Department of Kinesiology, University of Waterloo, Waterloo, Canada.
Ergonomics. 2020 Jan;63(1):101-108. doi: 10.1080/00140139.2019.1677944. Epub 2019 Oct 15.
Cervical spine flexion is a common posture for those using computers, tablets, and smartphones; the latter being dubbed 'text-neck' in recent years. Coincidentally, flexion has been flagged as a significant mechanical risk factor for the development of chronic neck pain. Unfortunately, few modelling endeavours have attempted to quantify the intervertebral joint loads throughout the cervical spine in flexion, while still accounting for muscular activation. Eight healthy male subjects undertook five trials beginning in a neutral posture, flexed to 45 degrees, and returned to a neutral posture. 3 D head-trunk angles and surface electromyography from 10 neck muscles (5 bilaterally) were used as inputs into an inverse dynamic cervical spine model based on a 50th percentile male to compute the compression and anteroposterior (AP) shear forces for this flexion task. In general, compression increases cranially to caudally throughout the cervical spine, but levels off at the C5-C6 level. Conversely, in a neutral posture, there is a constant 18 N of anterior shear at each joint level. Compression increased twofold throughout the cervical spine with flexion, whereas anterior shear increased fourfold in the upper cervical spine and dramatically decreased caudally. The dramatic change in joint kinetics provides some mechanical evidence for the role of posture and interplay with muscle activity in the development of chronic neck pain. Results from this study can reinforce the need for appropriate workstation and monitor configurations and support the increased loading hypothesised to occur in 'text neck' postures. The purpose of this investigation was to quantify the compression and shear forces in the neck in 45 degrees of flexion compared to neutral. Flexion increased compression throughout the cervical spine 1.6-fold compared to a neutral posture. In the upper cervical spine, AP-shear increased four-fold compared to neutral. AP: anteroposterior.
颈椎前屈是使用电脑、平板电脑和智能手机人群的常见姿势；近年来，人们将后者戏称为“短信脖”。巧合的是，颈椎前屈已被标记为慢性颈痛发展的一个重要机械危险因素。然而，很少有研究试图量化颈椎前屈时整个颈椎的椎间关节负荷，同时还要考虑肌肉激活的情况。8 名健康男性受试者进行了 5 次试验，起始姿势为中立位，前屈至 45 度，然后回到中立位。将 3D 头身角度和 10 块颈部肌肉（每侧 5 块）的表面肌电图作为输入，输入到基于 50 百分位男性的颈椎逆向动力学模型，以计算该前屈任务的压缩力和前-后向（AP）剪切力。一般来说，颈椎的压缩力从前到后逐渐增加，但在 C5-C6 水平趋于平稳。相反，在中立位，每个关节水平都有恒定的 18N 前向剪切力。颈椎前屈时，整个颈椎的压缩力增加了两倍，而上颈椎的前向剪切力增加了四倍，在颈椎下部急剧下降。关节动力学的显著变化为姿势的作用以及与肌肉活动的相互作用在慢性颈痛发展中的作用提供了一些力学证据。本研究的结果可以加强对适当工作场所和显示器配置的需求，并支持“短信脖”姿势下增加的负荷假设。本研究旨在比较 45 度前屈与中立位时颈部的压缩力和剪切力。与中立位相比，颈椎前屈时整个颈椎的压缩力增加了 1.6 倍。在上颈椎，AP 剪切力增加了四倍。AP：前-后向。
