Exploring the Role of Upper Extremity Inter-limb Asymmetry in Functional Tests and Its Association with Sports Injuries in Volleyball Players

Background: Volleyball is a fast-paced and dynamic sport that requires high agility and coordination, and it can be influenced by inter-limb asymmetries in the upper extremities, which affect both performance and injury risk. While previous studies have examined these asymmetries in relation to injury risk in some sports, limited research has explored their long-term effects in volleyball. Objectives: This study aims to investigate the relationship between inter-limb asymmetries and injury risk in volleyball players over a nine-month period. Additionally, the study evaluates the predictive accuracy of Y-balance test upper quarter (YBT-UQ), seated single arm shot put test, and closed kinetic chain upper extremity stability test) for identifying injury risk. Methods: This prospective cohort study, which began in June 2024, will run for nine months in Kermanshah. A total of 101 volleyball players participated, undergoing baseline assessments of their upper quarter performance. Injury data were collected biweekly throughout the study period. The data were analyzed using SPSS version 27, applying independent t-tests to compare injured and non-injured groups, and univariate logistic regression to examine the relationship between predictive variables and sports injuries. Results: Throughout the nine months, 20.8% of players sustained 51 new injuries, with an injury incidence rate of 4.01 injuries per 1000 hours of play. Acute injuries accounted for 56.7%, while overuse injuries made up 43.3%. Although no significant differences were observed in YBT-UQ scores between injured and non-injured players, significant inter-limb differences and asymmetries were found in the seated single arm shot put test and the closed kinetic chain upper extremity stability test (P < 0.03), suggesting a link between these differences and injury risk. Conclusions: This study emphasizes the importance of monitoring inter-limb differences in strength and stability to reduce injury risk in volleyball players. While YBT-UQ did not show significant differences, other assessments revealed notable asymmetries, highlighting the role of inter-limb discrepancies in injury status. Future research should focus on the long-term effects and corrective strategies to address these differences.