Intramuscular differences in shear modulus of the rectus femoris muscle during passive knee flexion

• Published in: European journal of applied physiology Vol. 121; no. 5; pp. 1441 - 1449
• Main Authors: Kodesho, Taiki, Taniguchi, Keigo, Kato, Takuya, Katayose, Masaki
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.05.2021; Springer Nature B.V
• Subjects: Biomedical and Life Sciences; Biomedicine; Human Physiology; Knee; Occupational Medicine/Industrial Medicine; Original Article; Sports Medicine; Clinical evaluation; Passive force; Stiffness; Muscle strain; Ultrasound imaging
• ISSN: 1439-6319; 1439-6327; 1439-6327
• DOI: 10.1007/s00421-021-04644-1

Purpose This study aimed to determine (1) intramuscular regional differences in the changes in the shear modulus of the rectus femoris (RF) muscle during passive knee flexion and (2) the relationship between shear modulus and passive knee extension torque. Method The shear modulus maps as an index of muscle stiffness and the passive torque were obtained at seven regions during passive knee flexion at 2°/s within a knee joint range of motion of 0°–130° in 16 healthy males. Results The shear modulus of RF increased with the knee angle of flexion. The shear modulus of each longitudinal region was greater in the order of proximal, central, and distal region ( p  < 0.05). The relationship between the shear modulus and passive torque was highly fitted for all 16 subjects ( p  < 0.05). The mean coefficient of determination ( R 2 ) at second-order polynomial model per subject was 0.96 (± 0.03; range 0.61–0.99), and whole group was 0.58 (± 0.03; range 0.54–0.64) in all regions. Conclusions The passive stiffness of RF was higher in the proximal region than in the other regions during passive knee flexion. Furthermore, the shear modulus–passive torque was related regardless of the measurement region within a muscle, and the results suggest that the passive knee extension torque reflects passive muscle stiffness of the RF.