Kang Sang Hyeon, Mirka Gary A
The Physical Ergonomics and Biomechanics Laboratory, Department of Industrial and Manufacturing Systems Engineering, Iowa State University, Ames, IA, USA; Human Performance Institute, Department of Industrial and Entrepreneurial Engineering and Engineering Management, Western Michigan University, Kalamazoo, MI, USA.
The Physical Ergonomics and Biomechanics Laboratory, Department of Industrial and Manufacturing Systems Engineering, Iowa State University, Ames, IA, USA.
J Biomech. 2025 May;184:112675. doi: 10.1016/j.jbiomech.2025.112675. Epub 2025 Apr 1.
In-vivo human experiments have previously shown significant effects of trunk flexion angle and exposure-recovery schedule on the creep response of the viscoelastic tissues of the lumbar spine. In the current study we explore the effects of trunk flexion, exposure-recovery schedules, and lumbar flexibility on this creep response. Sixteen participants, categorized into two groups based on lumbar flexibility (GROUP: low-flexible, high-flexible), performed four 30-minute protocols consisting of alternating periods of trunk flexion (exposure) and periods of upright standing (recovery). On four different days, combinations of two trunk flexion postures (POSTURE: Max, SubMax) and two exposure-recovery schedules (ER: Long (3 min:6 min), Short (1 min:2 min)) were tested. Trunk flexion-extension motions were performed before/after the 30-minute protocol to capture the changes in peak lumbar flexion angles and changes in the angles of flexion-relaxation in L3/L4 paraspinals that resulted from the protocols. The analysis of lumbar flexibility showed that the low-flexible group had significantly greater changes in the L4 flexion-relaxation angle in the Max posture (Δ2.2°) than in the SubMax posture (Δ1.0°), while the high-flexible group showed no POSTURE effect, indicating a POSTURE × GROUP interaction. In addition, the high-flexible group exhibited greater creep responses in the Short (1:2) condition (Δ2.5°) than in the Long (3:6) condition (Δ0.6°) while the low-flexible group showed no ER effect, denoting an ER × GROUP interaction. Collectively, these results support the complex, multi-dimensional nature of viscoelastic creep responses, and particularly note the impact of an individual's lumbar flexibility in these responses.
此前的人体体内实验已表明，躯干屈曲角度和暴露-恢复时间表对腰椎粘弹性组织的蠕变反应有显著影响。在本研究中，我们探究了躯干屈曲、暴露-恢复时间表和腰椎柔韧性对这种蠕变反应的影响。16名参与者根据腰椎柔韧性分为两组（组别：低柔韧性组、高柔韧性组），进行了四个30分钟的实验方案，包括交替进行的躯干屈曲期（暴露）和直立站立期（恢复）。在四个不同的日子里，测试了两种躯干屈曲姿势（姿势：最大屈曲、次最大屈曲）和两种暴露-恢复时间表（暴露-恢复：长时（3分钟：6分钟）、短时（1分钟：2分钟））的组合。在30分钟实验方案前后进行躯干屈伸运动，以记录由实验方案导致的腰椎最大屈曲角度变化以及L3/L4椎旁肌屈曲-放松角度变化。腰椎柔韧性分析表明，低柔韧性组在最大屈曲姿势下L4屈曲-放松角度的变化（Δ2.2°）显著大于次最大屈曲姿势下的变化（Δ1.0°），而高柔韧性组未显示出姿势效应，表明存在姿势×组别交互作用。此外，高柔韧性组在短时（1:2）条件下的蠕变反应（Δ2.5°）大于长时（3:6）条件下的反应（Δ0.6°），而低柔韧性组未显示出暴露-恢复效应，表明存在暴露-恢复×组别交互作用。总体而言，这些结果支持了粘弹性蠕变反应的复杂多维性质，尤其指出了个体腰椎柔韧性对这些反应的影响。
