[Purpose] This study was performed to determine which set of below-knee working conditions minimizes upper extremity muscle activity and which of upward- or downward-direction workstations poses the greater risk of upper extremity disorder. [Subjects] The study population consisted of 15 young male workers. [Methods] EMG activities of the right anterior deltoid, biceps brachii, and lower trapezius muscles were measured in two below-knee assembly workstation positions. [Results] The anterior deltoid and biceps brachii muscle activities of Position 1 were significantly higher than those of Position 2. The lower trapezius muscle activity of Position 2 was significantly higher than that of Position 1. [Conclusion] Upward-direction workstations appear to pose a greater risk of upper extremity disorder than downward-direction workstations in below-knee assembly work.
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