Can information on remaining time modulate psychophysiological parameters during an intermittent exercise?

AIM: The purpose of the present study was to verify the effect of information on remaining time on physiological and perceptual responses during an intermittent exercise. METHODS: Ten trained cyclists participated in this study (176 ± 0.4 cm; 78.5 ± 10.4 kg; 32.5 ± 6 years; peak power output: 369.8 ± 37.8 W; VO(2peak): 51.90 ± 10.37 mL/kg/min). An intermittent cycling protocol consisting of four minutes at low-intensity (50% PPO) intervals followed by one-minute high-intensity bouts (100% PPO) under three different conditions were performed: OL40=40 min open-loop with no information on remaining time; CLI40=40 min closed-loop with information on remaining time; and CLI20=20 min closed-loop with information on remaining time. Ventilatory data (VO2) and electromyographic signals (EMG) were continuously recorded, and rating of perceived exertion (RPE) was acquired at the end of the high-intensity periods. RESULTS: Results indicated that the oxygen consumption and muscle activity during OL40 were lower than CLI40. OL40 also demonstrated significantly lower VO2values compared to CLI20 during high-intensity periods at 10 and 20 min. Root mean square values from EMG data for OL40 during high-intensity periods were significantly lower at 40 min compared with CLI40, and when the high-intensity period median frequencies among protocols were compared, CLI40 presented significantly higher values than the other conditions at 5 and 10 min. CONCLUSION: Even when power output is maintained, information on remaining time may alter peripheral responses through a complex saving component to prevent higher energy expenditure during physical exercise.

Influencia de la música y su momento de aplicación en el rendimiento y en las variables psicofisiológicas durante una contrarreloj de 5 km / Influence of music and its moments of application on performance and psychophysiological parameters during a 5km time trial

Objetivo. El propósito de este estudio fue verificar la influencia de la música introducida en diferentes momentos en una contrarreloj de ciclismo de 5 km sobre las variables psicofisiológicas. Método. Diez ciclistas entrenados participaron en este estudio (24 ± 1 años; 73,5 ± 10,4 kg, 180 ± 12 cm). Los participantes realizaron la contrarreloj de ciclismo de 5 km en 3 condiciones diferentes: música durante el precalentamiento, música durante el protocolo y control. Durante todas las condiciones fue evaluado el tiempo, la potencia, la frecuencia cardíaca y la percepción subjetiva de esfuerzo, y el estado de humor fue evaluado con el cuestionario BRUMS. Después de la estadística descriptiva, la normalidad de los datos fue confirmada por el test de Shapiro-Wilk. La media de rendimiento, el rendimiento a cada 500 m, percepción subjetiva de esfuerzo a cada 1.000 m y el estado de humor fueron comparados con la ANOVA de 2 factores para medidas repetidas (momento x condición). El nivel de significancia fue fijado en p < 0,05. Una estadística paralela fue utilizada para encontrar la menor variación de valor de todas las variables y de esta forma verificar la posibilidad de que el efecto sea trivial, benéfico o perjudicial. Resultados. Ninguna de las variables presentó diferencia entre los grupos (p > 0,05), pero existe una posibilidad de que su percepción subjetiva de esfuerzo sea pequeña cuando el individuo escucha música durante (90%) o antes (93%) del test en comparación con el test de condición de control. Conclusiones. Nuestros resultados mostraron que con independencia del momento de aplicación (por ejemplo, antes o durante el ejercicio), la música no afectó al rendimiento y las variables psicofisiológicas durante una contrarreloj de ciclismo de 5 km(AU)

Objective. The purpose of this study was to verify the influence of music introduced in different moments in a 5-km time-trial cycling (TT5KM) on psychophysical variables. Methods. Ten trained cyclists participated in this study (24 ± 1 years; 73.5 ± 10.4 kg; 180 ± 12 cm). The participants performed the TT5KM in three distinct conditions: music during warm-up (MW), music during the protocol (MP) and control (C). During all conditions the time (T), power output (W), heart rate (HR) and rating of perceived exertion (RPE) was evaluated and the mood state was assessed with the BRUMS questionnaire. After descriptive statistics, data normality was confirmed using the Shapiro-Wilk's test. Mean performance, performance at each 500m, RPE at each 1000m and mood state were compared with ANOVA two way for repeated measures (moment x condition). The significance level was set at p<0.05. A parallel statistic was used to find the smallest worthwhile change of all variables to verify the possibility of the effect to be trivial, beneficial or prejudicial. Results. None of the variables showed any difference between groups (p>0.05), but there is a possibility of RPE to be smaller when the subject listen music during (90%) or before (93%) the test compared with control condition. Conclusion. Our results showed that regardless the time of application (i.e., before or during exercise), music did not affect performance and psychophysiological parameters during the TT5KM(AU)

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.

Influence of gender on the EMG signal of the quadriceps femoris muscles and performance in high-intensity short-term exercise.

The aim of this study was to investigate the influence of gender on the EMG signal of the muscles of the quadriceps femoris and the physical performance in high-intensity, short-term exercise. Fourteen volunteers (7 men = 29.1 +/- 2.8 years and 7 women = 22.6 +/- 2.9 years) performed a Wingate Test (WT) with a load of 7.5% of body mass. The variables analyzed during the WT were the Relative Peak Power (W.Kg(-1)) (RPP), Relative Mean Power (W.Kg(-1)) (RMP), Fatigue Index (%) (FI) and Peak Power Instant (s) (PPI). EMG signals of the superficial muscles of the quadriceps femoris (QF) from the right leg: rectus femoris (RF), vastus lateralis (VL) and vastus medialis (VM) were analyzed through root mean square (RMS) values and the normalized median frequency (MNF) determined using the Fast Fourier Transform (FFT). The RPP and the RMP were significantly higher in men when compared to women (9.99 +/- 0.96 vs. 7.66 +/- 1.00 W.kg(-1); 7.23 +/- 0.49 vs. 5.65 +/- 0.61 W.kg(1), P < 0.05; respectively). No significant difference between genders was found on RMS and NMF during WT (P > 0.05). Although RPP and RMP were influenced by gender, the RMS and the NMF of the superficial muscles of the QF did not show the same behavior, suggesting that other mechanisms, not related to motor unit recruitment and speed of nervous stimuli in the muscle fiber may be associated to the lower performance of women in high-intensity, short-term exercise.

Association between the electromyographic fatigue threshold and ventilatory threshold.

The objective of this study is to verify the coincidence between the occurrence of the electromyographic fatigue threshold (EMGth) and the ventilatory threshold (Vth) in an incremental test in the cyclosimulator, as well as to compare the calculation of the RMS from the EMG signal using different time windows. Thirteen male cyclists (73.7 +/- 12.4 kg and 174.3 +/- 6.2 cm) performed a ramp incremental test (TI) in a cyclosimulator until voluntary exhaustion. Before the start of each TI subjects had the active bipolar electrodes placed over the superficial muscles of the quadriceps femoris (QF) of the right leg: rectus femoris (RF), vastus medialis (VM) and vastus lateralis (VL). The paired student's t test, pearson's correlation coefficient and the analysis method described by Bland and Altman for the determination of the concordance level were used for statistical analysis. The significance level adopted was P < 0.05. Although no significant differences were found between Vth and the EMGth calculated from windows of 2, 5, 10, 30 and 60 seconds in the studied muscles, it is suggested that the EMGth values determined from the calculation of the RMS curve with windows of 5 and 10 seconds seem to be more appropriate for the calculation of the RMS curve and determination of EMGth from visual inspection.

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.