Moderate Associations of Muscle Elasticity of the Hamstring with Hip Joint Flexibility

The main purpose of the present study was to identify whether and to what extent the individual differences in range of motion and stiffness of the hip joint can account for that in muscle elasticity of the hamstring. Hip extension torque and shear moduli (a measure of elasticity) of the biceps femoris, semitendinosus, and semimembranosus were assessed in 21 young males during unilateral passive hip flexion in the knee-extended position from the anatomical position to the individual's maximal hip flexion angle. Muscle shear modulus was quantified by using ultrasound shear wave elastography. The maximal hip flexion angle correlated negatively with the shear modulus of each muscle (-0.750 ≤ r ≤ -0.612). The joint stiffness correlated positively with the shear modulus of each muscle (0.711 ≤ r ≤ 0.747). These findings suggest that hip flexion ROM and joint stiffness can reflect significantly but only moderately the muscle elasticity of the hamstring.