EFFECT OF THREE DIFFERENT SCAPULAR POSITIONS ON ISOMETRIC STRENGTH AND MUSCLE ACTIVITY RATIO OF SERRATUS ANTERIOR IN SUBJECTS WITH SCAPULAR WINGING

The purpose of this study was to compare the isometric strength of serratus anterior at three different scapular positions (retracted, neutral and protracted) and electromyography activity ratio of upper trapezius to serratus anterior and upper trapezius to lower trapezius during isometric arm elevation between the subjects with and without scapular winging. Thirty-three subjects with scapular winging and thirty-three subjects without scapular winging were recruited for this study. This study showed that isometric strength of serratus anterior was significant decreased in subjects with scapular winging group than without scapular winging group (p<.05). In both of subjects with and without scapular winging groups, isometric strength of serratus anterior showed significant difference at scapular positions (p<.05). Isometric strength of serratus anterior was strongest in retracted scapular position (p<.05). Electromyography activity ratio of upper trapezius / serratus anterior was significantly higher in subjects with scapular winging than subjects without scapular winging (p<.05). Based on these findings in this study, the isometric strength of serratus anterior in retracted scapular position was strongest in both of subjects with and without scapular winging group. The higher upper trapezius/serratus anterior of electromyography activity ratio in subjects with scapular winging than in subjects without scapular winging implies that upper trapezius muscle is used more dominantly among scapular upward rotators during shoulder elevation in subjects with scapular winging.