Effects of a Headsupport and Inclination Angle of the Head and Neck on the Shear Force Applied to the Buttocks during Comfortable Sitting on a Chair

Abstract

[Purpose] The purpose of this study was to investigate if the use of a headsupport and inclination angle of the head and neck would influence the shear force on the buttocks in a comfortable chair sitting posture. [Methods] Thirteen healthy males, mean age 21.2 ± 0.9 years, without any pathologies in the leg and/or trunk participated in this study. Experiments were conducted under six conditions, i.e. head extension angle 0 degrees, 20 degrees, and 40 degrees with or without a headsupport. The shear force on the buttocks was measured using a force plate. For statistical analysis, a two-factor factorial ANOVA was used with the level of significance set at p<0.05. [Results] The shear force increased as inclination angle of the head and neck increased without a headsupport, but it did not change much with a headsupport. There was a significant interactive effect between with or without the headsupport and the inclination angle of the head and neck on the shear force on the buttocks (p=0.012). [Conclusion] The results suggest that level of shear force applied to the buttocks depends on whether the patient is sitting on a chair with or without a headsupport, and that use of a headsupport is effective for decreasing the shear force on the buttocks.