Effects of upper body static deep flexion on spinal stability

描述（由申请人提供）：已知长时间保持深上身前屈姿势（弯腰姿势）有助于发生或发展与工作相关的下背部肌肉骨骼疾病，但其损伤机制和风险评估尚未得到充分研究。现有文献提出，静态深屈时脊柱组织的长时间拉伸可导致脊柱稳定性受损，原因是脊柱松弛和下背部伸肌被动产生疲劳，使下背部容易发生肌肉骨骼疾病。该提案的主要目的是量化静态屈曲对脊柱稳定性的影响，特别考虑脊柱松弛和下背部伸肌疲劳发展作为脊柱稳定性受损的中间因素。将在两年内进行一项实验室体内实验，通过获得反复静态屈曲之前、期间和之后的下背部的相关生物力学响应，定量评估脊柱松弛、下背部伸肌疲劳和脊柱稳定性的变化。将测试三种不同的重复静态屈曲模式（工作-休息时间表）。本项目的成功完成将产生关于伤害机制和风险评估的重要信息，并将促进进一步的研究项目，以实现制定伤害预防策略的长期目标，以减少与工作有关的腰部肌肉骨骼疾病的风险。拟议的工作涉及几个诺拉部门计划和跨部门计划，包括暴露评估和肌肉骨骼疾病计划。 公共卫生相关性：在一段时间内保持弯腰或上身深屈姿势对下背部来说是一种有问题的工作活动。本项目旨在通过量化不同负荷模式下静态屈曲对脊柱稳定性的影响，更好地了解与上肢静态深屈曲相关的工作相关的下背部肌肉骨骼疾病的损伤机制，并探索定量评估静态屈曲相关风险的方法。

DESCRIPTION (provided by applicant): Maintaining a deep upper body forward flexion posture (stooped posture) for a prolonged period of time has been known to contribute to the occurrence or development of work-related low back musculoskeletal disorders, but its injury mechanisms and risk assessment have not been adequately studied. Existing literature proposes that prolonged stretching of spinal tissues in static deep flexion can cause impairment in spinal stability due to laxity in the spine and passively developed fatigue in low back extensor muscles, placing the low back vulnerable to musculoskeletal disorders. The primary objective of this proposal is to quantify the effects of static flexion on spinal stability, with specific consideration of spinal laxity and fatigue development in the low back extensor muscles as intermediate factors to the impairment in the spinal stability. A laboratory in vivo experiment will be conducted in two years to quantitatively evaluate the changes in spinal laxity, fatigue in the low back extensor muscles, and spinal stability by obtaining relevant biomechanical responses of the low back before, periodically during and after a period of repetitive static flexion. Three different patterns (work-rest schedule) of repetitive static flexion will be tested. Successful completion of this project will produce important information on the mechanism of injury and risk assessment, and will facilitate further research projects towards a long-term goal of developing injury prevention strategies to reduce the risk of work-related low back musculoskeletal disorders. The proposed work addresses several NORA sector programs and cross-sector programs including Exposure Assessment and Musculoskeletal Disorders programs. PUBLIC HEALTH RELEVANCE: Maintaining a stooped or a upper body deep flexion posture for a period of time is a problematic work activity for low back. This project is aimed at providing a better understanding of an injury mechanism of work-related low back musculoskeletal disorders associated with upper body static deep flexion, and exploring a method to quantitatively assess the static flexion-related risks by quantifying the effects of static flexion on spinal stability under various loading patterns.