool that can modulate the excitability of specific regions of the cerebral cortex. Preliminary data have shown that tDCS anode is able to increase the excitability of motor cortex for up to one hour after its application and also increase the time until exhaustion in isometric exercise. These data suggest that tDCS can probably be used as a tool in research on mechanisms involved in the development of fatigue and perhaps as a potential ergogenic aid for athletes..

Enxágue bucal com carboidrato: recurso ergogênico capaz de otimizar o desempenho físico / Carbohydrate mouth rinse: an ergogenic aid able of optimizing the performance

Alguns estudos têm demonstrado que a simples presença de carboidrato na boca humana pode favorecer a ativação de algumas regiões cerebrais específicas com impacto positivo para a melhoria do desempenho físico. Assim, recentemente, a estratégia de enxágue bucal com carboidrato tem sido adotada com sucesso em exercícios físicos intensos (>70%VO2max) com duração de, aproximadamente, 60 min. Nesse sentido, o propósito deste estudo foi discutir, com base nas informações disponíveis na literatura, a eficácia ou não da estratégia de enxágue bucal com carboidrato para a melhoria do desempenho físico, bem como os possíveis mecanismos envolvidos. Os resultados produzidos, embora ainda preliminares, são bastante promissores, o que nos leva a acreditar que o enxágue bucal com carboidrato possa ser uma estratégia bastante interessante, sobretudo, pela fácil aplicabilidade, baixo custo e boa eficácia para a melhoria do desempenho físico em esforços físicos intensos e prolongados.

Studies have shown that the mere presence of carbohydrate in the human mouth promotes the activation of some specific brain regions, with a positive impact on physical performance. Thus, the strategy of carbohydrate mouth rinse has been recently adopted with success in strenuous exercise (> 70% VO2max) lasting approximately 60 min. In this respect, the objective of this study was to discuss, based on literature data, the efficacy of this strategy to improve physical performance, as well as the possible mechanisms involved. The results produced, although still preliminary, are promising and led us to believe that carbohydrate mouth rinse is an interesting strategy, especially because of its easy application, low cost and good efficacy in improving physical performance during intense and prolonged physical exercise.