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

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

A 20-year-old male national-level gymnast presented with left shoulder pain attributed to a superior labral anterior-posterior (SLAP) lesion. Physical examination revealed pain in the anterosuperior area at maximum shoulder elevation, with a positive combined abduction test and horizontal flexion test indicating a restriction in glenohumeral joint motion. Rather than directly addressing the SLAP lesion, ultrasound-guided hydrodissections of the thoracodorsal and axillary nerves were performed, leading to immediate alleviation of pain and mobility constraints. This innovative approach, emphasizing shoulder function, offers a novel therapeutic strategy for SLAP-associated shoulder pain in athletes.

Interindividual differences in upper limb muscle synergies during baseball throwing motion in male college baseball players

Throwing is a fundamental human motor behavior that has evolved to aid hunting and defense against predators. In modern humans, accurate throwing is an important skill required in many sports. However, the spatiotemporal coordination of muscles during baseball throwing has not been fully elucidated. We herein aimed to identify the muscle synergies involved in baseball throwing and determine whether their spatiotemporal patterns are shared among individuals. Ten college baseball players participated in this study. Electromyographic activity was recorded from 13 ipsilateral upper limb muscles during throwing using full effort. Non-negative matrix factorization was used to extract the motor module composition and temporal activation patterns during baseball throwing, followed by k-means analysis to cluster the extracted motor modules based on their similarity. Four motor modules were extracted for each player. These were classified into four clusters (Clusters 1-4), each reaching the peak activity sequentially from the early cocking phase to ball release. Spatiotemporal interindividual similarity in the muscle synergy cluster comprising the muscles activated during the transition from early cocking to late cocking (Cluster 2) was significantly lower than that in the other clusters. There was no individual-specific muscle synergy. These results suggest that the skilled baseball throwing motion acquired through years of practice may consist of four basic muscle synergies that are common among individuals with some differences in their spatiotemporal patterns.