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Compensatory mechanisms during scapular plane abduction by increased scapulothoracic joint upward rotation: A musculoskeletal model simulation study Cover

Compensatory mechanisms during scapular plane abduction by increased scapulothoracic joint upward rotation: A musculoskeletal model simulation study

Open Access
|Nov 2025

Abstract

Study aim: This study aimed to analyze the compensatory mechanisms during shoulder abduction by increased scapulothoracic joint upward rotation, focusing on acromiohumeral distance, shoulder muscle forces, and glenohumeral joint stability, using a musculoskeletal model simulation.

Material and methods: Fifteen healthy males performed shoulder abduction along scapular plane. Acromiohumeral distance, shoulder muscle forces, and glenohumeral joint stability were estimated using a musculoskeletal model. Data estimated from the three models with different scapulothoracic joint upward rotation were compared using one-dimensional statistical parametric mapping. Differences among three models were analyzed using one-way repeated measures analysis of variance. As a post hoc test, paired t-tests with Bonferroni correction for multiple comparisons were used.

Results: The model that increased scapulothoracic joint upward rotation showed significantly greater acromiohumeral distance, and greater muscle forces of supraspinatus and deltoid compared with the models with normal scapulothoracic joint upward rotation. Conversely, glenohumeral joint stability significantly decreased from the mid and late phase of arm elevation in the increased scapulothoracic joint upward rotation model.

Conclusions: During shoulder abduction, increased scapulothoracic joint upward rotation magnified acromiohumeral distance for pain avoidance and contributed to increased muscle forces; it also decreased glenohumeral joint stability. In conclusion, the current study revealed the positive and negative aspects associated with increased scapulothoracic joint upward rotation. Therapists engaging in shoulder rehabilitation should remain mindful of these issues.

Language: English
Page range: 309 - 318
Submitted on: Jun 9, 2025
Accepted on: Oct 23, 2025
Published on: Nov 17, 2025
Published by: University of Physical Education in Warsaw
In partnership with: Paradigm Publishing Services
Publication frequency: 1 issue per year

© 2025 Shobu Nakashima, Masayuki Kawada, Yasufumi Takeshita, Takasuke Miyazaki, Masafumi Fukuda, Rikuto Suzuki, Hisanori Matsuura, Ryoji Kiyama, published by University of Physical Education in Warsaw
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.