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.

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.

BackgroundThe 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.MethodsIn 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.ResultsSignificant 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).ConclusionThe results suggest that caffeine intake 60 min before 20-km time trials has no effect on the performance or physiological responses of cyclists.

Resumo -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. Palavras-chave: Atletas; Esporte; Fisiologia cardiovascular; Testes de aptidão. ]. 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. Abstract -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