Investigation Into Plantar Fascia Contribution to Gait Mechanics Using Robotic and Simulation Approaches

The plantar fascia (PF) plays a critical role in human locomotion by dynamically adjusting foot stiffness and enhancing energy efficiency through the windlass mechanism. This study investigates the trade-offs associated with altered PF mechanical properties using bipedal experiments and simulation models. Specifically, PF ligaments with varying mechanical properties were fabricated using braiding technology, where higher braiding courses resulted in a longer toe region and reduced stiffness. These ligaments were incorporated into a bipedal walking robot, and corresponding load-displacement curves were input into a simulation model for level walking tests. The results show that the mechanical properties of the PF ligaments significantly influence gait dynamics, muscle energy, and ground reaction forces. Increasing the number of braiding courses in the PF ligaments enhanced energy harvesting in the soleus and tibialis anterior muscles, with a 23.9% increase from 190.84 mJ to 236.47 mJ over the entire gait cycle. However, this improvement in energy storage was accompanied by a reduction in biomechanical stability, evidenced by a more pronounced heel-strike transient around 1.8% of the gait cycle and a longer stance phase. These findings highlight the balance between ligament stiffness, energy efficiency, and biomechanical stability, offering valuable insights for developing orthotics, prosthetics, and robotic systems aimed at optimizing gait dynamics and minimizing injury risks.