Shojaei Iman, Nussbaum Maury A, Bazrgari Babak
F. Joseph Halcomb III, M.D. Department of Biomedical Engineering, University of Kentucky, Lexington, KY 40506, USA.
Department of Industrial and Systems Engineering, Virginia Tech, Blacksburg, VA 24061, USA.
J Biomech. 2016 Oct 3;49(14):3147-3152. doi: 10.1016/j.jbiomech.2016.07.022. Epub 2016 Jul 27.
Reports of larger passive and similar intrinsic trunk stiffness in older vs. younger populations suggest a diminishing demand for reflexive contributions of trunk muscles to spinal stability with aging. It remains unclear, though, whether such diminishing demands result in deterioration of trunk muscle reflexive behaviors. A cross-sectional study was completed to assess age-related differences in the latency and likelihood of trunk muscle reflexive responses to sudden perturbations. Sixty healthy individuals, aged 20-70 years, were recruited to form five equal-sized and gender-balanced age groups. Using a displacement-control, sudden perturbation paradigm, the latency and likelihood of trunk muscle reflexive responses to sudden perturbations were estimated, and the influences of age, gender, and level of effort (20% versus 30% of maximum voluntary exertion-MVE) were evaluated. There were no consistent age-related differences found in any of the measures of trunk muscle reflexive behavior. However, the latency of muscle response to perturbation was generally higher among older individuals, and this difference was significant in the condition involving 30% MVE effort. With an increase in level of effort (from 20% to 30% of MVE), there was a ~7% increase in the latency of trunk muscle responses to anteriorly-directed perturbations as well as ~ 15% (21%) decrease (increase) in response likelihood during anteriorly (posteriorly) directed perturbations. Furthermore, the reflexive response likelihood of trunk muscles was 28% (58%) larger (smaller) in female vs. male participants during anteriorly (posteriorly) directed perturbations. Our results did not, in general, support the hypothesis of an age-related decay in reflexive trunk muscle behaviors. Larger reflexive responses were associated with lower trunk intrinsic stiffness among females and during a lower level of effort, suggesting a secondary role for reflexive responses in spinal stability. Such secondary compensatory responses appear, however, to be consistent over a wide age range.
与年轻人群相比，老年人群被动躯干刚度更大、内在躯干刚度相似，这表明随着年龄增长，躯干肌肉对脊柱稳定性的反射性贡献需求在减少。然而，目前尚不清楚这种需求减少是否会导致躯干肌肉反射行为的恶化。本研究完成了一项横断面研究，以评估躯干肌肉对突然扰动的反射反应潜伏期和可能性的年龄相关差异。招募了60名年龄在20至70岁之间的健康个体，组成五个规模相等且性别均衡的年龄组。采用位移控制的突然扰动范式，估计躯干肌肉对突然扰动的反射反应潜伏期和可能性，并评估年龄、性别和用力水平（最大自主用力的20%与30%）的影响。在躯干肌肉反射行为的任何测量中均未发现一致的年龄相关差异。然而，老年人中肌肉对扰动的反应潜伏期通常较高，且在30%最大自主用力的情况下，这种差异具有统计学意义。随着用力水平的增加（从最大自主用力的20%增加到30%），躯干肌肉对向前扰动的反应潜伏期增加约7%，而在向前（向后）扰动期间反应可能性降低约15%（增加21%）。此外，在向前（向后）扰动期间，女性参与者的躯干肌肉反射反应可能性比男性参与者大28%（小58%）。总体而言，我们的结果不支持反射性躯干肌肉行为随年龄衰退的假设。较大的反射反应与女性较低的躯干固有刚度以及较低的用力水平相关，这表明反射反应在脊柱稳定性中起次要作用。然而，这种次要的代偿反应在较宽的年龄范围内似乎是一致的。
