The Comparison of Different Stretching Intensities on the Range of Motion and Muscle Stiffness of the Quadriceps Muscles

Abstract

Muscle strain is one of the most frequent sports injuries, having the rectus femoris (RF) muscle as the reported preferred site of quadriceps muscle strain. The decrease muscle stiffness could be an effective RF muscle strain prevention. In recent studies, a high-intensity static stretching intervention decreased passive stiffness, though no study has investigated on the effect of the different static stretching intervention intensities on quadriceps muscle stiffness. The purpose of this study was to investigate the three different quadriceps muscle stiffness intensities (120 vs. 100 vs. 80%). Eighteen healthy, sedentary male volunteers participated in the study and randomly performed three intensities. The static stretching intervention was performed in knee flexion with 30° hip extension. Three 60-second stretching intervention with a 30-second interval were performed at each stretching intensity. We measured knee flexion range of motion and shear elastic modulus of the RF muscle used by ultrasonic shear-wave elastography before and after the static stretching intervention. Our results showed that the knee flexion range of motion was increased after 100% (p < 0.01) and 120% intensities (p < 0.01) static stretching intervention, not in 80% intensity (p = 0.853). In addition, our results showed that the shear elastic modulus of the RF muscle was decreased only after 100% intensity static stretching intervention (p < 0.01), not after 80% (p = 0.365), and 120% intensities (p = 0.743). To prevent the quadriceps muscle strain, especially the RF muscle, 100%, not 120% (high) and 80% (low), intensity stretching could be beneficial in sports setting application.

The acute effects of high-intensity jack-knife stretching on the flexibility of the hamstrings

“…Previous studies showed that alteration in the muscle–tendon unit stiffness was correlated with the intensity of static stretching in the hamstrings 15 , 16 . However, Nakamura et al 18 reported that high-intensity static stretching (120%ROM) was not effective for a decrement in muscle stiffness of the rectus femoris because it is overly stressful. These data indicated that the effects of high-intensity static stretching may differ depending on the targeted muscles.…”

“…To assess changes in the flexibility of the right hamstrings (dominant limb of all participants), knee extension ROM, passive torque at end ROM, and muscle–tendon unit stiffness were measured before and immediately after jack-knife stretching. The dominant leg was determined by asking the participant’s preferred leg when kicking a ball 18 . The flexibility measurements were performed without any warm-up.…”

“…Recently, high-intensity static stretching has been reported as a method to effectively decrease the muscle–tendon unit stiffness 14 – 16 . The intensity of static stretching is determined according to the range of motion (ROM) 14 , 17 , 18 or point of discomfort (POD) 15 , 16 of each participant. Previous studies performed high-intensity static stretching at the intensity of 120%ROM 14 and 120%POD or more 15 , 16 and reported that high-intensity static stretching effectively decreased the muscle–tendon unit stiffness of the hamstrings even if with a short duration of high-intensity stretching (≤ 20 s).…”

“…Previous studies performed high-intensity static stretching at the intensity of 120%ROM 14 and 120%POD or more 15 , 16 and reported that high-intensity static stretching effectively decreased the muscle–tendon unit stiffness of the hamstrings even if with a short duration of high-intensity stretching (≤ 20 s). However, high-intensity static stretching is associated with severe pain 14 – 16 , 18 , although safety at that intensity has been reported 15 , 16 . In previous studies, high-intensity static stretching was passively performed 14 – 16 , 18 .…”

“…However, high-intensity static stretching is associated with severe pain 14 – 16 , 18 , although safety at that intensity has been reported 15 , 16 . In previous studies, high-intensity static stretching was passively performed 14 – 16 , 18 . Therefore, it remains unclear whether high-intensity static stretching, which is accompanied by severe pain, can be performed effectively and safely by oneself.…”