Parkinson Robert J, Beach Tyson A C, Callaghan Jack P
Department of Kinesiology, Faculty of Applied Health Sciences, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1.
Clin Biomech (Bristol). 2004 May;19(4):330-6. doi: 10.1016/j.clinbiomech.2004.01.002.
To quantify the time-varying stiffness and kinematic responses of the in vivo lumbar spine exposed to dynamic repetitive flexion movements.
Changes in in vivo passive lumbar moment-angle relationships were monitored in response to dynamic repetitive flexion.
While previous in vitro studies have provided conflicting evidence on the effects of repetitive flexion movements on the stiffness of the lumbar spine, no previous studies have quantified the time-varying changes of the in vivo lumbar spine to dynamic repetitive flexion.
Subjects lifted and lowered a 4.5 kg load over two barriers at a rate of 7 lifts per minute for 1.5 h inducing at least 80% of the lumbar flexion range of motion. Prior to lifting and at 30 min intervals passive moment-angle relationships were obtained by pulling the subject into flexion on a customized frictionless table.
Repetitive lifting induced a decreasing stiffness trend after 30 min, followed by a recovery towards initial stiffness levels with further loading. The trends were non-significant for all measures studied.
The results indicate that after 30 min of lifting, creep within the passive tissues may allow workers to exceed their initial range of motion, altering joint mechanics and loading patterns potentially leading to an increased risk of developing low back pain.
Given the potential for time-varying changes to alter the spine's risk of injury and injury mechanisms, knowledge regarding the stiffness response of the in vivo lumbar spine exposed to repetitive flexion may lead to improved understanding and prevention of work related back pain.
量化体内腰椎在动态重复屈曲运动下随时间变化的刚度和运动学反应。
监测体内被动腰椎力矩-角度关系在动态重复屈曲时的变化。
虽然先前的体外研究对于重复屈曲运动对腰椎刚度的影响提供了相互矛盾的证据，但此前尚无研究对体内腰椎在动态重复屈曲时随时间变化的情况进行量化。
受试者以每分钟7次的速率在两个障碍物之间提起和放下一个4.5千克的重物，持续1.5小时，诱导出至少80%的腰椎屈伸活动范围。在提起重物之前以及每隔30分钟，通过在定制的无摩擦桌子上拉动受试者使其屈曲来获取被动力矩-角度关系。
重复提起重物30分钟后，刚度呈现下降趋势，随后随着进一步加载又恢复到初始刚度水平。所有研究指标的这些趋势均无统计学意义。
结果表明，提起重物30分钟后，被动组织内的蠕变可能使劳动者超出其初始活动范围，改变关节力学和负荷模式，这可能会增加患下背痛的风险。
鉴于随时间变化的改变可能会改变脊柱的受伤风险和损伤机制，了解体内腰椎在重复屈曲时的刚度反应可能有助于更好地理解和预防与工作相关的背痛。
