Biomechanical characterization of human plantar fascia through experimental tests

Plantar fascia is a complex structure, which stands between the calcaneus and the forefoot region of the foot. It plays a key role in foot biomechanics and its functionality can be compromised by different pathologies (e.g. plantar fasciitis). For these reasons, the aim of this study is the investigation of the plantar fascia's mechanical properties through experimental tensile tests. Mechanical tests have been performed on samples obtained from human plantar fascia considering different regions and directions. From failure tests, the ultimate tensile stress and the corresponding failure strain were obtained, while stress-relaxation tests were performed to compute the viscoelastic tissue parameters. Initial and final Young's moduli were determined for stress-strain curves from both failure and stress-relaxation tests. Experimental results showed a similar behaviour between proximal and distal plantar fascia regions, while it was different considering the proximal-distal and lateral-medial directions. Furthermore, the results highlighted the non-linear time-dependent behaviour and the anisotropy of the plantar fascia. As further steps, these results could be implemented in a computational model of the entire foot region to investigate the mechanical response of tissues in both healthy and pathological conditions.