Abstract
Past biomechanical studies on seated postures showed that effects of seat parameters, such as seat pan angle, back angle and friction coefficient, on muscle activities, shear force between buttocks and seat and spinal loads are complex. Reducing all these biomechanical loads at the same time may not be possible. Lowered muscle activation may require higher frictional shear force. It is interesting to investigate how people behave compared to biomechanical simulations. In this paper, the question whether sitters prefer a seat pan angle for reducing shear force was investigated using the data collected from a multi-adjustable experimental seat. Two imposed seat pan angles (A_SP = 0°, 5°) and one self-selected were tested for two backrest angles (A_SB = 10°, 20°, from the vertical). A flat seat pan surface was used. Other seat parameters such as seat height, length and position of three back supports were defined with respect to each participant’s anthropometry. As expected, results showed that shear force increased with backrest recline and decreased with seat pan recline. No significant difference in self-selected seat pan angle was found between two backrest angles. An average of 6.2° (±3°) was observed. The lowest shear was observed for the condition of self-selected seat pan angle, supporting the idea that seat pan should be oriented to minimize shear force. However, self-selected angle did not completely remove the shear. A zero shear would require a more reduced trunk-thigh angle, suggesting a minimum trunk-thigh angle should also be maintained.
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References
Beurier G, Cardoso M, Wang X (2017) A new multi-adjustable experimental seat for investigating biomechanical factors of sitting discomfort. SAE technical paper 2017-01-1393, https://doi.org/10.4271/2017-01-1393
Goossens RHM, Snijders CJ (1995) Design criteria for the reduction of shear forces in beds and seats. J Biomech 28(2):225–230
Mergl C, Klendauer M, Mangen C, Bubb H (2005) Predicting long term riding comfort in cars by contact forces between human and seat. SAE technical paper N° 2005-01-2690
Reed MP (2000) Survey of auto seat design recommendations for improved comfort. Michigan Transportation Research Institute (UMTRI), Michigan
Rasmussen J, de Zee M, Tørholm S (2007) Muscle relaxation and shear force reduction may be conflicting: a computational model of seating. SAE technical paper 2007-01-2456. https://doi.org/10.4271/2007-01-2456
Rasmussen J, de Zee M (2008) Design optimization of airline seats. SAE technical paper 2008-01-1863
Rasmussen J, Tørholm S, de Zee M (2009) Computational analysis of the influence of seat pan inclination and friction on muscle activity and spinal joint forces. Int J Ind Ergon 39:52–57
Keegan JJ (1953) Alterations of the lumbar curve related to posture and seating. J Bone Joint Surg 35A:589–603
Theodorakos I, Savonnet L, Beurier G, Wang X (2018) Can computationally predicted internal loads be used to assess sitting discomfort? Preliminary results. In: IEA 2018, Florence, Italy
Acknowledgement
The work is partly supported by Direction Générale de l’Aviation Civile (project n°2014 930818).
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Wang, X., Cardosso, M., Theodorakos, I., Beurier, G. (2019). Does Preferred Seat Pan Inclination Minimize Shear Force?. In: Bagnara, S., Tartaglia, R., Albolino, S., Alexander, T., Fujita, Y. (eds) Proceedings of the 20th Congress of the International Ergonomics Association (IEA 2018). IEA 2018. Advances in Intelligent Systems and Computing, vol 822. Springer, Cham. https://doi.org/10.1007/978-3-319-96077-7_30
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DOI: https://doi.org/10.1007/978-3-319-96077-7_30
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