Physical workload reduction is a significant factor in product design. However, experimental bioinstrumentation measurements involve substantial time and costs. This study proposed a simulation based ergonomic design method with digital human modeling (DHM) to accomplish efficient ergonomic product design. DHM simulation was applied to evaluate the joint moment ratios (JMRs). The product design for physical workload reduction was formulated as a minimization of the average and maximum JMRs to determine the optimal solution. The proposed method was applied to a problem of designing the forward distance of a handrail to support the sit-to-stand (STS) movement. The STS motion, the force exerted on the handrail, and the subjective perceived workload were measured for nine subjects. The STS motions and exerted force of the DHMs were predicted from the measured data, and physical workload simulation was performed with multiple DHMs to reflect anthropometric diversity. The response surfaces of the average and maximum JMRs were predicted as functions of the forward distance, and Pareto frontiers of each DHM condition were determined. The findings revealed that there were no trade-offs between the average and maximum JMRs, and that the optimal forward distance was in the range of 345-400 mm.
