The infraspinatus muscle activity during pitching motion in baseball players with shoulder instability

Abstract

Background Shoulder microinstability is often overlooked, which can be problematic, especially in overhead athletes. The slipping phenomenon is defined as posterior or lateral sliding of the humeral head in an elevated arm. When the shoulder is close to the end range of stability, the infraspinatus is highly activated and keeps the shoulder in the glenoid cavity. This study aimed to examine the characteristic physical function and infraspinatus activity during the pitching motion in baseball pitchers with shoulder instability. Methods Twenty-one male baseball pitchers participated and were divided into 2 groups based on radiograph findings at zero position: slipped (group S) and nonslipped (group N) groups. Physical function using Hara test and infraspinatus muscle activity during pitching were evaluated. Results The infraspinatus muscle activity during the acceleration phase was significantly greater in group S (59.5 ± 33.0%MVC) than in group N (33.0 ± 16.9%MVC) ( P < .05). Positive rate of the Hara test in group S was significantly high in the loose test and elbow push test. Conclusions This study shows that baseball pitchers with slipping phenomenon have capsular laxity and scapular instability that indicate high infraspinatus muscle activity during the acceleration phase. Therefore, repetitive pitching with hyperactivity of the infraspinatus on the slipping shoulder may cause fatigue and dysfunction.

Ultrasound-Guided Hydrodissection of the Thoracodorsal Nerve and Axillary Nerve in a Gymnast With Shoulder Pain Associated With Superior Labral Anterior-Posterior Lesions: A Case Report

“…CAT and HFT are tests performed while the patient is supine on the bed, with the scapula manually stabilized, and involve flexion or horizontal flexion of the shoulder joint. It is believed that the CAT detects tightness in the inferior aspect of the glenohumeral joint, while the HFT detects tightness in the posteroinferior aspect [ 10 ]. When there is tightness in the inferior or posterior aspect of the shoulder joint, it is believed that the centricity of the humeral head relative to the glenoid fossa changes during shoulder elevation [ 11 ].…”

Immediate Effects of Kinesio-taping and Joint Mobilisation on Shoulder in Over-head Athletes with Glenohumeral Internal Rotation Deficit

“…The infraspinatus muscle contributes significantly to compressive forces at the glenohumeral joint and along with the rotator cuff muscles, serves an important role of being a static and dynamic stabilizer of the glenohumeral joint (Choi et al, 2017). Measurements of muscle activity indicate that the infraspinatus begins to become highly active at ball release, and the activity level remains elevated throughout the follow-through phase (Kotoshiba et al, 2021). Due to repetitive use of the external rotators of the shoulder: infraspinatus and teres minor in overhead throwing, the muscles are prone to over activity and muscle tightness resulting in possible reduction in internal rotation and increased external rotation.…”