RESUMO
This study combined surface electromyography with panoramic ultrasound imaging to investigate whether non-uniform excitation could lead to acute localized variations in cross-sectional area and muscle thickness of the clavicular and sternocostal heads of pectoralis major (PM). Bipolar surface electromyograms (EMGs) were acquired from both PM heads, while 13 men performed four sets of the flat and 45° inclined bench press exercises. Before and immediately after exercise, panoramic ultrasound images were collected transversely to the fibers. Normalized root mean square (RMS) amplitude and variations in the cross-sectional area and muscle thickness were calculated separately for each PM head. For all sets of the inclined bench press, the normalized RMS amplitude was greater for the clavicular head than the sternocostal head (P < 0.001), and the opposite was observed during the flat bench press (P < 0.001). Similarly, while greater increases in cross-sectional area were observed in the clavicular than in the sternocostal head after the inclined bench press (P < 0.001), greater increases were quantified in the sternocostal than in the clavicular head after the flat bench press exercise (P = 0.046). Therefore, our results suggest that the PM regional excitation induced by changes in bench press inclination leads to acute, uneven responses of muscle architecture following the exercise.
Assuntos
Músculos Peitorais , Treinamento Resistido , Masculino , Humanos , Músculos Peitorais/diagnóstico por imagem , Músculos Peitorais/fisiologia , Músculo Esquelético/diagnóstico por imagem , Músculo Esquelético/fisiologia , Eletromiografia , Terapia por Exercício , Ultrassonografia , Treinamento Resistido/métodos , Levantamento de Peso/fisiologia , Força Muscular/fisiologiaRESUMO
Previous evidence suggests the intense resistance training session can increase the muscle hardness, while stretching protocols with high intensity and volume can decrease it. However, it remains unknown the effects of an exercise and a less intensive stretching maneuver on muscle stiffness of well-trained men. Herein we (i) analyze the acute effects of heavy bench press exercise on the pectoralis major muscle shear modulus of well-trained men and (ii) assess the effectiveness of a 1-min stretching maneuver applied on this muscle after the exercise using shear wave elastography. Fourteen participants performed three sets of bench press from 8 to 13 repetitions maximum. Immediately after the exercise, their right shoulder was passively stretched for 1 min (stretched side) while their left arm stayed relaxed along the side of the body (control side). Elastographic images were acquired for the pectoralis major mid-region of both sides before the exercise, immediately after the intervention and after 5 min of rest. Our results revealed that both the bench press exercise and the static stretching does not affect the pectoralis major shear modulus of well-trained men. Conversely, the shear modulus significantly decreased at 5 min after intervention with respect to immediately after, for both the stretched (from 5.52 to 4.29 kPa) and the control sides (from 5.87 to 4.56 kPa). Therefore, both resistance training session and 1-min static stretching were not sufficient to significantly change the pectoralis major muscle stiffness of well-trained men.
Assuntos
Exercícios de Alongamento Muscular , Treinamento Resistido , Braço , Humanos , Masculino , Força Muscular , Músculo Esquelético , Músculos Peitorais , OmbroRESUMO
O objetivo do estudo foi comparar a variação da espessura muscular (EM) ao longo do peitoral maior (PM) após três séries de 8 a 12 repetições máximas de supino reto. A amostra foi composta por 12 homens treinados. O comportamento da EM foi avaliado pré e imediatamente após a realização do exercício através de ultrassonografias, em três sítios do feixe esternal do PM: medial (próximo ao esterno), central e lateral (próximo ao úmero). Como resultado, o sítio medial apresentou variação relativa da EM de 14,78%, o central de 11,83% e o lateral de 10,04%, com diferença significativa apenas entre o sítio medial quando comparado ao lateral (p=0,036). Tal efeito pode estar relacionado a maior ativação do trecho medial do PM durante o supino reto ou pela específica morfologia do PM.
The aim of this study was to compare the variation of muscle thickness (MT) over the pectoralis major muscle (PM) after 3 sets of 8 to 12 repetitions of bench press. The sample was consisted of 12 trained men. Ultrasound images were acquired, to analyze the MT behavior, at three sites of the PM's sternal head: medial, central and lateral. The medial site had a MT relative variation of 14.78%, the central one of 11.83% and the lateral one of 10.04%, with a statistical difference observed only between the medial site when compared to the lateral site (p = 0.036); The possible cause of these effects might be related to a possible greater activation of the medial site during the bench press or due to PM's morphology. We conclude that the PM shows heterogeneous MT acute variation.
El objetivo del estudio fue comparar la variación de la espesura muscular (EM) a lo largo del pectoral mayor (PM) después de tres series de 8 a 12 repeticiones de press de banca. El comportamiento de la EM fue evaluado pre e inmediatamente después de la realización del ejercicio con ultrasonografías, en tres sitios de la cabeza esternal del PM: medial (cerca del esternón), central y lateral (cerca del húmero). Como resultado, el sitio medial presentó 14,78% de variación relativa de la EM, el central 11,83% y el lateral 10,04%, con diferencia significativa apenas entre el sitio medial cuando comparado al lateral (p = 0,036) . Este efecto puede estar relacionado con la mayor activación del sitio medial del PM durante el press de banca o por la morfología del PM.