MUSCLE OVEREXERTION DURING REPETITIVE LIFTING

职业性腰背部疾病(LBD)是造成工作日损失的主要原因，也是当今工业面临的最昂贵的职业安全和健康问题。LBD在制造、配送中心和仓储环境中尤其普遍，在这些环境中，重复提升是常见的。虽然评估已经成功地评估了单次用力过程中的LBD风险，但没有一项评估能够有效地评估在整个工作日以不同的提升频率重复提升过程中风险的变化。这项研究将评估随着时间的推移暴露在不同的抬起频率下如何导致不可接受的LBD的生物力学风险。我们的初步研究指出了两种风险机制。首先，不同的提举频率会影响提举运动学和随后的肌肉招募模式。这些变化改变了脊柱负荷的性质(方向)和大小，从而超过了脊柱的耐受极限。其次，在整个工作日中进行重复的提举也会导致肌肉招募模式在整个工作时间内发生变化，从而增加一天中的脊柱负荷。因此，在工作日早期可以接受的提举频率可能会随着工作日的进行而超过生物力学耐受极限。这项研究将探索当工人在延长的工作日内以六种不同的举重速度举起三种重量中的一种(对应于工业暴露的范围)时，肌肉招募和脊柱负荷的变化。当脊柱负荷超过记录的脊柱耐受限度时，抬起的频率和持续时间将被判定为危险和不可接受的。这些发现将有助于了解脊柱结构(椎间盘)损伤的风险人群作为负荷量、提举频率和提升期持续时间的函数。这些结果将为数百万在制造和配送中心环境中执行材料处理任务的工人提供与工作相关的LBD调解的量化指导。

Occupationally-related low back disorders (LBDs) are the leading cause of lost workdays and the most costly occupational safety and health problem facing industry today. LBDs are particularly prevalent in manufacturing, distribution center, and warehousing environments where repetitive lifting is common. Although assessments have successfully evaluated LBD risk during a single exertion, none have been able to effectively assess how risk changes during repetitive lifting at various lifting frequencies throughout a workday. This study will assess how exposure to different frequencies of lift over time can result in unacceptable biomechanical risk of LBD. Our preliminary studies point to two mechanisms of risk. First, different lift frequencies affect lifting kinematics and the subsequent muscle recruitment patterns. These changes alter the nature (direction) and magnitude of spinal loading, thereby exceeding spine tolerance limits. Second, exposure to a repetitive lift throughout the workday can also result in muscle recruitment pattern changes over the work period, thereby, increasing the spinal loading throughout the day. Hence a lift frequency that is acceptable early in the workday may exceed biomechanical tolerance limits as the workday progresses. This study will explore the changes in muscle recruitment and spinal loading when workers lift one of three weights (corresponding to the range of industrial exposures) at six different lift rates over extended workdays. The frequency and duration of lift will be judged risky and unacceptable when the spinal loads exceed documented spine tolerance limits. These findings will result in an understanding of the portion of the population at risk for spine structure (disc) injury as a function of load magnitude, lifting frequency, and lift period duration. These results will provide quantitative guidance for the mediation of work-related LBDs for the millions of workers performing materials handling tasks in manufacturing and distribution center environments.