Musculoskeletal models enable movement scientists to examine muscle function by computing the mechanical work done by muscles during motor tasks. To estimate muscle work accurately requires a model that is physiologically plausible. Previous models of the human shoulder have coupled scapula movement to humeral movement. While coupled movement produces a stereotypical scapulohumeral rhythm, it cannot model shrugging or independent movement of the scapula and humerus. The artificial coupling of humeral elevation to scapular rotation permits muscles that cross the glenohumeral joint, such as the rotator-cuff muscles and deltoids, to do implausible work to elevate and rotate the scapula. In reality, the motion of the scapula is controlled by thoracoscapular muscles, yet the roles of these muscles in shoulder function remains unclear. To elucidate the roles of the thoracoscapular muscles, we developed a shoulder model with an accurate scapulothoracic joint and includes scapular muscles to drive its motion. We used the model to compute the work done by the thoracoscapular muscles during shrugging and arm elevation. We found that the bulk of the work done in upper-extremity tasks is performed by the largest muscles of the shoulder: trapezius, deltoids, pectoralis major, and serratus-anterior. Trapezius and serratus anterior prove to be important synergists in performing upward-rotation of the scapula. We show that the large thoracoscapular muscles do more work than glenohumeral muscles during arm-elevation tasks. The model, experimental data and simulation results are freely available on SimTK.org to enable anyone to explore our results and to perform further studies in OpenSim 4.0.

中文翻译：

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从人体肩膀的肌肉骨骼模型对上肢运动和工作的肌肉贡献。

肌肉骨骼模型使运动科学家可以通过计算运动任务中肌肉完成的机械功来检查肌肉功能。要准确地估计肌肉活动，需要一个在生理上合理的模型。人类肩膀的先前模型已经将肩cap骨运动与肱骨运动耦合。虽然耦合运动会产生刻板印象的肩oh骨节律，但无法模拟肩or骨和肱骨的耸肩或独立运动。肱骨抬高与肩骨旋转的人工耦合使穿过肩肱关节的肌肉（例如肩袖肌肉和三角肌）无法完成抬高和旋转肩cap骨的艰苦工作。实际上，肩cap骨的运动受胸cap肌控制，但这些肌肉在肩部功能中的作用仍不清楚。为了阐明胸膜肩muscle肌的作用，我们开发了肩model骨模型，该肩骨模型具有精确的肩or胸关节，并包括肩cap肌来驱动其运动。我们使用该模型来计算耸肩和手臂抬高期间胸cos肌的工作量。我们发现上肢任务完成的大部分工作是由肩部最大的肌肉进行的：斜方肌，三角肌，胸大肌和锯齿前肌。斜方肌和锯齿前肌被证明是肩s骨向上旋转的重要增效剂。我们显示，在手臂抬高任务中，大型胸cap肌比肩肱肌做更多的工作。该模型，实验数据和仿真结果可在SimTK上免费获得。