Investigation of hand postures in manufacturing industries according to hand and object properties

• Five hand postures are commonly used in manufacturing companies.
• Works controlled commonly object shape of 3 types in manufacturing companies.
• Objects were mainly located on a table.
• Their use depended on whether the right or left hand was used and the object properties.
• Use of hand postures is affected by object shape, location, and orientation.

The aim of this study was to investigate the hand postures commonly used in manufacturing companies, according to the use of either the right or left hand and the object properties. Operations taking place over 1636 s were reviewed to record hand postures, right and left hands, object shapes, object locations, and object directions and to classify them according to a hand posture classification system developed in this study. The classification system considers R (resting), G (grasping), P (pinching), and T (touching), which are further subdivided based on the number and use of fingers-(T) thumb, (I) index, (M) middle, (R) ring, or (L) little-and palm (P). The hand postures classified as 5G (TIMRL), 3P (TIM), 5P (TIMRL), 2P (TI), and 4G (TMRL) were the most commonly used postures; however, their frequencies of use depended on whether the right or left hand was used and the object properties. The most commonly handled object shapes were cylinders, rectangles, and sheets, and the most common location for objects of these shapes was on a table. The use of hand postures depends on the type of activity. Unlike activities of daily living, which often require pinching an object, grasping is more often used in the manufacturing industry to manipulate hand tools and parts with force. The results of this study are anticipated to be useful in designing future research studies on hand postures.Relevance to industryThe investigation of commonly used hand postures is of special interest in ergonomics because of its association with musculoskeletal disorders of the hand. Information on commonly used hand posture can be used in designing future hand posture research studies to estimate and reduce hand stresses.