Effects of User Experience,Working Posture,and Joint Hardness on Powered Nutrunner Torque Reactions

Abstract

Powered hand tools produce reaction forces that may be associated with upper extremity musculoskeletal disorders. Fifteen experienced and fifteen novice male powered tool users operated pistol grip and right angle nutrunners in a laboratory study. A full factorial experiment examined the effects of operator experience, working height, distance, tool, and fastener joint hardness on handle displacement and grip forces due to torque reactions. The results show that in addition to working height and distance, experience significantly affected tool handle displacement resulting from reaction torque. Experienced users allowed an average of 7.9°, while novice users allowed 11.5° when pistol grip tools were used on a horizontal surface. Experienced users allowed less handle displacement for all working conditions, and exerted more force than novice users when using right angle tools, but less force when using pistol grip tools. Operator experience influences mechanical exposure during power tool usage.

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