Department of Biology of Physical Activity, University of Jyväskylä, Jyväskylä, Finland.
J Electromyogr Kinesiol. 2012 Jun;22(3):424-30. doi: 10.1016/j.jelekin.2012.02.002. Epub 2012 Mar 7.
The aim of the study was to evaluate differences in the loading of glenohumeral joint muscles between a cable pulley machine (CP) and variable resistance machine (VR) during axial humeral external rotation.
Eleven healthy male subjects took part in the study. Intramuscular electromyography from five muscles of the shoulder (medial deltoid, supraspinatus, infraspinatus and upper part of the trapezius), torque and power output was measured at different rotation angles and with different loads (10%, 50% and 100% of 1RM). Also the compressive and shear force in the glenohumeral joint was analyzed at the horizontal level at angles of rotation. External rotation was performed with a self-selected velocity on the scapular plane.
In the CP the range of movement became narrower than in the VR with increasing workload (P<0.05). The activity of the infraspinatus did not grow in the CP after 50% load, while it did in the VR (P<0.01). The upper part of the trapezius was activated less in the CP than in the VR (P<0.01) machine when using 50% and 100% loads. In comparison with the CP, the shear forces that pull the head of the humerus in a posterior direction were more evenly distributed in the VR than in the CP at different angles of rotation (P<0.001).
The VR seems to make a broader range of motion possible, lager activation the primary external rotators and evenly distributed shear forces than the CP. However, performing the exercise with VR and high load also activates the upper part of the trapezius.
These findings can be used in the development of exercise designs, methods and equipment for shoulder injury rehabilitation.
本研究旨在评估在进行轴向肱骨外旋时，缆绳滑轮机（CP）和变阻力机（VR）在盂肱关节肌肉加载方面的差异。
11 名健康男性受试者参与了本研究。在不同的旋转角度和不同的负荷（1RM 的 10%、50%和 100%）下，测量了肩部的 5 块肌肉（三角肌中部、冈上肌、冈下肌和上部分的斜方肌）的肌内肌电图、扭矩和功率输出。还在旋转角度的水平平面上分析了盂肱关节的压缩力和剪切力。外旋是在肩胛平面上以自选择的速度进行的。
随着负荷的增加，CP 的运动范围比 VR 变窄（P<0.05）。在 CP 中，50%负荷后，冈下肌的活动没有增加，而在 VR 中则增加了（P<0.01）。使用 50%和 100%的负荷时，CP 中斜方肌上部的激活程度低于 VR（P<0.01）。与 CP 相比，在不同的旋转角度下，VR 使将肱骨头向后拉的剪切力分布更加均匀（P<0.001）。
与 CP 相比，VR 似乎可以使运动范围更广，主要的外旋肌的激活程度更大，剪切力分布更均匀。然而，使用 VR 和高负荷进行练习也会激活斜方肌上部。
这些发现可用于肩部损伤康复的运动设计、方法和设备的开发。
