Purpose To explore the effect of different parametrical designs with carbon-fiber plate (CFP) structure in running shoes on the mechanical response of the forefoot and plantar fascia, so as to provide references for the prevention of running-related foot injuries and optimization of running shoes.

Methods Based on the established 3D foot-shoe finite element model, changes of forefoot plantar pressure and stress and strain in plantar fascia were analyzed at the impact peak of forefoot strike (FFS) running when wearing shoes with different CFP designs, including three different locations (high-loaded, HL(just below the insole), mid-loaded, ML(in between the midsole), and low-loaded, LL(just above the outsole)) and three thicknesses (1 mm, 2 mm, 3 mm).

Results When the CFP thickness was small (1 mm), the effects of its embedded locations on the mechanical response of the forefoot and plantar fascia was different. Compared with the no-CFP shoe (NC), the peak plantar pressure in HL and ML situations increased by 3.84% and 4.31%, respectively, while the peak stress and strain values of the proximal plantar fascia in the LL situation increased by 2.67% and 3.19%, respectively. With the increase of CFP thickness (3 mm), the plantar pressure, plantar fascia stress, and strain all decreased greatly, with the peak plantar pressure decreasing the most in the LL3 situation, which was 29.56% lower than NC. The peak plantar fascia stress and strain were also greatly lower than NC, and the effects of CFP at the three locations were basically the same.

Conclusions When the CFP thickness is small, different embedded locations may have varying effects on foot mechanics. However, as the CFP thickness increases, plantar pressure and plantar fascia loading gradually decrease, and low-loaded CFP achieves better results. Future studies should assess the influence of CFP features both on metabolic cost and plantar load in order to determine the best trade-off between greater running performance and lower foot injury risk.