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TECHNICAL PAPERS: Joint/Whole Body

Support Force Measures of Midsized Men in Seated Positions

[+] Author and Article Information
Tamara Reid Bush1

Department of Mechanical Engineering, Biomechanical Design Research Laboratory,  Michigan State University, 2555 Engineering Building, East Lansing, MI 48824reidtama@msu.edu

Robert P. Hubbard

Department of Mechanical Engineering, Biomechanical Design Research Laboratory,  Michigan State University, 2555 Engineering Building, East Lansing, MI 48824hubbard@msu.edu

1

Corresponding author.

J Biomech Eng 129(1), 58-65 (Aug 05, 2006) (8 pages) doi:10.1115/1.2401184 History: Received August 21, 2003; Revised August 05, 2006

Two areas not well researched in the field of seating mechanics are the distribution of normal and shear forces, and how those forces change with seat position. The availability of these data would be beneficial for the design and development of office, automotive and medical seats. To increase our knowledge in the area of seating mechanics, this study sought to measure the normal and shear loads applied to segmental supports in 12 seated positions, utilizing three inclination angles and four levels of seat back articulation that were associated with automotive driving positions. Force data from six regions, including the thorax, sacral region, buttocks, thighs, feet, and hand support were gathered using multi-axis load cells. The sample contained 23 midsized subjects with an average weight of 76.7kg and a standard deviation of 4.2kg, and an average height of 1745mm with a standard deviation of 19mm. Results were examined in terms of seat back inclination and in terms of torso articulation for relationships between seat positions and support forces. Using a repeated measures analysis, significant differences (p<0.05) were identified for normal forces relative to all inclination angles except for forces occurring at the hand support. Other significant differences were observed between normal forces behind the buttocks, pelvis, and feet for torso articulations. Significant differences in the shear forces occurred under the buttocks and posterior pelvis during changes in seat back inclination. Significant differences in shear forces were also identified for torso articulations. These data suggest that as seat back inclination or torso articulation change, significant shifts in force distribution occur.

FIGURES IN THIS ARTICLE
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Copyright © 2007 by American Society of Mechanical Engineers
Topics: Force
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Figures

Grahic Jump Location
Figure 1

BAC chair used for testing, foam pads removed

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Figure 2

BAC articulations erect (left) and slumped (right) postures

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Figure 3

Load cell orientations

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Figure 4

A comparison of the thoracic and pelvic supports in a reference position (a) and a test position (b)

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