F. Joseph Halcomb III, M.D. Department of Biomedical Engineering, University of Kentucky, Lexington, KY 40506, USA.
Department of Human Movement Sciences, Faculty of Behavioural and Movement Sciences, Amsterdam Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands.
J Biomech. 2018 Aug 22;77:163-170. doi: 10.1016/j.jbiomech.2018.07.005. Epub 2018 Jul 20.
The contribution of the trunk neuromuscular system (TNS) to spine stability has been shown in earlier studies by characterizing changes in antagonistic activity of trunk muscles following alterations in stability demands of a task. Whether and/or how much such changes in the response of TNS to alteration in stability demand of the task alter spinal stiffness remains unclear. To address this research gap, a repeated measure study was conducted on twenty gender-balanced asymptomatic individuals to evaluate changes in trunk bending stiffness throughout the lumbar spine's range of flexion following alterations in both stability and equilibrium demands of a load holding task. Trunk bending stiffness was determined using trunk stiffness tests in upright posture on a rigid metal frame under different equilibrium and stability demands on the lower back. Increasing the stability demand by increasing the height of lifted load ∼30 cm only increased trunk bending stiffness (∼39%) over the lower range of lumbar flexion and under the low equilibrium demand condition. Similarly, increasing the equilibrium demand of the task by increasing the weight of lifted load by 3.5 kg only increased trunk bending stiffness (55%) over the low range of lumbar flexion and under the low stability demand condition. Our results suggest a non-linear relationship between changes in stability and equilibrium demands of a task and the contribution of TNS to trunk bending stiffness. Specifically, alterations in TNS response to changes in stability and equilibrium demand of a given task will increase stiffness of the trunk only if the background stiffness is low.
躯干神经肌肉系统（TNS）对脊柱稳定性的贡献在早期研究中已经得到了证实，这些研究通过描述在任务稳定性需求发生变化时，躯干肌肉拮抗活动的变化来实现。TNS 对任务稳定性需求变化的反应是否以及在多大程度上改变了脊柱的刚度尚不清楚。为了解决这一研究空白，对 20 名性别均衡的无症状个体进行了一项重复测量研究，以评估在保持负载任务的稳定性和平衡需求发生变化时，整个腰椎前屈范围的躯干弯曲刚度的变化。使用刚性金属框架上直立姿势的躯干刚度测试，在不同的下背部平衡和稳定性需求下，确定躯干弯曲刚度。仅通过增加举起的负载的高度（约 30 厘米）来增加稳定性需求，仅在腰椎前屈的较低范围内和低平衡需求条件下增加了躯干弯曲刚度（约 39%）。同样，仅通过增加举起的负载重量（3.5 公斤）来增加任务的平衡需求，仅在腰椎前屈的低范围和低稳定性需求条件下增加了躯干弯曲刚度（55%）。我们的结果表明，任务的稳定性和平衡需求的变化与 TNS 对躯干弯曲刚度的贡献之间存在非线性关系。具体来说，只有在背景刚度较低的情况下，TNS 对给定任务的稳定性和平衡需求变化的反应改变才会增加躯干的刚度。
