Forefoot deformation during stance: Does the forefoot collapse during loading?

•Plantar pressure and 3D kinematics are combined to define forefoot deformation.•In agreement with previous studies, we report significant forefoot deformation.•At the beginning of stance the largest deformation indicates a flexible forefoot.•Through midstance the forefoot remains stable.•It transforms into a tight configuration during initial and final propulsion.

This study presents a specific description of forefoot deformation during the stance phase of normal human walking based on the combined analysis of pressure and three-dimensional optoelectronic measurements. Forefoot deformation is measured in forty healthy subjects using (1) a six-camera motion capture system (sampled at 250 Hz) tracking five reflective skin markers attached to the forefoot, (2) a pressure platform (sampled at 500 Hz) and (3) a forceplate (sampled at 1250 Hz). Forefoot deformation is characterized by the forefoot width, the mediolateral metatarsal arch height and the plantar pressure under the metatarsal heads. Using this setup, a typical pattern of forefoot motion is described during stance phase: From a flexible, compliant configuration at the beginning of stance phase, characterized by a decrease in mediolateral metatarsal arch height and a controlled increase in forefoot width, the forefoot turns into a stable configuration during midstance. Subsequently, the increase in mediolateral arch height and the decrease in forefoot width describe the transformation into a tight configuration during final stance. This transfer from a compliant into a rigid configuration through stance phase rejects the idea of the forefoot as a collapsing structure under increased loading.