A Study of Working Height through Physical Workload Evaluation for Repetitive Task in Upper Limbs

• Main Authors: Hsin-Yi Liao, 廖欣怡
• Other Authors: none
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/hv4zva

碩士 === 朝陽科技大學 === 工業工程與管理系碩士班 === 92 === Cumulative trauma disorders of upper limbs are one of the most common occupational illnesses in industries. There are three main ergonomics-related risk factors: awkward postures, overexertion and repetition. It is shown that physiological approach is more practicable to evaluate the workload of repetitive and long-duration tasks. When working surface is raised too high or too low, workers may lead to discomfort and even pains. However, there is little literature specifically related to systematical study in the issue of physical workload. In this study, an experiment was conducted to collect the measurements of electromyography and kinematics in the laboratory where EMG and motion systems are executed. Ten subjects were recruited and 9 tast patterns, which were the combinations of 3 working heights and 3 parts location levels, were designed and performed in the experiment. The discrete wavelet transform, a technique of time-frequency analysis, was explored to evaluate dynamic EMG and obtain instantaneous median frequency (IMF), root mean square (RMS) and range of motion. The results showed that trapezius and anterior deltoid revealed significant fatigue among the tested six muscle groups in the stidy. It was found that the number of subjects with fatigue became larger with the increase of working height. The muscular stress of subjects might be reduced when parts location levels were the same or below the working heights. It was suggested that working height should be designed with the elbow level or lower and the parts location levels should not exceed the working height while a repetitive tast of upper limbs was performed at worksites.