Non-uniform excitation of pectoralis major induced by changes in bench press inclination leads to uneven variations in the cross-sectional area measured by panoramic ultrasonography.

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.

Both the resistance training session and the static stretching after exercise does not affect the pectoralis major stiffness of well-trained men.

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.