Relationship of Physical Factors to the Acceptability and Unacceptability of Short Foot Exercise: A Preliminary Study.

Objectives: This study aimed to examine the physical characteristics of participants who can and cannot perform the short foot exercise (SFE). Methods: This prospective observational study was conducted in a university laboratory in Japan. University students (aged ≥18 years) enrolled between April and December 2024 were recruited as participants. We measured height, weight, foot length, medial longitudinal arch height, and toe grip strength. Ultrasonography captured transverse images of the intrinsic foot muscles, including the abductor hallucis, flexor hallucis brevis, and flexor digitorum brevis. Participants received single-instruction SFE training in a sitting position and were classified into two groups: SFE possible and SFE not possible. Those in the SFE not possible group received an additional 10 min of instruction before reattempting SFE. Based on performance, participants were categorized into three groups: those who succeeded after initial instruction (SFE-A), after practice (SFE-PT), or remained incapable (SFE-NP). Statistical analysis was conducted using one-way analysis of variance (ANOVA) and multiple comparison tests for each measurement and analysis item, with the significance level set at P < 0.05. Results: In female participants, toe grip strength was lower in the SFE-A group than in the SFE-PT and SFE-NP groups, whereas no significant differences were observed in male participants or in muscle morphology and the navicular drop index in either sex. Conclusions: These findings suggest that immediate performance of the SFE may not necessarily be associated with greater toe grip strength or larger intrinsic muscle size but may relate to coordination between intrinsic and extrinsic muscles.