Understanding buttock deformation in a seated posture

Abstract

This paper presents PhD research conducted at Loughborough University in the UK, into flesh deformation of the buttocks in a seated posture. Due to a lack of detailed understanding of how the soft tissues of humans behave when in contact with a seat surface, this research aims to explore the deformation behaviour of these tissues across the sitting task. In particular the research aims to understand the relationships between the three main degrees of freedom: compression (C), anterior-posterior spread (AP), and lateral-medial spread (LM). The paper presents the analysis of C, LM and AP deformation behaviour from a study of 42 participants. Data were collected using motion capture markers attached to tight fitting clothing across one buttock of each participant via the Codamotion system. A rigid platform was used to act as a ‘seat’. Participants were suspended via a hoist such that they could adopt a seated posture just short of the seat surface. Data were then captured through the sitting process from first contact to fully deformed. The resulting coordinate changes throughout this process were captured and analysed. In addition to buttock deformation data, a range of anthropometric data were captured from each participant to explore correlations between anthropometric measures and deformation behaviour to inform any later modelling activity. Findings identify clear deformation behaviour types for AP and LM spread and that participants can display predominant deformation behaviour in one axis. Typically, AP spread is greater than LM spread, and the maximum deformations occur in the lower regions of the buttocks closer to the seat surface. The development of useful models of deformation behaviour is ongoing.