Hum Factors. 2013 Dec;55(6):1077-87. doi: 10.1177/0018720813482328.
The objective of this study was to quantify shoulder muscle fatigue during repetitive exertions similar to motions found in automobile assembly tasks.
Shoulder musculoskeletal disorders (MSDs) are a common and costly problem in automotive manufacturing.
Ten subjects participated in the study. There were three independent variables: shoulder angle, frequency, and force. There were two types of dependent measures: percentage change in near-infrared spectroscopy (NIRS) measures and change in electromyography (EMG) median frequency. The anterior deltoid and trapezius muscles were measured for both NIRS and EMG. Also, EMG was collected on the middle deltoid and biceps muscles.
The results showed that oxygenated hemoglobin decreased significantly due to the main effects (shoulder angle, frequency, and force). The percentage change in oxygenated hemoglobin had a significant interaction attributable to force and repetition for the anterior deltoid muscle, indicating that as repetition increased, the magnitude of the differences between the forces increased. The interaction of repetition and shoulder angle was also significant for the percentage change in oxygenated hemoglobin. The median frequency decreased significantly for the main effects; however, no interactions were statistically significant.
There was significant shoulder muscle fatigue as a function of shoulder angle, task frequency, and force level. Furthermore, percentage change in oxygenated hemoglobin had two statistically significant interactions, enhancing our understanding of these risk factors.
Ergonomists should examine interactions of force and repetition as well as shoulder angle and repetition when evaluating the risk of shoulder MSDs.
本研究旨在量化类似于汽车装配任务中发现的运动的重复用力过程中肩部肌肉的疲劳程度。
肩部肌肉骨骼疾病（MSD）是汽车制造中常见且代价高昂的问题。
十名受试者参与了这项研究。有三个独立变量：肩部角度、频率和力。有两种类型的因变量：近红外光谱（NIRS）测量的百分比变化和肌电图（EMG）中频的变化。对三角肌前部和斜方肌进行了 NIRS 和 EMG 测量。此外，还对三角肌中部和肱二头肌进行了 EMG 采集。
结果表明，由于主要效应（肩部角度、频率和力），氧合血红蛋白显著降低。氧合血红蛋白的百分比变化具有显著的力和重复交互作用，表明随着重复次数的增加，力之间的差异幅度增加。前三角肌的氧合血红蛋白百分比变化的重复和肩部角度的相互作用也具有统计学意义。中位频率因主要效应显著降低;但是，没有交互作用具有统计学意义。
随着肩部角度、任务频率和力水平的变化，肩部肌肉疲劳显著。此外，氧合血红蛋白的百分比变化有两个具有统计学意义的相互作用，增强了我们对这些危险因素的理解。
当评估肩部 MSD 的风险时，人体工程学家应检查力和重复以及肩部角度和重复的相互作用。
