The Comparison of shoulder complex muscles strength between elite volleyball female players due to the scapula position

Scapula displacement has a noticeable impact on the muscles’ function around the shoulder girdle and scapular stabilizer muscles in particular. Current study aims to compare the strength of shoulder’s complex muscles between elite female volleyball players with regard to the scapula positioning. Twenty four elite female volleyball players who were selected randomly (ranging from 20 to 30 years old) and 5 year's experience of premier league, after matching considering hight, weight and shoulders width, divided into two groups consisted of athletes with retracted scapula and protracted scapula. Those with 16 to 18 cm scapular distance categorized as retracted scapula subjects and those with higher than 18 cm classified as subjects of protracted scapula. The lateral scapula slide test (LSST) method was applied to determine scapular positioning, and the performance of shoulder complex muscle strength was examined using an isometric myometer (MIE). Descriptive statistics were implemented and a normal distribution was confirmed. Student's paired t-test and independent t-test were used to assess the differences between the two groups and between dominant and non-dominant sides (p<0.05). This study indicated significant difference between the two protracted and retracted groups in retraction movement (p= 0.001). This means that the abducted scapula group had higher retraction movement than retracted scapula players. In addition, the dominant side of both groups exhibited higher strength than the non-dominate side (p<0.05). Furthermore, no significant difference was observed in relative strength of agonist to the antagonist muscles, except in the protraction to retraction movement, which implies higher strength of the retracted scapula players (p= 0.001). Comparison of scapular distance in both groups had no effect on dominant side; both groups had higher strength in dominant side. Findings indicate that among the implemented movements by the two elite athletics groups, significant difference is observed only in the retraction movement of the protracted scapular group and the ratio of protraction to retraction in the retracted scapular group. Moreover, the distance of scapula had no significant impact on the dominant and non-dominant side, because the dominant side had more strength rather than the non-dominant side in the both groups.