van den Hoorn Wolbert, Cholewicki Jacek, Coppieters Michel W, Klyne David M, Hodges Paul W
The University of Queensland, NHMRC Centre of Clinical Research Excellence in Spinal Pain, Injury & Health, School of Health and Rehabilitation Sciences, Australia.
Center for Orthopedic Research, Department of Osteopathic Surgical Specialties, Michigan State University College of Osteopathic Medicine, MI, USA.
J Biomech. 2020 Nov 9;112:110053. doi: 10.1016/j.jbiomech.2020.110053. Epub 2020 Sep 28.
Movement adaptations to low back pain (LBP) are believed to protect the painful area. Increased trunk stiffness and decreased trunk damping have been shown in people with recurrent LBP. However, no study has examined these properties using external force perturbations to the trunk during acute LBP when protective adaptations might be expected to have most relevance. Adaptations to an acute painful stimulus via unilateral injection of hypertonic saline into the right longissimus muscle were assessed using a trunk force perturbation paradigm and a mass-spring-damper model to describe effective trunk dynamical properties. Equal weights (15% body weight) were connected to the front and back of the trunk via a cable. Either one was dropped at random to perturb the trunk. Effective trunk dynamical properties were estimated in fourteen males (mean (standard deviation) age 25 (6) years) assuming that trunk movement can be modelled as a second order linear system. Effective trunk dynamical properties were compared before, during and after the experimentally induced painful period. Estimates of effective trunk stiffness (K) decreased and damping (B) increased during pain compared to both before ([mean contrast, 95% CI] K: -403 [-651 to -155] Nm, B: 28 [9-50] Nms) and after (K: -324 [-58 to -591] Nm, B: 20 [4-33] Nms) the experimentally induced painful period. We interpret our results to show that, when challenged by a step force perturbation, a healthy system adapts to noxious input by controlling trunk velocity rather than trunk displacement, in contrast to observations during remission from recurrent clinical LBP.
人们认为，针对下背痛（LBP）的运动适应性变化是为了保护疼痛区域。复发性下背痛患者的躯干僵硬度增加，躯干阻尼减小。然而，尚无研究在急性下背痛期间使用外力干扰躯干来检验这些特性，而在急性下背痛期间，保护性适应可能最为相关。通过向右侧最长肌单侧注射高渗盐水来评估对急性疼痛刺激的适应性变化，使用躯干力扰动范式和质量-弹簧-阻尼模型来描述有效的躯干动力学特性。通过电缆将同等重量（体重的15%）连接到躯干的前后。随机掉落其中一个，以干扰躯干。假定躯干运动可建模为二阶线性系统，在14名男性（平均（标准差）年龄25（6）岁）中估计有效的躯干动力学特性。在实验诱导的疼痛期之前、期间和之后比较有效的躯干动力学特性。与实验诱导的疼痛期之前（[平均对比，95%CI]K：-403[-651至-155]Nm，B：28[9-50]Nms）和之后（K：-324[-58至-591]Nm，B：20[4-33]Nms）相比，疼痛期间有效的躯干僵硬度（K）降低，阻尼（B）增加。我们对结果的解释是，当受到阶跃力扰动挑战时，与复发性临床下背痛缓解期的观察结果相反，健康系统通过控制躯干速度而非躯干位移来适应有害输入。
