Abstract: ObjectiveTo evaluate the usefulness of an ultrasonography-based method to examine quadriceps femoris contracting. MethodsThe thickness of bilateral rectus femoris (RF) and vastus intermedius (VI) and the cross-sectional area (CSA) of RF was measured in 10 healthy subjects （n=20） in a relaxed position and 3 isometric contraction states using ultrasonography by two examiners. The date was compared with paired t test. Half of these subjects （n=10） were also measured with MRI at rest. The date was also compared with paired t test. ResultsThere was no significant difference between MRI and static compound ultrasonography, nor between two examiners. There was a significant difference (P<0.05) in thickness of RF and VI between relaxed and isometric contraction conditions. There was no significant difference among isometric contraction conditions. There was no significant difference among measurements of RF-CSA. Conclusionultrasonography shows good validity and reliability in measuring quadriceps shape.

Key words: ultrasonography, quadriceps femoris, thickness, cross-sectional area, measurement