Surface electromyography assessment of infraspinatus injuries in competitive volleyball players

Abstract

Problem Statement: In volleyball, effective blocking is essential for successful defense, but due to specific sports dynamic demands, the risk of shoulder injury is higher. The infraspinatus muscle, crucial for shoulder stability, is particularly prone to strain, which can compromise blocking performance. Despite this, there is limited research on how infraspinatus injuries influence muscle activation during volleyball-specific movements. Purpose: This study assesses the impact of previous infraspinatus strain (IS) on muscle activation during a volleyball blocking task and focuses on asymmetries that could affect performance and increase injury risk. Approach: Muscle activation patterns were examined using surface electromyography (sEMG) in collegiate male volleyball players, comparing those with and without a history of IS. The analysis aimed to determine whether infraspinatus injuries lead to persistent neuromuscular imbalances during blocking movements. Materials and Methods: Twenty-four right-hand dominant male players were divided into two groups: (I) With Grade I/II IS (WGIS), and (II) Without IS (WtGIS). sEMG electrodes were placed bilaterally to record muscle activity during a standardized blocking maneuver set-up. Statistical comparison between groups and muscles has been analysed. Results: Players in the WGIS group demonstrated significantly reduced infraspinatus activation (57.6 ± 12.99) compared to the WtGIS group (82.3 ± 11.75). Notable differences were found in the right medial infraspinatus (RMI) (p = 0.031, p = 0.034) and right inferior infraspinatus (RII) (p = 0.015, p = 0.028), indicating an apparent asymmetry (p < 0.001) in muscle engagement. Conclusions: Volleyball players with a history of infraspinatus injury exhibit significant muscle activation asymmetries and persistent weakness in the affected shoulder during blocking movements. These findings underscore the importance of targeted rehabilitation and conditioning strategies to enhance shoulder function and prevent recurrent injuries.