Abstract
[Purpose] The purpose of this study was to consider the effect of the height of a backrest on shear force on the buttocks in comfortable sitting. [Subjects] Thirteen healthy adult men (age: 21.3 ± 2.4) participated in the study. [Methods] We measured the shear force on the buttocks in sitting using a force plate. Considering morphological effects, the measure of shear force after eliminating the body weight of each subject was adopted. The measuring position was the long sitting position with the buttocks on the force plate and lower legs outside the force plate. Instead of a backrest, parallel bars were used which were set laterally not to touch the force plate. The experiment was conducted under two conditions by adjusting the height of the backrest (46 and 49 cm from the floor). [Results] The shear force with the backrest height of 46 cm from the floor was 0.8 ± 0.27 [N/kg], and at 49 cm from the floor it was 0.71 ± 0.25 [N/kg], showing a significant difference between two conditions (p=0.014). [Conclusion] The result suggests that when the height of backrest is high, the shear force on the buttocks is small.
