生物力學法人工抬舉姿勢評估圖之製作

Development of Evaluation Diagrams for Manual Lifting Based on Biomechanical Approach

人工抬舉（manual lifting）工作是造成肌肉骨骼過度傷害的主要原因之一。依據勞委會勞工安全衛生研究所在八十七年度對配送業人力搬運作業省力化之研究，發現搬運工曾因搬運工作而發生骨骼肌肉傷痛之比例中，以中下背部所佔之比例57%最高。另外，在一項物料搬運工作危害評估調查發現，下背部不舒適者佔90.7%，而搬運方式中又以抬舉為主。根據統計在美國約有1/3的工業傷害屬於此類，其每年造成的損失超過300 億美元。勞工下背痛即是人工抬舉工作的主要傷害之一，勞工常常因為不當的抬舉姿勢或抬舉過重的負荷導致嚴重的肌肉骨骼疾病。目前除了美國NIOSH所提出的抬舉工作規範與公式，能評估並建議現場抬舉的抬舉重量限值（recommended weight limit）外，很少有其他有效的方法能夠直接用於現場，對抬舉過程的傷害風險做立即且簡單的分析。本研究是製作一種可應用於工作現場，評估人工抬舉姿勢的評估圖。此一評估圖以生物力學為基礎，利用Chaffin二維靜態生物力學模式，配合國內勞工人體計測值，撰寫生物力學模式計算程式，此程式可計算在不同的抬舉姿勢與抬舉重量下，不同國內勞工人體尺寸的L5/S1椎間盤受力情況。所製作之評估圖將可簡單的對現場人工抬舉工作姿勢進行初步評估，可提供安全衛生管理人員作為改善之參考依據。

Manual lifting is one of the most important factor to cause musculoskeletal disorders. In a IOSH’s study[1] on lifting aids for manual handling, the injury occurred at low back is 57% which is the highest percentage among all those workers who have musculoskeletal disorders. In another investigation on manual material handling[2] conducted by IOSH, it shows that 90.7% workers complain low back pain, and the lifting action is a great part of their daily handling activity. Also, based on an American statistics, the cost of these injuries is in excess of 30 billion dollars per year. Low back pain (LBP), however, is one of the major harm of manual materials handling. Severely musculoskeletal disorders often occur in heavy-load occupations because of poor postures and overload. How to evaluate the risk of manual lifting has become a very important issue. Besides NIOSH guidelines and lifting equation[3-4] which shall propose working guide and recommended weight limit, only a few method is available and can be used easily for onsite evaluation of manual lifting. In this study, a series of evaluation diagrams used to assess the working postures is established. Based on a two-dimensional statically biomechanical model, the compression stress on L5/S1 is calculated for various lifting postures and loads by applying anthropometry database of domestic worker population. The developed diagrams can be applied easily to risk evaluation of low back pain for manual lifting and other symmetrical working postures, and provide guidance to reduce low back pain occurrence on workplace.