Nieminen H, Niemi J, Takala E P, Viikari-Juntura E
Technical Research Centre of Finland, Medical Engineering Laboratory, Tampere.
J Biomech. 1995 May;28(5):555-66. doi: 10.1016/0021-9290(94)00107-f.
Patterns of load-sharing between the shoulder muscles during isometric flexion tasks were studied by using both a biomechanical shoulder model and electromyographic (EMG) recordings of ten subjects. The effect of changes in several model parameters and shoulder stiffness constraints on the predicted load-sharing patterns were studied, while the arm position, hand load and precision requirements of the tasks were varied. The results calculated using the model were, when compared to the EMG recordings, plausible predicting a high level of synergistic contraction of muscles of the shoulder muscles during flexion tasks. The trends of the model-predicted muscle forces corresponded well to the EMG recordings. At low hand load levels the increasing of the shoulder stiffness strongly increased the muscle force levels, thus increasing also the level of synergistic contraction of muscles. At higher load levels the increase in the muscle forces was not so high, because the model predicted a high level of simultaneous contraction of muscles already at a low level of shoulder stiffness. Cluster analysis of the EMG recordings revealed large inter-individual differences in the load distribution patterns during flexion tasks. The constraint angle of the glenohumeral joint contact force direction was found to be an important model parameter affecting both the predicted forces and the maximum force production ability of the shoulder.
通过使用生物力学肩部模型和对十名受试者的肌电图（EMG）记录，研究了等长屈曲任务期间肩部肌肉之间的负荷分担模式。研究了几个模型参数的变化以及肩部刚度约束对预测的负荷分担模式的影响，同时改变了手臂位置、手部负荷和任务的精度要求。与肌电图记录相比，使用该模型计算出的结果合理地预测了屈曲任务期间肩部肌肉的高水平协同收缩。模型预测的肌肉力量趋势与肌电图记录非常吻合。在低手部负荷水平下，肩部刚度的增加强烈增加了肌肉力量水平，从而也增加了肌肉的协同收缩水平。在较高负荷水平下，肌肉力量的增加没有那么高，因为该模型预测在低肩部刚度水平时肌肉已经处于高水平的同时收缩。肌电图记录的聚类分析揭示了屈曲任务期间负荷分布模式存在较大的个体差异。发现盂肱关节接触力方向的约束角度是一个重要的模型参数，它既影响预测的力量，也影响肩部的最大力量产生能力。
