Effect of reduced force requirements on neuromuscular inputs and movement patterns in manual materials handling tasks

起重是人工搬运材料作业中最常见的任务之一，也是最常报告的受伤原因。机械式脱体起重辅助设备(即提升机或手推车)减少关节负荷并提高效率，特别是在举起和移动重物以及操纵超出人的能力范围的笨重物品时。然而，当负载在人类举起能力范围内时，工人有手动举升的趋势，因为大多数机械提升机和起重设备无法快速操作，迫使工人放慢速度。尽管一个解决方案是使脱体举重辅助更快，另一种解决方案是设计身体上的举重辅助装置。这项申请的目的是检查一种新的动态的身体上的个人举重辅助装置(PLAD)对躯干和腿部肌肉活动和脊柱上的力和力矩的安全性和有效性，以及在手工搬运材料任务中由此产生的运动模式。更具体地说，我特别感兴趣的是工人在佩戴动态辅助装置时如何举起负荷，以及它是否安全有效地使用。为了实现这一目标，将有四项研究。第一项研究将从以下方面考察不使用符合人体工程学的起重辅助装置(NO-PLAD)和佩戴动态举起辅助装置(PLAD)对脊柱累积载荷的影响：a)对L4/L5节段累积力矩的影响；B)在幅度和频率域中处理的累积肌电；c)设备导致的技术变化；d)从抬起开始到结束时受试者之间抬起技术的变化；以及e)主观和心率条件的差异。第二项研究将考察PLAD在不同躯干姿势角度和不同弹性元素张力的静态握持和动态任务中对躯干稳定性的影响。在第三项研究中，男性和女性将重复这些实验，以确定性别的差异影响。最终的研究将确定这种动态辅助设备在工业环境中佩戴八周是否会导致肌肉去适应和/或运动模式的改变。

Lifting is the one of the most common tasks performed in manual materials handling jobs and is the most frequently reported cause of injury.  Mechanical off-body lifting aids (i.e., hoists or trolleys) reduce joint loading and increase efficiency, especially when lifting and moving heavy loads and manipulating awkward objects that are beyond human capability.   However, when loads are within human lifting capacity, there is a tendency for workers to lift manually since most mechanical hoists and lifting devices cannot be operated quickly and force workers to slow down.  Although one solution is to make faster 'off-body' lift assists, another solution is to design 'on-body' lifting assists.  The purpose of this application is to examine the safety and effectiveness of a new dynamic 'on-body' personal lift assistive device (PLAD) on the trunk and leg muscle activity and forces and moments on the spine and the resulting movement patterns in manual materials handling tasks.  More specifically, I am particularly interested in how workers lift loads when wearing a dynamic assistive device and whether it is a safe and effective device to use.  To accomplish this objective, there will be four studies.  The first study will examine the effects of no ergonomic lifting aid (no-PLAD) and wearing a dynamic lift assist (PLAD) on cumulative loading on the spine in terms of: a) the impact on cumulative moments at L4/L5 disc; b) cumulative EMG as processed in amplitude and frequency domains; c) changes to technique as a result of the device; d) changes in lifting technique between subjects from beginning to end of the lift; and, e) subjective and heart rate differences by condition.  The second study will examine the effect of the PLAD on trunk stability during both static holding and dynamic tasks at different trunk postural angles with different elastic element tensions.  In the third study, these experiments will be repeated for men and women to determine the differential effect of sex. The final study will determine if such a dynamic assistive device when worn over an eight week period in an industrial situation will cause de-conditioning of muscles and/or alterations in movement patterns.