Biomechanical Effects of Industrial Eccentric Exertions

描述：本研究研究了工业动力手工具操作中重复性偏心动作对肌肉和肌腱生物力学特性的影响，以便更好地了解与工作相关的肌肉骨骼疾病的病因和预防。假设电动工具反作用力和建立时间的增加与上肢动力特性的更大变化相对应。基于实验室的实验将定义重复偏心动作（即反作用力大小和建立时间）与上肢特性（即刚度、粘性阻尼和惯性质量）之间的短期关系。受试者将反复抵抗前臂旋向电机，以模拟手枪握力手工具操作的偏心用力水平。峰值扭矩水平和积累时间将实验控制。前臂的机械性能将在一段时间工作之前和之后测量。机械参数将使用一种独特的装置来确定，该装置将前臂建模为单自由度动态机械系统，当受试者使用最大的努力来反对其运动时，通过测量自由振荡中已知机械系统的扰动的角位移来确定机械参数。我们的初步数据显示，当在相似强度水平下偏心运动时，观察到显著的刚度和惯性质量变化。血液肌酸激酶（CK）的生化测量和前臂MRI T2变化的解剖学测量将与随机选取的受试者在重复偏心运动之前和之后的生物力学参数进行比较。主观不适将使用视觉模拟量表进行评估，前臂水肿和力量也将被测量。第二个实验将评估工业工人的上肢生物力学特性，这些工人经常在选定的工业工作中进行不同强度、积累时间和重复率的重复性偏心动作。受试者将从当地汽车装配线的工具操作岗位招聘。这项研究最终可以通过定量的手动工具设计指南和工作实践来实现更好的人体工程学干预，这些指南和实践基于对暴露于特定水平的反作用力、积累时间和重复的破坏性影响的理解，并为流行病学研究提供新的结果测量方法。

DESCRIPTION: This research studies the effects of repetitive eccentric exertions in industrial power hand tool operation on biomechanical properties of muscle and tendon in order to better understand the etiology and prevention of work related musculoskeletal disorders. It is hypothesized that increased power tool reaction force and build-up time corresponds with greater changes in the dymanic characteristics of the upper limb. A laboratory-based experiment will define the short-term relationship between repetitive eccentric exertions (i.e. reaction force magnitude and build-up time) and upper limb properties (i.e. stiffness, viscous damping and inertial mass). Subjects will repetitively resist forearm supination against a motor for simulating eccentric exertion levels representative of pistol grip power hand tool operation. Peak torque levels and build-up time will be experimentally controlled. Forearm mechanical properties will be measured before and following a period of work. Mechanical parameters will be ascertained using a unique apparatus that models the forearm as a single degree-of-freedom dynamic mechanical system by measuring the angular displacement of a disturbance to a known mechanical system in free oscillation when the subject uses maximal effort to oppose its motion. Our preliminary data reveals that significant stiffness and inertial mass changes are observed when exercising eccentrically at similar intensity levels. Biochemical measures of blood creatine kinase (CK), and anatomical measures using T2 changes in an MRI of the forearms will be compared with biomechanical parameters prior to, and following repetitive eccentric exertions for a random subset of the subjects. Subjective discomfort will be assessed using a visual analog scale, and forearm edema and strength will also be measured. The second experiment will assess similar upper limb biomechanical properties for industrial workers who regularly perform repetitive eccentric exertions of varying intensity, build-up time and repetition rate in selected industrial jobs. Subjects will be recruited from tool operation jobs on a local automobile assembly line. This research can ultimately lead to better ergonomic interventions through quantitative power hand tool design guidelines and work practices based on understanding the damaging effects of exposure to specific levels of reaction force, build-up time and repetition, as well as providing new outcome measures for epidemiological studies.