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. 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.