2008 Volume 20 Issue 3 Pages 157-162
[Purpose] The purpose of the present study was to prepare an experimental model for estimating the shear force for a person sitting in a comfortable posture while leaning against a backrest, and then to verify its validity. [Subjects] The subjects were 16 healthy adult men without leg and trunk diseases (age: 21.6 ± 0.8 years; height: 172.5 ± 5.3 [cm]; and body weight: 63.4 ± 6.4 [kg]). [Methods] Using the model, the shear force applied to the gluteal region in a sitting posture was estimated, and at the same time, the shear force was measured using a force plate. The model's validity was assessed by comparing the estimated and measured values in terms of correlation coefficients. [Results] The average estimated shear force was 36.6 ± 11.8 [N], and the average reaction force in the posterior direction as part of the anteroposterior components of the floor reaction force (shear force in the anterior direction) was 35.9 ± 15.8 [N]. No significant difference existed (p=0.797), and the correlation coefficient was 0.897 (p<0.0001), thus exhibiting a strong positive correlation. [Conclusion] This result shows that the validity of the present experimental model is high, and the model is useful in clinical settings because shear force in a comfortable sitting posture can be relatively easily estimated without a special device.