18/01/2023
Longitudinal bending stiffness is a key consideration for both marathon shoes and track spikes. Although sprint spikes have been stiffened with carbon fiber plates for more than 20 years, the exact effect of increased longitudinal bending stiffness on sprinting performance is still not well understood.
One benefit of increased bending stiffness is decreasing the amount of energy lost at the metatarsal-phalangeal (MTP) joint. While running and sprinting, the MTP joint dorsiflexes during stance phase, absorbing mechanical energy, and remains dorsiflexed throughout the majority of the push-off, returning little of that energy. On average, energy loss at the MTP joint has been reported to be ~ 48 J during sprinting at 7.1–8.4 m/s and 13–21 J during running at 4.0–4.4 m/s [31, 32]. Stiffening the sole will limit MTP dorsiflexion, and, in turn, limit the amount of energy lost. Along with altering MTP mechanics, increasing longitudinal bending stiffness shifts the point of force application more anteriorly, creating a larger moment arm at the ankle. Moreover, the change in moment arm might offer the potential to improve the effectiveness of horizontal force application, thereby improving sprint performance, as suggested by Willwacher et al. [14]. However, increasing the bending stiffness will increase force demands from the plantar flexor muscles, which can be detrimental for performance
