An experimental and simulation-based evaluation of the effect of seat angle on muscle load for perching

Abstract

Once fully automated driving has been implemented, passengers will be able to take advantage of not only the sitting posture but also standing and perching postures. Physical workload of these postures should be investigated in order to design car seats that provide passengers appropriate physical workload. This study aimed to investigate the feasibility of simulation-based physical workload evaluation of these postures by a musculoskeletal model. Twelve male students participated, and four electromyograms (EMGs) of the rectus femoris, tibialis anterior, gastrocnemius, and erector spinae were recorded with varying seat angle against the horizontal surface: 0° (i.e., sitting), 30°, 45°, 60° (i.e., perching), and 90° (i.e., standing). Results showed that the effect of the seat angle condition was significant for the EMGs of rectus femoris and erector spinae. In particular, the EMG of rectus femoris was relatively higher than the other three EMGs. The EMG of rectus femoris increased with the increase in seat angle in the range from 0° to 60°and decreased in the range of 60° to 90°. The musculoskeletal analysis was carried out with the same condition as the EMG measurement. The average height and weight of the participants were applied to the analysis model, and the muscle activities of the four muscles were estimated. As expected, the trend of muscle activity in the rectus femoris estimated by the musculoskeletal analysis agreed with the experimental result. The average absolute error of muscle activity in the rectus femoris between the experiment and the analysis was approximately 2.5%. From these results, it is suggested that musculoskeletal analysis can be utilized to estimate muscle activity of a spectrum of static posture from sitting to standing through perching.

Keywords

• ergonomics
• electromyogram
• digital human modeling
• biomechanics
• stand-sitting
• chair design