Kim Kyungsoo, Kim Yoon Hyuk
Institute of Natural Sciences, Kyung Hee University, Yongin-si, Gyeonggi-do 446-701, Korea.
J Biomech Eng. 2008 Aug;130(4):041005. doi: 10.1115/1.2907739.
Recently, experimental results have demonstrated that the load carrying capacity of the human spine substantially increases under the follower load condition. Thus, it is essential to prove that a follower load can be generated in vivo by activating the appropriate muscles in order to demonstrate the possibility that the stability of the spinal column could be maintained through a follower load mechanism. The aim of this study was to analyze the coordination of the trunk muscles in order to understand the role of the muscles in generating the follower load. A three-dimensional finite element model of the lumbar spine was developed from T12 to S1 and 117 pairs of trunk muscles (58 pairs of superficial muscles and 59 pairs of deep muscles) were considered. The follower load concept was mathematically represented as an optimization problem. The muscle forces required to generate the follower load were predicted by solving the optimization problem. The corresponding displacements and rotations at all nodes were estimated along with the follower forces, shear forces, and joint moments acting on those nodes. In addition, the muscle forces and the corresponding responses were investigated when the activations of the deep muscles or the superficial muscles were restricted to 75% of the maximum activation, respectively. Significantly larger numbers of deep muscles were involved in the generation of the follower load than the number of superficial muscles, regardless of the restriction on muscle activation. The shear force and the resultant joint moment are more influenced by the change in muscle activation in the superficial muscles. A larger number of deep trunk muscles were activated in order to maintain the spinal posture in the lumbar spine. In addition, the deep muscles have a larger capability to reduce the shear force and the resultant joint moment with respect to the perturbation of the external load or muscle fatigue compared to the superficial muscles.
最近，实验结果表明，在随动载荷条件下，人体脊柱的承载能力会大幅增加。因此，有必要证明通过激活适当的肌肉可以在体内产生随动载荷，以便证明通过随动载荷机制维持脊柱稳定性的可能性。本研究的目的是分析躯干肌肉的协调性，以了解肌肉在产生随动载荷中的作用。建立了从T12到S1的腰椎三维有限元模型，并考虑了117对躯干肌肉（58对浅层肌肉和59对深层肌肉）。随动载荷概念在数学上被表示为一个优化问题。通过求解优化问题来预测产生随动载荷所需的肌肉力。估计所有节点处的相应位移和旋转，以及作用在这些节点上的随动力、剪切力和关节力矩。此外，分别将深层肌肉或浅层肌肉的激活限制在最大激活的75%时，研究了肌肉力和相应的反应。无论肌肉激活的限制如何，参与产生随动载荷的深层肌肉数量都明显多于浅层肌肉。剪切力和合成关节力矩受浅层肌肉激活变化的影响更大。为了维持腰椎的脊柱姿势，更多的深层躯干肌肉被激活。此外，与浅层肌肉相比，深层肌肉在抵抗外部载荷扰动或肌肉疲劳方面具有更大的降低剪切力和合成关节力矩的能力。
