Abstract

A model of human foot is proposed in which the foot is represented as 8 rigid segments and 8 monocentric, single-degree-of-freedom joints. The soft tissue under the foot is divided into 7 independent sites of contact, or loading, and each of these is modelled as a nonlinear spring and a nonlinear damper in-parallel. The model was used to estimate the kinematics and kinetics of the foot during the stance phase of walking. Force sustained at each loading site was calculated from walking trials in which only portions of the foot landed on a small force platform. The position of the calcaneus was defined by surface markers, whereas the position of the distal segments were based upon chalk footprints and an estimate of the compression of the plantar soft tissue. Results suggest that the joints that constitute the longitudinal arch extend slightly when the forefoot is loaded. During push-off, these joints flex as the metatarsophalangeal joints extend. Similar kinematic results were estimated when the distal segments of the foot were defined by surface markers. The magnitude of joint moments of force depended largely on the distribution of the load under the foot which varied considerably between subjects. The stable, yet resilient properties of the foot, as highlighted by this model, should be considered in 3-dimensional dynamic models used to study human locomotion. The model provides an objective tool to quantify foot motion and loading, which may prove useful for describing foot function in normal and pathological conditions. Verf.-Ref.