Abstract
The aim of this study was to investigate the effects of knee separation and backrest inclination on the curvature of the lumbar spine. Data were gathered on 18 males and 18 females between the ages of 18 and 54. All subjects were free of any known spinal abnormalities or musculoskeletal disorders. Anthropometric measurements were made to describe the population. Spinal contour measurements were made at nine different postural positions by utilizing three different distances of knee separation (5.08, 20.32, and 35.56 cm) and three different angles of backrest inclination (90, 105, and 120-deg). Descriptive statistics and one-way ANOVA were used to evaluate the results. Tukey's test was used to compare significant differences among means of lordotic angles. The results suggest that knee separation does not significantly affect lordotic angle. However, the angle of backrest inclination did significantly affect the lordotic curvature. For females the lordotic angle decreased significantly (representing an increase in lumbar lordosis) as the backrest inclination angle increased from 90 to 120-deg, but there was no significance as the angle increased from 90 to 105-deg nor from 105 to 120-deg. For males, significance occurred as the backrest changed from 90 to 120-deg and from 105 to 120-deg, but not from 90 to 105-deg.
Bolen, Bradley Kyle (1999). The effect of knee separation and backrest angle on lumbar lordosis angle in various seated postures. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1999 -THESIS -B655.