Dynamic evaluation and comparative analysis of foam materials and carbon plates in sport shoe soles

Engineering of Sport 15 - Proceedings from the 15th International Conference on the Engineering of Sport (ISEA 2024)

Plates made of carbon-based composites are becoming widely used within various running disciplines, not only among professional athletes, but also by recreational runners. The quantification of their advantages when integrated as insoles or within the midsole of running shoes and their precise mechanisms of action remain subject of ongoing debates within the scientific community. Different models are under debate to define the underlying mechanisms, such as the well-known gear ratio and teeter-totter effects. We started this study concentrating on the spring-like effect that facilitates energy return following bending or the alteration of metatarsal-phalangeal and ankle joint biomechanics. Several studies have suggested that the design of the insole may influence performance outcomes. Despite numerous designs and materials having emerged in recent years, no scientific research has systematically compared the effect of these designs and materials on the flexural stiffness, rebound capacity and damping characteristics of insoles. Consequently, we have developed a novel testing methodology to assess these characteristicsin various materials and geometric configurations of carbon plates and soles. In our initial test series, we have compared the characteristics of two soles of the same trail running shoe model, with and without an integrated carbon plate. We have studied the individual materials employing Dynamic Mechanical Analysis (DMA). The obtained results have been correlated with rebound velocities and vibration damping characteristics. In this new part of the project, we have subjected to a novel dynamic mechanical test a new set of diverse soles, incorporating distinct, foam materials and various carbon plate configurations. Utilizing a specialized algorithm, we have measured the elastic modulus E’, and the complex modulus E'' of the soles, correlating the results with the rebound speed of the soles as a function of the materials employed. The aim of the study is to find the correlation between the composition of the insoles, the resulting viscoelastic properties, with the vibration and rebound parameters. Consequently, trying to understand how this set of data can be useful to predict the response of the shoe during the sportive gesture.