Upper Quarter Functional Stability in Female Volleyball Players with and without Anterior Shoulder Instability, with Consideration of Arm Dominance

Objective: The aim of this study was the comparison of the functional stability of dominant and non-dominant shoulder in female volleyball players with and without anterior shoulder instability, using YBT-UQ. Materials and methods: In this descriptive study, 28 female university volleyball players (age=20 to 25 years) were categorized into healthy (n=14) and anterior shoulder instability (n=14) group. Upper quarter y balance test (YBT-UQ) was used for measuring functional stability of both dominant and non-dominant shoulder. After checking the normal distribution of the results with 1-s Kolmogorov-Smirnov, paired sample t-test and independent sample t-test were used for comparing the dominant and non-dominant shoulder's functional stability and for comparing the results between groups, respectively. Results: Higher YBT-UQ composite score was observed in non-dominant shoulder and dominant shoulder of the healthy group and the non-dominant shoulder and dominant (injured) shoulder of shoulder instability group, respectively. No significant difference was observed between functional stability of both shoulders of the healthy group (p=0.144), while the functional stability of the non-dominant shoulders of the instability group was significantly higher than the dominant unstable shoulders (p=0.001). The results of functional stability of the unstable shoulders of the injured group were significantly lower than the results of the dominant shoulders of the healthy group, while in non-dominant side, all directions but the Superolateral direction showed significant difference. Conclusion: Based on the results of this study, functional stability of the unstable shoulder of female university volleyball players is lower than the functional stability of their non-dominant side or the functional stability of the healthy subjects therefore, we suggest that the upper extremity stabilization exercises, specially the closed kinetic chain exercises should be added to the shoulder rehabilitation programs.