| Summary: | 碩士 === 國立清華大學 === 工業工程與工程管理學系 === 102 === The purpose of this study is to propose an ergonomic concept in preserving a large torso-to-thigh angle for the design general-purpose chairs, aiming at lowering musculoskeletal stresses. General-purpose chairs are the chairs we use most daily, like office chair, dinning chair and so forth. When we are sitting on the chair, a 90 degree torso-to-thigh angle will result in significant adverse musculoskeletal stresses in various body tissues. Nevertheless, past research found that the musculoskeletal stresses decreased as the torso-to-thigh angle 135 degree. Therefore, based on this finding, it is proposed that a chair be configured in maintaining a large torso-to-thigh angle for lower musculoskeletal stresses.
The new chair configuration is to raise the height of the seat-pans to pose the
thigh in a 20 degree downward, and assisted by a 25 degree slanted backrest, a seated man is able to maintain a large torso-to-thigh angle, up to135 degree The seat-pan must be configured as consists of two sections, a rear horizontal and a front slanted. The former is used to support upper body without shear force, and the latter is to support the underside of the thigh without tissue compression.
To design the chair, 3 key measurements must be obtained: seat height, depth of the rear section, and the length of the front section. The seat height is derived from anthropometrical data while the thigh is assumed at a 20 degree downward posture. The depth of rear horizontal section was determined by the distance between the gluteal fold and the posterior aspect of the buttocks. The depth of front slanted was determined by the 1/3 distance between the gluteal fold and popliteal. Ten young male students were recruited as subjects for these 3 measurements.
The results show that the height of seat-pan is 55cm; the depth of horizontal seat-pan is 21 cm; and the depth of thigh support is 10cm. When we are sitting on this new chair, our torso-to-thigh angle will be larger than general purpose chair about 20 degree. And torso-to-thigh angle will be 135 degree when leaning on back-support. This 135 degree is the neutral posture named by Keegan. The new chair will increase torso-to-thigh angle, and decrease musculoskeletal stress.
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