The influence of rocker outsole design on the ground reaction force alignment during walking

Rocker outsole shoe is commonly prescribed to diabetic patients to reduce the risk of plantar ulceration. It is well stablished that the primary biomechanical role of the rocker outsole is to offload the plantar aspect of the forefoot [1]. Shear stresses have been previously affiliated to the etiology of diabetic foot ulcers [2]. However, there is a paucity of research on the effect of the rocker outsole design on the shear components in diabetic patients. While shear impulses can be measured during walking [3], the majority of studies concentrated on the vertical component of the Ground Reaction Force (GRF).
Anterior-posterior (AP) shear impulses which are termed positive and negative impulses respectively [4], change the momentum of the body in forward direction. However, Medial-lateral (ML) shear impulses act to push the body away (negative) and towards (positive) the contralateral side [4]. It is envisaged that the rocker outsole design can alter these impulses by changing the contact angles and forces during the shoe-ground interaction. Therefore, the purpose of this study was to investigate the effect of different rocker outsole designs on AP or ML shear impulses.