Effect of Eight Weeks of Corrective Exercises on Scapulohumeral Rhythm, Isometric Strength of Shoulder Girdle Muscles and Functional Stability in Volleyball Players With Scapular Downward Rotation Syndrome

Abstract

Background and Aims Movement impairment is common among overhead athletes and can make them susceptible to shoulder injuries. This study aims to invesigate the effect of an eight-week corrective exercise program based on Sahrmann’s approach on scapulohumeral rhythm, isometric strength of shoulder girdle muscles, and functional stability in volleyball players with scapular downward rotation syndrome (SDRS). Methods The is a quasi-experimental study with a pre-test/post-test design. Participants were 34 volleyball players with SDRS who were randomly divided into two equal groups of training (n=17) and control (n=17). Participants were selected based on observance of SDRS under the scapular dyskinesis test (SDT) in both flexion and abduction states, Kibler’s lateral scapula slide test (LSST), and scapulohumeral rhythm assessment. Before exercises, range of motion (ROM), isometric strength of shoulder girdle muscles, scapulohumeral rhythm, and functional stability were evaluated in both groups. Then, the training group performed the corrective exercises for eight weeks, three sessions per week. The control group performed no exercise and had their daily activities. At the end of training, post-test assessments were codncuetd in both groups. For the evaluation of isometric strength and ROM, a manual dynamometer and a goniometer were used, respectively. Scapulohumeral rhythm was measured at 4 positions (0, 45°, 90°, and 135°) with two inclinometers, and the Y-Balance Test Upper Quarter was used to measure the functional stability of the upper extremity. Paired sample t-test was used to compare the pretest and posttest means, and independent t-test was used to compare the differences between the two groups. The significance level was set at 0.05. Results After 8 weeks of training program, there were significant increase in the strength of the isometric strength of shoulder external rotaion (P=0.003), upper trapezius (P=0.001), middle trapezius (P=0.027), lower trapezius (P=0.001), and serratus anterior (P=0.002) as well as scapulohumeral rhythm at 0-45° (P=0.012), 45-90° (P= 0.025), and 90-135° (P= 0.037) abduction; the ROM of the shoulder flexion (P=0.002), abduction (P= 0.001), internal rortation (P= 0.001) and external rotaion(P= 0.004); and pectoralis minor muscle length (P= 0.001) compared to pre-test scores in the training group. Moroever, the functional stability of the upper extremity after training program increased significantly in the training group (P=0.001), but the training program had no significant effect on the strength of shoulder internal rotaion (P=0.165), rhomboid muscule strength (P=0.283) and supraspinatus muscule strength (P=0.214). In the post-test phase, between group comparison showed a significant difference in scapularhumeral rhythm, functional stability, ROM, pectoralis minor length, and strength of trapezius, serratus anterior, and strength of shoulder external rotation between the control and training groups (P<0.05), but no significant difference was observed in the strength of supraspinatus and rhomboid muscles and strength of shoulder internal rotation (P>0.05). Conclusion Eight weeks of corrective exercise program based on Sahrmann’s approach can improve the functional stability of the upper etermity, the scapulohumeral rhythm, and isometric strength of shoulder girdle muscles in volleyball players. This exercise protocol is recommended as an effective method to improve alignment and performance in athletes with SDRS.