Risk Management Research Group, National Institute of Occupational Safety and Health, Japan, Kiyose, Tokyo, Japan.
Department of Teacher Training, National Institute of Special Needs Education, Yokosuka, Kanagawa, Japan.
Work. 2022;72(2):677-685. doi: 10.3233/WOR-210079.
Manual operations of the hydraulic jack device can become ergonomic stressors for the musculoskeletal system because of the required operational forces, muscle activities, or working postures. However, the usability of the hydraulic jack has not been fully explored for non-professional personnel.
To evaluate the musculoskeletal loads during manual operations of a hydraulic jack based on the ergonomic postural analysis and electromyographyMETHODS:Nine men operated the lever of a hydraulic jack with three positions: parallel to and near (P-N), parallel to and far from (P-F), and orthogonal to the jack lever (O). Postural loads were evaluated by Loading on the Upper Body Assessment (LUBA), an ergonomic observational method, and were classified into action categories. The surface electromyogram of eight muscles and the subjective sense of burden were also measured.
The initial force for lever pushing reached 40-80 N and exceeded the recommended forces for the unusual postures. The overall assessment of LUBA showed that 31% of working postures observed in O position require immediate consideration and corrective action and the maximum holding time estimated was < 1 minute. The postural load increased due to the shoulder joint abduction in the P-F and O positions and due to the trunk rotation in O position.
The results suggest that operating the hydraulic jack cause considerable postural loads and manual forces insufficient for several minutes of manual task. Therefore, improving working methods and tool designs are needed to improve usability and decrease the risk of musculoskeletal disorders during jack operations.
由于所需的操作力、肌肉活动或工作姿势，手动操作液压千斤顶装置可能会对肌肉骨骼系统造成人体工程学方面的压力。然而，非专业人员尚未充分探索液压千斤顶的可用性。
根据人体工程学姿势分析和肌电图评估手动操作液压千斤顶时的肌肉骨骼负荷。
9 名男性以三种位置操作液压千斤顶的杠杆：平行且靠近（P-N）、平行且远离（P-F）和垂直于千斤顶杠杆（O）。姿势负荷通过人体负荷评估（LUBA）进行评估，这是一种人体工程学观察方法，并分为动作类别。还测量了 8 块肌肉的表面肌电图和主观负担感。
推压杠杆的初始力达到 40-80N，超过了非常规姿势的推荐力。LUBA 的总体评估显示，O 位置观察到的 31%的工作姿势需要立即考虑和采取纠正措施，估计最大保持时间<1 分钟。在 P-F 和 O 位置，由于肩关节外展，在 O 位置由于躯干旋转，姿势负荷增加。
结果表明，操作液压千斤顶会导致相当大的姿势负荷和手动力，不足以进行几分钟的手动任务。因此，需要改进工作方法和工具设计，以提高可用性并降低千斤顶操作过程中肌肉骨骼疾病的风险。
