Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan; Research Fellow of the Japan Society for the Promotion of Science, Tokyo, Japan.
J Shoulder Elbow Surg. 2019 Dec;28(12):2438-2446. doi: 10.1016/j.jse.2019.04.059. Epub 2019 Aug 10.
Shoulder external rotation at abduction (ER) is a notable motion in overhead sports because it could cause strong stress to the elbow and shoulder joint. However, no study has comprehensively investigated the effect of different trunk postures during ER. This study aimed to investigate the effect of different trunk postures on scapular kinematics and muscle activities during ER.
Fourteen healthy men performed active shoulder external rotation at 90° of abduction with the dominant arm in 15 trunk postures. At maximum shoulder external rotation in 15 trunk postures, including 4 flexion-extension, 6 trunk rotation, and 4 trunk side-bending postures, as well as upright posture as a control, scapular muscle activities and kinematics were recorded using surface electromyography and an electromagnetic tracking device, respectively. The data obtained in the flexion-extension, trunk rotation, and trunk side-bending postures were compared with those obtained in the upright posture.
In the flexion-extension condition, scapular posterior tilt and external rotation significantly decreased, but the muscle activities of the lower trapezius and infraspinatus significantly increased in maximum trunk flexion. Moreover, scapular upward rotation and the activity of the serratus anterior significantly increased in maximum trunk extension. In the rotation condition, scapular posterior tilt and external rotation significantly decreased, but the activity of the serratus anterior significantly increased in the maximum contralateral trunk rotation posture. In the trunk side-bending condition, scapular posterior tilt and the external rotation angle significantly decreased.
Trunk postures affected scapular kinematics and muscle activities during ER. Our results suggest that different trunk postures activate the lower trapezius and serratus anterior, which induce scapular posterior tilt.
外展时的肩部外旋（ER）是上肢运动中的一个显著动作，因为它可能会对肘部和肩部关节造成强烈的压力。然而，目前还没有研究全面调查 ER 过程中不同躯干姿势的影响。本研究旨在探讨不同躯干姿势对 ER 时肩胛骨运动学和肌肉活动的影响。
14 名健康男性以优势臂在 15 个体干姿势下进行 90°外展的主动肩部外旋。在 15 个体干姿势（包括 4 个体干前屈-后伸、6 个体干旋转和 4 个体干侧屈姿势）和直立姿势（作为对照）的最大肩部外旋时，分别使用表面肌电图和电磁跟踪装置记录肩胛骨肌肉活动和运动学。将前屈-后伸、躯干旋转和躯干侧屈体位获得的数据与直立体位获得的数据进行比较。
在前屈-后伸位，肩胛骨后倾和外旋明显减小，但下斜方肌和冈下肌的肌肉活动明显增加；在最大躯干伸展位，肩胛骨上旋和前锯肌的活动明显增加。在旋转位，肩胛骨后倾和外旋明显减小，但在最大对侧躯干旋转位时前锯肌的活动明显增加。在躯干侧屈位，肩胛骨后倾和外旋角度明显减小。
躯干姿势影响 ER 时的肩胛骨运动学和肌肉活动。我们的结果表明，不同的躯干姿势激活下斜方肌和前锯肌，从而引起肩胛骨后倾。
