Relationship between transverse arch height and foot muscles evaluated by ultrasound imaging device.

[Purpose] Few studies on the transverse arch (TA) in the forefoot have been conducted. The forefoot is where pains occur most frequently and is related to walking and balance; hence, paying attention to TA is vital. However, the relationship between TA and foot muscles has not been investigated. Therefore, this study aims to investigate muscles related to TA. [Subjects and Methods] Nineteen healthy young males were included. Measurements of their feet, excluding one foot with recent foot pain (n=37), were obtained. The height of TA (TAH) was measured in two ways: during 10% and 90% loading of body weight. The cross-sectional area and thickness of five muscles were measured: flexor digitorum longus, peroneus longus and brevis, flexor hallucis brevis, flexor digitorum brevis (FDB) and abductor hallucis (ABH). All measurements were performed with an ultrasound device. [Results] FDB and ABH were correlated with TAH during 10% and 90% loading after removing the effect of body mass index and age. The greater FDB and ABH, the higher TAH. [Conclusion] As FDB becomes larger, the second, third and fourth metatarsal heads are raised more. Furthermore, the height of the first metatarsal head is lowered by a larger ABH. These mechanisms may increase TAH.