Quantification of buttocks and thigh deformation in seating: a multi-modality approach

Human body models (HBMs) have become one of the most widely utilized tools employed by crash safety engineers to address contemporary challenges related to automotive safety. There is a gap in the literature, however, related to quasi-static interaction between the human body and its seated environment. We report a holistic dataset describing the deformation characteristics of the buttocks and thighs during seating for use in improving HBM biofidelity.

This multi-modality dataset comprises anthropometric measurements, 3D surface scan data, pressure mat data, and MRI imaging in the supine position to quantify deformation of the human body in the buttocks and posterior thigh under load. Eight males and nine females were recruited for this study (age range: 24-44 years; BMI range: 20.1-29.9). An upper-body harness was used to suspend participants without external load on the buttocks and thighs, and these data were compared to a loaded seating configuration in which participants were seated with the hips, knees, and ankles each positioned at 90°. A 2.5-cm translucent acrylic sheet was used as a flat-rigid seating surface, and an adjustable footrest was used to achieve the desired lower-extremity posture. Post-collection analyses compared the two configurations and investigated how age, BMI, sex, anthropometric measures, and cross-sectional adipose ratio (CSAR; derived from MRI) influenced body displacement under load.

Descriptive statistics are provided for all outcome measures related to seated morphological changes. For example, the change in hip breadth from the suspended to seated configuration was 28 ± 16.1 mm, while the change along the anterior-posterior axis of the mid-thigh was -36 ± 8.3 mm. Significant sex-based differences were identified in CSAR at the mid-thigh (p = 0.00073) and greater trochanter (p = 0.0011), as well as in the anterior-posterior axis of the mid-thigh (p < 0.0001). Following stepwise selection to retain only significant parameters (p < 0.05), linear models were developed to estimate key outcome measures. Significant linear relationships for average pressure, contact area, anterior-posterior leg deformation, and lateral hip breadth deformation are provided.

We integrated multiple measurement modalities to develop a dataset that quantifies body-to-seat interactions and supports the development of predictive models for calculating validation targets related to the quasi-static settling of HBMs. The findings indicate that relatively few parameters significantly predict these interactions, and that sex-based differences in morphological changes exist and should therefore be accounted for in HBMs. This study provides data focused on human-to-seat interaction in automotive safety applications.