The Effect of Sole Design on Foot Stress Distribution to Runner

There is an increased stress on the metatarsal when running due to repeated loadings that cause ankle injury. The solid foam structure of the sole may not provide optimum strength and good absorption shock, as demonstrated by previous studies. So, this study aimed to design the shoe sole models of various patterns or topologies and compare the effects of shoe sole design on the foot stress distribution. This study was conducted using three different softwares which were 3-Matic, Solidworks and ANSYS. Three different topologies of sole including circular, elliptical and hexagonal patterns were designed using Solidworks software. A 23 years old female foot with 45 kg weight and 25 cm foot length was scanned using three-dimensional (3D) scanner and modified using 3 Matic software. Foot-sole simulation was carried out in finite element analysis (FEA) platform called ANSYS, considering the nonlinearity and viscoelastic properties of the sole material to reflect the stress distribution on the foot plantar that in contact with three different midsoles of various topologies. The result showed the hexagonal sole pattern has the lowest stress with a maximum of 0.1 MPa. It has the potential to enhance the area of contact between the foot and the sole. The stresses on the foot were more uniformly distributed. The highest stress was found on the elliptical design with 0.19 MPa because the struts will buckle as the compression load changes dramatically thus, it cannot avoid concentrating the stress on the foot. Meanwhile, the circular pattern has a maximum of 0.12 MPa. The increased stress caused by repeated external impact loads when running will cause ankle injury. Therefore, the hexagonal sole design is the most comfortable that will help to reduce ankle injuries. Lastly, more subjects should be involved in the future for the FEA to achieve a solid conclusion.