Author(s): KOYAMA, K., HOSONO, S., Institution: TOIN UNIVERSITY OF YOKOHAMA, Country: JAPAN, Abstract-ID: 1017

INTRODUCTION:
Foot force-generating capacity plays an important role in jump performance (Yamauchi & Koyama, 2020). This capacity is generated through the coordinated interaction between foot muscles and arch dynamics. Training programs aimed at improving this capacity have been implemented, and our previous study demonstrated that performing the same training barefoot resulted in sustained improvements in toe flexor strength compared with training performed while wearing shoes (Koyama & Hosono, 2026). However, the effects of barefoot training on jump performance remain unclear. The purpose of this study was to clarify the effects of barefoot training by comparing longitudinal changes in toe flexor strength, arch structure, and jump performance during an 8-week exercise program performed under barefoot and shod conditions.
METHODS:
Healthy adults aged 20–50 years participated in this study. Participants were assigned to a barefoot training group (BARE), a shod training group (SHOD), or a control group (CON), ensuring no significant differences in baseline measurements among groups. The training groups completed a combined foot and lower-limb exercise program (Koyama & Yamauchi, 2023) for 60 minutes per session, twice per week, over an 8-week period. Measurements were conducted every 2 weeks, for a total of eight sessions. Foot length, arch height, toe flexor strength, vertical jump height, and standing long jump distance were assessed. Jump performance was evaluated using squat jump (SJ) and countermovement jump (CMJ), and standing long jump tests. Percentage changes relative to baseline (week 0) were calculated at each 2-week interval, and within- and between-group comparisons were performed.
RESULTS:
Toe flexor strength increased at all measurement points compared with baseline in BARE, whereas in SHOD, significant improvements were observed only from week 4 onward. At week 8, toe flexor strength in BARE was higher than at baseline and week 2 (p ≤ 0.01), as well as week 4 (p ≤ 0.01). In contrast, SHOD showed a significant increase only compared with baseline (p ≤ 0.01). Regarding jump performance, CMJ height increased only in BARE at week 8 compared with baseline (p ≤ 0.01), week 2 (p ≤ 0.01), and week 4 (p ≤ 0.05), whereas no significant changes were observed in SHOD. In the standing long jump, BARE also demonstrated greater improvements than CON (p ≤ 0.05). Arch structure variables did not show significant changes over the 8-week period in any group, and no between-group differences were observed. No significant changes were observed in any variables in CON.
CONCLUSION:
Eight weeks of barefoot training induced early and sustained improvements in toe flexor strength and enhanced jump performance, particularly in tasks involving the stretch–shortening cycle. These findings suggest that barefoot training may promote neural adaptations in foot function.