2017 Volume 20 Issue 2 Pages 61-69
The aim of this study was to examine the effect of hip joint angle on muscle stiffness of the adductor longus（AL） during hip fl xion task. Ten healthy young adults（men）were recruited for this study. To investigate the effect of hip joint angle on muscle stiffness, shear modulus of AL was measured during the isometric hip flexion tasks at 0%, 25%, 50%, 75%, and 100% of maximum voluntary contractions of the hip flexors for each hip flexion joint angle of －20°, 0°, 20°, 40°, 60°, and 80° using ultrasound shear-wave elastography. The changes in muscle stiffness of AL with the hip flexion tasks were different between hip joint angles. During hip flexion, a significant interaction of hip joint angle and contraction intensity on the muscle stiffness of AL was found (P < 0.001). Active stiffness normalized to the hip flexion maximal torque at hip flexion angles of －20°, 0° and 20° were significantly higher than at hip angles of 40°, 60° and 80°（P < 0.05）. These results demonstrate that muscle stiffness of AL with hip flexion were influenced by the hip joint angle, and it was higher at the hip angles of －20° to 20°. The findings suggest that the mechanical stress of AL with hip flexion might be higher in the extended region and shallow flexion region of hip joint range motion.
