Role of active joint position sense on the upper extremity functional performance tests in college volleyball players.

Background: It has been well established that proprioception plays a decisive role in shoulder stability and sport performance. Notwithstanding, there is a lack of clear association between active joint position sense (AJPS) and the performance of upper-extremity functional performance tests. The aim of this study was to determine whether the AJPS of the shoulder complex is associated with the performance of college volleyball players with the following functional tests: Y-Balance Test-Upper Quarter (YBT-UQ), Closed Kinetic Chain Upper-Extremity Stability Test (CKCUEST), and Seated Medicine Ball Throw (SMBT). The secondary aim was to investigate whether the magnitude of the proprioception error through the AJPS had the ability to act as a predictor for functional test scores. Methods: Cross-sectional study with a convenience sampling. Healthy college volleyball players (≥12 h of training/week), 30 males and 22 females, between 18 and 26 years of age were included. AJPS of the shoulder (90° of flexion (90°Flex), 90° of internal rotation at 90° of abduction (90°IR/ABD), 90° of external rotation at 90° of abduction (90°ER/ABD)) and three upper-extremity functional performance tests (YBT-UQ, CKCUEST and SMBT) were assessed. A Pearson's test and a stepwise multiple linear regression analysis were used to determine possible associations and relationships between outcome measures, respectively. Results: The analysis revealed that AJPS at 90°IR/ABD and 90°ER/ABD were the only proprioceptive variables with an association to the YBT-UQ and SMBT. Despite these relationships, only the AJPS at 90°IR/ABD was associated with the performance of the YBT-UQ in; superolateral direction (ß = -0.7; 95% CI [-1.3 to 0.1]; p = 0.025); inferolateral direction (ß = -1.5; 95% CI [-2.1 to -0.8]; p = 0.001); and composite score (ß = -0.8; 95% CI [-1.3 to -0.3]; p = 0.002). From these, AJPS at 90°IR/ABD mainly explained the variability of YBT-UQ (inferolateral direction) performance (R2 = 0.32; %R2 = 0.32). Our findings allow for a possible expanded role for proprioception as a contributing factor in upper limb motor control during functional movements. Further research is required to explore and distinguish the associations between proprioception, motor control and sport performance involving the upper limbs.

Relationship between upper limb physical performance tests and muscle strength of scapular, shoulder and spine stabilizers: A cross-sectional study.

INTRODUCTION: Performance tests of the upper limb have been frequently used in the evaluation of individuals to identify risk of injury and to determine improvement in physical performance. Understanding the variables related to the performance of the tests is important for better applicability and interpretation of test results. The aim of this cross-sectional study was to investige the correlation between isometric strength of scapular, shoulder and spine muscles with physical performance test of upper limb in men and women. EXPERIMENTAL: Forty-nine healthy and physically conditioned individuals, men (n = 24) (22,7 ± 3,2 years; 74,6 ± 8,1 Kg; 176,7 ± 7,1 cm) women (n = 25) (23 ± 2,7 years; 61,5 ± 9,1 Kg; 163,2 ± 5,6 cm), were evaluated for shoulder abductor isometric strength (S-ABD); Middle (MT) and lower (LT) trapezium; lateral shoulder rotators (S-LR); flexors (T-FLEX), lateral incliners (T-INCL), and trunk extenders (T-EXT). Evaluation of upper limb physical performance was carried out by Upper Quarter Y Balance test (YBT-UQ) and Chain upper extremity stability test (CKC-UEST). Pearson's test (r values) p ≤ 0.05 was used to analyze the correlation. RESULTS: The results reveal strong correlations between S-ABD and CKC-UEST in male group; and strong correlations in female group between S-ABD strength with CKC-UEST; and S-LR with all YBT-UQ directions and score and between T-EXT strength with CKC-UEST. CONCLUSION: Therefore, strength of shoulder and spine stabilizers influences performance in upper limb tests, but with different correlations as to sex. To improve test performance, it may be important to increase the strength of the shoulder and spine muscles.