Investigation of the relationship between shoulder rotator muscle strength and upper extremity explosive strength and single leg squat test, y balance test and core endurance test results in women volleyball players

Introduction: The shoulder joint is at risk for injuries due to repetitive loads during overhead activities. Shoulder pathologies may be related to a problem not only in the shoulder joint but also in other links of the kinetic chain. A good balance of shoulder rotator muscle strength, good explosive power, good core strength are important for both optimal performance and injury prevention in overhead sports. Especially female athletes are at risk for shoulder injuries. Objective: To investigate the relationship between shoulder rotator muscle strength, upper extremity explosive strength and single leg squat test, Y balance test and core strength in female volleyball players. Methods: Healthy female volleyball players aged 16-40 years were included in the study. Shoulder internal rotation (IR) and external rotation (ER) strengths, medicine ball throw test (MBTT), single leg squat test (SLST), superolateral (SL) inferolateral (IL) medial (M) directions and composite score (YBT-CS) of the Y balance test (YBT), and double leg lowering test (DLLT) were evaluated. The results of the measurements were analyzed by correlation and regression analyses. Results: No significant association was found between IR and SLST (p>0.05). No significant association was found between IR and nondominant YBT (p>0.05). No significant association was found between nondominant IR and dominant YBT-SL, dominant IR and dominant YBT-IL (p>0.05), while significant association and weak correlation were found in other directions (p<0.05). There was a significant association and weak correlation between IR and dominant YBT-IL (p<0.05), but not with nondominant YDT-IL (p>0.05). YDT-M was found to explain YBT-CS more than the other two directions (p<0.05). There was a significant association and a weak negative correlation between dominant IR and DLLT (p<0.05), but not with nondominant IR (p>0.05). No significant association was found between ER and SLST, YBT, DLLT (p>0.05). No significant association was found between MBTT and SLST also MBTT and DLLT (p>0.05). No significant association was found between MBTT and nondominant IR-IL (p>0.05), whereas significant association and weak correlation were found between MBTT and all other IR components (p<0.05). Conclusion: The relationship of the Y balance test with internal rotation strength and explosive strength should be kept in mind during injury prevention, post-injury rehabilitation, decision to return to sport and in developing a good performance. The medial aspect of the Y balance test can be practically used for this assessment. Shoulder isometric strength is related to double leg lowering test. Key Words: Volleyball, Overhead Activity, Rotator Muscle Strength, Y Balance, Explosive Power, Core Strength, Single Leg Squat, Kinetic Chain