Deformation mechanisms in marathon running shoes elucidated by X-ray micro-computed tomography and digital volume correlation analysis.

The design of high-performance marathon running shoes plays a critical role in optimizing energy return, reducing fatigue, and enhancing comfort for elite athletes. A comprehensive understanding of the internal deformation mechanisms within these complex, multi-material structures is essential for developing new strategies to optimize their performance under realistic loading conditions. In this study, we have integrated x-ray micro-computed tomography (XCT) and digital volume correlation (DVC) to investigate the internal mechanics of a marathon shoe's stiffening element, a critical component used for optimization of energy return and stability to the athlete. Using XCT, we non-destructively imaged the shoe's internal architecture, revealing the intricate geometry of midsole and the stiffening elements within the sole of the shoe. Using a unique 3D printed bending frame, were able to deform the midsole of the shoe and used DVC analyses to quantify the three-dimensional displacement and strain fields under the simulated loading conditions. Our results demonstrate that localized strain patterns near the metatarsophalangeal joint can be used to accurately replicate and understand the foot's natural biomechanics during propulsion. By bridging advanced imaging techniques and computational modeling, this research provides actionable insights for the rapid prototyping of next-generation marathon shoes. The findings and frameworks discussed here help contribute to optimizing performance, setting a new standard for athletic footwear design tailored to the rigorous demands of endurance running.