Effects of backrest inclination on spinal posture

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Effects of backrest inclination on spinal posture

 

Author: So, Tsz-wah Patrick
Title: Effects of backrest inclination on spinal posture
Degree: M.Sc.
Year: 2002
Subject: Hong Kong Polytechnic University -- Dissertations
Lumbar vertebrae
Department: Multi-disciplinary Studies
Jockey Club Rehabilitation Engineering Centre
Pages: xiv, 77 leaves : ill. (some col.) ; 30 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1627733
URI: http://theses.lib.polyu.edu.hk/handle/200/1075
Abstract: The purpose of this study was to investigate the effects of backrest inclination on spinal posture. A non-contact measurement technique with the application of laser sensing technology was established to quantify spinal posture from the lumbar to the cervical region. High repeatability (ICC = 1.0000) and negligible error (Percentage of absolute error = 0.32%) was demonstrated for this technique. The spinal postures (in terms of spinal height and depth) were measured in ten adults for four backrest inclinations. Spinal curvatures of the lumbar, thoracic and cervical regions were estimated, using a numerical method, from the spinal heights and depths measured. Reproducibility of spinal postures at different backrest inclinations was determined using an ICC (3,1) and most of the values for spinal height and depth were above 0.75. Lumbar curvatures were also found to be reproducible for all four backrest inclinations examined (ICC > 0.75), but decreased from thoracic and cervical regions. Repeated measures ANOVA together with post-hoc multiple comparison with Bonferroni correction was adopted to determine the differences in spinal posture at different backrest inclinations. Statistically significant differences were only shown in spinal height, length of spine in contact with the backrest, spinal depth at T12 and the peak of the lumbar region. These differences justified the need for adjustability in these parameters so that the design of back support could then accommodate the changes in spinal posture at different backrest inclinations. Regression analysis was conducted to explore the relationship between spinal posture and backrest inclination. Linearity was demonstrated in spinal heights at all levels but the coefficient of determination values only ranged from 0.173 to 0.691. The limited power of using the degree of backrest inclination to predict spinal posture favoured user adjustment of the height of the back support (at different levels) rather than a built-in backrest design with automatic rectification. This study served as a starting point far investigations into how spinal posture adapts to different chair designs. Future studies could include a series of investigation scomposed of postural evaluation and spinal loading measurements combined with the chair-users' ratings of comfort level. In this way, a model of optimal sitting posture for the entire spine could possibly be developed and utilized in the design of the shape/contour of the backrests of chairs.

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