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Eighteen co-ordination postures with shoulder flexion angles (0°, 45° and 90°) and elbow flexion angles (0°, 45° and 90°) in standing and sitting positions were evaluated to identify the effects of co-ordination postures on maximum grip strength and muscle activities of the upper limb in this study. Thirty-nine subjects were recruited and their maximum grip strengths were measured. According to the analysis of grip strength, grip strength was shown to be stronger in a standing posture (297.4 N) than in a sitting posture (274.6 N). In addition, grip strength (293.8 N) at 90° shoulder flexion angle was significantly higher than that at 0° and 45°shoulder angles. There was no statistically significant difference in grip strength from the effects of elbow angles in this study. The results of muscle activities for all muscle groups showed a similar trend with the results of grip strength associated with shoulder angles.
This paper presents a heuristic procedure for assigning assembly tasks to workstations where both productivity and ergonomics issues are considered concurrently. The procedure uses Kilbridge and Wester’s algorithm to obtain an initial task–workstation assignment solution which minimizes the balance delay of an assembly line. A task reassignment algorithm was applied to improve the initial solution by exchanging assembly tasks, which smooth postural load among workers, between workstations. A composite index of variation was used to measure the effectiveness of the task–workstation assignment solution. On the basis of clothes assembling, it was found that the task–workstation assignment solution with a minimum composite index of variation can be obtained with relatively equal weights in balance delay and postural load.
The aim of this study was to verify a theoretical model for upper extremity work space optimization. In order to do that, experimental studies were conducted in which two parameters of the electromyography (EMG) signal were analyzed: AMP (amplitude calculated as Root Mean Square) and SZC (coefficient of the slope of the regression line between time and Zero Crossing values). Values of forces in muscles (parameter MOD) were calculated from theoretical studies. A comparison of experimental (AMP, SZC) and theoretical (MOD) parameters was performed by analyzing the coefficient of correlation between those parameters and differentiation of muscular load according to external load value. Analysis showed that the theoretical and experimental results are in step, which means that the developed model can be used for upper extremity work space optimization.
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