Changes in muscular activity depending on infraspinatus muscle fibers involved in different glenohumeral joint positions

Abstract

The infraspinatus muscle consists anatomically of transverse and oblique fibers, and the different fi bers have different functions in view of the direction.

The purpose of this study was to evaluate the muscle activity level of the different fibers of the infraspinatus muscle by surface electromyography to determine the function of each fiber type during abduction and external rotation of the glenohumeral joint. The activity of the transverse fibers change during abduction depending on the internal rotation angle of the shoulder joint. The activity of the oblique fibers as related to the transverse fibers changed during shoulder joint abduction movement depending on changes in the shoulder abduction angle. The activity of the respective fibers of the infraspinatus muscle is indicated by differences in shoulder abduction and the internal rotation angle. When we perform functional evaluation and exercise, the function of the respective fi bers of the infraspinatus must be considered.