AUTHOR=Takeuchi Kosuke , Sato Shigeru , Kiyono Ryosuke , Yahata Kaoru , Murakami Yuta , Sanuki Futaba , Yoshida Riku , Nakamura Masatoshi TITLE=High-Intensity Static Stretching in Quadriceps Is Affected More by Its Intensity Than Its Duration JOURNAL=Frontiers in Physiology VOLUME=12 YEAR=2021 URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2021.709655 DOI=10.3389/fphys.2021.709655 ISSN=1664-042X ABSTRACT=

A previous study reported that 3-min of high-intensity static stretching at an intensity of 120% of range of motion (ROM) did not change the muscle stiffness of the rectus femoris, because of the overly high stress of the stretching. The purpose of this study was to examine the effects of high-intensity static stretching of a shorter duration or lower intensity on the flexibility of the rectus femoris than that of the previous study. Two experiments were conducted (Experiment 1 and 2). In Experiment 1, eleven healthy men underwent static stretching at the intensity of 120% of ROM for two different durations (1 and 3 min). In Experiment 2, fifteen healthy men underwent 3-min of static stretching at the intensity of 110% of ROM. The shear elastic modulus of the quadriceps were measured. In Experiment 1, ROM increased in both interventions (p < 0.01), but the shear elastic modulus of the rectus femoris was not changed. In Experiment 2, ROM significantly increased (p < 0.01), and the shear elastic modulus of the rectus femoris significantly decreased (p < 0.05). It was suggested that the stretching intensity (110%) is more important than stretching duration to decrease the muscle stiffness of the rectus femoris.