The foot arch and viscoelastic properties of plantar fascia and Achilles tendon

Plantar fascia reduces ground reaction force on metatarsal heads. It serves to stiffen medial and lateral longitudinal arches and reduce longitudinal arch flattening. Mechanical characteristics of plantar fascia and Achilles tendon can provide significant information on fascia and tendon functional condition as well as the risks of irregularities. The objectives of this study were: (a) to identify plantar fascia and Achilles tendon oscillation frequency, decrement and stiffness, and to evaluate the reliability of differences between normal, low and high foot arch; (b) to identify the relation between plantar fascia and Achilles tendon mechanical characteristics. 42 feet of 21 soccer players were investigated in order to determine plantar fascia and Achilles tendon oscillation frequency, decrement and stiffness of feet with normal, low and high foot arch. 164 feet of 32 soldiers, 21 football players and 29 basketball players were analyzed to determine the link between plantar fascia and Achilles tendon mechanical characteristics. The medial longitudinal foot arch was evaluated according to arch index by Williams (WAI). The Achilles tendon and plantar fascia oscillation frequency, decrement and stiffness were evaluated using Myoton-3 system. This study revealed that relaxed plantar fascia of feet with normal arch is statistically reliably more elastic than fascia of feet with low arch. A very strong relationship was discovered between mechanical characteristics of plantar fascia and Achilles tendon.