STABILITY OF MUSCULAR LOADING OF THE LUMBAR SPINE

肌肉刚度和脊柱运动节段刚度的结合可以保护腰椎免受屈曲不稳定的可能性。 这是一个应用程序，以支持继续研究（R 01 AR 44119）分析和量化肌肉刚度的程度，所需的稳定性在各种负荷条件和脊柱姿势。 以前的分析预测，拮抗性肌肉激活将增加稳定性，并且这种拮抗活性的存在已经在记录肌肉激活肌电图的实验研究中得到证实。 总的假设是，受损的肌肉控制可能使腰椎易受伤害屈曲事件。建议的后续研究将集中在四个主要领域的工作：（1）人体实验，以表征在逐渐增加的努力和扰动负荷条件下的肌肉激活模式，并测量躯干的驱动点刚度，由此推断在不同激活条件下的肌肉刚度;（2）在轴向压缩载荷和周围流体介质的生理条件下，腰椎运动节段（有和没有完整的后部元件）的刚度的实验量化。 （3）这些实验的模拟将使用新的分析模型进行，该模型计算优化五个成本函数分量的可变组合所需的肌肉激活模式，所述五个成本函数分量即脊柱的整体运动、椎间位移、椎间运动节段的载荷、立方肌肉应力和稳定性的总和（通过系统刚度的特征值的大小）。 一些来自人体主体和运动片段研究的实验数据将被用来为模型中的参数赋值，其他数据将被用来验证模型。(4)对间歇性腰痛患者肌肉功能的纵向研究将表明这些人是否具有有助于脊柱不稳定的肌肉激活行为。这些研究将有助于确定肌肉刚度和脊柱刚度在稳定脊柱中的相对作用。他们将确定（1）运动节段刚度降低，（2）肌肉刚度降低或（3）肌肉募集异常模式可能使腰椎在明显良性外部负荷条件下处于自我伤害屈曲发作风险的条件。 此外，个别肌肉的具体作用将得到更好的阐明，这将有助于指导治疗腰痛功能障碍的人。

A combination of muscle stiffness and spinal motion segment stiffness protect the lumbar spine against the possibility of buckling instabilities. This is an application to support continued research (of R01 AR 44119) analyzing and quantifying the degree of muscle stiffness required for stability under a variety of loading conditions and spinal postures. Previous analyses have predicted that antagonistic muscle activation would increase stability, and the existence of such antagonistic activity has been confirmed in experimental studies documenting muscle activation electromyographically. The overall hypothesis is that impaired muscular control might predispose the lumbar spine to injurious buckling episodes. The proposed continuation studies will focus on four main areas of work: (1) human subject experiments to characterize muscle activation patterns under gradually increasing efforts and under perturbed loading conditions, and to measure driving point stiffness of the trunk, from which muscle stiffness will be deduced under differing activation conditions; (2) Experimental quantification of the stiffness of lumbar spinal motion segments (with and without intact posterior elements) under physiological conditions of axial compressive loading and surrounding fluid medium. (3 Simulations of these experiments will be performed using a new analytical model which calculates the muscle activation pattern required to optimize a variable combination of five cost function components, namely the global motion of the spine, intervertebral displacements, loading of intervertebral motion segments, the sum of cubed muscle stress and stability (via the magnitude of eigenvalues of the system stiffness). Some of the experimental data from human subject and motion segment studies will be used to assign values to parameters in the model, other data will be used to validate the model. (4) Longitudinal studies of muscle function in subjects with intermittent low back pain will indicate whether these individuals have muscle activation behaviors conducive to spinal instability. These studies will help to define the relative roles of muscle stiffness and spinal stiffness in stabilizing the spinal column. They will identify the conditions under which (1) reduced motion segment stiffness, (2) reduced muscular stiffness or (3) abnormal patterns of muscle recruitment might place the lumbar spine at risk for self-injurious buckling episodes under apparently benign external loading conditions. In addition, the specific roles of individual muscles will be better elucidated, which will be helpful in guiding therapy for people with low back dysfunction.