Discipline of Biomedical Science, Sydney Medical School, The University of Sydney, Australia.
J Sci Med Sport. 2010 Nov;13(6):651-6. doi: 10.1016/j.jsams.2010.03.008. Epub 2010 May 7.
The aim of this study was to compare activity in shoulder muscles during unsupported internal and external rotation to examine their functional roles, and determine whether they retain their 'stabiliser' or 'mover' role regardless of the shoulder task. Electromyographic recordings in the dominant shoulder of 15 normal subjects were taken from 13 shoulder muscle sites using a combination of surface and intramuscular electrodes during isometric shoulder internal and external rotation in an unsupported abducted position under conditions of increasing load. During internal rotation significantly higher activity levels were found in subscapularis (p<0.001). During external rotation significantly higher activity levels were demonstrated in supraspinatus, infraspinatus, trapezius and serratus anterior (p<0.05). There were no significant differences in activity levels in deltoid, pectoralis major and latissimus dorsi during internal and external rotation. As rotational forces increased there was a significant increase in activity in all muscle sites activated above low levels (r(2)=0.93±0.07; mean±s.d.). This study has shown that shoulder muscle function is task specific and that shoulder muscle motor strategy for a particular task does not change with increasing torque. As the only shoulder rotators that demonstrated direction specificity the rotator cuff muscles are likely to be functioning to provide rotation torque while the deltoid is likely to be providing dynamic shoulder stability during the task examined. Higher scapulothoracic muscle activity during external rotation indicated the need for greater dynamic scapular stability as a result of higher rotator cuff activity during external than internal rotation.
本研究旨在比较在无支撑的内、外旋运动中肩部肌肉的活动，以研究它们的功能作用，并确定它们是否仍然具有“稳定器”或“推动者”的作用，而与肩部任务无关。使用表面和肌内电极的组合，对 15 名正常受试者的优势肩部进行了 13 个肩部肌肉部位的肌电图记录，在无支撑外展的情况下，在增加负荷的条件下进行等长肩部内、外旋运动。在内部旋转时，肩胛下肌的活动水平明显较高（p<0.001）。在外旋时，冈上肌、冈下肌、斜方肌和前锯肌的活动水平明显较高（p<0.05）。在内部和外部旋转时，三角肌、胸大肌和背阔肌的活动水平没有显著差异。随着旋转力的增加，所有被激活的肌肉部位的活动水平都显著增加（r(2)=0.93±0.07；平均值±标准偏差）。本研究表明，肩部肌肉功能是特定于任务的，并且特定任务的肩部肌肉运动策略不会随着扭矩的增加而改变。由于只有肩旋转肌表现出方向特异性，肩袖肌肉可能在提供旋转扭矩，而三角肌可能在被检查的任务中提供动态肩部稳定性。外旋时肩胛骨胸肌的活动水平较高，表明由于外旋时肩袖肌肉的活动水平高于内旋时，需要更大的动态肩胛骨稳定性。
