Effects of low-intensity and short-duration isometric contraction after static stretching on range of motion, passive stiffness, and isometric muscle force

Abstract

Although static stretching is commonly performed to improve flexibility, it has been reported to have detrimental effects on muscle force and performance. Previous studies have reported that low-intensity and short-duration isometric contraction after static stretching inhibits stretch-induced force loss. However, the detailed effects of low-intensity short-duration isometric contraction after static stretching on flexibility, such as passive torque and stiffness, are currently unclear. Therefore, the current study sought to reveal the effects of low-intensity and short-duration isometric contraction after static stretching on flexibility and muscle force. Sixteen healthy participants (eight men, eight women) performed 300-s static stretching (SS), 300-s static stretching followed by 6-s 30% maximum isometric voluntary contraction (MIVC) (SS-30% MIVC), and 6-s 30% MIVC (30% MIVC) of the right hamstring on three separate days, in random order. Range of motion (ROM) and passive stiffness during knee extension, peak passive torque, and MIVC torque were obtained before and after exercise. ROM and peak passive torque were significantly increased after all exercises, whereas passive stiffness and MIVC torque were significantly decreased after SS only. Moreover, ROM after SS and SS-30% MIVC were significantly greater than that of 30% MIVC, and peak passive torque after SS-30% MIVC was significantly greater than that of SS, while passive stiffness after SS was significantly lower than that of 30% MIVC. These results indicate that low-intensity and shortduration isometric contraction after static stretching is effective for inhibiting stretch-induced force loss while also inhibiting the effects of static stretching on passive stiffness.