本研究では，立位姿勢で検査対象物の取り回しを伴う目視検査作業を想定した実験を行い，そのときの上肢負担を明らかにすることを目的とした.被験者は健常成人男性10名，実験条件は検査対象面が6水準，検査対象物の大きさが2水準とし，これらを組み合わせた計12条件で実験を行った.評価項目は，筋電図を用いた筋負担，関節角度を用いた関節モーメント，被験者の主観による評価の3項目とした.実験の結果，検査対象面が下面のときに上肢の筋負担が最も高くなることが明らかとなった.そのとき肩関節，肘関節，および手関節の動作に関与する筋の%MVCは10%を超えるため，長時間の作業は避けるべきである.また，検査対象物の大きさが大きくなると，検查対象物の取り回し量が増加することによって頸部および上肢の筋活動が活発になるため，頸部および上肢の筋負担は高くなることが明らかとなった.%Visual inspection is one way to ensure product quality, and although automated visual inspection has been introduced, it is costly and associated with technical issues. Thus, human visual inspection still plays a major role in visual inspection in the industry. Many studies have focused on the visual fatigue of the inspectors. However, upper limb load caused by handling objects and maintaining a specific posture is also considered a problem in visual inspection. If the inspection object is lightweight but large in size (e.g., a plastic part), the inspectors tend to maintain an awkward posture due to difficulty in handling the object. Despite these findings, few studies have elucidated the effect of upper limb load. In this study, we intended to assess the effect of inspection side and object size on upper limb load. Ten healthy male subjects were instructed to inspect objects using a combination of six inspection side conditions (i.e., the sides of front with horizontal LED, top, under, front with vertical LED, right, and left) and two object size conditions (i.e., big: a square, 450 mm each side, and small: a square, 150 mm each side). Muscle activity and joint moment were the evaluation indices. We also investigated subjective indices for burden and task difficulty. Electromyography was performed on the subjects' sternomastoid muscle, the upper part of the trapezius, the clavicular part of the pectoralis major, the middle part of the deltoid, the biceps brachii, the extensor carpi radialis, and the flexor carpi ulnaris muscle. The results showed that the muscle load of the upper limb is highest when the inspection side condition is under side. Additionally, if the object is big, the muscle load of the neck and upper limb is greater.
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