Relationship between plantar fascia thickness in static standing and calf raise positions and the medial longitudinal arch height ratio in healthy adults

[Purpose] To evaluate plantar fascia thickness during static standing and calf raise positions using ultrasound imaging and to examine its relationship with medial longitudinal arch height ratio and physical factors. [Participants and Methods] We measured plantar fascia thickness in 30 healthy adults (18 males, 12 females) using ultrasound at a site 1.5 cm distal to the calcaneal origin in static standing and calf raise positions. Additionally, we assessed their medial longitudinal arch height ratio (arch height using navicular height divided by foot length) and other physical characteristics to examine possible correlations. [Results] Ultrasound measurements of plantar fascia thickness showed high reliability in both static standing and calf raise positions, with thickness reduced significantly from standing to the calf raise position. In the overall analysis, plantar fascia thickness was positively correlated with body weight in both positions, and a positive correlation between plantar fascia thickness and height was observed in the standing position. In contrast, no significant correlations were found between plantar fascia thickness and the medial longitudinal arch height ratio or body mass index in the overall analysis, nor between plantar fascia thickness and physical parameters in sex-specific analyses. In males, the change in plantar fascia thickness between positions was negatively correlated with age; however, no significant correlations were observed in the overall sample or in females. [Conclusion] Plantar fascia thickness decreases during calf raises compared with standing and is influenced by body weight, supporting that the calf raise position places stretching stress on the plantar fascia and may be used for evaluating load response and physical function.