Henrique Bortolotti

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.

Electromyographic activity and rate of muscle fatigue of the quadriceps femoris during cycling exercise in the severe domain.

Camata, TV, Altimari, LR, Bortolotti, H, Dantas, JL, Fontes, EB, Smirmaul, BPC, Okano, AH, Chacon-Mikahil, MPT, and Moraes, AC. Electromyographic activity and rate of muscle fatigue of the quadriceps femoris during cycling exercise in the severe domain. J Strength Cond Res 25(9): 2537-2543, 2011—This study compared the activation pattern and the fatigue rate among the superficial muscles of the quadriceps femoris (QF) during severe cycling exercise. Peak oxygen consumption (&OV0312;o2peak) and maximal accumulated oxygen Deficit (MAOD) were established by 10 well-trained male cyclists (27.5 ± 4.1 years, 71.0 ± 10.3 kg, 173.4 ± 6.6 cm, mean &OV0312;o2peak 56.7 ± 4.4 ml·kg−1·min−1, mean MAOD 5.7 ± 1.1 L). Muscle activity (electromyographic [EMG] signals) was obtained during the supramaximal constant workload test (MAOD) and expressed by root mean square (RMS) and median frequency (MF slope). The RMS of the QF, vastus lateralis (VL) and vastus medialis (VM) muscles were significantly higher than at the beginning after 75% of exercise duration, whereas for the rectus femoris (RF), this was observed after 50% of exercise duration (p ≤ 0.05). The slope of the MF was significantly higher in the RF, followed by the VL and VM (−3.13 ± 0.52 vs. −2.61 ± 0.62 vs. −1.81 ±0.56, respectively; p < 0.05). We conclude that RF may play an important role in limiting performance during severe cycling exercise.

Determinação do máximo déficit acumulado de oxigênio: efeito da duração dos testes submáximos para predição da demanda de oxigênio

O objetivo do presente estudo foi verificar a influencia de diferentes tempos de analise dos testes submaximos para determinacao do maximo deficit acumulado de oxigenio (MAOD), adotando diferentes janelas de tempo 4-6min, 6-8min e 8-10min. Participaram do estudo 10 ciclistas com idade media de 27,5 ± 4,1 anos, massa corporal 74,4 ± 12,7kg e tempo medio de pratica de 9,8 ± 4,7 anos. Os atletas realizaram um teste de esforco progressivo para determinacao do consumo de oxigenio de pico (VO2pico) e quatro testes retangulares submaximos (60, 70, 80 e 90% VO2pico) com 10min de duracao para estimar os valores da demanda de O2 (DEO2). Os valores medios de VO2 obtidos nas cargas para o tempo 4-6min, 6-8min e 8 a 10min foram aplicados em uma regressao linear entre a intensidade e o consumo de O2 para cada janela de tempo. Os sujeitos realizaram ainda um teste retangular supramaximo (110% VO2pico) para a quantificacao do MAOD. Nao foi constatada nenhuma diferenca significativa no VO2 entre os diferentes periodos de tempo dos testes submaximos (P > 0,05). Da mesma forma, nenhuma diferenca significativa foi constatada no DEAO2 e MAOD nos diferentes periodos de analise (P > 0,05). Verificou-se ainda que os valores de MAOD obtidos nos tres intervalos de tempo apresentaram boa concordância e forte correlacao. Dessa forma, os dados sugerem que os testes submaximos utilizados para gerar os valores do MAOD podem ser reduzidos ao menos nesse tipo de amostra e com a utilizacao de ciclossimulador.