[Purpose] The purpose of this study was to determine the changes in the supraspinatus cross-sectional areas according to shoulder abduction angles, using ultrasonography. [Subjects and Methods] The subjects consisted of 40 individuals (20 males and 20 females). The cross-sectional areas of the supraspinatus of all subjects were measured with ultrasonography at abduction angle of 0°, 30°, 60°, 90°, and 120°. We set four abduction angle levels (I, II, III, and IV), 0° to 30°, 30° to 60°, 60° to 90°, and 90° to 120°, respectively, when determining the largest change in cross-sectional area. [Results] The results revealed that cross-sectional areas of the supraspinatus increased at all levels, but the abduction angle level with the largest increase in cross-sectional area of the supraspinatus was Level III. [Conclusion] The above results indicate that performing exercises at an abduction angle between 60° and 90° will be the most effective for supraspinatus strengthening in clinical practice.
Keywords: Rotator cuff; Supraspinatus cross-sectional area; Ultrasonography.