Short-term changes in upper extremity dynamic mechanical response parameters following power hand tool use
Dynamic mechanical response parameters (stiffness, damping and effective mass), physiological properties (strength and swelling) and symptoms of the upper limb were measured before power tool operation, immediately following and 24h after power tool operation. Tool factors, including peak torque (3 Nm and 9 Nm) and torque build-up time (50ms and 250ms), were controlled in a full factorial design. Twenty-nine inexperienced power hand tool users were randomly assigned to one of four conditions and operated a pistol grip nutrunner four times per min for 1h in the laboratory. Isometric strength decreased immediately following tool use (15%) ( p < 0.01) and 24h later (9%) ( p < 0.05). Mechanical parameters of stiffness ( p < 0.05) and effective mass ( p < 0.05) were affected by build-up time. An average decrease in stiffness (43%) and effective mass (57%) of the upper limb was observed immediately following pistol grip nutrunner operation for the long (250ms) build-up time. A previously developed biomechanical model was used to estimate handle force and displacement associated with the tool factors in the experiment. The conditions associated with the greatest predicted handle force and displacement had the greatest decrease in mechanical stiffness and effective mass, and the greatest increase in localized discomfort.
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Document Type: Research Article
Department of Industrial Engineering, University of Wisconsin, Madison, WI, 53706, USA
Department of Biomedical Engineering, University of Wisconsin, Madison, WI, 53706, USA
Department of Mechanical Engineering, University of Wisconsin, Madison, WI, 53706, USA
June 1, 2005
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