PHYSICAL THERAPY RESEARCH ORIGINAL ARTICLE This work is licensed under a Creative Commons Attribution International License. ©2023 Japanese Society of Physical Therapy Biomechanical Characteristics of Scapular and Glenohumeral Movements during Pitching Motion in Injury-prone College Baseball Pitchers Koji MIYASHITA, PT, PhD 1 , Sentaro KOSHIDA, ATC, CSCS, PhD 2 , Taro KOYAMA, PT, MS 3 , Kenichiro OTA, PT, MS 4 , Yusuke TANI, PT, MS 5 and Ryoji OKAMUNE, PT, MS 3 1) Department of Physical Therapy, College of Life and Health Sciences, Chubu University, Japan 2) Department of Judotherapy and Sports Medicine, Faculty of Health Sciences, Ryotokuji University, Japan 3) Matsushita Orthopedics, Japan 4) Watanabe Orthopedics and Rehabilitation Clinic, Japan 5) Advanced Reha Co. Ltd., Japan ABSTRACT. Objectives: The coordination of glenohumeral (GH) and scapular movements is central to the injury prevention of baseball pitchers. However, there is no objective data establishing the direct rela- tionship between pitching injuries and associated GH and scapular movements. Therefore, this study demonstrated the biomechanical differences in the scapular and GH movements during pitching between injury-prone pitchers and healthy college baseball pitchers. Methods: A total of 30 collegiate baseball pitchers were classifed into two groups according to their injury status: injury-prone group (n = 15) and control group (n = 15). We obtained pitching motion data using three-dimensional motion analysis tech- nique. Results: The horizontal abduction angles of the GH joint during cocking and acceleration phases were considerably greater in the injury-prone pitchers (19.0° at stride foot contact [SFC], −4.0° at maxi- mum external rotation [MER], and −0.3° at ball release) than those in healthy controls (11.7° at SFC, −10.0° at MER, and −6.9° at ball release). Additionally, in the cocking phase, the amount of angular change in the scapular external rotation (ER) was signifcantly smaller in the injury-prone group than that in the control group (mean difference, −13.0). Conclusion: These results suggest that the injury-prone pitchers have less internal rotation of the scapula and a more horizontal abduction of the GH joint during the cocking and acceleration phases. Therefore, sports medicine practitioners may need to pay consider- able attention to the coordination of scapular and GH horizontal movements during pitching for preven- tion of shoulder injuries. Key words: Scapula movement, Glenohumeral joint movement, Pitching motion, Injury-prone (Phys Ther Res 00: 00–00, 0000) The scapula plays a pivotal role in the kinetic chain, transferring energy derived from the trunk rotation to the pitching arm 1,2) . Therefore, scapular dysfunction is believed to lead baseball pitchers to injuries, often occur- ring in the glenohumeral (GH) joint 3,4) . However, despite evidence suggesting a link between the scapula dysfunc- tion and shoulder pain, there is no consensus on a direct relationship between scapular malposition/malorienta- tion and the pitching injuries 5) . Burkhart et al. proposed the concept of scapular malposition, inferior medial border prominence, coracoid pain and malposition, and Received: May 26, 2023 Accepted: September 20, 2023 Advance Publication by J-STAGE: October 27, 2023 doi: 10.1298/ptr.E10254 Correspondence to: Koji Miyashita, Department of Physical Therapy, College of Life and Health Sciences, Chubu University, 1200 Matsu- moto, Kasugai, Aichi 487-8501, Japan e-mail: kmiyashita@isc.chubu.ac.jp Advance Publication by J-STAGE: October 27, 2023