Valdinar de Araújo Rocha Júnior

EFFECTS OF EXERCISE ORDER ON UPPER-BODY MUSCLE ACTIVATION AND EXERCISE PERFORMANCE

With the purpose of manipulating training stimuli, several techniques have been employed to resistance training. Two of the most popular techniques are the pre-exhaustion (PRE) and priority system (PS). PRE involves exercising the same muscle or muscle group to the point of muscular failure using a single-joint exercise immediately before a multi-joint exercise (e.g., peck-deck followed by chest press). On the other hand, it is often recommended that the complex exercises should be performed first in a training session (i.e., chest press before peck-deck), a technique known as PS. The purpose of the present study was to compare upper-body muscle activation, total repetitions (TR), and total work (TW) during PRE and PS. Thirteen men (age 25.08 = 2.58 years) with recreational weight-training experience performed 1 set of PRE and 1 set of PS in a balanced crossover design. The exercises were performed at the load obtained in a 10 repetition maximum (10RM) test. Therefore, chest press and peck-deck were performed with the same load during PRE and PS. Electromyography (EMG) was recorded from the triceps brachii (TB), anterior deltoids, and pectoralis major during both exercises. According to the results, TW and TR were not significantly different (p ≥ 0.05) between PRE and PS. Likewise, during the peck-deck exercise, no significant (p ≥ 0.05) EMG change was observed between PRE and PS order. However, TB activity was significantly (p ≤ 0.05) higher when chest press was performed after the peck-deck exercise (PRE). Our findings suggest that performing pre-exhaustion exercise is no more effective in increasing the activation of the prefatigued muscles during the multi-joint exercise. Also, independent of the exercise order (PRE vs. PS), TW is similar when performing exercises for the same muscle group. In summary, if the coach wants to maximize the athlete performance in 1 specific resistance exercise, this exercise should be placed at the beginning of the training session.

Análise eletromiográfica da pré-ativação muscular induzida por exercício monoarticular

OBJETIVO: Verificar se a execucao de um exercicio monoarticular de baixa intensidade para os extensores do joelho e uma estrategia eficaz para aumentar o numero de unidades motoras recrutadas no musculo vasto lateral durante a realizacao de um exercicio multiarticular subsequente. METODOS: Nove sujeitos saudaveis do sexo masculino (23,33±3,46 anos) foram submetidos a rotinas de treinamento nas quais os exercicios cadeira extensora e leg press 45° eram realizados em sequencia. Na rotina de baixa intensidade (R30), foram realizadas 15 extensoes unilaterais de joelho, seguidas de 15 repeticoes de leg press 45° com cargas de 30% e 60% de uma repeticao maxima (1-RM), respectivamente. Na rotina de alta intensidade (R60), a mesma sequencia foi executada, porem a carga dos dois movimentos foi de 60% de 1-RM. Uma serie simples de 15 repeticoes leg press 45° com carga de 60% de 1-RM foi utilizada como exercicio controle (RC). A eletromiografia de superficie foi registrada no musculo vasto lateral por meio de um arranjo linear de eletrodos. O valor RMS foi calculado para cada repeticao do leg press 45° e, a partir desses resultados, foram calculadas regressoes lineares. As inclinacoes das retas obtidas foram entao normalizadas pelos coeficientes lineares das equacoes de regressao e comparadas por meio da ANOVA de um fator para medidas repetidas. RESULTADOS: As inclinacoes observadas na rotina RC foram significativamente inferiores as de R30 e as de R60 (p<0,05). CONCLUSOES: Os resultados indicaram um recrutamento mais efetivo de unidades motoras nas rotinas de exercicio multiarticular precedidas de exercicio monoarticular. Artigo registrado na Australian New Zealand Clinical Trials Registry (ANZCTR) sob o numero ACTRN12609000413224.

Comparação entre a atividade EMG do peitoral maior, deltóide anterior e tríceps braquial durante os exercícios supino reto e crucifixo

The identification of the characteristics of each movement and its adjustment to the training goals are tasks that demand the interaction of many knowledge areas. These tasks are essential to the success in sports activities and training programs designed with athletic, aesthetic or healthy purposes. The objective of the present study was to compare the electromyographic (EMG) activity of the pectoralis major (PM), anterior deltoids (DA) and triceps brachii (TB) muscles during the barbell bench press (SP) and the peck deck (PD) exercises. EMG activity of TB, PM and DA were assessed during 10 maximum repetitions performed in SP and PD in 13 trained men. The results did not show any differences between exercises for PM and DA activity; however, TB activity was higher for SP than PD exercise. During SP, the PM muscle activity was higher than TB. There were no differences between PM and DA, or between DA and TB. During the PD exercise, the PM and DA muscle activities were higher than TB. There were no differences between PM and DA. It was concluded that the prime movers of both exercise are DA and PM, and there are no differences between them. Therefore, both PD and SP could be performed with the purpose to stimulate DA and PM muscles, depending on the availability of the equipments and/or the specificity of the motor tasks.La identificacion de las peculiaridades de cada movimiento y su adecuacion a los objetivos de entrenamiento es una tarea que exige la interaccion de varias areas de conocimiento. Tal tarea es fundamental para el exito en las diversas modalidades deportivas y programas de entrenamiento con fines de rehabilitacion y/o estetica. El objetivo del presente estudio ha sido comparar la actividad electromiografica (EMG) de los musculos pectoral mayor (PM), deltoides anterior (DA) y triceps braquial (TB) durante la ejecucion de los ejercicios supino recto con barra (SP) y de cruz en maquina (CR). Las actividades EMG de los musculos PM, DA y TB fueron evaluados durante la realizacion de 10 repeticiones maximas en CR y SP en 13 hombres entrenados. Los resultados no revelaron diferencias en la actividad de PM y DA entre los ejercicios. La actividad de TB fue mayor en la realizacion de SP en comparacion con CR. Durante SP, la actividad de PM fue mayor en relacion a TB, sin diferencias entre PM y DA o DA y TB. En CR, la actividad de PM y DA fueron mayores en relacion a TB, sin diferencias entre DA y PM. De acuerdo con los resultados obtenidos en el presente estudio se puede concluir que en caso de que el objetivo de entrenamiento sea promover estimulos para DA o PM, ambos ejercicios pueden ser usados, dependiendo de la disponibilidad de materiales y/o de la especificidad de la actividad motora en la cual se procure mejorar el desempeno.

Relationship between ventilatory threshold and muscle fiber conduction velocity responses in trained cyclists.

The relationship between surface electromyography (SEMG) amplitude and the ventilatory threshold has been extensively studied. However, previous studies of muscle fiber conduction velocity (MFCV) are scarce and present insufficient evidence concerning the relationship between MFCV and metabolic responses during cycling. Based on that fact, the purpose of this study is twofold: (1) to investigate the existence of a MFCV threshold (MFCVT) during cycling and (2) to verify if this possible breakpoint is correlated with the ventilatory threshold (VT) and the SEMG threshold (SEMGT). Eight trained male cyclists (age 36.0±9.7years) performed an incremental cycling test with initial workload of 150W gradually incremented by 20Wmin(-1) until the exhaustion. Gas analyses were conducted using a breath-by-breath open-circuit spirometry and SEMG were registered from vastus lateralis in each pedaling cycle with a linear array of electrodes. A bi-segmental linear regression computer algorithm was used to estimate VT, MFCVT and SEMGT respectively in the carbon dioxide production (VCO2), MFCV and electromyography root mean square (EMG RMS) curves. The one way ANOVA for repeated measures did not reveal any significant difference among VT (77.1±7.5% of VO2max), MFCVT (80.3±10.4% of VO2max) and SEMGT (81.9±11.7% of VO2max). The Bland and Altman procedure confirmed a good concordance between SEMGT and VT (Bias=5.5 of %VO2max) as well as MFCVT and VT (Bias=5.2 of %VO2max). The present findings suggest that muscle fiber conduction velocity threshold is a valid and reliable non-invasive tool to obtain information about ventilatory threshold in trained cyclists.

Study of muscle fatigue in isokinetic exercise with estimated conduction velocity and traditional electromyographic indicators

INTRODUCTION: In the study of human biomechanics, it is often desirable to evaluate fatigue in the muscles that are involved in performing a particular task. Identifying the phenomena responsible for this condition is a problem that in most cases is complex and requires appropriate research mechanisms. Isokinetic dynamometry (ID) and surface electromyography (SEMG) are two techniques widely used in studies on strength and muscle fatigue. Their effectiveness is conditioned upon a good understanding of their limitations and the adoption of procedures to fully exploit the potential of each one. The main goal of the present study is to verify whether the electromyographic parameters, especially the conduction velocity (CV), are sensitive to the fatigue instauration process within sets of maximal isokinetic contractions. CV is a basic physiological parameter directly related to muscle activity and still little explored in experiments combining ID and SEMG. METHODS: Instrumentation architecture that combines ID and SEMG was used to estimate electromyographic and biomechanical parameters in protocols of maximum intensity isokinetic knee extension exercises. This architecture allows for limiting the parameter estimates to a specific region of isokinetic exercise, called the isokinetic load range (ILR), where one can consider that the angular velocity is constant and the SEMG signals are cyclo-stationary. Electromyographic signals were acquired using an array of electrodes. CONCLUSION: The results suggest that CV and the other SEMG parameters, including amplitude and frequency descriptors, are sensitive to detect a fatigue process only in protocols that restrict the analysis to ILR and that also bring the subject to a state of fatigue quickly.

Fadiga muscular entre séries de exercícios isocinéticos em mulheres jovens

Abstract: OBJECTIVE: To examine the effect of two rest interval (RI) on isokinetic Peak Torque (PT) and total work (TW) produced by young women. METHODS: 17 untrained women (27.2 ± 4.1 yrs; 56.8 ± 6.9 kg; 162.6 ± 7.0 cm) performed three sets of 10 unilateral isokinetic knee extension repetitions at 60° and 180°/s with one and two minutes of RI. Statistical evaluation was performed using a two x three ANOVA [RI (one and two minutes) x set (1 st , 2 nd , 3 rd )] with α < 0.05. RESULTS: One minute was not enough to keep PT and TW between sets (p<0.05) at 60o (reduction of 15.7% in PT and 19.8% in TW) and 180o/s (reduction of 3.6% in PT and 5.6% in TT). Two minutes was enough only at 180o/s. However, two minutes of RI was greater (p<0.05) than one minutes at 60°/s for PT during the 2 nd and 3 rd sets. CONCLUSION: Two minutes is sufficient to keep PT within typical isokinetic resistance training protocols at 180o/s, but not at 60o/s in young women. Keywords: Torque. Muscle fatigue. Knee extension. Isokinetic.

Comparison among the EMG activity of the pectoralis major, anterior deltoidis and triceps brachii during the bench press and peck deck exercises (200/2005)

The identification of the characteristics of each movement and its adjustment to the training goals are tasks that demand the interaction of many knowledge areas. These tasks are essential to the success in sports activities and training programs designed with athletic, aesthetic or healthy purposes. The objective of the present study was to compare the electromyographic (EMG) activity of the pectoralis major (PM), anterior deltoids (DA) and triceps brachii (TB) muscles during the barbell bench press (SP) and the peck deck (PD) exercises. EMG activity of TB, PM and DA were assessed during 10 maximum repetitions performed in SP and PD in 13 trained men. The results did not show any differences between exercises for PM and DA activity; however, TB activity was higher for SP than PD exercise. During SP, the PM muscle activity was higher than TB. There were no differences between PM and DA, or between DA and TB. During the PD exercise, the PM and DA muscle activities were higher than TB. There were no differences between PM and DA. It was concluded that the prime movers of both exercise are DA and PM, and there are no differences between them. Therefore, both PD and SP could be performed with the purpose to stimulate DA and PM muscles, depending on the availability of the equipments and/or the specificity of the motor tasks.La identificacion de las peculiaridades de cada movimiento y su adecuacion a los objetivos de entrenamiento es una tarea que exige la interaccion de varias areas de conocimiento. Tal tarea es fundamental para el exito en las diversas modalidades deportivas y programas de entrenamiento con fines de rehabilitacion y/o estetica. El objetivo del presente estudio ha sido comparar la actividad electromiografica (EMG) de los musculos pectoral mayor (PM), deltoides anterior (DA) y triceps braquial (TB) durante la ejecucion de los ejercicios supino recto con barra (SP) y de cruz en maquina (CR). Las actividades EMG de los musculos PM, DA y TB fueron evaluados durante la realizacion de 10 repeticiones maximas en CR y SP en 13 hombres entrenados. Los resultados no revelaron diferencias en la actividad de PM y DA entre los ejercicios. La actividad de TB fue mayor en la realizacion de SP en comparacion con CR. Durante SP, la actividad de PM fue mayor en relacion a TB, sin diferencias entre PM y DA o DA y TB. En CR, la actividad de PM y DA fueron mayores en relacion a TB, sin diferencias entre DA y PM. De acuerdo con los resultados obtenidos en el presente estudio se puede concluir que en caso de que el objetivo de entrenamiento sea promover estimulos para DA o PM, ambos ejercicios pueden ser usados, dependiendo de la disponibilidad de materiales y/o de la especificidad de la actividad motora en la cual se procure mejorar el desempeno.

Comparación entre la actividad EMG del pectoral mayor, deltoide anterior y tríceps braquial durante los ejercicios supino recto y cruz

The identification of the characteristics of each movement and its adjustment to the training goals are tasks that demand the interaction of many knowledge areas. These tasks are essential to the success in sports activities and training programs designed with athletic, aesthetic or healthy purposes. The objective of the present study was to compare the electromyographic (EMG) activity of the pectoralis major (PM), anterior deltoids (DA) and triceps brachii (TB) muscles during the barbell bench press (SP) and the peck deck (PD) exercises. EMG activity of TB, PM and DA were assessed during 10 maximum repetitions performed in SP and PD in 13 trained men. The results did not show any differences between exercises for PM and DA activity; however, TB activity was higher for SP than PD exercise. During SP, the PM muscle activity was higher than TB. There were no differences between PM and DA, or between DA and TB. During the PD exercise, the PM and DA muscle activities were higher than TB. There were no differences between PM and DA. It was concluded that the prime movers of both exercise are DA and PM, and there are no differences between them. Therefore, both PD and SP could be performed with the purpose to stimulate DA and PM muscles, depending on the availability of the equipments and/or the specificity of the motor tasks.La identificacion de las peculiaridades de cada movimiento y su adecuacion a los objetivos de entrenamiento es una tarea que exige la interaccion de varias areas de conocimiento. Tal tarea es fundamental para el exito en las diversas modalidades deportivas y programas de entrenamiento con fines de rehabilitacion y/o estetica. El objetivo del presente estudio ha sido comparar la actividad electromiografica (EMG) de los musculos pectoral mayor (PM), deltoides anterior (DA) y triceps braquial (TB) durante la ejecucion de los ejercicios supino recto con barra (SP) y de cruz en maquina (CR). Las actividades EMG de los musculos PM, DA y TB fueron evaluados durante la realizacion de 10 repeticiones maximas en CR y SP en 13 hombres entrenados. Los resultados no revelaron diferencias en la actividad de PM y DA entre los ejercicios. La actividad de TB fue mayor en la realizacion de SP en comparacion con CR. Durante SP, la actividad de PM fue mayor en relacion a TB, sin diferencias entre PM y DA o DA y TB. En CR, la actividad de PM y DA fueron mayores en relacion a TB, sin diferencias entre DA y PM. De acuerdo con los resultados obtenidos en el presente estudio se puede concluir que en caso de que el objetivo de entrenamiento sea promover estimulos para DA o PM, ambos ejercicios pueden ser usados, dependiendo de la disponibilidad de materiales y/o de la especificidad de la actividad motora en la cual se procure mejorar el desempeno.