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.