Does prefrontal cortex transcranial direct current stimulation influence the oxygen uptake at rest and post-exercise?

The study evaluated the effect of transcranial direct current stimulation (tDCS) applied over prefrontal cortex on the oxygen uptake (V˙ O2) at rest and during post-exercise recovery. The V˙ O2 was assessed in eleven healthy subjects before, during tDCS (sham or anodal tDCS, 2 mA, 20 min), and 30-min following isocaloric aerobic exercise (~200 kcal). During tDCS, no changes were observed on V˙ O2 compared to baseline (P=0.95) and sham condition (P=0.85). The association between isocaloric exercise and anodal tDCS increased the V˙ O2 throughout 30-min recovery compared to sham condition (P<0.001). Therefore, the energy expenditure within the excess post-exercise oxygen consumption (EPOC) period, after anodal tDCS was approximately 19% higher compared to the sham condition (P<0.05). In conclusion, anodal tDCS applied on the prefrontal cortex combined with submaximal aerobic exercise increased the EPOC, enhancing the V˙ O2 and energy expenditure at least for 30-min of recovery.

The relationship between rating of perceived exertion and muscle activity during exhaustive constant-load cycling.

The aims of this study were to verify the relationship between rating of perceived exertion (RPE) and electromyography (EMG) increases during exhaustive constant-load cycling bouts and, to compare and to correlate the power outputs corresponding to perceived exertion threshold (PET) and neuromuscular fatigue threshold (NFT). 11 men completed 3-4 different exhaustive constant-load cycling bouts on a cycle ergometer, being RPE and EMG measured throughout the bouts. The linear regression of the RPEslope and EMGslope against the power output identified the PET and NFT intensity, respectively. There was a significant relationship between RPEslope and EMGslope (R(2)=0.69; P<0.01). However, the linearity of RPEslope (R(2)=0.93±0.07) was significantly higher (P<0.001) than EMGslope (R(2)=0.63±0.25). In addition, the RPEslope and EMGslope were related to time to exhaustion (r=-0.59 and r=-0.60; P<0.001). There was no significant difference (P=0.42) between PET (201.5±27.9W) and NFT (210.3±22.6W) and they were significantly correlated (r=0.78; P=0.005). Therefore, the RPE and EMG increases during exhaustive constant-load cycling bouts are related and, PET and NFT intensities are similar and closely associated.

Comparison of electromyography fatigue threshold in lower limb muscles in trained cyclists and untrained non-cyclists.

The purpose of this study was to identify and compare the Electromyographic Fatigue Threshold (EMG(FT)) determined in the Vastus Lateralis (VL), Rectus Femoris (RF), Biceps Femoris (BF), Semitendinosus (ST) and Tibialis Anterior (TA) during stationary cycling in trained cyclists and non-cyclists. Using a cycle ergometer, 13 cyclists (28.4 +/- 6.9 years; 70.3 +/- 13 kg; 176.1 +/- 8.5 cm) and 11 non-cyclists (25.8 +/- 4 years; 73 +/- 9.1 kg; 175 +/- 6.4 cm), performed a maximum incremental test (ITmax) (90 rpm) to determine the (EMG(FT)). Maximal power output (W(PEAK)) reached by cyclists was higher than for non-cyclists (372.6 W and 248.9 W respectively) (P < 0.01). For the five muscles analyzed in cyclists, EMG(FT) occurred at 85.7% of cases in the VL, 92.9% in RE 78.6% in BE 78.6% in ST and 50% in TA, while in the non-cyclists group, this occurrence was 100% to muscle VL, 100% to RF, 92.6% to BF, 78.6% to ST, and 78.6% to TA. Analyzing the percentage corresponding to the power at EMG(FT) in relation to W(PEAK) reached, no differences between groups were observed for RF, BF and ST, however VL and TA, as well as the mean from all muscles were lower for cyclists than non-cyclists (P < 0.05). The present results showed that EMG(FT) is more easily identified in RF and VL muscles for both groups, and it may be an interesting method to evaluate the adaptive responses from aerobic and anaerobic metabolisms during cycling training programs.

The efficiency of pedaling and the muscular recruitment are improved with increase of the cadence in cyclists and non-cyclists.

The objective of this study was to compare the efficiency of pedaling (EP) and the electromyographic activity (EMG) between cyclists and non-cyclists during cycling in different cadences. Using a cyclosimulator, 12 cyclists (26.5 +/- 4.5 years; 68.2 +/- 10.5 kg; 175.6 +/- 8.2 cm) and 9 non-cyclists (25.1 +/- 4.3 years; 72.6 +/- 9.8 kg; 174.6 +/- 6.2 cm), performed a maximum incremental test (ITmax), and subsequently, two constant load tests (Tconst) in different cadences (60 and 90 rpm) at the intensity of the electromyographic fatigue threshold (EMGth) determined in ITmax. Before the Tconst, the subjects performed a maximum isometric voluntary contraction (MIVC) for the normalization of the EMG data of Tconst. During Tconst, the EMG of the studied muscles was recorded, as well as the EP Although there was a trend of higher values in all occasions for the cyclists, there were no statistical differences in EP and the EMG when compared in a same cadence between groups. However, when the EMG is compared in different cadences in the same group, there was a significant increase (p < 0.05) in the muscles that work during the recovery phase with the increase in cadence, in both groups, being more evident in the cyclists. In conclusion, the hypothesis that cyclists had better technique than non-cyclists was not confirmed statistically. However, it was found that the increase in cadence improves the EP and the recruitment in both groups.

Behavior of emg activation of rectus femoris, vastus lateralis and vastus medialis muscles during maximum contraction before and after a series of repeated efforts.

The proposal of this study was to analyze the behavior of electromyographic activity of the Rectus Femoris, Vastus Lateralis and Vastus Medialis muscles during Maximum Isometric Voluntary Contraction (MIVC) performed before (MIVC-1) and after (MIVC-2) the series of repeated effort (four series of 12 repetitions) of the movement of extending the knee performed on an extending table with 80% of maximum load (1RM) during 15 seconds each MIVC. The participants were 10 soccer players (average age of 17.7 +/- 0.67, average corporal mass of 67.07 +/- 6.06 kg and average height of 174.6 +/- 4.98 cm). Surface electrodes (disposable) were used. The frequency established was 1024 Hz (Low/High pass at 600/10 Hz). The statistical treatment employed analysis of variance (ANOVA) for repeated measurements followed by the HSD post hoc test of Tukey. The level of significance adopted for all analyses was p < 0.05. For the Rectus Femoris muscle the value expressed in RMS referring to MIVC-1 was 346.97 +/- 63.93 and MIVC-2 was 287.58 +/- 61.03 (p = 0.06) corresponding to 82.88% of MIVC-1. Regarding the Vastus Lateralis muscle the value in MIVC-1 was 385.50 +/- 120.23 and in MIVC-2 it was 316.87 +/- 67.85 (p = 0.04) corresponding to 82.19% of MIVC-1. For the Vastus Medialis muscle MIVC-1 value was 430.88 +/- 84.23 and MIVC-2 was 396.32 +/- 70.40 (p = 0.03) corresponding to 91.97% of MIVC-1. Results demonstrated that the muscles presented action potencies during the actions performed, being greater in MIVC-1. The Rectus Femoris muscle presented electromyographic signals of lesser amplitude than the Vastus Lateralis and Vastus Medialis muscles. The Vastus Medialis muscle presented a greater percentage value between MIVC-1 and MIVC-2. The Rectus Femoris muscle was the first to present signs of fatigue.

Analysis of knee movements on leg extension machine: an electromyography study of the rectus femoris muscle.

The Rectus Femoris muscle was analyzed by electromyography in 10 female subjects between 19 and 22 years old. Surface electrodes were utilized by placing them at the middle of the muscle. The course of the flexing/extending movements of the knee were analyzed on a Leg Extension Machine. The results showed that the MIC value was greater in the series with loads than in the series without loads. For the Maximum Isometric Contraction (MIC) the value was 144.00. In the movement executed without load the value was 73.96. In the first series with the initial 15 Kg load the value was 163.7 and in the last series of the initial load the value was 194.9. With the 19 Kg load in the first series the value was 182.5 and in the last series the value was 205.1. In the first series with the 21 Kg load the value was 165.1 and in the last series with the 21 Kg load the value was 23.09. The values reflecting the need to recruit more muscle fibers to continue executing the movement. The value 23.09 shows the difficulty in proceeding with the movements and can be considered the beginning of a muscular fatigue process in the Rectus Femoris muscle.

Using weights in abdominal exercises: electromyography response of the Rectus Abdominis and Rectus Femoris muscles.

Among persons who do regular exercises, many include abdominal exercises in their customary routine. For this, there are a growing variety of movements being created for strengthening the abdominal muscles. This work aims to know, through electromyography analysis, the action potencies of the supra and infra umbilical of the Rectus Abdominis and Rectus Femoris muscles during the execution of abdominal exercises with and without the addition of weights. Lying on the backside, seven flexing movements of the trunk--one without weight, three with 2 Kg on the neck, elbow and chest and three with 4 Kg on the same points--were executed. Nine female university students between 18 and 23 years old participated in the study. Surface electrodes were fixed to the supra and infra umbilical areas of the Rectus Abdominis and Rectus Femoris muscles. The results showed that the utilization of weights in the abdominal exercises did not appear to be effective for the Rectus Abdominis muscle since greater action potencies were only verified in the Rectus Femoris muscle. We concluded that the differences observed in the RMS were not relevant to the point of indicating the utilization of weights to improve abdominal exercises because greater action potencies were only observed in the Rectus Femoris muscle.

Análise eletromiográfica do músculo reto femoral durante a execução de movimentos do joelho na mesa extensora / Electromyographic analysis of the rectus femoris muscle during the execution of movements of the knee in leg extension machine

O músculo reto femoral foi analisado por meio da eletromiografia, utilizando eletrodos de superfície, durante os movimentos de flexão e extensão do joelho. Participaram do estudo dez sujeitos do sexo feminino, na faixa etária entre 19 e 22 anos. Inicialmente, foi realizada uma máxima contração isométrica (MCI). Posteriormente, realizou-se uma série de 12 repetições sem carga (SC); 12 séries de 12 repetições com diferentes cargas (15, 17, 19 e 21 kg). Para este trabalho selecionamos os dados referentes à MCI, movimentos sem cargas, movimento com 15 Kg, com 19 Kg e 21Kg. Os valores médios, expressos em RMS, demonstraram que na MCI o RMS foi de 139,55; no movimento realizado sem carga foi de 51,54; na carga de 15 kg foi de 134,65; na carga de 19 Kg foi de 136,54 e com 21Kg o RMS foi de 10,09. Os valores de RMS obtidos no movimento SC e com 21 kg foram inferiores aos encontrados nas condições MCI, 15 kg e 19 kg. O valor de 10,09 referente à carga de 21 Kg reflete a dificuldade em prosseguir a execução dos movimentos, podendo ser considerado o início do processo de fadiga muscular do músculo reto femoral.

The rectus femoral muscle was analyzed by electromyography, in 10 female subjects between 19 and 22 years old, during the flexing/extending movements of the knee. Surface electrodes were utilized. Initially a maximum isometric contraction (MIC) was performed. Afterwards, a series of 12 repetitions without load, and then 12 series of 12 repetitions with different loads (15, 17, 19, and 21kg) were performed. For this study, we chose data referring to the MCI, the movements without load, and those with 15kg, 19kg, and 21kg loads. The average values, expressed in RMS, were: for the Maximum Isometric Contraction (MIC), 136.55; for the movements executed without load, 51. 54; for the first series with the initial 15kg load, 134.65; for that with the 19kg load, 136.54; and for the last series with the 21kg load, 10.09. RMS values obtained from the movements without load and those with the 21kg load, reflects the difficulty in proceeding with the execution of movements and can be considered the beginning of the muscular fatigue process of the rectus femoral muscle.