Granata K P, Gottipati P
Department of Engineering Science & Mechanics, The Kevin P. Granata Musculoskeletal Biomechanics Lab, Virginia Polytechnic Institute & State University, Blacksburg, VA 24061, USA.
Ergonomics. 2008 Aug;51(8):1258-71. doi: 10.1080/00140130802030722.
Fatigue in the extensor muscles of the torso affects neuromuscular recruitment and control of the spine. The goal of this study was to test whether fatigue influences stability of dynamic torso movements. A controlled laboratory experiment measured the change in the maximum finite-time Lyapunov exponent, lambda(max), before and after fatigue of the extensor muscles. Non-linear analyses were used to compute stability from the embedding dimension and Lyapunov exponent recorded during repetitive dynamic trunk flexion tasks. Torso extensor muscles were fatigued to 60% of their unfatigued isometric maximum voluntary exertion force then stability was re-measured. Independent variables included fatigue, task asymmetry and lower-limb constraint. lambda(max) values increased with fatigue suggesting poorer dynamic stability when fatigued. Embedding dimension declined with fatigue indicating reduced dynamic complexity when fatigued. Fatigue-related changes in spinal stability may contribute to the risk of low-back injury during fatiguing occupational lifting tasks. The findings reported here indicate that one mechanism by which fatigue contributes to low back disorders may be spinal instability. This information may contribute to the development of ergonomic countermeasures to help prevent low back disorders.
躯干伸肌疲劳会影响神经肌肉的募集以及脊柱的控制。本研究的目的是测试疲劳是否会影响动态躯干运动的稳定性。一项对照实验室实验测量了伸肌疲劳前后最大有限时间李雅普诺夫指数λ(max)的变化。使用非线性分析从重复动态躯干屈曲任务期间记录的嵌入维度和李雅普诺夫指数计算稳定性。将躯干伸肌疲劳至其未疲劳时等长最大自主用力的60%，然后重新测量稳定性。自变量包括疲劳、任务不对称性和下肢限制。λ(max)值随疲劳增加，表明疲劳时动态稳定性较差。嵌入维度随疲劳下降，表明疲劳时动态复杂性降低。脊柱稳定性与疲劳相关的变化可能会增加疲劳性职业举重任务期间下背部受伤的风险。此处报告的研究结果表明，疲劳导致下背部疾病的一种机制可能是脊柱不稳定。这些信息可能有助于开发有助于预防下背部疾病的人体工程学对策。
