MUSCLE OVEREXERTION DURING REPETITIVE LIFTING

与职业相关的腰背部疾病（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，因为这些环境中重复提升是常见的。虽然评估成功地评估了单次用力时的LBD风险，但没有一个能够有效地评估在整个工作日中以不同的举重频率重复举重时风险是如何变化的。本研究将评估随着时间的推移，暴露于不同频率的抬升如何导致LBD不可接受的生物力学风险。我们的初步研究指出了两种风险机制。首先，不同的举重频率会影响举重运动和随后的肌肉恢复模式。这些变化改变了脊柱负荷的性质（方向）和大小，从而超过了脊柱的承受极限。其次，在整个工作日中进行重复的举重也会导致肌肉在工作期间的招募模式发生变化，从而增加全天的脊柱负荷。因此，在工作日早期可接受的提升频率可能会随着工作日的进展而超过生物力学公差极限。本研究将探讨当工人在延长的工作日内以六种不同的提升率举起三种重量（对应于工业暴露范围）中的一种时，肌肉恢复和脊柱负荷的变化。当脊柱负荷超过记录的脊柱耐受极限时，抬升的频率和持续时间将被判定为有风险和不可接受。这些发现将有助于了解脊柱结构（椎间盘）损伤风险人群的比例与负荷大小、举重频率和举重时间的关系。这些结果将为在制造和配送中心环境中执行材料处理任务的数百万工人的工作相关lbd的调解提供定量指导。

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.